Rubber Coe W. Wadelin and Gordon S. Trick, Research Division, The Goodyear Tire and Rubber Co., Akron, Ohio 44316
T
and chemical analysis of rubber are covered by this review. Methods are included for the identification and determination of rubber or materials in rubber. Analysis of rubber chemicals before they are added to rubber is not included. The literature on chemical analysis which became available to the authors betlveen September 1966, the end of the period covered by the last review in the series (212), and July 1968 is covered. The section on polymer characterization by physical methods includes material up to September 1968. Abbreviations recommended in ASTM Designation D1418-67 have been used (12). For convenient reference, they are listed in Table I.
POLYMER IDENTIFICATION
HE CHARACTERIZATION
GENERAL INFORMATION
The review article by Tyler is a valuable critical discussion of recent developments, bringing broad experience to bear (203). The importance of proper chemical preparation before the measuring step in instrumental methods is emphasized. The necessity for calib r a t i n g o n s t a n d a r d s a s closely analogous to the unknown samples as possible is also stressed. d review of methods for tire stocks contains a flow chart relating the various analyses (63). -4STM Designation D297-67T for Chemical .inalpis of Rubber Products has been modernized (8). It noiv includes an EDTX titration for Zn, a method for rapid determination of ash, a method for sulfated ash, a pyrolysis method for carbon black, and an allglass extraction apparatus. D1416-671' for Chemical Analysis of Synthetic Elastomers has been rearranged and a method for determination of carbon black by vacuum pyrolysis has been added (11). Methods which either rely on instrumental measurements or have not been accepted as ASTLI standards have been compiled (200). They cover polymer composition as well as nonrubber constituents. -1note of caution might be added here on Parr peroxide bomb decomposition of rubber, which is recommended for determination of sulfur. An intimate mixture of sample with sodium peroxide is required for complete combustion. It is sometimes difficult to subdivide rubber or other polymers to a small enough particle size for this. The bromine-nitric acid method (9) has been more reliable in our experience.
Pyrolysis- Gas Chromatography. As more experience has been gained with this method, i t has become apparent t h a t the pyrolysis step is the most critical part of the procedure. A variety of chromatographic conditions can adequately resolve the pyrolysis products. The requirement for achieving a reproducible pyrolysis seems to be rapid decomposition with prompt removal of the products from the hot zone to prevent secondary fragmentation. If any generalizations can be made from the variety of approaches reported, they are t h a t a small sample should be pyrolyzed a t a high temperature in a flowing stream of carrier gas. The controlling factor on pyrolysis rate is not the equilibrium temperature of the heating device, but rather the rate of heat transfer to the sample (83). Deposition of a thin film of sample on a ferromagnetic metal which can then be heated rapidly in an induction field was chosen as preferable to use of a heated filament, a tube furnace, or an electrical discharge (164). Temperature control is good as the energy from the induction coil heats the metal rapidly to its Curie point and this temperature is then maintained. X pyrolysis furnace was superior to pyrolysis on a heated filament and gave peak heights reproducible to k2.0% (69). Recommended sample sizes range from 50 ng ( I S ) to 1 pg (112) to 50 pg (205) to ((1 mg (83). Small sample sizes require a flame ionization detector to get adequate sensitivity. Thermal conductivity is out of the question in this range. One of the benefits of small samples is that simple chromatograms result which are easy to interpret (112). Another advantage is that the superior
Table 1. Abbreviations Recommended b y ASTM ( 7 2 )
BR CR IIR IR NBR NR SBR
Butadiene rubbers Chloroprene rubbers Isobutylene-isoprene rubbers Isoprene rubbers, synthetic Nitrile-butadiene rubbers Isoprene rubber, natural Styrene-butadiene rubbers
CShI Chloro-sulfonyl-polyethylene EPM Ethylene-propylene copolymer EPDhl Terpolymer of ethylene, propylene, and a diene with the residual unsaturated portion of the diene in the side chain Ill Polyisobutylene
resolving power of capillary columns can be realized without an inlet splitter (18). Small sample sizes have not been universally adopted, however. I n one case, 0.3 g is recommended with ability to distinguish NR, SBR, CR, NBR, E P D M , and CShl (204). IIR and halogenated IIR can be distinguished from the rest of the group but not from each other. Pyrolysis of polyisoprene was complete to monomer and dimers in 6 see a t 500 "C (205). Above 700 "C, secondary fragmentation was observed. Hydrogenation of the pyrolysis products leads to simple compounds t h a t can be related to specific polymers (216). For instance, NR gives 2-methyl butane from hydrogenation of 2-methyl-l,3butadiene and CR gives butane from exhaustive hydrogenation of 2-chloro1,3-butadiene. Polyester urethane containing adipic acid gives cyclopentane via decarboxylation to cyclopentanone and then hydrogenation. More positive identifications can be made by comparing chromatograms made without hydrogenation and those made with hydrogenation. A review of the field was published (3). Infrared. h British Standard method for identifying polyisoprene, SBR, BR, KBR, CR, I I R , EPM, and CSM has been published (81). After extraction t o remove extender oils, plasticizers, and other compounding ingredients, the sample is pyrolyzed and the spectrum of the pyrolyzate is recorded. Identification is made empirically by comparing the spectrum with those from known compounds. Mixtures, acrylates, and urethanes are beyond the scope of the method as published. The type of polymer in latex paint can be identified without pyrolysis (17 2 ) . For SBR, the pigment is precipitated by diluting the latex, then a film is cast on a silver chloride disk or on photographic paper. For polyacrylonitrile, vinyl chloride-acrylonitrile copolymer, or polyvinyl acetate, the latex is diluted with hot acetone to separate the pigment. A film is then cast from the acetone solution. There was no indication of how to tell which procedure should be applied to an unknown sample. The presence of a polyurethane can be detected (114). 11 film of the sample is cast on a NaCl plate and the 2270 cm-1 region is scanned to make sure it is free of interfering bands. Then a red hot stainless steel spatula is rubbed across the film. If the sample is a polyVOL. 41, NO. 5, APRIL 1969
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urethane, a n isocyanate forms and a band appears at 2270 ern-'. Polyurethanes can be hydrolyzed by 2% S a O H in a nickel Parr bomb (151). The products are separated by ion exchange resins chosen on the basis of a preliminary infrared examination to see whether the prepolymer mas polyether or polyester and whether the diisocyanate was aliphatic or aromatic. The isolated hydrolysis products can be identified by infrared or thin-layer chromatography. Other Methods. The KMR spectra of polyurethanes in AsCla solution a t 100 "C can identify them as polyethers or polyesters (33). Toluenediisocyanate can be distinguished from methylene bis(Ppheny1 isocyanate). If the sample is polyester-based, ethylene glycol, propylene glycol, and diethylene glycol can be distinguished. The detection by thin-layer chromatography of @-sitosterol in the extract of natural rubber can be used to distinguish S R from I R (66). The method is sensitive to as little as 5% NR in a mixture of N R and IR. A new technique called TVA (thermal volatilization analysis) may be used in the identification of rubbers (135). The sample is put into a continuously evacuated system and the temperature is increased in a linear manner. A recording of the pressure near the sample shows the variation of rate of volatilization as a function of temperature. Thermograms of polyisoprene, BR, IIR, CR, and C S I I are sufficiently characteristic to identify the polymer. POLYMER CHARACTERIZATION BY PHYSICAL METHODS
General. As in the previous review, the literature surveyed for this section is primarily concerned with experimental techniques that have been, or can be, applied to the characterization of elastomeric materials in the uncured state. I n the past two years, a number of important books and general review articles have appeared covering this general subject area. The review of Tyler is of considerable interest t o those concerned with the characterization of polymers by physical methods (203). I n 1967, a conference was held aimed a t assessing the ability t o characterize macromolecules in terms of size, shape, and the distribution of such parameters. I n particular, the conference was concerned with methods of characterization which have general applicability and which can be carried out either in commercially available instruments or in instruments that have been described in the literature. The published proceedings of this conference are a valuable summary of many experimental methods for polymer characterization (133). 300 R
