Rubber - American Chemical Society

(S85) Rietyeld, B. J., J . Polym. Sci., Pt. A-2,8,1837 (1970). (586) Rifkind, J. M., Applequist, J., J . Amer. Chem. SOC.,90,3650 (1968). (S87) Romberger, A. B., Eastman, D. P., J . Chem. Phys., 51,3723 (1969). (S88) Ruland, W., Pure Appl. Chem., 18,489 (1969). (S89) Sale, P., Rev. Belge Matieres Plast., 9 (7), 469 (1968). (S90) Samedova, T. G., Gavrilenko, I. F.,

Karpacheva, G. P., Davydov, B. E., Stefanovskaya, N. N., Izv. Akad. Nauk SSSR, Ser. Khi.m., 1970 (3), 682. (S91) Scharschmidt, J., Farbe Lack, 76 (2),

115 (1970). (592) Schiedermaier, E., Klein, J., Angew. Makromol. Chem., 10 (117), 169 (1970). (593) Schmalz, E. O., Faserforsch. Teztiltech., 21,209 (1970). (594) Schneider, N. S., Allen, A. L., J . Macromol. Sci., B3, 767 (1969). ( S Q 5 ) Schneider, N. S., Dusablon, L. V., zbid., B3,623 (1969).

Schollner. R.. Schmidt. J.. Fette Seifen Anstr. hlitte?,69, (lo), 766 i1967). (597) Schroeder, E., Thinius, K., Weissmann, L., Plaste Kaut., 17 (6), 387 (1970). (S98) Schulz, G. V., Lechner, M.,J . Polym. Sci., Pt. A-2,8, 1885 (1970).

(8961 \ - - - ,

(S99) Seki, J., Sen4 Gakkaishi, 25 (l), 16, 24 (1969). (S100) Sewell, P. A,, Skirrow, G., Polymer, 11, 2 (1970). (5101) Shindo, Y., Stein, R. S., U. S.

Clearinghouse Fed. Sci. Tech. Inform., 1968, AD-666625; U. S. Govt. Res. Develop. Rep., 68, 50 (1968). (S102) Smith,-H. F., Amer. Chem. SOC. Div. Org. Coatings Preprints, 30 (a), 112 (1970). (5103) Stein, R., Ann. N . Y . Acad. Sci., 155 (2), 566 (1969). (5104) Stein, R. S., Hashimoto, T., J . Polym. Sci., Pt. A-2,8, 1503 (1970). (S105) Sugai, S., Kamashima, K., ibid., Pt. A-2. Polurn. Phus.. 6. 1065 (1968). (Sl06) Sukhnevich, 'V'. 'S.,Zh. Prikl. Spektrosk.,. 9 (51, . . . 772 (1968). (S107) Tome, O., Crisan,' T., Mater. Plast., 7 (2), 83 (1970). (5108) Tomita, A., J . Phys. SOC.Japan, 28 (3), 731 (1970). (S109) Tosi, C., Eur. Polym. J., 6, 161 (1970). (5110) Truscott, E. D., ANAL. CHEM., 42.1657 (1970). ( S l l i ) Tuzar, Z., Kratochvil, P., J . Polym. Sci., Pt. B, 7 (12), 825 (1969).

(S112) Utiyama, H., Sugi, N., Kurata, M., Tamura, M., Bull. Inst. C h m . Res., Kyoto Univ., 46 (2), 77 (1968). (S113) Vassil'ev, R. F., Makromol. Chem., 126,231 (1969). (S114) Velickovic, J., Vukajlovic, J., Angew. Makromol. Chem., 13, 79 (1970). (S115) Venkateswaran, A., J. Appl. Polym. Sci., 13,2469 (1969). (5116) Vilim, O., Novak, J., Plust. Hmoty Kauc., 6 (8), 240 (1969). (S117) Wessling, R. A., J. Appl. Polym. Sci., 14,1531,2263 (1970). (5118) Williams, J. L., Hopfenberg, H. B., J . Macromol. Sci., B3,711 (1969). (5119) Witt, H., Rheude, A., Heusinger, H., Radial. E$., 5 (3-4), 213 (1970). (S120) Woods, J., Appl. Spectrosc., 22 (6), 799 (1968). (5121) Yasuda, H., Stannett, V., J . Macromol. Sci., B3, 589 (1969). (S122) Yoshioka, N., Yoshihara, T., Chem. High Polymers (Japan), 27, 366 (1970). (5123) Zand, R., Encycl. Polym. Sci. TechnoZ., 9,610 (1968). (S124) Zelenina, E. N., Shemyakin, F. M., Novikov, P. D., Zhukov, M. A., PZast. Massy, 1968 (8), 59.

Rubber Coe W. Wadelin and Gordon S. Trick, Research Division, The Goodyear Tire and Rubber Co., Akron, Ohio 4431 6

C

HEMICAL ANALYSIS OF RUBBER and the characterization of rubber by physical, chemical, and spectrometric methods are covered by this review. Methods for the characterization, identification, and determination of rubber and materials in rubber are included. Analysis of rubber chemicals before they are added t o rubber is not included. The literature which became available t o the authors between July 1968, the end of the period covered by the last review in the series (218), and September 1970, is covered. Polymers other than rubber are covered in another review (144,145). Abbreviations recommended in ASTN Designation D1418-69 have been used ( 5 ) . They are listed in Table I.

GENERAL INFORMATION

The use of radioisotopes and activation methods (SS), the application of differential thermal analysis and thermogravimetric analysis to rubber ( I s h ) , and the use of the electron microscope in rubber research were reviewed (185). The second edition of the excellent book by Wake on the analysis of rubber was publkhed (219). POLYMER IDENTIFICATION

General Information. Before subjecting an unknown polymer, or any 334 R

other unknown material, for that matter, to sophisticated instrumental measurements, it is worthwhile to learn as much as possible about the history of the sample, to make a preliminary examination of it, and to find out which elements are present and which are absent (181). This preliminary information can help in pointing to some possible identifications and eliminating others.

Pyrolysis

-

Gas Chromatography.

Work has continued to go on in the area of pyrolysis devices. Measurements of temperature rise time of filaments were made (125). Temperature rise time is very important because much of the pyrolysis takes place during the temperature rise. Therefore, the rise time should be specified for reproducible results. It was found that a filament which required 10 seconds to heat a t constant voltage could be heated in 15 milliseconds by discharging a large capacitor through it (124). The decomposition time of the polymer is several orders of magnitude slower than temperature rise time. With a Curie point pyrolyzer, temperature rise time was less than 0.3 second (225). An alloy of 3: 2 nickel and iron has a Curie point of 610 "C (902). Another source of high energy for pyrolysis is the laser. It caused predominant decomposition to small frag-

ANALYTICAL CHEMISTRY, VOL. 43, NO. 5, APRIL 1971

ments with considerable amount of monomer. Only small amounts of tars and byproducts were formed (6). Two years ago, the preferred pyrolysis temperature seemed t o be high, i.e., 700 "C or above, so that a rapid pyrolysis to monomer took place, giving a simple chromatogram. Since then, the tendency has been to choose lower temperatures. For instance, 480 "C was chosen because less fragmentation occurred and more features of the original polymer were retained in polyolefins having different degrees of branching (625). Pyrolysis of tire stocks was done a t 540 "C in order to have 4-vinyl cyclohexene (butadiene dimer) as a product (154). It is used to detect B R in the presence of SBR. Below 650 "C, B R forms twice as much 4-vinyl cyclohexene as SBR. Above 650 "C, no 4vinyl cyclohexene survives, as it is all cracked to butadiene monomer. The use of short pyrolysis times at low temperatures is by no means universal. A scheme to identify a number of polymers, each when present by itself, uses pyrolysis a t 750 "C for 15 seconds (73). The whole pyrogram is compared with those of knowns. Two other compilations of pyrograms were published (72,153). N R was distinguished from IR by the fact that K R gave more dipentene and less butene and isoprene (101). HOW-

Table I. Abbreviations Recommended by ASTM (5). EPDM Terpolymer. of ethylene, pr? ylene, and a dlene with the resiiual unsaturated portion of the diene in the side chain EPhl Ethylene-propylene copolymer IM Polyisobutylene ABR Acrylate-butadiene rubber BR Butadiene rubber CR Chloroprene rubber IIR Isobutylene-isoprene rubber IR Isoprene rubber, synthetic NBR Nitrile-butadiene rubber NR Isoprene rubber, natural SBR Styrene-butadiene rubber AU Polyester urethane rubber EU Polyether urethane rubber

ever, the I R used was the Li-catalyst lype which has about 50% trans-1,4and 50y0cis-1,4- structure, so one would expect a difference. High cis-1,PIR was not tested. The presence of cyclopentanone in the pyrolyzate of a polyurethane indicates a polyester based on adipic acid (228). The use of gas chromatography in polymer analysis was the subject of a book by Stevens (191). Infrared. A new method was described for solubilizing vulcanizates (46). The sample is treated with 2,2’dibenzamidodiphenyldisulfide in boiling 1,2-dichlorobenzene. It has been applied to SBR and BR and presumably would work for other rubbers with sulfur curing systems. Catalogs of spectra of pyrolyzates were compiled for rubbers used in hydraulic seals (138), mastics (175), and general applications (46, 53). Samples were extracted to remove plasticizers and oil.

Nuclear

Magnetic

Resonance.

