(1413) Weyers, J., Skora, XI., Disserta-
tiones Pharm. 14,201-5 (1962); C.A. 57, 16746i(1962). (1414) Wichlinski, L., Trzebinski, J., ilcta Polon. Pharm. 20 ( l ) ,31-34 11963): Anal iibstr. 10., 4875 - - (1963) (1415) Wichtl,-~>I. k., 'Fuchs, L., Arch. Pharm. Berlin 295 (5), 361-373 (1!)6%):Anal. Abstr. 9 , 5395 (1962). (1416) Wichtl, M., Peithner, G., Fiichs, L.. Planta Med. 10. 304-17 (1962): C.A. 58, 10040d (1963). 11417) Wilkie. J. B.. * J . d s s o c . O f i c . Aar. " Chemists 46 Ii),92b-5 (1963). (1418) Wilkomirsky, F. T., RJeier, G. H., Hrieva, A. J., Anales Kea1 Acad. Farm. 28. 14) 311-17 (1962); C.A. 58, 10041d (1963). (1419) Windheuser, J. J., Higuchi, T., J . Pharm. Sei. 51, 354-64 (1962). (1420) Winek, C. L., Beal, J. I,., Cava, AI. P., J . Chromatog. 10 ( 2 ) , 246-247 (1963). (1421) Wisniewski, J. V., Spencer, S. F.. J . Gas Chromatoa. 2 (1). 34-5 , ., (1964). 422) Wisniewski, W., Jablonski, S., Wojtyra, J., Acta Polon. Pharm. 19 (4), 325-32 (1962); C.A. 60, 5 2 7 7 ~ (1964). 423) Wisniewski, W., Pietura, A , , Ibid., 20 ( l ) , 43-51 (1963); Anal. Abstr. 10, 4876 (1963). 424) Wojahn, H., Boll. E., Deut. -4pofheker-Ztg. 100 (50)) 1453-5 (1960); C.,4. 60, 369s (1964). 425) Rojciak, IT.,Wolska, E., M e d . Doswiadczalna Jfickrobiol. 15 ( 3 ) , 25562 (1963);C.A. 6 0 , 3 9 5 2 ~(1964). 426) Wolff, J., J . Pharm. Sei. 52, 93-5 (1'363). 427) Wollenweber, P., J . Chromatog. 7 (4), 557-560 (1962); Anal. .4bstr. 10, 229 (1963). 428) Wollmann, Chr., Schulz, D., Pharm. Praxis, Beilage Pharmazie 1963 ( 7 ) j 128-30; C.=l. 59, 15122~(1963). 429) Xu, Li-Xin, Zhou, Tong-Hui, Acta Chim. Sinica 28 (61, 391-393 (1962);Anal. Abslr. 10,4354 (1963). ~~~
- w
\~
1430) Yalcindag, 0. N., Folia Pharm. (Istanbul) 4 536-40 (1962); C.A. 57, 47623' (1962); 1431) Yamagiichi, K., Ito, XI., J . Pharm. SOC.Japan 81 (2), 179-181 (1961); Anal. Abstr. 9, 4881 (1962). 1432) Yamaguchi, S., Seki, I., Okuda, S., Tsuda, K.,- Chem. Pharm. Bnll. (Tokyo) 10 (8), 155-7 (1962); C..4. 59, 2590a (1963). 1433) Yamamoto, R., Fujisawa, S., Yakugaku Zasshi 82, 1396-9 11962): C.A. 58, 5456c (1963). 1434) Ibid., pp. 1400-4. 1435) Yamamura, J., Kato, K.,Kagaku Keisatsir Kenkyusho Hokoku 15, 223-5 (1962); C.A. 57, 12635~(1962). 1436) Yamana, T., AIizukami, Y., Niikana, Y., AIurakami, Y., Yamamoto, Y., Setokawa, K., Yakuzaigaki/ 23, 72-3 (1963); C..4. 69, 11194a (1963). 1437) Yamana, T., Sato T., Ibz'd., 22, 189-90 (1962); C.A. 5 8 , 8 8 5 5 ~(1963). 1438) Yamanaka, T., A.ai, S., Aoki, J., Arch. Pract. Pharm., Japan 22 ( l ) , 6 6 6 3 (1962): Anal A b s t r . 10, 5300 (1963). (1439) Yamazaki, T., J . Pharm. SOC. Japan 83 (4), 402-405 (1963); Anal. Abstr. 11, 321 (1964). (1440) Yamazaki, T., Yakugaku Zasshi 83, 402-5 (1963); C.A. 59, 2590d (1963). (1441) Yampol'ska, 41. 4I., Farmatsevt. Zh. (Kiev) 18 (5), 8-12 (1963);C.il. 60, 7871d (1964). (1442) Yaskina, D. S., Filichkina, 44. P., iiptechn. DeZo 11 (4),33-6 (1962); C.A. 60, 10478a (1964). 11443) Yates. S. G.. J . Chromatoa. 12 ' (3),'432-6 (1963). ' (1444) Yavors'kii, RI. P., Farmatsevt. Zh. (Kiev) 16 ( 5 ) , 38-44 (1961): C . A . 59, 3829 (1963). (1445) Yoshimura, AI., Deki, >I., Bunseki Kagaku 12 ( l o ) , 941-5 (1963); C.A. 60, 1541b (1964). (1446) Yoshimura, 4I., Deki, 41.) Tsukamoto, H., Yakugaku Zasshi 83, 223-6 (1963); C . A . 59, 383a (1963).