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I n providing information on a more limited subject, a n extensive compilation has been made on the fractionation of polymers (58). The rapid development of gel permeation chromatography resulted in a symposium on analytical aspects of this technique (111) and reprints are available on the latest meeting of a series devoted exclusively to G P C (175, 176). Molecular Weights. During the period covered by this review, there have been few developments in instrumentation for measuring molecular weights, but considerable progress has been made in the application and interpretation of existing methods. A useful review has appeared covering types of apparatus and experimental methods for measuring various average molecGlar weights (150). Some of the specific problems encountered in measuring the molecular weights of copolymers have been outlined (182). The most widely used experimental technique for absolute molecular weights appears to be the measurement of equilibrium osmotic pressures using one of the commercially available instruments. X new commercial instrument incorporating a flexible diaphragm and a strain gauge has appeared since the last review (142). The theory involved in such measurements has been revien-ed and a description given of the various types of osmometers that have been reported in the literature (55). -1summary has been prepared on the construction and performance of three commercially available high speed membrane osmometers (14). -1survey of the performance of various types of membranes concludes that there remains a need for more satisfactory membranes for measurements above 100 "C (55). However, such experimental conditions are not usually required for elastomeric materials. To extend the applicability of membrane osmometers to nonideal systems and particularly to the measurement of low molecular \veights for which strictly semipermeable m e m b r a n e s a r e n o t available, a number of investigations have been made using dynamic osmometry. I n this technique, osmotic pressures are measured as a function of time and the data treated to predict the true osmotic pressure. The various theoretical and practical aspects of this technique have been reviewed ( 7 7 ) . ;1numb e r of specific applications of t h i s technique have been reported ( b y ) , including a n investigation concluding that the method is not reliable for molecular weights less than 10,000 to 20,000 (106). Another paper deals with the effect of membrane selectivity, a factor that is particularly important with mixtures of diffusible and nondiffusible molecules ( 9 0 ) . This experimental method offers potential for measurements of lo^ and intermediate molecular weight polymers
provided care is taken with techniques and interpretation. To avoid some of the complications encountered with semipermeable membranes, work has continued on vapor phase osmometry methods. Since the last review, a new commercial instrument has become available (56). A review of progress in this area concludes that useful measurements may be made up to molecular weights of 40,000--i.e., to the range where normal membrane osmometry can usually be directly applied (207). I n a n application of the technique, the osmotic concentration of small latex samples was measured (157). Efforts have been made to define the time dependence of measured temperature differences in terms of mass and thermal flow (115). The direct measurement of boiling points of polymer solutions offers cert a i n a d v a n t a g e s over v a p o r p h a s e osmometry, especially if the measurements must be made a t high temperatures. The Schon-Schulz ebulliometer (185) has been modified and a n analysis of its performance given (86). It is concluded that, if applicable, vapor phase osmometry is a preferred technique (82). Some of the problems that may be encountered in ebulliometry have been described (197, 215). The application of the equilibrium ultracentrifuge to determine a number of molecular weight averages has been described with a discussion of the role of rotor speed in such measurements (187). -1n experimental technique useful for number average molecular weights of less than 5000 requires information on the nature of the end groups combined with precise density measurements (136). I n connection with the required density measurements, a n examination of the gradient column method has concluded that it leads to valid results (26, 162). Another experimental technique that has not yet gained wide acceptance, perhaps because of the need for very careful experimental observations, involves measurement of the desmelling of a cross-linked elastomeric material placed in a polymer solution. The deswelling is related to the number average molecular weight of the solute. Instead of measuring deswelling directly, changes i n retractive force (elastoosmometry) allow measurements of molecular weights of 100,000 to a n accuracy of 4y0 (208). An extensive compilation of molecular weight results obtained by various techniques and various investigators on a number of standard samples allows some assessment to be made of the accuracy to be expected from such measurements (125). Molecular Weight DistributionGPC. I n the last two years, the availability of more and more gel permeation
chromatography (GPC) units, the realization of the potentiality of the results from such measurements, and the recognition of the effort required to explore fully the results have brought about a spectacular growth in the literature available. Consequently, this review will consider only selected publications to point out the general areas in which research has been conducted, the status of progress in these areas, and some applications of GPC of interest in analyses of elastomers. Extensive reviews on GPC have recently appeared (6, 148) and the results of meetings devoted exclusively to GPC are available (111, 175, 176). X brief review summarizes the technique and the Waters Model 200 G P C apparatus ( 4 9 ) . Published results have been aimed in a. number of directions-mechanism of the separation process, improved methods for column calibration, establishmen t of e s p e ri m en t a1 conditions t o obtain distribution curves insensitive to the exact experimental techniques, and methods for conversion of the GPC curves to molecular weight distribution. The penetration and partition of solute polymer molecules into porous gels has been considered (45, 46, 98, 218) and it has been pointed out t h a t solute diffusion into gels can lead to apparent long tails on the distribution curve (101). By a combination of information on pore size, distribution of gel, and coil size of the polymer molecules in solution it has been possible to calculate calibration curves in good agreement with experimental curves (41, 42). These results indicate t h a t a t least for some polymer-gel systems, the mechanism of separation is well understood. I t was pointed out t h a t GPC differs from other chromatographic techniques by having, in the absence of adsorption, an upper limit of retention time ( 9 1 ) . The number of theoretical plates for a given column arrangement may be assessed using broad distribution polymers ofknown ;Mw/M.vratio ( 2 9 ) .Thenumber of plates depends upon the elution volume of interest, but is independent of polymer type ( 2 9 ) . I n the area of instrumentation, porous glass is a Tery useful column packing material and should be free of problems resulting from porosity changing with solvent treatment, thermal treatment, etc. (40). The preparation of polystyrene gels and techniques for packing to give high column plate count have been described (161). The importance of operational variables (temperature, solvent, concentration, injection time, and flow rate) in affecting the GPC curves has been examined thoroughly and methods of minimizing such effects are reported ( S I ) . The dependence of GPC results on the flow rate arises from solvent evapo-
ration in the siphon chamber and the continuous flow of solution during the time of discharge. Methods for avoiding or correcting these problems are presented (219). The negative peaks obtained in GPC chromatographs arise from water, nitrogen, and oxygen ( 4 ) . Another paper points out the need for a clear understanding of how GPC curves should be rigorously c o n v e r t e d t o molecular weight distribution curves and suggests t h a t in papers reporting GPC results, the calibration curve and method of data treatment should be clearly spelled out (217). From the shape of calibration curves for columns of different permeabilities, it was concluded that the analysis of high molecular weight polymers should be carried out in a series of columns, each with a high permeability limit (156).
Calibration techniques for GPC columns have progressed considerably from the initial methods requiring narrow distribution samples of a range of molecular weights and of the same chemical nature as the sample to be measured. By the use of only one polymer sample with a broad, well characterized distribution, it is possible to obtain a calibration curve covering a range of molecular weights (44). Other methods which allow calibration with broad distribution samples have been reported ( 5 , 86). relatively simple empirical method which also removes the necessity for narrow distribution samples of the material to be investigated has been reported (179). h more general approach to the calibration of column systems has been given by a number of investigations on universal calibration-Le., calibration on the basis of some fundamental parameter that is independent of the nature of the polymer. All of these methods involve some size or shape parameter (usually related to viscosity and molecular weight) of the polymer molecule in the particular solvent being used (52, 43, 58, 9 3 ) . I n view of experimental errors involved, the relative merits of the various techniques are difficult to assess a t this time. I n the precise conversion of GPC curves to molecular weight distribution, one of the more complex computations involves corrections for imperfect resolution of the chromatograph. The previous review in this series mentioned two methods available (102, 201), and recently two other techniques were reported (166, 195). I n addition, computational improvements have been made ( 2 , 167) on one of the original methods (201). The relative merits of the different methods for resolution correction have been extensively investigated, and some comments have been made on the computations involved (72, 7 8 ) .
Among the applications of GPC to specific problems are studies on the irradiation of polyethylene (129) and paraffins (185). Polymer degradation has been studied using GPC to measure product distribution and gain information on reaction mechanisms (100). An analysis of the GPC curves of copolymers of tetrahydrofuran and propylene oxide detected the presence of two peaks, apparently related to the method of preparation ( 2 7 ) . Without the necessity for rigorous quantitative analysis of the GPC curves, information may be obtained on elastomer mastication, blending, and chemical reactions ( 9 5 ) . X number of applications of GPC in the coatings industry have been illustrated, including quality control and quantitative analysis (19). Some comments have been made on the potential use of GPC as a process control tool necessitating rapid generation and interpretation of measurements (149).