Vulcanizates were solubilized in hot hexachloro-l13-butadieneand run without removing carbon black (35). The diene component in E P D N can be identified if time averaging is used to enhance its signal, which is of low intensity due to its low concentration (2, 186). Methylenenorbornene, ethylidene norbornene, and 1,4-hexadiene were identified (186). Cyclooctadiene and dicyclopentadiene cannot be distinguished from each other, as they both give the same chemical shift. They can, however, be distinguished by the fact that they split out different amounts of hydrogen iodide after treatment with iodine monochloride (210). The use of N M R spectra to identify elastomers in solution was reviewed (41). Other Methods. Pyrolysis followed by thin layer chromatography was used to identify N R , CR, CSM, I I R , E P M , and urethane rubbers (166). The diamines and polyether or dicarboxylic acid and glycol in E U and

AU, respectively, were identified by thin layer chromatography after hydrolysis (68). The article also contains a good literature review of chemical tests for polyurethane components. Gas chromatography was also used to examine polyurethane components after degradation by transesterification and aminolysis (136). Methods for the identification of B R and E P D M in the presence of other elastomers are the subjects of two G.S. patents. BR is treated with phenylhydrazine, then mercuric acetate, then nitric acid to give a red-brown color (169). It is difficult to understand how this method would distinguish BR from SBR when SBR contains the same basic structure as BR. E P D M is nitrated, reduced with zinc and acetic acid, and then treated with p-aminobenzaldehyde (160). Again, it is hard to see how E P D M is specifically nitrated in the presence of NR, I R , CR, SBR, NBR, BR, and I M , as is claimed. A new technique combining thermogravimetry with gas chromatography of evolved products was described (43). Temperature is increased slowly so that the pyrolysis is done with minimum thermal energy. This gives simple distributions of products. POLYMER CHARACTERIZATION BY PHYSICAL METHODS

General. As in the previous review, the published information to be discussed in this section will be restricted to experimental techniques and results that are considered to be of interest to readers who are specifically involved in the physical characteristics believed t o be of technical importance. No attempt or pretense has been made towards completeness of the literature coverage. On the contrary, emphasis has been placed on pointing out the directions which research is taking, documented by representative published work which can serve as a starting point for those more interested in specific subject areas. A much more extensive compilation of literature references is available (144) covering some of the same subject matter as applied t o high polymers in general. I n addition, other review articles (1, 187, 224) contain sections of interest to those concerned with the physical characterization of raw elastomers. Molecular Weights. The combination of intense activity in molecular weight analysis based on gel permeation techniques and the availability of several commercial instruments which give reasonably satisfactory molecular weight measurements (number average and weight average) has brought about a marked decrease in reported research activity on new methods for measuring

molecular weights. A detailed description has been presented (217) of the operation of a specially designed (66) vapor phase osmometer together with a discussion of various methods for treatment of the experimental data. The method was applied to various narrow molecular weight polystyrene standards using three different solvents and the results compared with those obtained by membrane osmometry. It was concluded that the techniques described allowed measurements of molecular weights in the range of 600 t o 400,000 with a standard deviation of 1% to 12%. The various critical design features of a n ebulliometer have been described (56) and it was found that the use of three thermistors (two in the vapor and one in the effluent liquid) resulted in more rapid measurements with improved reproducibility. The instrument was successfully applied to samples with molecular weights up t o 30,000. A new commercial source of the PinnerStabin membrane osmometer has recently become available (176). An entirely new type of experimental measurement, termed a “macromass spectrometer]’, has been reported (66). The method involves (106) isolation of individual polymer molecules by formation of tiny drops from a dilute polymer solution with the actual analysis being performed by a mass spectrometer. The technique shows promise for allowing measurements of both molecular weight and molecular weight distribution.

Molecular Weight Distribution (GPC). Work continues unabated on the gel permeation chromatography (GPC) of polymers. I n addition to cases where GPC efforts have been applied to specific problems] much effort has been aimed a t examining various methods for calibrating and for correcting for non-ideal behavior under the particular experimental conditions used in making measurements. Only a fraction of the published papers of the last two years will be discussed in this review. An extensive bibliography of GPC arranged by subject is available (221) covering 516 references through October 1969. A number of meetings have been devoted exclusively to GPC and the papers presented have been made available (170-1 73) in either complete or abstract form. A review of experimental methods employed in GPC and methods for evaluating data has been published (140). A book covering all phases of gel chromatography, including GPC, is now available in an English translation (62), but of necessity does not cover recent developments. A symposium on GPC (S), although aimed primarily a t applications in petroleum chemistry, contains much useful information of a general nature including several papers describing the “state of


335 R

the art” of a number of important aspects. A description has been given (89) of the nature and performance of various packing materials and other papers (60, 189) describe the characteristics and separation efficiency of a porous glass substrate. Another review (18) is concerned with the instrumentation of GPC, experimental techniques, and effluent detection system. Of great interest in the application of GPC measurements has been work aimed a t obtaining more rapid separations under carefully controlled experimental conditions together with computational techniques to correct for the effect of operational parameters on the experimental results. A number of papers have been published in this subject area (27, 127-129) and in general it appears that valid quantitative results may be obtained a t high flow rates. A high flow pumping system has been made available (221) for the Waters Model GPC-200, and it allows traces t o be obtained in a few minutes. In addition to the obvious time saving, high flow rate conditions offer certain advantages in data treatment including elution volumes which are independent of flow rate and reduced skewing of peaks from viscosity effects. Some loss in resolution is observed, but with a highly stable system proper corrections may be applied t o the data. Recently, announcement has been made (269) of the development of a computer-controlled high speed GPC that provides computed molecular weight distribution data with a minimum of elapsed time and manual operations. All these recent developments are aimed at allowing GPC to be used not only as a research tool but also in production monitoring and/or process control. For the analysis of complex polymeric systems containing more than a single structural component, it is often useful to employ an additional detector system besides the normal refractive index detector. I n fact, if the structural composition of a polymer depends upon molecular weight, it is essential to have compositional information in order to obtain a correct size distribution. A discussion of this problem has been published (180) including a description of combining UV or I R with refractive index measurements. A slightly different approach to the treatment of the data from such a system has been made (58) with somewhat different conclusions, depending on the nature of the GPC calibration curves of the separate components. It is also possible to carry out a complete spectral analysis of the eluting solution since it has been shown (49) that the solution flow may be temporarily stopped without significantly affecting the instrument resolution and 336R

resulting size distribution. The design of a belt detector for GPC has been described (48) and an appraisal given of its advantages, particularly in the low molecular weight region. I n the application of GPC measurements to elastomeric materials, experimental results have been published (212) on a number of SBR samples prepared in emulsion with various mercaptan modifiers and in some cases in the presence of divinylbenzene. The results were compared t o theoretical molecular weight distributions and the effect of modifier depletion and branching was discussed. I n the same paper, GPC results are presented on a number of SBR 1500, 1502, 1503, and 1712 samples selected a t random from commercial samples. For samples of SBR 1500, significant differences were found between samples from different sources. An investigation has been made (54) of the molecular weight and chemical composition distribution of SBR using a number of experimental techniques including GPC with refractive index and ultraviolet detection. A detailed structural and molecular weight examination (17’) of ethylene-vinyl acetate (EVA) and SBR copolymers has been made using a standard analytical GPC and a specially designed preparative GPC combined with solution viscosity, osmotic molecular weight, and infrared measurements. For the EVA samples, the copolymer composition was essentially independent of molecular weight and the samples exhibited considerable long chain branching. For the SBR samples, the higher molecular weight components showed a marked decrease in styrene content. It was also concluded that the samples examined contained no detectable long chain branching. An examination of the milling behavior of SBR and EPDM samples has been made (16) using GPC to follow changes in molecular weight and molecular weight distribution. The effect of time and temperature was measured and it was concluded that a nonrandom chain degradation took place with a narrowing of the molecular weight distribution. I n order to assess the quantitative precision of molecular weight distributions from GPC measurements, an extensive investigation has been made (84) of the short term and long term repeatability of measurements. Initial experiments localized some sources of experimental error in the standard instrument used and improved repeatability was obtained after modifications to the automatic sample injector, photoelectric detector of the refractometer, and after the installation of an evaporation control system on the siphon arrangement. With such a modified system, measurements on I I R and I M control standards over a one-year period


showed a standard deviation of 3% in M W and 8% in MN. I n an independent investigation using I I R samples (160), replicate fractionation gave standard deviations in MWand MNof about 2y0 or less. These papers illustrate the high precisions that are attainable for measurements made on a routine but carefully controlled system. Since raw GPC results are subject to some disturbances resulting from nonideal separation, precise quantitative calculations necessitate the assessment and incorporation of several correction terms. The most thoroughly investigated correction term involves peak broadening which is readily observed in monodisperse samples. A general review (108) is devoted to this subject. A summary of one type of approach for correcting for instrument spreading has been reported (208). A simplified method for experimentally determining instrument spreading parameters involves (209) simply the use of the leading halves of GPC curves of several standard polystyrene samples with the same curves being used for calibration purposes. It was found that the spreading parameters depended upon elution volume but not upon the chemical nature of the polymer. I n some cases ( 1 5 ) , the GPC chromatograms of narrow distribution standards show an unsymmetrical broadening or skewing believed to arise from a nonuniform velocity profile in the chromatograph columns. Correction parameters for skewing may be obtained from normally run GPC traces. With the choice of a t least five methods for correcting for band broadening, a summary has been presented (69) of the characteristics of each of the treatments as applied t o specific experimental data. Some of the methods of treatment lead to oscillations in the molecular weight distribution curves, believed to arise from GPC noise and difficulty in reading trace heights. A recently published approach (39) has been found to reduce some of the oscillation problems. A theoretical (21) and experimental (158) examination has been made of factors contributing to peak broadening. Possible sources of broadening considered were the columns, connecting tubing, and detector cell. When a slightly modified standard GPC instrument was used, the columns led t o symmetrical dispersion while connecting tubing gave skewness depending on tubing length and diameter, solute concentration, and solute molecular weight. The chemical nature of many elastomeric materials is such t h a t it would be expected that materials of technical interest could contain long chain branching. Such structural units affect the viscosity behavior of polymers (115, 224) and could affect their processing behavior. Hence, considerable efforts

have been expended in applying GPC techniques to estimate long chain branching. I n addition, in the presence of long-chain branching] the usual treatments of GPC data will give an incorrect molecular weight distribution. I n one related experimental approach using fractionation of branched polyethylene with a sand column, it was shown (137) that by measuring the viscosities of all fractions and the absolute molecular weight of one fraction and combining with a known Mark-Houwink relation, it was possible to determine the long chain branching frequency. The effect of branching upon the molecular weight distribution curve was illustrated. I n a subsequent paper (67) the effect of various branching models and degrees of branching upon GPC calibration curves is illustrated. Assuming that the ratio of number of branch points per molecule to molecular weight is constant, information may be obtained on branching in either fractions or whole polymers. The application of this approach to polyethylene has been shown (68). A somewhat more general theoretical approach to the same problem has been made (188) treating polydisperse polymers with randomly distributed trifunctional and tetrafunctional branch points. A different method (207) for the estimation of degree of branching in polydisperse polymers involves a combination of GPC results with sedimentation velocity measurements on the same sample. The method is illustrated by applying it to a styrene-divinyl benzene copolymer. Progress has been made in methods for absolute calibration of GPC systems for specific polymers without the necessity of preparing narrow molecular weight distribution samples of the same polymer. One particularly convenient method (222) requires the use of a single broad distribution sample of known intrinsic viscosity and MNor two broad distribution samples of known and different intrinsic viscosities. Combining GPC traces of these standards with similar data for narrow distribution polystyrene standards provides a calibration curve for the particular polymer of interest. Actually the method provides a convenient means for determining Mark-Houwink parameters for combining with a universal calibration curve of log (7) 31 us. elution volume. A thorough examination of this technique has been applied (150) to I M samples and it was found that repetitive measurements on a single standard 131 of known (7) and 31 resulted in considerable variation in the computed Mark-Houwink parameters. However, the errors in the two parameters were largely cancelling and resulted in having little effect on the molecular weights computed for a single

unknown using replicated standard traces. The technique was also successfully applied to SBR samples (150). A somewhat different method of calibration (223) does not assume a universal calibration curve but rather assumes that the molecular weight distribution of an unknown polymer may be represented by a general two-parameter function. If M N and Mv or M N and M w are known, the GPC calibration curve may be generated. The method was successfully tested with samples of poly (methyl methacrylate).

Molecular Weight DistributionOther Methods. Among new techniques proposed for polymer fractionation and determination of molecular weight distribution is one involving the use of an endless moving belt (23) onto which is applied a t one point a thin coating of polymer solution. The coating passes through a drying region and then through a series of thermostated tubes containing solvent-nonsolvent mixtures of increasing solvent power. I n such a system, each tube dissolves out a fraction of increased molecular weight. Detailed molecular weight distribution results are presented (24) for Neoprene FV and a low molecular weight poly(tetramethy1ene ether glycol), and the results are considered to be in good agreement with those obtained by other techniques. I n addition to providing molecular weight distribution data, the technique allows large scale preparative fractionations and results are reported on several polymers including Neoprene W, Nordel hydrocarbon elastomer, and Viton fluorelastomer. As in most preparative scale fractionations a compromise must be reached between size of fractions] narrowness of fraction, and time required for fractionation. Another new experimental technique (157) aimed a t assessing molecular weights and distribution involves thin layer chromatography on a silica gel or alumina substrate. Separation is made by applying mixed solvents or a solvent gradient. A discussion is given of the present status of the technique and directions the research must take to make the method more useful. I n a subsequent paper (156) a densitometer is used for analysis of the chromatogram and good agreement with GPC results is attained. An appraisal is made of the experimental conditions necessary for successful fractionation, particularly the role played by solubility and adsorption. Another fractionation technique (13) involves separation by ultrafiltration using membranes with sharp molecular weight cutoffs. Among reports involving more conventional techniques, the effect of temperature and temperature gradient has been reported (102) for the column elution fractionation of IM. Only for

low molecular weights was a temperature gradient effective. A comparison has been made of a number of techniques (227) t o determine the molecular weight distribution of a blend of two monodisperse samples. Of potential assistance in the selection of a suitable solvent-nonsolvent system for fractionation of copolymers is a technique (104) involving a cloud point titration of the corresponding homopolymers. It is possible to choose systems that will make fractionation based upon either molecular weight or chemical composition. Of particular interest to those desiring a clearer understanding of the meaning of various molecular weight averages] is a review (179) pointing out the origin and significance of such concepts. Transition Behavior. The growth in the number of readily available monomeric materials plus the development of more versatile catalyst systems has caused a marked increase in the number and complexity of polymers that may be prepared. I n order to assess possible applications of such materials and in particular to obtain details on the complex microstructure that may occur, the application of many sophisticated techniques is necessary. Measurements on transition behavior have proved particularly useful and the development of a large number of commercial instruments has placed such measurements on a routine basis. I n general, such instruments] although varying widely in the details of construction and operation, are based on some form of differential thermal analysis (DTA). A listing of equipment sources has been presented (182). Not all instruments are intended for operation down to the - 12OOC required for characterization of some elastomers. One commercial instrument (167) has, in addition to a differential scanning calorimetry (DSC) function, a thermal mechanical analyzer (TMA) mode of operation. The TMA attachment can operate in either a penetration mode or linear expansion mode using a LVDT detector suspended through a high density, low viscosity fluid. Another commercial instrument (70) also provides a DSC cell operating on a somewhat different principle and a TMA attachment involving a LVDT suspended by a spring arrangement. In addition, the TMA mode has been adapted (122) to measure volume coefficients of expansion and hence fulfill the functions of a dilatometer. I n the area of principles of operation of differential thermal analysis instruments] an extensive survey has been made (226) on instruments, operational methods, data treatment, and qualitative and quantitative applications, including applications to polymers. This survey is particularly detailed and emphasizes the kind of useful informa-


0

337 R

tion that may be obtained with proper instrumentation, calibration, and experimental methods. Another report (168) is concerned with the various forms of thermal analysis systems and some of the problems encountered in the nomenclature used t o report measurements of this type. I n addition, a book chapter (19) has been devoted t o theory and applications of DTA. -4s a general observation, the past two years have seen considerable emphasis on the details of DTA operation, particularly aimed a t pointing out the quantitative usefulness of measurements made with proper instrumentation and good experimental methods. For applications of D T A t o elastomeric systems, an extensive review has been published (134) which contains sections on experimental techniques, general areas of application, and specific results. Gathered together are experimental results on many elastomeric materials of commercial importance, both alone or as blends, together with a discussion of the effect of process oils and plasticizers on the transition behavior. Another review (118) contains an extensive collection of melting and glass transition temperature for a variety of polymers, and a general review on thermal analysis (151) includes some work on polymers. hmong applications to specific polymer systems is a general description (47) of DTA application to ethylenepropylene copolymers in order to obtain information on monomer distribution, tacticity, and crystallinity. Only melting transitions are considered, but the addition of measurements in the glass transition region would also provide useful information, particularly for samples displaying little or no crystallinity. Another paper (203) reports first and second order transition results on EPXI and E P D N samples prepared with different ethylene/propylene ratios. Of particular interest is an endothermic transition in some samples a t about 50°C. The origin of the transition is not clear and although the transition is small, it might have considerable effect upon room temperature green strength and other rheological properties. The effect of the concentration of various side groups (methyl, ethyl, and longer branches) on the melting point and degree of crystallinity of polyethylene has also been examined (86). Thermomechanical measurements have been reported (115) on polybutadienes with different proportions of cis and trans content. Among new types of polymers that have been examined by thermal analysis are polyoctenamers, polydecenamers, and polydodecenamers (80), all containing a range of trans double bond content, cis-polypentenamer (64), and trans-polypentenamer (88). -4number of papers have been con338 R

cerned with the transition behavior of N B R polymers. I n one report (37), a series of NBR samples of various copolymer ratios was prepared by a batch emulsion polymerization process. Glass transitions were determined from DTA measurements and it was found that copolymers containing less than 36 per cent acrylonitrile had two well defined glass transitions. The two transitions were considered to arise from incompatible phases differing in copolymer composition and perhaps molecular structure. Another investigation has been made (46) on commercial samples of N B R polymers containing 20 and 40 weight per cent of acrylonitrile using several experimental techniques including DTA. I n addition to the main glass transition, a weak endothermic first order transition was observed and attributed t o crystalline regions made up of cis-1,4-polybutadiene sequences. Another investigation (7‘8) combining DTA with other techniques resulted in similar observations and conclusions, i e . , the NBR samples examined showed some type of ordering that was attributed to the polybutadiene component. I n another application of DTA methods to complex polymers, measurements have been made (?‘) on the glass transition behavior of butadiene styrene block copolymers. Refractive index measurements were used t o determine the average copolymer composition, and by comparing the measured glass transition temperature of the elastomeric block of the copolymer it was possible, with suitable calibration, to determine the amount of block styrene and the composition of the elastomeric component. It is unfortunate that DTA measurements are rather insensitive to polystyrene block and direct measurements on the polystyrene block are often not possible. I n an examination of narrow molecular weight distribution sharp block copolymers of styrene with isoprene or butadiene (96), thermograms of samples containing two monomers showed two distinct T, regions, with the temperature of the T,‘s being constant over the cntire composition range examined. From the size of the T, steps, copolymer compositions were calculated and found t o agree with other methods of measurement. On the other hand, for isoprene-styrenebutadiene block copolymers, only one transition from the elastomeric phase is observed, suggesting phase blending of the two diene components. In the examination of another complex polymer system, DTA and TMA measurements were made (146, 143) on polyurethane elastomers and on the polyols used in preparing the elastomers. The combination of the two techniques was useful in identifying the position and nature of the various transitions.