A combination of GPC with infrared analysis has proved valuable in the analysis of polymer mixtures and copolymers (198). Provided the polymers contain groups absorbing in the infrared region, this technique can be much more informative than the normal differential refractometer detector (198). Qualitative observations of GPC curves give information on the mechanism of polymerization reactions and the reactions taking place in the formation of butadiene-styrene block copolymers (159). I n the analysis of carboxy-terminated BR by GPC, it vias necessary to avoid complications arising by absorption by the columns (191). GPC is useful for determining the oil content of extended rubbers (138). The performance characteristics of preparative scale GPC have been reported (64) in terms of experimental conditions used for separation. Provided the columns are not overloaded, samples with MW/&f.%< 1.5 can be obtained. The full potential of this technique, in combinations with other analytical tools, will be appreciated as more instruments become available. Molecular Weight DistributionOther Methods. The long established technique for making molecular weight separations based upon changes in solubility with molecular weight remains a useful method, particularly when large enough fractions t o allow further measurements must be obtained. B general treatment has been presented concerned with polydispersity, fractionation theory, and fractionation efficiency ( 10 7 ) . Separation on the basis of molecular weight may be made by either selective precipitation or selective solution. Fractional precipitation from a polymer solution may be brought about by nonsolvent addition, solvent evaporation, or solution cooling (123). If measVOL. 41, NO. 5, APRIL 1969
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urements are made by cooling a solution, then specific heat data can serve as a measure of the polymer remaining in solution (164). Summative fractionation is a convenient method of carrying out such fractionations and the methods for treating such data have been discussed (21). The fractional solution approach may be carried out by a number of techniques (78) but most experimental approaches reported recently involve some form of the Baker-Williams column (169, 170). B y a combination of fractional precipitation followed by fractional solution, the column technique actually combines the characteristics of both methods. It has been concluded that fractional solution is preferred to fractional precipitation for preparative scale work ( 119) but t h a t neither technique is suitable for accurate determination of molecular weight distribution (120). A valuable investigation has been made on column fractionation of B R and IIR on a preparative scale using up t o 45 g of polymer (99) and it was found that column overload should be avoided by using a temperature gradient of only 10 "C along the column. Under such experimental conditions the large scale fractionation results were in good agreement with those obtained for small (1 g) samples. +4large scale fractionation (3000 g) of poly(viny1 chloride) by fractional precipitation has been reported (165). I n connection Lvith column chromatography techniques, a belt detector is reported useful for sample collection (110). An interesting technique involving separation a t a lower critical solution temperature by adjusting the pressure on the system gives poor selectivity in the low molecular weight range ( I 7 ) . With column techniques, the molecular weight distribution of a number of BR samples has been measured ( 1 6 ) . Extraction methods have been used to determine the distribution of KR (84) and N R latex (214). The latter material showed a bimodal distribution. A number of other experimental methods have been applied to obtain information on polydispersity. An extensive review has been made of turbidimetric titration methods and results, including data for a number of elastomers (92). This technique is useful only for the high molecular weight components because precipitation of the low molecular meight materials is influenced by the high molecular meight fractions (61). The technique has been applied to I R of various microstructures (168). X number of other useful techniques have been reviewed recently, including sedimentation velocity and sedimentation equilibrium (130, 213), isothermal diffusion (36)) and thermal diffusion 302 R
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(79). A thorough review of sedimentation equilibrium techniques as applied t o monodisperse and polydisperse systems has been published covering many aspects of the technique ( 1 ) . Other papers deal with methods for calculating molecular weight distributions from equilibrium ultracentrifuge techniques (177, 188). An analysis has been made of boundary spreading in a sedimentation transport measurement and it is concluded that results at a single concentration can provide a distribution curve (122). X combination of flow birefringence measurements with conventional viscosity measurements allows the calculation of a molecular weight distribution parameter sensitive t o high molecular weight components (65). Permeation of solute molecules through the membrane of a quick-acting osmometer can provide information on the low molecular weight portion of a polymer (206). If a test for monodispersity of a polymer sample is desired, a combination of cloud point and critical point results provides qualitative information ( 181). Some brief comments have been made on a number of experimental methods for molecular weight distribution, which have, as yet, found only limited application (39). A valuable table has been prepared listing results in the literature on the fractionation of a great variety of polymers, including many elastomers (39). Transition Behavior. Measurements of the transition behavior of elastomers can often provide valuable information on polymer microstructure or distribut i o n of microstructure. Significant measurements include glass transition temperature, melting temperature, crystallization temperature, etc. The most widely used experimental technique involves some form of differential thermal analysis and a variety of commercial instruments are available (192). A recent symposium mas concerned with analytical calorimetry techniques applied t o polymers ( 7 ) . For more detailed investigations, particularly of melting and crystallization, dilatometry is often preferred and a recording microdilatometer has been described that simplifies such measurements (202). An application of dilatometry has shown how shearing action on a mill affects the rate of crystallization of cis-l,4-BR
(144).
A review on the structure of g R includes data on glass transitions and melting points as a function of microstructure; the unexpectedly high melting point of Alfin BR suggests that it contains nonrandom trans units (16). The observation of two glass transition temperatures in certain NBR preparations indicates a complex distribution of copolymer units (48). A general article surveys the applica-
tion of differential thermal analysis to a number of problems connected with polymers, including transition behavior (194). Another report is specifically concerned with the glass transitions of elastomeric materials with emphasis on the effects of sample preparation and experimental methods upon the experimental results (140). Sequence Distribution. I n addition t o differing in molecular weight, the molecules of a polymeric material may also differ in chemical composition. A thorough review has been made of the various types of chemical inhomogeneity that may be exhibited by a polymer; this has been combined with a summary of techniques of investigation (mainly fractionation) and a compilation of results from the literature (87). One of the more useful techniques for the detection of gross differences in microstructure distribution involves some characteristic of the first- or second-order transition. A technique termed melting point fractionation is useful for polymers containing ethylene and propylene units distributed in a nonrandom manner (193). A treatment has been made relating theory of crystallization to sequence distribution and applying it t o copolymers of ethylene (62)* By suitable thermal treatment of polymer solutions, it is possible to crystallize fractionally polymer mixtures and t o obtain information on the various components (163). Crystallinity effects were found in samples of polyvinyl chloride when attempts were made t o fractionate on the basis of molecular weight (89). Light scattering is useful for investigating compositional heterogeneity of copolymers, provided the two homopolymers have sufficient difference in refractive index (113). Ozonation of poly(propy1ene oxide) has shown the presence of head-to-head and tail-totail monomer placements with these structures contributing to the noncrystalline fractions of such polymers (174).
Polymer Blends. Activity has continued on the evaluation of polymer blends in association with the realization that blends can exhibit unique physical properties of great technological importance. The overall aim of such work is to relate fundamental measurements on the nature of a blend to observed mechanical behavior. Progress appears t o have been slow, reflecting the complexity of the problem and the difficulty of defining and evaluating significant structural parameters. A useful review article has been published which divides various polymer combinations into compatible and incompatible systems and gives a summary of optical and transition behavior t o characterize the mixed systems (SO).
I n addition, the phase morphology of two-phase systems is considered in terms of phase distribution and identification of dispersed and continuous phases (SO). Another general review of blends has appeared with a discussion of the importance of cohesive energy density and molecular weight in governing mutual solubility (160). Some parameters of interests for blends of polyvinyl chloride with various rubbers have been evaluated (160). Another general paper reports on the use of a variety of physical methods for characterizing copolymers and polymer blends (97). With optical clarity used as a criterion of compatibility, an examination has been made of a number of two- and three-component polymer systems, some of which are of interest as high impact materials (183). A most interesting system involves blends of two polymers with their corresponding block copolymer. A proper choice of molecular weights and copolymer composition can lead to optically clear systems over a limited range of blend ratios (185). Some unexpected results dealing with the extraction of plastic components from natural rubber vulcanizates have been reported (60). I n an examination of polymer blends involving two elastomeric components, a combination of electron and phase microscopy with differential thermal analysis showed that blends of SBR-cis-1,4-BR and SBR-emulsion BR mere homogeneous (137). With the use of the compatibility behavior of chlorinated rubber and poly(ethy1ene-vinyl acetate) copolymer in several solvents, it has been shown t h a t this polymer pair exhibits unusual compatibility behavior (178). Closely related to .rvork on the characterization of polymer blends is research on block and graft copolymers. A book on graft copolymers includes a discussion of compatibility, fractionation, and various characterization techniques (20). A thorough survey has been made of the solution behavior of block and graft copolymers (147). Such materials may show complex behavior in selective solvents if the components have a large difference in solubility parameters. Among techniques useful for characterization are solvent fractionation, turbidimetric titration, density gradient centrifugation, and light scattering (147). A general review of polymer inhomogeneity includes work on grafts, blocks, and blends (87). One class of materials of great technological interest involves block copolymers containing rubbery and plastic components. An electron microscope examination of such materials after treatment with osmium tetroxide has shown how the texture changes with composition (108). Viscosity. Because of the relative ease of experiments and the ready avail-
ability of a number of measuring devices, viscosity measurements remain the most popular technique for determiningrelative molecular weights. Some progress has been made on relating rheological measurements on concentrated solutions or bulk polymers to molecular weight or molecular weight distribution (190),but measurements are more commonly made on dilute solutions. A review has been made of the application of capillary viscometers to measurements on dilute solutions; a summary of possible experimental errors arising from viscometer design is included (209). A commercial instrument allowing automatic measurement of flow times has become available (103). The area of greatest experimental and theoretical activity concerns the manner in which viscosity varies with solution concentration. Such efforts are aimed either a t allowing the calculation of a precise intrinsic viscosity or the calculation of intrinsic viscosity from a single measurement a t a finite concentration. A summary has been made of the manner in which concentration dependence is governed by polymer characteristics and instrumentation ( 2 3 ) . The calculation of intrinsic viscosity from single-point measurements has been discussed (28, 62). A number of papers report on different methods for expressing viscosity as a function of concentration ( I58, 196). I t has been concluded t h a t different methods of extrapolation are required for poor solvent and good solvent systems (184). I n a different application, measurements of flow time fluctuations of dilute solutions in a capillary viscometer show promise as an absolute method for measuring weight average molecular weights (75, 76).