The transition behavior and other properties were related to segment size and size distribution. Using a torsional pendulum technique, results have been reported (79) for a number of elastomeric homopolymers, random copolymers, block copolymers, and blends. Some form of thermal scanning appears to have almost entirely replaced older methods such as dilatometry in measuring transition behavior. However, some newer techniques show promise of providing similar and sometimes additional information. I n one technique (11?’) termed a “molecular probe” method, the polymer is used as a stationary phase in a gas chromatograph. On passing a low molecular weight solute vapor through the column and measuring retention volumes as a function of temperature, it was possible t o determine the glass transition of the polymer. I n an extension of this technique (87) to semi-crystalline polymers, it was found possible to make a quantitative assessment of the regions that were impermeable t o the probe molecules. The impermeable regions appeared to be related to the degree of crystallinity, but a quantitative comparison has not yet been made. I n a somewhat different approach aimed a t measuring polymer order (55, 131) measurements of the vapor pressure of polymer solutions was used to measure order in polypropylene and IM. The development and application of a dynamic permeation analyzer with programmed temperature scan has been described (165), showing, among many applications, the melting behavior of gutta-percha. A commercial version of the instrument is available (97). Sequence Distribution. A number of experimental techniques that can provide information on sequence distribution in polymers have been discussed in this review in the section on GPC and transition behavior. A new chemical method which may be applied to polymers containing residual double bonds has been reported (141). The technique involves reaction of the polymer with unique catalysts which bring about olefin-metathesis (31). The well established mechanism of the reaction allows the prediction of the metathesis reaction products t o be expected from different structural sequence, and analysis of the products by VPC is convenient. At the moment the technique has been used to determine diad and triad structures but shows promise of characterizing more complex sequences. Another experimental approach involves use of thin layer chromatography (96). The choice of a suitable developing liquid brought about separations of styrene-methylacrylate copolymers based upon chemical composition. The use of phase diagrams to

facilitate the choice of mixed solvent systems for separation by chemical composition has been discussed (201). Polymer Blends. Among blended materials t h a t have been examined is a gum blend of 50NR/30CR/20EPDM (138),using a combination of phase and electron microscopy. I n such a mix it was found t h a t N R is a continuous phase and C R is a three-dimensional stranded network with the E P D M as globules. By preparing mixes with carbon black by various methods it was concluded that the black does not readily transfer from one elastomer phase to another on milling. Another paper (32) reports results from optical and electron microscopy and DTA. Included is a technique for automatic measurement of zone sizes in the heterogeneous blends. A review article on DTA (134) contains information on a number of elastomer blends including SBR/BR and I I R / E P T mixes. Another review article (184) on the application of electron microscopy to rubber contains information on elastomer blends. Another paper (74) deals with blends of BR and SBR samples of different styrene content. The blends were characterized by microscopy, dielectric loss, and dynamic properties. It was found t h a t blends made with SBR of less than about 30 to 4oy0 styrene were microhomogeneous; if the styrene content was higher, microheterogeneous blends resulted. A paper that indicates some of the complexities on measurements of polymer blends is concerned with blends of polystyrene and poly (dimethyl phenylene ether) (192) that were examined by a mechanical loss measurement of 110 Hz and by a thermal analysis technique. The blends appeared to be two-phase systems by the mechanical loss method but one-phase by thermal analysis. The paper points out that compatibility can be present over a range of complexities and that the two experimental methods appear to distinguish between two ranges of molecular motion. Similar observations arise (111) from a comparison of dynamic and thermal analysis measurements on an interpenetrating polymer network system. Miscellaneous Methods. The desirability of monitoring the output from GPC instruments with some instrument to measure a quantity related to molecular weight has led to the development (139) of a viscometer which automatically fills, times flow rate by an optical system, and empties the sample. With a similar purpose in mind, another automatic viscometer has been described (83). A versatile instrument (84) which shows promise of yielding high precision (0.0170) intrinsic viscosity values with a minimum of actual operator time consists of a photoelectric detection system on a capillary vis-

cosimeter plus a system for automatically diluting the polymer solutions. An experimental method has been described (40) for determining the density of polymeric melts. It has been found (214) possible to predict amorphous polymer densities by the additivities of quantities related to the structural components. POLYMER CHARACTERIZATION BY CHEMICAL AND SPECTROMETRIC METHODS

General Information. The study of the nuclear magnetic resonance of elastomers in solution for determination of their microstructure was reviewed (41). The importance of having the correct absorptivities when determining microstructure was pointed out. Initial estimates were made on a series of samples, each of which was predominantly one configuration. Then, by iteration, a self-consistent set of constants was calculated. If a good set of absorptivities is established, the total unsaturation found agrees with that found by a chemical method. The method was applied to both polyisoprenes and polybutadienes (28). IR. The absorptivities of cis-1,4-, trans-1,4-, and 3,4-structures in polyisoprene were studied a t 1377 and 1383 cm-I as a function of spectral width. The infrared and N M R results for samples containing all three structures agree well for 3,4- but not for 1,4- structures ( 9 ) . Raman spectra of the three structures in polyisoprene revealed characteristic bands for only total 1,4- content and total vinyl content (68). NMR spectra taken a t 100 MHz can differentiate the methyl protons in the 3,4- structure from those in trans-1,4-. The assignments of the a-tertiary proton and the @-methyleneprotons in 3,4groups were confirmed (8). Pyrolysis a t 600°C followed by gas chromatography gave an unidentified hydrocarbon and a dipentene whose ratios are proportional to the ratio of 1,4- to 3,4- structures (813). Mass spectrometry, infrared, and N M R indicate that the dipentene is either 1,4dimethyl-4-vinylcyclohexene or 2,4dimethyl-4-vinylcyclohexene (76). BR. Microstructure was measured by the infrared band a t 967 cm-1 for trans-1,4-, 910 cm-I for 1,2-, and the integrated absorbance from 635 to 835 cm-I for cis-1,4-. There is no single, general-purpose best combination of bands. It depends on the objective and upon what is available for calibration (IO). Overlapping bands were resolved with the use of a computer (81). Heating of an acetone-extracted vulcanizate for 10 minutes a t 2OOOC degrades it enough so that a carbon disulfide solution can be made. The

solution does not contain polymers from polymer blends in the same proportions in which they are present in the vulcanizate, but the solution is useful for determination of cis-1,4-, trans-1,4-, and 1,2-structures in the butadiene fraction of the sample (36). Agreement of Raman analysis with infrared is good for high cis-1,4-, high trans-1,4-, liquid-, Li-, and Na-Br, but not for emulsion BR (61). Polyurethanes. Residual isocyanate groups in rigid foams were determined by infrared. One method uses a KBr disk of the powdered foam. The ratio of absorbances a t 2270 and 2950 cm-l is used. The average relative error is 10% and the sensitivity is 0.05% (229). The other method uses CCL to fill the voids in a section of foam 1 t o 3 mm thick. The sample is then squeezed down to a thickness of 0.5 mm. The ratio of the absorbances a t 2270 and 2870 cm-l is accurate to 6.lYO relative (110). Pyrolysis a t 850°C followed by gas chromatography was used to determine toluene diisocyanate or PAPI (polyarylpolyisocyanate). The ratio of area % (aniline plus phenyl isocyanate) to (aniline plus phenyl isocyanate plus benzonitrile) can determine PAPI accurate to 5% in the range 0 to 50% (197). Other Rubbers. Block styrene sequences as small as two or three monomer units can be determined in SBR by using an analog computer to resolve overlapped NMR peaks of aromatic protons (147). The average length of methylenic sequences in E P M was related to the center of gravity of a doublet a t 5780 to 5800 cm-'. The band a t 5780cm-1 was assigned to polyethylene and the band a t 5800 cm-I to polypropylene (204). The chlorine atom of the 1,2- structure in CR is on a tertiary carbon atom. It is more labile and more readily removed in thermal dehydrochlorination than the chlorine in the 1,4- structure. The amount of 1,2- structure can be found from the rate of HCI removal a t constant temperature (103). DETERMINATION OF POLYMERS IN POLYMER MIXTURES AND CONSTITUENTS IN COPOLYMERS

NR-SBR-BR. This commercially important polymer mixture was the subject of several papers. However, successful analysis still requires prior knowledge of the styrene content of the SBR. Pyrolysis a t 54OOC followed by gas chromatographic measurement of dipentene, styrene, and 4-vinyl cyclohexene gives results accurate to 1.5Y0 for N R and 2.570 for SBR and B R (164). When the pyrolysis was done a t 56OoC, and the monomers isoprene, styrene, and

ANALYTICAL CHEMISTRY, VOL. 43,

NO. 5,

APRIL 1971

339 R

butadiene were measured, the accuracy was 5% (206). N M R was applied to solutions in hexachloro-1,3-butadiene and good results were obtained (55). Pyrolysis by temperature programming a t 4OoC per minute from ambient temperature to 5OOOC a t 1 mm pressure gives a liquid product which dissolves in CS2. The infrared spectrum of this solution gives results which are good to 3% absolute (99). SBR-BR. This binary mixture can be analyzed without prior knowledge of the styrene content of the SBR if the BR is of high ~ i s - 1 ~ 4content, Le., 93% or higher (46). The vulcanizate is degraded sufficiently by heating with 2,2'-dibenzamidodiphenyldisulfide in 1,2-dichlorobenzene so that a solution can be made and a film cast. The infrared spectrum is run and the SBR is characterized by the amount of bound styrene, trans-1,4-butadiene1 and 1,2butadiene. The cis-1,4-butadiene is all assigned to BR. If the BR is 50yo ~ i s - 1 ~ 4and 50% trans-l,4- and this fact is not known, the characterization fails. Further work is being done to extend this method to include NR. BR-IR. Infrared analysis using absorptivities found on pure homopolymers gives results accurate to 2yo relative (22). SBR. If a sample of uncured polymer is dissolved or suspended in hexane, any polystyrene present can be extracted into dimethyl formamide. After evaporating the hexane solution to a film, the SBR can be selectively dissolved in dioxane, leaving BR behind. Measurements are made by weighing the residues after vacuum drying. Results are accurate to 5% absolute (98). The p-nitrobenzoic acid formed by nitration of the bound styrene in SBR can be determined by polarography (a20). This is a variation of Hilton's method (92). EPDM. Propylene content can be found from the absorbance ratio of the 720 and 1160 cm-' bands of pressed films if propylene content is greater than 15%. If less than 15%, the 1355 and 1380 cm-l bands are recommended. Calibration was done on weighed mixtures of homopolymers. Accuracy is 6% absolute (196). Ethylidene norbornene was determined by measuring the absorbance a t 1700 cm-1. Comparison with NMR results and addition of dichlorocarbene followed by chlorine analysis showed good agreement (180). Dicyclopentadiene was determined by the absorbance ratio of the 695 and 1160 cm-l bands. Calibration was by bromination (196). Dicyclopentadiene, 1,4-hexadiene1 and ethylidene norbornene can be determined by NMR if time averaging is 340 R

used to enhance the signals. The precision is 10 to 15% relative (2) EPM. T h e absorbance ratio of the bands a t 4006 and 4250 cm-l is recommended for measurement of propylene content. These bands are preferred to those a t 4330 and 4390 cm-1 due to the sensitivity of the position of the 4330 cm-l band to composition. Calibration must be done on copolymers, as data from blends of homopolymers were not satisfactory. Results were accurate to 0.4% (198). NBR. Pyrolysis of 0.2- to 0.5-mg samples a t 550 "C, followed by gas chromatography gave copolymer composition with average deviation of O.4y0 on uncured samples. On vulcanizates average deviation was 2% (166). The nitrogen content of an extracted sample still seems to be the most straightforward way to determine the composition of the copolymer. ABR. The ratio of the infrared absorbances a t 910 and 1705 cm-1 correlates with the acrylic acid content found by titration in pyridine solution (183). The band a t 1705 cm-l is due to the carboxylic acid group in acrylic acid. Polyurethanes. The validity of the method of determining polyurethane fibers in mixtures by dissolution in cyclohexanone (156) was confirmed (SO). It was recommended that the boiling time be increased from 15 to 60 min. DETERMINATION O F RUBBER