POLYMER CHARACTERIZATION BY CHEMICAL A N D SPECTROMETRIC METHODS
General Information. The attachment of an initiator to the end of a polymer chain can be followed by isotopic tracers ( 2 4 ) . Stable isotopes are readily detected by N M R or infrared, particularly if deuterium is used to replace hydrogen. Radioactive isotopes are followed by counting. NR and IR. Binder found t h a t cis-l,4polyisoprene made with a Zeigler-type catalyst had a total found unsaturation of approximately 90% ( 2 5 ) . This evidence together with N M R data led to the conclusion t h a t there could be as much as 10% cyclic structure present. Chen says t h a t the N M R bands interpreted as being caused by cyclohexane rings are really due to C13 coupling and spin sidebands ( 5 1 ) . He feels that there is insufficient evidence to conclude t h a t cyclic structure is present. This does
not, however, explain the discrepancy of total found from 1 0 0 ~ o . I n another study of Ziegler-Natta cis-1,4-polyisoprene and NR, the principal difference was found to be 0.5 k 0.2% trans-1,4- in the synthetic polymer ( 5 0 ) . There was no trans structure detected in N R and no 1,2- or 3,4structure detected in either sample. The absence of 1,2- addition in n'R was confirmed by absence of a band a t 910 em-' ( 4 7 ) . The formation of formic acid by ozonolysis of NR led to the conclusion t h a t there is 5% 3,4- structure ( 4 7 ) . I n view of the series of steps necessary to work up the reaction mixture after ozonolysis, it seems t h a t formic acid could come from some side reaction and not necessarily from 3,4-structure. Pyrolysis produced isoprene, dipentene, and a third hydrocarbon closely related to dipentene (205, 206). The products were separated by gas chromatography and the ratio of the third hydrocarbon to dipentene was proportional to the ratio of 3,4- addition to 1,4- addition in the polymer. The 888-cm-1 methylene band of the isopropenyl side chain in 3,4- addition mas studied ( 1 5 ) . The theoretical molar absorptivity was obtained with slit widths of 1 em-' or less. I t was difficult to use 2,3-dimethyl-l-pentene or 1hexene as model compounds. This illustrates the complex relationship between polymers and simple models which portray only portions of the structure. Xear 1450 em-', cyclopolyisoprene has a band which is only 10 em-1 away from a cis-1,4-polyisoprene band (118). The bands are too close together for a simple measure of cyclic content. However, a differential method using cis-1,4in the reference beam gives a linear relationship of absorbance t o cyclic content. The polymers can be in CC1, solution or in KBr pellets. SBR. Polymers made with butyl lithium catalyst were studied in 10% solution in CCla by XMR (145). 1,2Butadiene, l14-butadiene, total styrene, and styrene in blocks of two or three monomer units or larger mere measured. The nonblock styrene was then determined by difference. Normally, NMR needs no calibration for quantitative work, but an adjustment was made in the calculation of 1,2butadiene to get better agreement with infrared. The results are accurate to k 0.5% on 1,2-butadiene and block styrene. BR. It was concluded t h a t the presence of cyclic structure in Ziegler-type polymer causes the failure of total found unsaturation to reach 1 0 0 ~ oin the same manner as for I R (25). The use of the 911-em-' band to measure 1,2addition and the 967-em-1 band for trans-1,4- a d d i t i o n is generally acVOL. 41, NO. 5, APRIL 1969
e
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cepted. The cis-1,4- content has been measured by any of several infrared bands or by difference from 100% or from total unsaturation found by chemical means (211). The 1308-em-' band gives precision of 5y0 relative (88). The use of attenuated total reflectance to determine microstructure has the prospect of being applicable to vulcanizates as well as to raw polymers (96). EPM. The 750-, 732-, and 722-cm-1 bands were used to measure methylene sequences of 2, 3, and 4 or more, respectively ( 7 1 ) . Bands a t 937, 960, and 972 em-' were used for propylene sequences of 1, 2, and 3 or more, respectively. These bands are not resolved because of their broad half widths and close positions. Therefore, the spectra were digitized and a computer mas used to calculate intensities. A similar study of propylene sequences was made using only the 935and 972-cm-' bands (55). The (CH,), groups which were also found could be due to propylene inversion or to propylene inversion combined with ethylene insertion. I t was concluded that the latter is the case as more (CH2),'s are found in EPM with 50 to 60% propylene than in polypropylene. Apparently, the presence of ethylene favors propylene inversion. The ratio of isolated propylene groups to sequences of two or more propylene groups has been correlated with the degree of alternation of propylene (199). This information can be used to calculate the reactivity ratios of ethylene and propylene in the copolymerization reaction. IIR. Nuclear magnetic resonance measurements showed that all of the isoprene in I I R is in the 1,4- configuration (52). Polyurethanes. n-Butyl amine in dimethyl acetamide reacts with biuret and allophanate crosslinks faster than with urethanes or ureas in the main chain (155). NMR spectra of the dimethyl sulfoxide or dimethyl acetamide solutions of the degraded polymers are characteristic of the glycol or diamine cross-linking agents used. Butadiene-Isoprene Copolymers. S M R spectra of 5% solutions in CS, or hexadeuterobenzene were used to determine 1,2-butadiene, 1,4-butadiene, cis-1,4-isoprene, trans-1,4-isoprene, 1,2isoprene, and 3,4-isoprene (145). Physical mixtures of BR and I R , each made with butyl lithium catalyst, and emulsion copolymers which had been run to 95Yc conversion were used for calibration. Accuracy is 20/0 absolute. Poly-1,3-pentadiene. The relative merits of Y M R and infrared were compared (54). The infrared bands for 1,2- and 1,4- addition are difficult to use because they are close together. However, NMR can make good determinations of 1,2- and 1,4- if cyclic 304 R
ANALYTICAL CHEMISTRY
structure is absent. The infrared bands a t 965 em-' and 1405 or 760 em-' are preferred for trans and cis, respectively.
DETERMINATION OF POLYMERS IN POLYMER MIXTURES AND CONSTITUENTS IN COPOLYMERS
General Information. If n - 1 monomers in a system of n monomers can be tagged with isotopic tracers, an analysis of copolymer composition can be made (24). This is useful for calibrating other physical methods such as infrared. The experience of Perry has been that precision of 10% relative is the present capability of pyrolysis-gas chromatography for determination of copolymer composition (164). He feels that this can possibly be improved to 5% relative by further refinement of methods. SBR. Bound styrene was determined from the ratio of absorbances a t 970 and 760 cm-1 (171). The spectra were measured on polymer films to accommodate insoluble samples. The average difference between determinations by this method and by nitration was 0.7yc in the range 45 to 8070. The band a t 970 em-1 is due to trans-1,4-butadiene addition, so accuracy depends on having the same proportion of trans-1,4addition in the unknown sample as in the calibration standards. For styrene levels of 80 to 90%, the ratio of absorbances a t 970 and 3078 cm-1 was preferred (173). .igain, the results agreed within 0.7% n i t h those found by nitration. T h e nitration method mentioned above (173) is a modification of that of Hilton (104). X version of it is also an ASThI method (YO). The modification provides for more careful control of conditions such as time of nitration, adjustment of acidity before extraction, thoroughness of extraction, and thoroughness of washing. K i t h this degree of care, good results mere obtained. Styrene present as polystyrene or as bound styrene can be determined by an ultraviolet measurement a t 269 mp (121). A film of polymer is scanned in a Baly cell and a baseline method is used to detect as little as 0.1%. EPM. Calibration of the 1378-em-' band in CC1, solution for bound propylene content must be done with a polymer such as hydrogenated NR or polypropylene (116). K h e n n-alkanes were used to calibrate, lower absorptivities were found. The baseline measurement was made on a solution whose concentration was 1 g/l. The standard deviation was 0.27% a t a level of 25 wt % CHI. Themethodwas preferred to NMR because of peak overlap in NMR spectra of solutions in perchloroethylene. IIR. N M R as refined by a timeaveraging method can determine 2% bound isoprene (52). Kithout time
averaging, it probably could not be detected. NBR. The fundamental method for determining bound acrylonitrile via the nitrogen content of an extracted sample has been investigated ('74). Nitrogen can be determined by the Vecera method (Dumas with CorOa catalyst in the sample boat) or by the Kjeldahl method with CuSO, and K2S04catalysts. The Kjeldahl method is preferred as it gives standard deviation of 0.1% us. 0.2% for the Vecera method. Both methods, however, give average values in agreement with theory when applied to polyacrylonitrile. Hg can be used to shorten the Kjeldahl digestion time, but the use of H 2 0 2 ,H C l O , or KMnO, causes low results. NR-SBR-BR. This ternary mixture is of considerable importance because of its wide commercial use. Either of the methods cited here is also applicable to mixtures of any two of these. Both methods rely on pyrolysis to break the sample down to a tractable form. I n one approach, the liquid pyrolyzate is examined by infrared (134). The ratio of absorbances a t 700 and 1450 em-1 is used for SBR content and the ratio of absorbance a t 850 cm-l to the sum of the absorbances a t 850 and 962 em-1 is used for BR-NR ratio. The lower limit of detection for any component is 575 and standard deviation is 4% for any component in a three-component blend. K h e n gas chromatography is used to examine the pyrolyzate, the relative standard deviation is 10% (70). I n both of these methods, the bound styrene content of the SBR must be known, as the SBR calculation is based on the measurement of styrene. K e still do not know how to distinguish a mixture of BR with a high styrene butadiene-styrene resin from an SBR with the same total styrene content. .I simpler case of the binary mixture of NR-SBR was analyzed with accuracy of 3% by pyrolysis-gas chromatography (204). CR-SBR. The accuracy of pyrolysisgas chromatography of this mixture is 5a/o (204). I t would seem that a more straightforward way to analyze this mixture is via the chlorine content. IIR-EPDM. Differential thermal analysis can be used to locate the glass transition temperature. It, in turn, can classify the I I R content of the blend as 70% (139).
EPM-Acrylonitrile Grafts. The intensity of the nitrile band a t 2246 em-1 is proportional to the amount of acrylonitrile grated onto EPM (35). IIR-Polypropylene. The liquid pyrolyzate of this blend is incorporated into a KBr disk. The log of the ratio of absorbances a t 1235 and 1170 em-' is proportional to I I R content in the range 5 to 30y0(124). Accuracy is 1.5%.
IM-Polypropylene. If the blend contains I M instead of I I R as above, the I M can be extracted by boiling benzene and the amount determined by weight loss (128). The standard deviation is 2.3% a t a level of 12%. Ethylene-1-Butene Copolymer. The ratios of absorbances of infrared bands at 772, 733, and 722 cm-1 are useful to determine the composition (11 7 ) . They are assigned to C H 2 in the ethyl side chain, three adjacent C H 2 groups, and five or more adjacent C H 2 groups, respectively. The spectra are measured on a melt a t 120 "C to eliminate crystallinity effects. Polyurethanes. Cyclohexanone will dissolve polyurethane fibers out of mixtures Ivith wool, cotton, rayon, nylon-6, nylon-66, and polyacrylonitrile (141). This property is the basis of a method for determination of polyurethanes in the presence of one or more of the other fibers. Acetate and polyvinyl chloride interfere as they are attacked by cyclohexanone. DETERMINATION O F RUBBER
Total polymer in cured, filled samples is frequently determined by difference by subtracting the sum of extract, ash, carbon black, and total sulfur from 100%. A direct measurement of total polymer can be made by pyrolyzing a n acetone-extracted sample in nitrogen a t 850 "C and measuring weight loss (63). This is applicable only to NR, I R , SBR, and I I R . SBR paint latex was diluted and centrifuged to precipitate the pigment (121). -4film of polymer is scanned in a poured into methanolic HCl to coagulate the polymer, which was then filtered, washed, dried, and weighed. UNSATURATION
h new method was proposed for the long-standing problem of determination of unsaturation in I I R (126). An eightor ninefold excess of mercuric acetate in methanol is allowed to react with the sample in CHC13or CC1, solution. The excess reagent is then backtitrated with HCl to the thymol blue end point. Exposure to light and normal variations in room temperature have no noticeable effect and no empirical correction factor is required. Results agreed within -0.23 t o +0.l2Y0 in the range 1 t o 3y0 with those obtained using iodine as reagent. -1radiochemical method utilizing the addition of 36Cl to determine unsaturation in I I R has been extended to I M (131). Work with the model compounds diisobutylene and triisobutylene indicates t h a t the reaction is substitution rather than addition as only one atom of 36Cl is incorporated per double bond rather t h a n two a s was originally thought (132). This method is very
sensitive, measuring unsaturation down to 0.01yo. An article describing determination of unsaturation in E P D M in which the diene monomer is dicyclopentadiene was previously reviewed (212). It is now available in English translation (94). SULFUR AND SULFIDES