After extraction with methyl ethyl ketone to remove extender oil, an I I R sample was heated to constant weight in nitrogen at 500 to 550°C in a thermal gravimetric analyzer. The weight loss was calculated as the rubber content (133). The same approach was successful when the pyrolysis was done in a muffle furnace (99). The rubber binder in an explosive was AU made from adipic acid which forms cyclopentanone upon pyrolysis. Gas chromatographic measurement has a standard deviation of 0.1% at the 10% level (228). Washing the coagulated rubber in running water was found to be as effective as washing on a mill in determination of the dry rubber content of Hevea brasilensis (107). SULFUR A N D SULFIDES

For determination of total sulfur, the sample was burned in an oxygen flask containing carbon black to prevent formation of SOa. The SO2 which is formed is measured by the pararosaniline method (150). The sulfate formed by burning the sample in a Wurzschmitt bomb can be measured in either of two ways (149).

ANALYTICAL CHEMISTRY, VOL. 43, NO. 5 , APRIL 1971

Reduction to HzS, which is converted to methylene blue and measured photometrically, gives results good to 0.03% in the range 1 to 2%. Titration with Pb(NO& to an amperometric end point gives results good to 0.03% in the range 1 to 3%. Free elemental sulfur was removed by acetone extraction and separated on a thin layer chromatogram. Spraying with a solution of NaNa and iodine forms a spot whose area can be measured with a standard deviation of 2% relative. Common curing agents and age resisters do not interfere (61). The study of polysulfide crosslinks by LiA1H4analysis has been reviewed (193). An excess of methyl iodide will condense with a mercaptan to form a methyl sulfide and H I which can be titrated with NaOH to a phenolphthalein end point in ethanol, thus determining the mercaptan (85). C U R I N G AGENTS

Identification, There were several papers on thin layer chromatography for separation of curing agents extracted from rubber. Both the Rr values and the colors developed by sprays are helpful in the identification (116, 152). Benzothiazyldisulfide and sulfenamides derived from 2-mercaptobenzothiazole decompose to 2-mercaptobenzothiazole on curing so that they cannot be distinguished in vulcanizates (58). I n the case of sulfenamides, detection of the amine can help to make the proper identification. Two-dimensional chromatography is a more powerful separating tool (159). Thiuram disulfides and dithiocarbamates were detected by spraying thin layer chromatograms with 3Yo CuS04 solution (190). Thirty-nine color-forming reagents were applied to acetone extracts containing curing agents. For more positive identification the use of spectroscopy and chromatography is recommended ($0). Determination. Uncured masterbatches were dissolved in CHClI. After centrifuging to remove ZnO, hexamethylene tetramine was titrated with acid to the dimethylaminoazobenzene end point with an error of less than 1% a t the 20Yo level (148). A G E RESISTERS

Identification. Some of the thin layer chromatography methods applied to curing agents also include age resisters within their scope (58,116,159). More positive identification of N-phenyl-2naphthylamine and AT-phenyl-N'-2-propyl-p-phenylenediamine is made by supplementing thin layer chromatography with their characteristic ultraviolet spectra (216). As in the case of curing agents, color

tests can be confirmed by chromatography and spectroscopy (20). Mass spectra of volatile age resisters were obtained by placing the rubber sample on a direct probe. Tris-(nonylphenyl)phosphite, N-phenyl-2-naphthylamine, and 6-dodecyl-2,2,4-trimethyl-l,2-dihydroquinoline were successfully identified a t the 0.5y0 level in the absence of oil and a t the 1% level in the presence of naphthenic oil. The method requires no prior sample treatment and can be carried out in 20 minutes (91). The usefulness of ultraviolet spectra of phenols can be extended by recording them in neutral and alkaline ethanol and in the same two solvents after treating with nickel peroxide. I n this way, 2,6-di-tert-butyl-4-hydroxy phenol, bis-(3,5-di- tert - butyl-4-hydroxy phenyl) methane, and lJ3,5-trimethyl-2,4,6tris- (3,5-di-tert - butyl-4 - hydroxybenzyl)benzene, whose spectra in neutral ethanol are identical, can be distinguished (17 8 ) . Determination. ASThf has adopted a method for N,N’-diary1 or N alkyl-N’-aryl-p-phenylenediamines in raw polymers. The age resister is oxidized by benzoyl peroxide to the quinone diimine which is measured spectrophotometrically. Provision is made for correcting for interference by extender oil (4). The benzoyl peroxide method as applied to h--phenyl-N’-2propyl-p-phenylenediamine was compared to ultraviolet measurement without prior treatment, to spectrophotometric measurement of the semi-quinone formed by treatment with K;\lnOq, to gas chromatography, to measurement of the spot on a paper chromatogram, and to potentiometric titration with HClOl in acetonitrile (105). N-phenyl-2-naphthylamine and 2,Z-dimethyl-6-(3-methyl-2- butenyl) - 1,2,3,4tetrahydroquinoline were determined by two-component ultraviolet spectrophotometry. The mean relative error was 5y0 (205). ASTRS has adopted hydrous 2-propanol-toluene azeotrope as an alternative extractant for SBR. The recovery of N-phenyl-2-naphthylamine is good, of heptylated diphenylamine is slightly low, and of the reaction product of acetone and diphenylamine is quite low (166).

Amine and hydroquinone types were determined by measuring spots on thin layer chromatograms. A linear calibration curve in the range 0 to 50 pg resulted from plotting the square root of the spot area against the log of the amount present (59). Alkylated phenols (63) and pentachlorophenol (60) xere determined by thin layer chromatography with precision of 10% a t the 0.1 to 0.270 level. Gas chromatography was used to determine 2,6-di-tert-butyl-p-cresolJ N-

phenyl-2-naphthylamine, N-(Cmethyl2-pentyl)-N’ -phenyl - p - phenylene - diamine, and butylated 2,2-bis(4-hydroxypheny1)propane with a relative error within 5%. Extender oil does not interfere (76). N - Cyclohexyl- N ’ - phenyl- p - phenylenediamine can be determined polarographically with precision of 4 to 10%. 6-Ethoxy-l,2-dihydro- 2,2,4 - tri - methylquinoline does not interfere (121). RESIDUAL MONOMER

A technique was described in which the volatiles liberated during thermal gravimetric analysis are run through a gas chromatograph. If the temperature is kept below the pyrolysis temperature of the polymer, residual monomer can be identified and also determined (43). Volatiles can also be trapped by sweeping onto a gas chromatography packing, which is then flash heated to release them into a gas chromatograph for identification and measurement (177). A section of Stevens’ book on gas chromatographic analysis of polymers is devoted to residual monomers (191). Free acrylonitrile in NBR latex was determined by adding NaZS03 to the double bond. In the presence of water, KaHS08 is effectively added. A byproduct of the addition reaction is NaOH, which is titrated with HC1. Results were accurate to 2% relative a t the 15% level and to 15% relative a t the 0.1% level (199). The parameter measured was changed to temperature rise when the sample and reagent were mixed in a continuous flow cell. Results were accurate to 10% relative in the range 3 to 15% and to 0.2% absolute a t levels less than 1% (200). Free styrene in SBR latex was determined by steam distilling and collecting in a modified Dean and Stark trap where the volume of the water-immiscible layer can be measured. The determination is complete in 10 minutes and recovers 100yG of the styrene in the range 2 to 14% (109). CARBON BLACK

Carbon black was extracted from rubber by ultrasonic vibrations. The sample was placed between charged metal electrodes upon which the carbon black was deposited (119). A method for identifying carbon black consists of determining how much nitrobenzene is adsorbed on its surface. A measured excess of nitrobenzene is added, then the unadsorbed portion is measured polarographically (149). Thermal gravimetric analysis in an air atmosphere can be used to determine carbon black after extractables have been removed and the polymer has

been distilled off in a nitrogen atmosphere (133). The same thing can be done without thermal gravimetric analysis equipment by heating a boat or crucible successively in different atmospheres (99). METALS

EDTA titrations were used to analyze the ash of a rubber compound. The KHSO4 fusion cake was taken up in acid, then treated with ”,OH to precipitate Ti, Fe, and Al. After filtration, the precipitate was taken up in acid. One aliquot was treated with H202 and titrated for the sum of Ti and Fe. Another aliquot was titrated for Fe alone in strongly acid solution. Ti was found by difference. The p H of the aliquot which had been used to determine Fe was increased to 4 and 8 1 was titrated. Accuracy is 0.008% absolute in the range 0.05 to 0.270. Ca, hIg, and Zn could be determined in the filtrate from the precipitation (26). Carbon-bound Li is determined in polymer cements by a modification of the Gilman method. The total of RLi and ROLi is determined by treating with a measured excess of benzoic acid and backtitrating the excess with alcoholic KOH. RLi is then reacted with allyl bromide after which the residual ROLi is determined as before. The difference between the two titrations is RLi. Recoveries are -5 to +2% in the range 0.5 to 1.5 millimoles of RLi per hundred grams of polymer (211). ZnO was determined in master batches by burning the sample in an oxygen flask and measuring polarographically. The error was less than 1% relative a t the 30% level (148). Polarography was also used to measure traces of metals. The sample was ashed in the presence of KzS04 and the ash was taken up in HCl. One aliquot was used to determine Cu. Another portion was made alkaline and used to determine Mn and Fe. Results agree with those obtained by spectrophotometry (44). &In was determined by neutron activation. Results, however, tended to be too high, and the KI0~-colorimetric method was recommended for international standardization (146). Cu and Ni were determined in the concentration range 1 t o 10 ppm and Zn in the range 10 to 100 ppm, also by activation analysis (11). A method for silicon in the range 1 to 10 ppm was described. Measurement is by atomic absorption spectrophotometry of the sample in an organic solvent. This approach avoids ashing the sample (161). Na, K, and Li were determined by flame photometry. Use of CsCl as a buffer made it possible to determine the three elements in the same solution.


341 R

Al, Ti, Mn, Cu, Fe, and Zn do not interfere even at 50-fold excesses (112). Ca was also determined with a relative error of less than 0.1% (113). The successful determination of A1 requires adjustment of the Ca concentration to a standard level and prior determination of Ti. With this information, A1 can be determined with relative error of less than 1.4% (113). X-ray fluorescence was also used to determine metals. Limits of detection are given for Cu, Mn, Ti, Sb, P, and Na. The preparation of standards in the proper matrix is a major problem. Wet chemical analysis is not accurate enough at trace levels to use for calibration (67). Emission spectrographic analysis was carried out by introducing the rubber sample directly into the arc. This saves the time needed for preparation of ash. Fe, Ca, Al, Cu, and T i were determined (194). Ash was measured as the residue remaining after determination of polymer content by heating in a n inert atmosphere and of carbon black by thermal gravimetric analysis (133). ORGANIC ACIDS

The 2-propanol-toluene azeotrope is preferred over the ethanol-toluene azeotrope for extraction of fatty acids from alum-coagulated SBR and fatty and rosin acids from SBR containing carbon black. Thymol blue is then used as the indicator for the titration (162). The method has been adopted as a n alternative by ASTM (4). The sodium salts of alkylbenzene sulfonic acids were determined by forming a complex with methylene blue. Average error is 5% in the range 0.1 t o 0.7% (14). Carboxylic acid not bound to a polymer was determined by titrating the latex with alkali to p H 6.0 t o 6.5. Polymer-bound carboxyl groups were determined by continuing the titration to pH 9.5 (71). WATER

Karl Fischer titration was used to measure water in ethanol-toluene azeotrope extracts. The relative error is 5% a t the level of 0.5% (64). Water was also determined by heating the sample in an isolated loop of tubing, then sweeping it into a gas chromatograph with a thermal conductivity detector. Accuracy is 5% relative in the range 0.02 to 0.5% (100). EXTRACTS

An interlaboratory test on extraction by water and by hexane was reported. The results were reported as mg per sq in. of surface area (114). Actually, in the 7-hour extraction time used, one should get essentially complete extrac342R

tion and not just the material on the surface; therefore, sample thickness should be taken into account or else the report should be in wt yo. A report on extractables determined by methods in the Food Law of Germany was published. There is information on age resisters, curing agents, and metals in N R and synthetic rubbers (93)’ OILS

Castor oil was saponified, then the ricinoleate salt formed was converted to the trimethyl silyl derivative which was determined by gas chromatography. Results tend to be high at the 0.1% level and slightly low a t the 1% level (126). Vegetable oils were saponified and converted to the methyl esters before determination by gas chromatography (17 5 ) . OTHER DETERMINATIONS

The unsaturation of N R and cyclized natural rubber was determined with m-chloroperbenzoic acid. The reagent is more stable than perbenzoic acid. Results of 97 to 103% of theory were obtained on NR with reproducibility of 2% relative (82). Traces of chlorine were determined in fluoroelastomers by decomposing the sample in a platinum-lined oxygen bomb, then titrating with Hg(KO& (126). Azobis(i-butyronitrile) was determined polarographically during polymerization of chloroprene. tert-Dodecylmercaptan does not interfere and relative error is 6% or less (12). Sodium diethyldithiocarbamate was determined polarographically in SBR latex. After removal of the rubber by coagulation, CoC12, NHaOH, and KH4C1 were added so that a catalytic hydrogen wave would appear. Cumene hydroperoxide and disodium-1 ,l’-methylenebis (6-naphthalene sulfonate) interfere (164). Polarography was also used to determine 4,4’-dihydroxydiphenyl sulfide. The sample is nitrosated t o form a product which will produce a suitable wave (163). Residual ethylene oxide in rubber sterilized with it can be determined by gas chromatography. Ethylene chlorohydrin is also detected; apparently it is formed by the reaction of ethylene oxide with chlorides in the rubber. The detection limit of either is 25 mg (29). Hydroperoxides were determined by adding a ferrous salt in methanol to a benzene solution of the polymer. The decrease in ferrous concentration is measured colorimetrically with 1 , l O phenanthroline. Relative standard deviation is 3.5y0in the range lo-’ to 10-6 mole (26).


Normal gel in solutions of NR, IR, SBR, NBR, BR, and acrylonitrilebutadiene-styrene terpolymer was determined by centrifugation a t 2500 rpm for 1 hr. Total gel was determined by centrifugation and ultrafiltration, then microgel was determined by difference (174). Microscopy can help define contamination problems. Frequently infrared, emission spectroscopy, X-ray diffraction, and X-ray fluorescence can also help (77). LITERATURE CITED (1) Alliger, G., Weissert, F. C., Ind. Eng.

Chem., 60, (S), 51 (1968). (2) Altenau, A. G., Headley, L. &I.,Jones, C. O., Ransaw, H. C., ANAL.CHEM.,42, 1280 (1970). (3) American Chemical Society, Sympc-

sium on Gel Permeation Chromatography, Division of Petroleum Chemistry, Preprints, Houston, Texas, (t970. (4) Amer. Soc. Testing Mater., 197: Book of ASTM Standards, Part 28, Philadelphia, 1970, p 595. ( 5 ) Zbid., p 607. (6) Anderson, D. H., Guran, G. T., O’Brien, R. J., Znd. Res., March, p 30, 1970.

(7) Anderson, J. N., Weissert, F. C., Hunter, C. J., Rubber Chem. Technol.,

42.918 11969). - -, (8) Assioma, F., Rlarchal, J., C. R. Acad. sci., Paris, Ser. C , 266 (3), 195 (1968). (9) Zbid., 266 (6), 369 (1968). (10) Avstriiskava, E. E., Xel’son, K. V. Sou. Rubber Pechnol. (English transl.), 27 (9), 9 (1968). ( 1 1 ) Azuma. T.. Sato. Y.. Tsurei. J. ‘ Imaura, K.,Annu. Rip. Radiat. &nter Osaka Prefect., 7,21 (1966). (12) Bagdasaryan, R. V., Khizarchyan, A. A., hlelkonyan, L. G., Arm. Khim. Zh., 21, 990 (1968). (13) Baker, R. W., J. Appl. Polym. Sci., 13.369 (1969). (14) ’Balandinaj V. A,, Afalkina, N. I., Sou. Plastics (English transl.), 1968, (I), 61. (15) Balke, S. T., Hamielic, A. E., J. Appl. Polym. Sci., 13, 1381 (1969). (16) Baranwal, K., Jacobs, H. L., ibid., p 799. (17) Barlow, A,, Wild, L., Roberts, T., Reference 17.9, page 487. (18) Barrall, E. AI., Johnson, J. F., Reference 3, page A17. (l?) Barrall, E. AI., Johnson, J. F., \

Thermal Characterization Techniques,” P. E. Slade and L. T. Jenkins, Editors, hlarcel Dekker, New York,

1970. (20) Bhatnagar, S. K., Rubber ATews,8 (5), 28 (1969). (21) Biesenberger, J. A., Ovano, A., J. A p p l . Polym. Sci., 14, 471 (1970). (22) Binder, J. L., A p p l . Spectry., 23, 1 ( 1969). (23) Blair, D. E. (to Du Pont Co.), U.S. Patent 3,392,158 (July 9, 1968). (24) Blair, D. E., Polym. Prepr., Amer. Chem. SOC.,Diu. Polym. Chem., 11, 967 1197ni. (25) Bocek, P., Chem. Prum., 17, 439 (1967). (26) Bogina, L. L., Martyukhina, P. O., Proizvod. Shin., Rezino Tech. AsbestoTekh. Iseldii, 1966 (4), 30. (27) Bombaugh, K. J., Levangie, R. F., ANAL. CHEM.,41, .1357 (1969). (28) Braun, D., Mal, E., Kunststofe-Ger. Plast. (English transl.) 58 (9), 14 (1968). (29) Brown, D. J., J. Ass. O#c. Anal. Chem., 53,263 (1970). \--

- z -

(30) Bukosek, V., Melliand Textilber., 50, 435 11969).

Z.E., Paper presented a t ACS ‘Rubber Division Meeting, Los Angeles, April 1969. (33) Campbell, D. R., Warner, W. C., Rubber Chem., Technol., 42, 1 (1969). (34) Cantow, H. J., Probst, J., Stajanov, C., Kaut. Gummi Kunstst., 21, -609 (1968). (35) Carlson, D. W., Altenau, A. G., ANAL.CHEM..41. 969 11969). (36) Carlson, b. -W., -Ransaw, H. C., Altenau, A. G., ibid., 42, 1278 (1970). (37) Chandler, L. A., Collins, E. A., J . Appl. Polym. Sci., 13, 1585’(1969).’ (38)m wChang, F. S.C., Reference 173, page ’

1

1 1I

(39) Chang, K. S., Huang, R. Y . RI., J . Appl. Polym. Scz., 13, 1459 (1969). (40) Chee, K. K., Rudin, A., Znd. Eng. Chem., Fundam., 9, 177 (1970). (41) Chen, H. Y., Rubber Chem. Technol., 41,47 (1968). (42) Cheng, F. S., Kardos, J. L., Polym. Prepr., Amer. Chem. Soc., Dzv. Polym. Chem., 10, 615 (196!3), (43) Chiu, J., ANAL. CHLV., 40, 1516 (1968). (44) Cianetti, E., Di Cerbo. ll., illatcr. Plast. Elastomerz, 35, 60 (1969). (45) Clark, G. J., Granquist, R. Rubber Age ( S . Y . ) ,100 (l),77 (1968). (46) Clark, J. K., Scott, R. A., J . Appl. Polym. Scz. 14, 1 (1970). (47) Clegg, G. A , , Gee, D. R., RIelia, T. P., Makromol. Chem., 120, 210 (1968). (48) Coll, H., Johnson, H. W., Polgar, A. G., Seibert, E. E., Stross, K. H., J . Gas. Chronzatogr., 7, 30 (1969). (49) Cooper, A. R., Bruzzone, A. R., Johnson, J. F., J . Appl. Polym. Scz., 13, 2029 (1969). (50) Cooper, .4.R., Cain, J. H., Barrall, E. ll.,Johnson, J. F., Reference 3, page A9.i. (51) Cornell, S. W., Koenig, J. L., Macromolecules, 2, 540 (1969). (52) Zbid., p 346. (53) Cummins, R. A., Aust., Commonwealth, Dep. Supply, Def. Stand. Lab.