The study of sulfur crosslinks in rubber has been reviewed (186). Hydrogen sulfide formed in the putrefaction of XR latex can be detected down to 0.05 ppm by adding boric acid and holding moist lead acetate paper in the vapor. For quantitative determination in the range 0.002 to 100 ppm, air is bubbled through the acidified sample to carry the H2S to a zinc acetate-sodium hydroxide scrubber. Methylene blue is then formed and measured colorimetrically (210). CURING AGENTS
Thin-layer chromatography was used to identify curing agent blooms washed from the rubber surface with CHCll (13). Data are given for 2-mercaptobenzothiazole and its zinc salt, benzothiazyl disulfide, tetramethyl thiuram monosulfide, tetramethyl thiuram disulfide, tetraethyl thiuram disulfide, zinc dimethyldithiocarbamate, a n d zinc diethyldithiocarbamate. AGE RESISTERS
Identification. The combination of from thin-layer chromatograms and the colors developed by spray reagents make possible the identification of many age resisters (109). 2,6Dichloroquinone chlorimine is a useful spray for phenols and NaT\;02-HC1 is useful for amines. The use of selective color-forming reagents prevents interference from other compounds present in the extracts. The R, values and colors for many commercial age resisters are listed. Stable free radicals formed by S , S ' diphenyl-p-phenylenediamine a n d phenyl-8-naphthylamine form narrow lines in electron paramagnetic resonance spectra (180). They can be distinguished from inorganic fillers which form broad lines. Determination. Both S-alkyl-iLr 'aryl-p-phenylenediamines and S,A' Idiaryl-p-phenylenediamines are oxidized to the corresponding quinonediimines by benzoyl peroxide. This is the basis for a colorimetric determination of these materials (37). A benzene solution of the sample is used, although an extract can also be used. Extender oil interferes as it forms a colored oxidation product also. This is taken care of by including oil in the calibration standards. The color must be measured a t a fixed time after adding the reagent
R, values
as the color due to oil continues to become more intense up t o 24 hrs while t h a t due to quinonediimine is constant after 15 min. If good recovery is expected on known stocks, the rubber should be protected by a phenolic antioxidant during coagulation and drying. If age resister-free rubber is used, as recommended in this article, some p phenylenediamine will be destroyed by residual peroxides. An electron capture detector on a gas chromatograph is about as sensitive to 2,6-di-tert-butyl-p-cresol as a flame ionization detector (127). However, electron capture has little or no response to many possible interferences, so i t is much more nearly specific with no sacrifice in sensitivity. The precision is 3% relative to the range 0.005 to 0.05%. Age resisters with sufficient volatility, such as 2,6-di-tert-butyl-p-cresol and 2,2 '-methylene bis(4-methyl-6-tertbutyl phenol), can be separated from the polymer by vacuum distillation a t 150 to 200 "C and 0.01 to 0.1 mm Hg (220). This is claimed to be superior to extraction. Recoveries were 95 t o 100%. To get these recoveries in a reasonable time, it is probably necessary to have the sample in a thin sheet, which is the same requirement as for extraction. Isotopic tracers can be used to study the loss of age resisters by volatilization (24). CARBON BLACK
Kew work on carbon black has been directed toward identification rather than determination. This task has been made more difficult with the intrbduction of various degrees of structure within a given type. The subject has been thoroughly studied by Nabors and Studebaker (162). T h e carbon black is isolated b y vacuum pyrolysis, washed with HC1 to remove Zn compounds, dried, compressed, and screened through 200mesh. Usually it is adequate to make a reflectance measurement to find the particle size and a specific volume measurement to find the structure. The reference data should be taken on carbon black isolated from known stocks of the same type of polymer containing the same amount of carbon black as the unknown. Measurements on fresh carbon black t h a t has not been through compounding and isolation will not be the same as after isolation. Channel blacks are more difficult to classify than furnace blacks and require measurement of resistivity also. Another way to measure particle size is by the ratio of absorbances of an aqueous suspension in the violet and red parts of the visible spectrum (67). The ratios range from 0.95 to 1.55 and VOL. 41,NO. 5, APRIL 1969
305 R
have a standard deviation of 0.01. Pyrolysis under nitrogen is preferred to decomposition with tert-butyl hydroperoxide and osmium tetroxide for isolation of the black. This method yields only particle size, and gives no information about structure. METALS
h rapid method for determination of zinc was reported (146). By burning the sample in an oxygen flask and making a polarographic measurement, the determination can be completed in 30 min. Recoveries were 100 k 2%. Talc, Fe, Cu, and Ti were detected by broad lines in electron paramagnetic resonance spectra (180). PLASTICIZERS A N D OILS
Plasticizers were classified into eight groups by pyrolysis of the acetone extract followed by gas chromatography (85). The acid part of esters can be further identified by converting to the methyl ester and noting characteristic retention time. Mineral oils all behave similarly in pyrolysis-gas chromatography, so the ultraviolet and infrared spectra were examined. By the use of appropriate bands, one can tell whether they are paraffinic, naphthenic, or aromatic (84). Gel permeation chromatograms of oil-extended rubber can be used to determine the oil if the proper permeation columns are chosen (138). In the examples shown, paraffinic oil gave a bimodal response, one peak above baseline and one below, and naphthenic oil gave a symmetrical, positive peak. Three aromatic oils gave a partly positive, partly negative response in one case, all negative in another, and all positive in still another. Therefore, calibration must be made with the same lot of oil as is in the sample. The precision was 5.5% on paraffinic and 1.5% on naphthenic oil. Castor oil in hevea crumb NR is separated from the naturally occurring glycerides by thin-layer chromatography (68). The area of the spot developed by phosphomolybdic acid was accurate to 5% of the amount present in the range 0.2 to 0.5%. OTHER DETERMINATIONS
Fatty acid soap in CR latex is precipitated as the Ca salt which is washed, dried, and weighed (80). A syringe-like device was described to sample and lock in the gas contained in a closed cell foam such as polyurethane (163). Total oxygen in rubber was determined in the range 0.3 to 5y0 with accuracy of 1 to 2y0 relative by irradiating i t to generate radioactivity (53). As little as 0.03% can be detected. Di306 R
ANALYTICAL CHEMISTRY
tionation,” Academic Press, New York, N.Y.. 1967. (39) Cantow, M.J. R., &id.> p 461. (40) Cantow, hl. J. R., J . Appl. Polym. Sci., 11, 1851 (1967). (41) Cantow, M. J. R., Johnson, J. F., J . Polym. Sci., Part A - f , 5 2835 (1967). (42) Cantow, PIT. J. R., Johnson, J. F., Pol mer, 8 , 487 (1967). (43) antow, M. J. R., Porter, R. S., Johnson, J. F., J . Polym. Sci., Part A - f , 5 , 987 (1967). (44) Cantow, 11. J. R., Porter, R. S., LITERATURE CITED Johnson, J. F., ibid., p 1391. (1) Adams, E. T., Reference 133, p 84. (45) Carmichael, J. B., ibid., Part A d , (2) Aldhouse, S. T. E., Stanford, D. lL, 6. 017 (1968). Reference 176. (46j Casassa, E. F., ibid., Part B, 5 , 773 (3) Alishoev, V. R., Berezkin, V. G., Russ. 11967). Chem. Rev. (English transl.), 36, 545 (47) Chakravarty, S. N., Sircar, A. K., (1 967). J . Appl. Polym. Sci., 11, 37 (1967). (4) Alliet, D., J . Polym. Sci., Part A-1, 5 , (48) Chandler, L. A . , Collins, E . A , , 1783 (1967). Polymer Preprints, 9, 1416 (1968). (5) Almin, K. E., Polymer Preprints, 9, (49) Chem. Process. (London) 12, (9). 48 (1966). 727 11968). (6) Altgelt, k.H., Moore, J. C., Reference (50) Chen, H. Y., J . Polym. Sci., Part B, 58, p 123. 4, 891 (1966). (7) American Chemical Society, Symposi(51) Zbid., p 1007. um on Analytical Calorimetry, San (52) Chen., H. T., Field, J. E., ibid., 5 , 501 Francisco, Calif., 1968. (1967). (8) Am. Soc. Testing blater., “l9:8 Book (53) Chepel, L. V., Chapyzhnikov, B. A , Llikhailova, G. S . ,Zhuravskaya, E. V., of ASTM Standards. Part 28. PhilaKuzminskii, A. S., Sou. Rubber Technol. delphia, 1968, p 114.’ (9)Ibid.. D 130. (English transl.), 25, ( 3 ) , 39 (1966). (10)-Zbid.: p 155. (54) Ciampelli, F., Lachi, 11.P., Venturi, (11) Zbid., p 647. Ll. T., Porri, L., Eur. Polym. J., 3, 353 (12) Zbid., p 676. (1967). (13) Amos, R., J . Chromatog., 31, 263 (55) Ciampelli, F., Valvassori. A , , J . (1967). Pol mer Sd.,Part C, 16,377 (1967). (14) Armstrong, J. L., Reference 133,p 51. 156) &oleman Instruments. Mavwood. Ill. (15) Assioma, F., Cornibert, J., Marchal, Technical Bulletin (1968). J., C.R. Acad. Sci., Paris, Ser. C, 265, (57) Coll, H., Makromol. Chem., 109, 38 1023 (1967). (1967). (16) Bahary, W. S., Sapper, D. I., Lane, (58) Coll, H., Prusinowski, L. R., J . Polym. J. H., Rubber Chem. Technol., 40, 1529 Sci., Part B , 5 , 1153 (1967). (59) Coll, H., Stross, F. H., Reference 133, (1967). 117) Raker. C. H.. Clemson. C. 9.. Allen. p 10. G., Polymer, 7,525 (1966)’. (60) Cooper, W.,Smith, R. K., Rubber Chem. Technol., 40, 1553 (1967). (18) Barlow. A., Lehrle, R. S., Robb, J. C., Sunderland, D., ibid., 8, 523 (1967). (61) Cornet, C. F., Polymer, 9, 7 (1968). (62) CLaubner, H., Kolloid-Z., 220, 111 (19) Bartosiewicz, R. L.. J . Polvm. Sei., Part C , 21, 329 (1968). (1961). (20) Battaerd, H. A. J., Tregear, G. W.) (63) Dale, J. G., Rubber J.,149. (6), 38 “Graft Cooolvmers.” Interscience. Sew (1967). York. N . 9 . . i967. (64) Dark, R. A , , Levangie, R. F., Bombaugh, K. J., Reference f76. (21) Battista, 0. 4.,Reference 38, p 307. (22) Baur, H., Kolloid-Z., 212, 97 (1966). (65) Daum. U., J . Polym. Sci., Part A-2, 6, 141 (1968). (23) B_erger, R., Plaste Kautschuk, 14, 11 (146,) (66) Davies, J. R., J . Chromatog., 28, 451 ,_”-.,. (1967). (24) Bevington, J. C., ChemZnd. (London), 1967,p 1821. (67) Davies, J. R.. Kam, F. JY.j J . Znst. Rubber Znd.. 1, 231 (1967). (25) Binder, J. L., J . Polym. Sci., Part B, (68) Davies, J. R., Tannicliffe, &I. E., 4, 19 (1966). (26) Blackadder, D. A , , Lewell, P. h., J . Chromatog., 30, 125 (1967). (69) Deaur-Siftar, D., Bistricki, T., Tandi, Polymer, 9, 249 (1968). (27) Blanchard, L. P.. Baijal, LI. D.. T., i b i d , 24, 404 (1966). (70) Dolinar, J., Jernijcic, 11.. Premru, J . Polvm. Sci., Part A-1, 5 . 2045 (1967). L.. i b i d , 34, 89 (1968). (28) Blak, E., Langhammer. G.. Plaste Kautschuk. 14. 248 11967). (71) Drushel, H. V.,Ellerbe, J. S., Cox, R. C., Lane, L. H., ANAL. CHEM.,40, (29) Bly, D.’D.,’J. Polym. Sci., Part A - , f 6,2085 (1968). 370 (1968,. (72) Duerksen. J. H., Hamielec, A. E., (30) Bohn, L., Rubber Chem. Technol., 41, J . Polym. Sci., Part C , 21, 83 (1968). 495 (1968). (73) Duerksen, J. H., Hamielec, A. E., 131) Boni, K. A . , Sliemers, F. A., Stickney, Reference 176. P. B., J . Polym. Sci., Part A-2, 6, 1567 (74) Dunke, If.,Faserfosch. Teztiltech., (1968). (32) Zbid., p 1579. 18, 123 (1967). (75) Eitel, hl. J., Polymer Preprints 8, 415 (33) Brame, E. G., Jr., Ferguson, R. C., Thomas. G. J.. Jr.. ANAL.CHEM..39. (1967). (76) Zh-id, p 419. (34) Bristo;,, G. M., Westall, B., Polymer, (77) Elias, H-G., Reference 133, p 28. (78) Elliot, J. H., Reference 38, p 67. 8,609 (1967). (79) Emery, A. H., ibid., p 181. (35) Bunyat-Zade, A. A,, Karaev, S. F., (80) Engovatov. A. A,, Russian Patent Portyanskii, A. E., Sadikhov, R. B., Sou. Plastics (English tranel.), 1966, (9), 181,368 (Jan. 1967). (81) Eur. Chem.News, 12,(295),48 (1967). P 6. (82) Ezrin, hl. Reference 133, p 3. (36) Burchard, W., Cantow. H. J., Reference 38, p 285. (83) Farre-Rim, F., Guiochon, G., ANAL. (37) Campbell, R. H.. Young. E. J., CHEM.,40, 998 (1968). Rubber Age (X.Y,), 100, (3). 71 (1968). (84) Fischer, W.,Leukroth, G., Gummi (38) Cantow, M. J. R., “Polymer FraAsbest, Kunststofle, 20, 1266 (1967).
butyl phthalate is milled in for calibration. An interlaboratory program evaluated accuracy and precision of determination of 12 elements in rubber tree leaves (143). It was established that field sampling errors are greater than those associated with chemical analysis.
\__._
!i
(85) Fischer, W.,Meuser, H., ibid., p 17. (86) Frank, F. C., Ward, I. hl., Williams, T., J . Polym. Sci., Part A d , 6, 1357 (1968). (87) Fuchs, O., Schmieder, W.,Reference 38, p 341. (88) Galenko, N. V., Zorina, V. B., Sou. Plastics (English transl.), 1967 ( 5 ) , p 58. (89) Garbuglio, C., Mula, A., Chinellato, L., J . Polym. Sci., Part C, 16, 1529 (1967).
(gdj-Ghosh, K. K., Swenson, H. A., J . Appl. Polym. Sci., 12, 1531 (1968). (91)Giddings, J. C., ANAL. CHEM.,39, 1027 (1967). (92)Giesekus, H., Reference 38, p 191. (93)Grubisic, Z.,Rempp, P., Benoit, H., J . Polym. Sci., Part B, 5,753(1967). (94)Hank, R., Rubber Chem. Technol., 40, 936 (1967). (95) Harmon, D. J., J . Appl. Polym. Sci., 11, 1333 (1967). (96) H a y a s h i , J . , F u r u k a w a , J . , Yamashita, S., Polym. Repts. (Japan), 102. 11 11966). (97)Heinze, D’., Makromol. Chem., I.01, 166 (1967). (98)Heitz, W., Platt, K. L., Ullner, H., Winau, H., ibid., 102, 63 (1967). (99) Henderson, J. F., Hulme, J. hI .. J . Appl. Polym. Sci., 11, 2349 (1967). 1100) Hendrickson. J. G.. ibzd.. 1419. (101) Hermans, J. J., J . Polym: Sci., Part A-2, 6, 1217 (1968). (102)Hess, hl., Kratz, R. F., ibid, 4, 731 (1966). (103)Hewlett-Packard, Palo Alto, Calif., p 51, 1969 catalogue. (104) , , Hilton. C. L.. Newell. J. E.. Tolsma. J.. ANAL.CHEM..’ 31. 915 11959). (105) Hoffmann, il.,‘Unbehend,’ M.,J . Polym. Sci., Part C, 16, 977 (1967). (106)Holleran, P. RI., Billmeyer, F. W., ibid., Part B , 6, 137 (1968). (107)Huggins, RI. L., Okamoto, H., Reference 38, p 1. (108) Inoue, T., Soen, T., Kawai, H., Fukatsu, AI., Kurata, M., J . Polym. Sci., Part B , 6, 75 (1968). (109)Jentzsch, J., Martin, R., Plaste Kautschuk, 13, 464 (1966). (110) Johnson, H. W.,Seibert, E. E., Stross, F. H., ASAL. CHEM..40. 403 (1968). (111)Johnson, J. F.,Porter, R. S., Eds., J . Polymer Sci., Part C, 21, (1968). (112) Jones, C. E.R., Reynolds, G. E. J., J . Gas Chromatog., 5, 25 (1967). (113) Jordon, E. F.,J . Polym. Sci., Part A-1, 6, 2209 (1968). (114) Kaczaj, J., Appl., Spectrosc., 21, 180 (1967). (115) Kamide, K., Sanada, RI., Polym. Rmts. iJaDan’, 116. 14 11967). , (1161 Key, ‘L. C.,-Trent, F. M.>Lewis, 11.E., Appl. Spectrosc., 20, 330 (1966). (117) Khodzhayeva, V. L., Mamedova, V. >I., Polum. Sci. USSR (English . transl.), 9, 503 (1967). (118) Koessler, I., Vodehnal, J., ANAL. CHEM.,40, 825 (1968). (119) Koningsveld, R., Staverman, A. J., J . Polum. Sci.. Part A-2. ., 6., 367 (1968’ - _ _ _ ). (120)Zb;d., p 383. (121)Iioren, J. G., Hirt, R. C., Appl. Spectrosc., 21, 124 (1967). (122) Kotaka, T., Donkai, N., J . Polymer Sci., Part A-2, 6, 1457 (1968). (123) Kotera. A.. Reference 38. D 44. (124) Kral, I., Plaste Kautschhh. 14. 88 (1967). (1:s) Iiratohvil, J. P., Reference 133, p 09. (126) Kreshkov, A. P., Balyatinskaya, L. N., Sou. Rubber Technol. (English transl.), 24, (10).45 (1965). (127) Long, R. E., Guvernator, G. C., 111, ANAL.CHEM.,39, 1493 (1967). (128) Longworth, R., Funck, D. L., J . A p p l . Polym. Sci., 10, 1612 (1966). I
-
-
\ - - -
~
(129) Lyons, B.J., Fox, A. S., J. Polym. Sci., Part C, 21, 159 (1968). (130) McCormick, H. W., Reference 38, D 251. (131)-&Guchan, R., McNeill, I. C., J. Polym. Sci., Part A-1, 4, 2051 (1966). (132) Zbid., 5, 1425 (1967). “Characterization of (133) RIcIntvre. D.. hfacromol&ular ’Structure,” National Academy of Science, Washington, D.C.,
(172) Zbid., p 315. (173) Post, ?A., *I J. . Paint Technol., 38, 336 11966’1. (174) Price,‘C. C., Spector, R., Tumolo, A. L., J . Polym. Sci., Part A-1, 5, 407
,--”.,.