Rep. No. 302 (1968). (54) Dall’Asta, G., Scaglione, P., Rubber Chem. Teehnol., 42, 1235 (1969). (55) Daniels, C. A., Maron, S. H., J . Alacromol. Scz.-Phys., B4, 227 (1970). (56) Daniels, T., Lehrle, R. S.,J . Polynz. Scz., Pt. C, 16, 4,533 11969). (57) Davidson, E., Jones, R. E., M o d . Plast , 45 (14), 157 (1968). (58) Davies, J . R., Kam, F. W., J . Znst. Rubber Znd., 2, 86 (1968). (59) Zbid., p 89. (60) Davies, J. R., Thuraisingham, S. T., J . Chromatogr., 35, 43 (1968). (61) Zbtd., p 513. (62) Determann, H., “Gel Chromatography,” Springer-Verlag, Xew York, lQ6Q -__I.

(63) Dobies, R. S., J . Chronzatogr., 40, 110 (1969). (64) Dobroborskaya, T. I., Rloskaleva, D. A,, Sou. Rubber Technol. (English transl.) 27 ( l ) ,40 (1968). (65) Dohner, R. E., Wachter, A. H., Simon, W., Helv. Chim. Acta., 50, 2193 (1967). (66) Dole, RI., Rlach, L. L., Ilines, R. L., Rlobley, R. C., Ferguson, L. D., Alice, RZ. B., J . Chem. Phys., 49, 2240 (1968). (67) Drott, E. E., Rlendelson, R. A., J . Polym. Sci., Pt A%,8 , 1361 (1970). (68) Zbid., p 1373. (69) Dnerksen, J. H., Reference 3, page A47.

(70) Du Pont de Nemoum and Co. (Inc.), Instruments Division. Wilmington. Del. (71) Ezrielev, A. I., ‘ Peizner; A: -B., Utkina, L. V., U.S.S.R. Patent 226,228 (Sept. 5, 1968). (72) Fischer, UT.G., Glas-Znstrum-Tech., 11, 562, 567, 775, 1086, 1091 (1967). (73) Foxton, A. A., Hillman, W. E. Meam, P. R., J . Inst. Rubber Ind., 3, 179 (1969). (74) Fujimoto, K., Yoshimura, N., Rubber Chem. Technol., 41, 1109 (1968). (75) Gaeta, L. J., Schlueter, E. W., Altenau. A. G.. Rubber Aae 1S.Y.1. 101 (3). 47 119691. ’ (76) ‘Galin-Vacherot, AI., Eustache, H., Eur. Polym. J., 5, 211 (1969). (77) Garrett, H. L., Travlor, P. -4.. Mircoscope, 16, 295 (1968)- ’ (78). Geiszler, W. A., Koutsky, J. A,, Dibenedetto, A. J., J . Appl. Polym. Sci., 14, 89 (1970). (79) Gergen, W. P., Keelen, T. L., Proceedings 11th Annual Meeting, Int. Inst. of Synthetic Rubber Producers (1970). (80) Gianotti, G., Capizzi, A., Eur. Polym. J.. 6. 743 119701. (8l)’Gibson, J. D:, Sears, W. C., Bull. Ga. Acad. Sci., 27, 159 (1969). (82) Gipstein, E, Nichik, F., Offenbach, J. A., Anal. Chim. Acta, 43, 129 (1968). (83) Goedhart, D., Opschoor, A, J . Polum. Sci.. Pt A-2. 8. 1227 11970). (84) Gramain, P., Libeyre, R:,J . Appl. Polym. Sci. 14, 383 (1970). (85) Gregg, Jr., E. C., Katrenick, S. E., Rubber Chem. Technol., 43, 349 (1970). (86) Griskev, R. G.. Foster. G. S.. J . Polym. S&., Pt A l , 8 , 1623’(1970). ’ (87) Guillet, J. E., Stein, A. N., Jlacromolecules. 3. 102 11970). (88) Haas, ’ F:, Nutzel, K.,Pampus, G., Theisen, D., Rubber Chem. Technol., 43, 1116 (1970). (89.)- Harmon, D. J., Reference 3, page Y

\

AlU.

(90) Harrell. L. L.. Macromolecules., 2., 607 (1969). ‘ (91) Hays, 11.W., Altenau, A. G., Rubber Age (N. Y . ) .102 (5), 39 (1970). (92) Hilton, C. L., Newell, J. E., Tolsma, J., A N ~ LCHEM., . 31, 915 (1959). (93) Hofmann, W., Ostromow, H., Kaut. Gummi, Kunstst., 21, 244, 318, 322, 368, 432, 481, 560, 620, 695, (1968), 22, 14 (1969). (94) Hudson, B. E., Reference 173, page 585.

(95) Ikeda, R. ll., Wallach, RI. L., Angelo, R. J., Polymer Preprints 10, 1446 (1969). (96) Inagaki, H., Matsuda, H., Kamiyama, F., Macromolecules, 1 , 520 (1968). (97) Infotronics, ?\Iountain View, California. (98) Irako, K., Anzai, S., Onishi, A., Bull. Chem. SOC.Jap., 41, 501 (1968). (99) Jasper, B. T., J . Inst. Rubber Znd., 3, 72 (1969). (100) Jeffs, A. R., Analyst, 94,249 (1969). (101) Jernejcic, AI., Premru, L., Rubber Chem. Technol., 41, 411 (1968). (102) Johnson, J. F., Bruzzone, -4.R., Barrall, E. M.,J . Colloid Interface Sci., 31,253 (1969). (103) Juhasz, K., Varga, J., Doszlop, S., Zubonyai, L., Plaste Kaut., 15, 636 (1968). (104) Juranicova, V., Florian, S., Berek, D., Eur. Polym. J . , 6, 57 (1970). 4 (10.5) Ka isinska, V., Kosljar, V., Kardos, E., OrEk, I., Plast. Hmoty Kauc., 6, 359 (1969). (106) Karasek, F. W., Res.lDeuelop., 20 ( 5 ) , 34 (1969). (107) Kartowardojo, S., J . Rubber Res. Znst. Malaya, 22, 389 (1969). (108) Kelley, R. N., Billmeyer, F. W., Reference 3, p A35.

(109) Kennedy, T. Taubinger, R. P., Analyst, 94, 625 (1969). (110) Kitukhina, G. S., Zharkov, V. V., Sou. Plastics (English transl.), 1968 (6), 61. (111) Klempner, D., Frisch, H. L., J . Polymer. Sci., Pt. B, 8 , 525 (1970). (112) Kolosova, I. F., Martyukhina, I. P.,

Proiz. Shin Rezino-Tekh. Asbesto-Tekh. Zzdelii No. 6, 37 (1966). (113) Zbid., KO. 7, 12 (1966). (114) Korte, D. E., J . Assoc. Oflc. Anal. Chem., 53, 43 (1970). (115) Kraus, G., Gruver, J. T., SOC. Chem. Industry (London)26, 30 (1967).

(116) Kreiner, J. G., Warner, W. C., J , Chromatogr., 44, 315 (1969). (117) Lavoie, A., Guillet, J. E., Macromolecules, 2, 443 (1969). (118) Lee, W. A., Knight, G. J., British Polym. J., 2, 73 (1970). (119) Leont’eb, V. A., Sou. Rubber Techno/. (English transl.), 26, (6), 51 (1967). (120) Levine, I. J., Haines, R. G., Rubber Chem. Tcqhnol., 43, 443 (1970). (121) Levitin, I. A, Kalacheva, A. V.,

Proiz. Shin, Rezino-Tekh., Asbesto-Tekh. Zzdelii S o . 1, 20 (1968). (122) Levy, P. F., Miller, G. W., Casey, D. L., Loehr, A. .4.,Pittsburgh Conference on Analytical Chemistry, Cleveland, Ohio, 1970. (123) Levy, R. L., Fanter, D. L., AXIL. CHEM.,41, 1465 (1969). (124) Levy, R. L., Wolf, C. J., Amer. Chem. SOC.,Diu. Anal. Chem., Sept., 1969. (123) Li Gotti, l.,Bonomi, G., Piacentini, R., Mater. Plast. Elastomerz, 34, 541 11968). (126) Lim, R., U.S. At. Energy Comm., UCID-15100 (1967). (127) Little, J. N., Pauplis, W. J., Separ. Sci., 4, 313 (1969). (128) Little, J. N,, Waters, J. L., Bombaugh, I(.J., Pauplis, W. J., J . Polym. Sct.. Pt A-2. 7. 177e5. 11969). 11291 ’Zbid.. Rifirence h . ~D ,4121. (130) Majemda, J., Chim. Anal. (Warsaw),12, 183 (1967). (131) Maron, S. H., Daniels, C. A., J . Maeromol. Sci.-Phys, B2, 463 (1968). 1132) lIarsh. P. 4..~Iullens.T. J.. Price. L. I],, Rvhbrr Chcm. Technol., 43, 406 11970). (133) llaurer, liaurer, JJ. J., Rubber Age (N. Y . ) . 102 ( 2 ) , 447 (1970). (134) Naur Naurer, J. J., Rubber Chem. Technol., 42, 110 (1969). (1 (133) Neckel, L., Burmeister, H. J., Xelliand Tezctzlber., Tezctilber., 49, 105 (1968). (136) Nelaerts, W., Ann Scz. Textiles Belg., 1969 12). ( 2 ) , 16 16. (137) JIendelson, JIend R. A,, Drott, E. E., J . Polym. Scz., Sci., Pt B , 6, 79. 795 (1968). (138) Mentley, A. A A,, , , 1LeRoy, W. W., Lubric. Eng., 23, 4‘ 492 (1967). (139) Meverhoff. G. G., Jfakromol. Chem.. 118. 26% (19681. (140) ‘Zbzd., I C P A C Pure Appl. Chena., 20,309 (1969). (141) LIichajlov, L., Harwood, H. J., Polym. Prepr., Amcr. Chem. SOC.,Diu. Polvm. Cherri., 11, 1198 (1970). (142) -bIiller, G. W., Saunders, .J. H., J . A p p l . Polym. Sei., 13, 1277 (1969). (143) Zbid., Pt A-1, 8 , 1921 (1970). (144) lIitchel1, Jr., J., Chiu, J., ANAL. CHEM., 41, 248R (1969). (14j) Zbid., 43, (1971). (146) Mlitz? P., Neider, R., Schmitt, B. F., Steiner, N., Kaut. Gummi Kunstst., 22, 233 (1969). 1147) Mochel. V. D.. Jlacronzolecules. , 2.. 337 (1969). (148) JIocker, F., Frech, A., Gummi Asbest. Kunstst., 21, 200 (1968). (149) Mocker, F., Schrafft, R., Schwinn, H., ibid., 22, 352 (1969).


343 R

(150) Morris, M. C., Reference 173, page 603. (151) Murphy, C. B., ANAL. CHEM.,42, 268R, (1970). (152) Nagasawa, K., Ohta, K., Rubber Chem. Technol., 42, 625 (1969). (153) Namiki, Y., Nishizawa, H., Morita, M., Nippon Gomu Kyokaishi, 42, 856 (1969). (154) Ney, E. A., Heath, A. B., J. Znst. Rubber Znd., 2, 276 (1968). (155) Okumoto. T.. Takeuchi. T.. Tsuee. - , ‘ S.,’Bunseki Kugaku, 18, 1483 (1969). (156) Otocka, E. P., Macromolecules, 3, 691 (1970). (157) Otocka, E. P., Hellman, M. Y., ibid., p 362. (158) Ovano, A., Biesenberger, J. A., J. Appl. Polym. Sci., 14, 483 (1970). (159)- Panagoulias, P. L., U.S. Patent 3,479,153 (Nov. 18, 1969). (160) Zbid.. U.S. Patent 3.484.202 (Dec. , , ‘ 16; i969j. (161) Paralusz, C. hl., Appl. Spectr., 22, 520 (1968). (162) Parks, E. J., Linnig, F. J., Nut. Bur. Std. (U.S.), Tech. Note No. 485 (1969). (163) Pasciak, J., Chem. Anal. (Warsaw), 12,787 (1967). (164) Zbid., 13, 263 (1968). (165) Pasternak, R. A., Burns, G. L., McNulty, J. A., Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Cleveland, 1970. (166) Pastuska, G., Gummi Asbest. Kunstst., 22, 718 (1969). (167) Perkin-Elmer Corporation, Instruments Division, Norwalk, Conn. (168) Zbid., “Thermal Analysis Newsletter,” Number 9, (1970). (169) Problematics, Inc., West Concord, Mass. (170) Proceedings Sixth International Seminar, Gel Permeation Chromatography, Preprints, Miami Beach, Fla., October 1968. (171) Proceedings Seventh International Seminar, Gel Permeation Chromatography, Preprints, Monaco, October 1969. (172) Proceedings Eighth International Seminar, Gel Permeation Chromatography, Abstracts, Prague, July 1970. (173) Proceedings Ninth International Seminar, Gel Permeation Chromatography, Miami Beach, Preprints, October 1970. (174) Purdon, J. R., Mate, R. D., J. Polym. Sci., Pt. A-1, 8 , 1306 (1970). (175) Reynolds, W. G., Frie, M. S., Chem. Ind. (London), 1969, p 1247. ’

344R

(176) Rho Scientific, Inc., Commack, New York. (177) Roper, Jr., J. N., ANAL.CHEM.,42, 688 (1970). (178) Ruddle, L. H., Wilson, J. R., Analyst, 94, 105 (1969). (179) Rudin, A,, J. Chem. Educ., 46, 595 (1969). (l8Oi Runyon, J. R., Barnes, D. E., Rudd, J. F., Tung, L. H., J. Appl. Polym. Sn’., 13,2359 (1969). (181) Saunders, K. J. “Identification of Plastics & Rubber.” ChaDman and Hall, London, 1966.’ (182) Scherago, E. J., Science, 162A, 45 (1Q88) \ - _ - _

(183) S&m, A. J., Anal. Chim. Acta, 42, 177 (1968). (184) Seward. R. J., Rubber Chem. Tech‘ noi., 43,1 (i970). ’ (185) Seward, R. J., Rubber J., 150 (6), 47 (1968). (186) Sewell, P. R., Skidmore, D. W., J. Polym. Sci., Pt. A-1, 6, 2425 (1968). (187) Seymour, R. B., Znd. Ena. Chem., 62 (9),-47 (1970). (188) Shultz. A. R.. Eur. Polum. J.., 6., 69’(1970).’ (189) Sliemers, F. A., Boni, K. A,, Nemzer, D. E., Nance, G. P., Reference 170, page 463. (190) Sluzewska, L., Rocz. Panstw. Zakl. Hig., 20, 177 (1969). (191) Stevens, hl. P., “Characterization and Analysis of Polymers by Gas Chromatography,” Dekker, New York, 1969. (192) Stoelting, J., Karasz, F. E., MacKnight, W. J., Polym. Prepr. Amer. Chem. SOC.,Diu. Polym. Chem., 10, 628 (1969). (193) Studebaker, 31. L., Rubber Chem. Technol., 43, 624 (1970). (194) Sukhnevich, V. S., Zh. Prikl. Spektrosk., 9, 772 (1968). (195) Szewczyk, H., Polimery, 14, 233 (1969). (196) Szewczyk, H., Zielasko, A,, ibid., 13,415 (1968). (197) Takeuchi, T., Tsuge, S., Okumoto, T., J. Gas Chromatogr., 6, 542 (1968). (198) Takeuchi, T., Tsuge, S., Sugimura, Y., ANAL.CHEM.,41, 184 (1969). (199) Taubinger, R. P., Analyst, 94, 628 (1969). (200) Zbid., p 634. (201) Teramachi, S., Nagasawa, M.,J. Macromol. Sci.-Chem. A2. 1169 (1968). , , (202) Thompson, W. C., Lab. Pract., 18, 1074 (1969). (203) Tokita; N., Scott, R., Rubber Chem. Technol., 42, 944 (1969). (204) Tosi, C., Makromol. Chem., 112,303 (1968).


(205) Travnikova, N. I., Sotchenkova, T. M., Probl. Lab., Khim. Vysolcomol. Soedin., vo’oronezh.Cos. Univ., No. 4, 231 (1966). (206) Tsuge, K., Ando, I., Okubo, N., Nippon Gomu Kyokaishi, 42,851 (1969). (207) Tung, L. H., J. Polym. Sci., Pt Ad, 7.47 - ~- (1969). (208) Ibid., Reference S, p A41. (209) Tung, L. H., Runyon, J. R., J. Appl. Polym. Sci., 13, 2397 (1969). 1210) Tunnicliffe. M. E.. MacKilloD. D. A.; Hank, R., ’Eur. Polym. J., i,‘259 i196.5). (211) Turner, R. R., Gaeta, L. J., Altenau A. G., Koch, R. W., Rubber Chem. Technol., 42, 1054 (1969). (212) Uraneck, C. A., Burleigh, J. E., J. Appl. Polym. Sci., 14, 267 (1970). (213) Vacherot, M., Marchal, J., Rubber Chem. Technol., 41, 418 (1968). (214) Van Krevelen, D. W., Hoftyzer, P. J., J. P p p l . Polym. Sci., 13, 871 (1969). (215) Vinogradov, G. V., Malkin, A. Y., Kulichikhin, V. G., J. Polym. Sci., Pt. A2, 8 , 333 (1970). (216) Vinoeradova. N. I. Gulimov. V. N.. ‘ Martyukuhina, I. ‘P., Proiz. Shin ’Rezinol Tekh. Asbesto-Tekh. Izdelii, Xo. 6, 30 (1966). (217) Wachter, A. H., Simon, W., ANAL. CHEM.,41, 90 (1969). (218) Wadelin, C. W., Trick, G. S.,ibid., p 299R. (219) Wake, W. C., “The Analysis of Rubber and Rubber-like Polymers,” 2nd Ed., Wiley-Intencience, New York, 1969. (220) Watanabe, T., Minekawa, H. Mem. Fac. Eng., Kobe Uniu., 1968, No. 14, 129. (221) Waters Associates, Framingham, I

\ - - - - I -

~

\ - -

~~I

Mass.

(222) Weiss, A. R., Cohn-Ginsberg, E., J. Polym. Sci., Pt B, 7,379 (1969). (223) Ibid., Pt. A I,8, 148 (1970). (224) Weissert, F. C., Ind. Ena. Chem., 61’(8), 53 (1969). ‘ (225) Willmott. F. W.. J. Gas Chromatogr., 7, 101 (1969); ’ (226) Wunderlich, B., Differential Thermal Analysis” To be published in A. Weissberger “Physical Methods of Analysis”, Interscience Publishers, New York, 1971. (227) Yamamoto, A., Noda, I., Nagasawa, X,Polymer J., 1, 304 (1970). (228) Yasuda, 8. K., J. Chromatogr., 37, 393 (1968). (229) Zhokhova, F. A., Zharkov, V. V., Sou. Plastics (English transl.), 1967, (8), 65. ’

~

CONTRIBUTION No. 463 from the Research Division, The Goodyear Tire & Rubber Co., Akron, Ohio 44316.

Rubber - American Chemical Society

Recommend Documents