(1 Q67)
(175) Proceedings Fourth International Seminar, Gel Permeation Chromatography, Miami Beach, Fla., May 1967. (176) Proceedings Fif th International Sem1968. -. ._ inar, Gel Permeation Chromatography, (134) MacKillop, D. A., ANAL. CHEM., London, England, May 1968. 40, 607 (1968). (177) Provencher, S. W.,Gobush, W., (135) McNeill, I. C., Eur. Polym. J., 3, Reference 133, p 143. 409 (1967). (178) Purcell, A., Thies, C., Polymer Pre(136) Margerison, D., Nyss, V. A . , Pulat, prints, 9, 115 (1968). E..Polumer. 8. 269 (1967). (179) Purdon, J. R., Mate, R. D., J . (137) Makh, P. k >Voet, A., Price, L. D., Polym. Sei., Part A-1, 6, 243 (1968). Mullens, T. J., Rubber Chem. Technol., (180) Raevskii, A. B., Gainulin, I. F., 41. 344 Sou. Rubber Technol. (English transl.), - - f1968) (138) -Mate, R. D., Lundstrom, H. S., 25 (9),8 (1966). J. Polym. Sci., Part C, 21, 317 (1968). (181) Rehage, G., Wefers, ITr.> J . Polym. Diu. (139) Maurer, J. J., Am. Chem. SOC., Sci.. Part A-2. 6. 1683 (1968). 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Chem., 2, 197 (1954). Asbest. Kunststoffe. 20.-608 (1967). (190) Schurz, J., Reference 38, p 317. (147)Molau, G. El, Reference i33, p 245. (191) Screaton, R. M.,Seemann, R. W., (148)Moore, J. C., ibid., p 273. J . Polym. Sci., Part C , 21, 297 (1968). (149)Zbid., Reference 176, p 175. (192) Slade, P. E., Jenkins, L. T., “Tech(150)Moore, W. R.. Tidswell, B. 11.. niques and Rlethods of Polymer EvaluChem. Znd. (London), 1967, p 61. ation,” Marcel Dekker, New York, 1151) Mulder, J. L., Anal. Chim. Acta, 38, N.Y., 1966. 563 11967). (193) Slonaker, I>. F., Combs, R. L., (152) Nabors, L. G., Studebaker, M. L., Coover, H. W.,J . Macromol. Sci., A-1, Rubber Chem. Technol., 40, 1323 (1967). 539 (1967). (153)Nadeau, H. G., (to Upjohn Co.), (194) Smith, D.A., Rubber J . , 150 (4),21 U.S.Patent 3,353,411 (Nov 21, 1967). (1968). (154) Nagasawa, M.; Asai, Y., Sigiura, I., (195) Smith, W.N., J . Appl. Polym. Sei., Polym. Repts., (Japan), 102, 22 (1966). 11, 639 (1967). (155)Okuto, H., Makromol. 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(213) ivales, AI., Reference 133, p 343. (214) Westall, B., Polymer, 9, 243 (1968). (215) Williamson, G. R., J. Polym. Sci., Part A-2, 5 , 394 (1967). (216) Yasuda, S. K., J. Chromatog., 27, 72 (1967).
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Contribution No. 423 from the Research Division, The Goodyear Tire and Rubber Co., Akron, Ohio 44316.
Solid and Gaseous Fuels R . F. Abernethy and 1. G. Walters, Bureau of Mines, U.S. Department of the Interior, Pittsburgh, Pa.
T
in this series on methods of sampling, analyzing, and testing solid mineral and gaseous hydrocarbon fuels have been issued. This one covers the period from October 1966 through September 1968 inclusive, and, except for minor changes, follows the general format of the previous reports. EA- REVIEKS
SOLID FUELS
This section covers ivork done on methods of sampling and chemical and physical testing of coal, coke, and related materials. There are really few innovations and most of the reports consist of refinements in existing procedures to give greater accuracy and saving of testing time. Selected items have been included under the pertinent headings or in the miscellaneous section to supplement standard test methods and to indicate new testing trends. Sampling. Committee D-5 on coal and coke of the American Society for Testing and Materials (ASTAI) has revised t h e standard coal sampling methods, D 271 and D 492, and replaced them with A S T l I Designation D 2234, Sampling of Coal, and MThI Designation D 2013, Preparing Coal Samples for Analysis ( 1A ) The standard sampling procedure covers general purpose or commercial. sampling and special or referee sampling. The sample preparation standard covers the entire procedure from the gross sample to the analysis sample. Proximate Analysis. The proximate analysis of coal measures the moisture, volatile matter, fixed carbon, and ash content. Moisture, volatile matter, and ash are determined by specified procedures. Fixed carbon is calculated by subtracting the sum of the three determined values from 100. Humphreys and Lan rence (1223) used the proximate analysis from a large number of coals to develop control charts for coal preparation plants. Computer results of these analyses were used to determine the ultimate analyses and calorific value from the proximate analyses for plant control ( I S B ) . Hinz (10B) dereloped a procedure of proximate analysis for semimicro sample quantities. I
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ANALYTICAL CHEMISTRY
MOISTURE.Rees (27B) used the twostep ASTM method for total moisture on the petrographic components of coal to show how moisture could be lost in grinding coals for the preparation of the analysis sample. Vapor pressure measurements made by Stewart and Evans (35B) indicated that 40% of the ivater in bron-n coal was bonded to the coal. Viktorin (4OB) used gravimetric methods to establish equivalent moisture contents of four different lignites a t different temperature levels to indicate the binding of the moisture t o the lignite. The N l I R spectra of coals were used by Ladner and Wheatley (BOB)to measure the moisture in all coals regardless of rank, mineral matter content, or size less than 6 mm. It is possible t o adopt the principle to a moving stream of coal. Seutrons were employed in slightly different ways for determination of moisture in moving streams of coal and coke. Stewart and Hall (36B) were able to check moisture values within 0.275 in coal moving a t 20 tons/hour. Gee and Laslo (9B) used a neutron gage to measure moisture in coke and automatically make corrections in the weight of material charged to the blast furnace. Egami, Kano, and Semoto ( 7 B ) reported the neutron moisture gage very effective for coke with high moisture content. The total error for coke moisture w s 5 1.6%. Luckers (21B) reported tn-0 years of stable and reliable performance of a neutron probe used in measuring moisture in a coke bin. The standard deviation was 0.550.60%. Chernyshov and Gruzintsev ( 4 B ) described apparatus to measure continuously the moisture in a coal stream on a belt, using a meter to register the dielectric properties of coal. Industrial tests over a tno-year period showed that 977, of all determinations fell within & 0.5% of values by the national standard. Kersting (14B) discussed the factors involved in measuring the moisture in the briquetting stock by the dielectric constant and also by -/-rays from 137Cs. -1summary of ten methods of measuring moisture contents of solids was
prepared by Roth (SIB). I t covers intermittent, continuous, and partially automatic t o completely automatic devices. VOLATILEMATTER. hST?*I Designation D 121 defines volatile matter as follows: “Those products, exclusive of moisture, given off by a material as gas or vapor, determined by definite prescribed methods m-hich may vary according to the nature of the material.” The portion of the statement, “definite prescribed methods,” is intended to show that the method is empirical and t h a t adherence t o specifications is mandatory. Shipley (SdB) reported, in the revision of BS 1016 parts 3 and 4, volatile matter in coal and coke, respectively, that experimental evidence of suitable nature made it possible to reduce the testing temperature from 925 to 900 “C. This change brought the British Standard in line with the recomniendations of Technical Committee 27 on Solid Mineral Fuels of t h e International Organization for Standardization (ISO). The empiric nature of the volatile matter determination has motivated numerous workers to delve into the several factors that influence the pyrolysis of the coal or coke. Zielinski (41B) explored the rate of heating as one of the major factors. Selson, Korrall, and Kalker (26B) conducted experiments under isothermal and nonisothermal conditions on the release of volatile matter from anthracite. Special attention nas given to rate of heating and to particle size. Volatile release was constant IT ith respect to temperature and particles ranging in size from 53 4 to 12 mm. Isothermal tests on rates of H evolution obeyed a logarithmic time law and exhibited a complex dependency upon particle size. A correlation between the volatile matter a n d ash contents was shown b y Kononenko ( I Q B ) from a statibtical evaluation of experimental data. The volatile matter from a specific deposit could be calculated from the ash content. .1study on the discharge of volatile matter on the degasification of a number of coals led Salcewics and Kijeiwka