(1447) Yoshino, T., Seno, A., Sugihara, RI., J . Pharm. Soc. Japan 80 (lo), 1484-1486 (1960); Anal. Abstr. 9, 4454 11962). (1448) Yoshino, T., Seno, A., Sugihara, R l . , Kagaku T o Kogyo (Osaka) 36, 404-9 (1962); C.A. 58,2475f(1963). (1449) Yung, D. K., Pernarowki, AI., J . Pharm. Sci. 52 (41,365-370 (1963). (1450) Zabrak, I]., Zoltai, L., ilcta Pharm. Hung. 33 (51, 206-11 (1963); C . A . 60. 670% 11964). (1451) Zachari&,'R. i I . , Talky, E. A , , J . Chromatog. 7, 51-55 (1962). (1452) Zaitsev, Y. A . , Sb. Sauchn. Tr. Tsentr. dplechn. Salichn.-Issled. Inst. 2, 101-13 (1961); C.A. 58, 1 3 0 4 ~(1963). (1453) Zajta, E., Acta Pharm. Hung. 32, 129-39 (1962); C.A. 57,4772d (1962). (1454) Zak, B.. Cohen, J. S.,J . Pharm. S C ~ 52 . (Y), 912-14 (1963); C..4. 59, 1 3 7 7 0 ~(1963). (1455) Zalai, K., Gyogyszereszet 5, 214-16 (1961); C . A . 60, 52809 (1964). (1456) Zaputryaev, B. A., Sil'vestrova, T. E., M e d . Prom. SSSK 17 (8), 37-9 (1963);C.d. 60, 369e (1964). (1457) Zarnack, J., Pfeifer, S.,Pharmazie 17, 431-6 (1962); C.A. 58, 3 2 7 1 ~ (1963). (1458) Zarnack, J., Pfeifer, S., Zbid., 19 (2), 111-23 (1964); C.A. 60, 10477~ (1964). (1459) Zathurecky, L., Bauerova, O., Somoskeoy, G., Molnar, L., Suchy, S., Ceskosl. Farm. 12 (4), 171-177 (1963); Anal. Abstr. 11, 1893 (1964). 01460) Zinner, G., Deucker, W., 3 a turwissenschaften 49 113). 300 11962): ,, Anal. Abstr. io, 1061 (1963). (1461) Zommer, S., Lipiec, T,, Acta Polon. Pharm. 20 (3), 229-232 (1963); Anal. Abstr. 11, 1469 (1964). (1462) Zuch, 1). A., Conine, J. W., J . Pharm. Sei. 52, 59-63 (1963). (1463) I b i d . , pp. 63-6. (1464) Zurkowska, J., Lukasxewski, lI., Ozarowski. A,. Acta Polon. Pharm. 20 ( 2 ) , 115-120 (1963); Anal. Abstr. 11, 744 (194) ~
Rubber Coe W . Wadelin Research Division, Goodyear Tire and Rubber Co., Akron, Ohio
T
the eleventh in a series of review articles on rubber (7-12, 95, 112, 147, 149). The scope has been changed from previous reviews to include only chemical analysis. I n general, rubber has been covered, but not' plastics. For instance, ethylene-propylene rubber is included but not polyethylene or ~iolypropylene. This requires arbitrary choices as the dividing line bet,neen rubber and plastics is not aln-ays clear. The previous policy of including methods for identification or determination of compounding ingredients in rubber but, omit'ting methods dealing wit,h the analysis of the compounding ingredient,s themselves has been continued. The literatlire available to the author from October 1962, t8heend of the period covered by the last review ( I I Z ) , HIS IS
21 4 R
ANALYTICAL CHEMISTRY
443 7 6
through September 1964 is covered. T h e labor of searching was taken over by the information retrieval system in the Technical Information Center of Goodyear's Research Division (60). The thoroughness of this system was checked by manually searching Chemical .4bstracts' subject indexes for Volumes 57, 58, and 59. I n no case was an article missed by the information retrieval system except where the original source was not available to the literature searchers. The system covers only the 350 periodicals received by the Goodyear Research Library but not secondary sources such as Chemical Abstracts and Rubber Abstracts. The section on polymer characterization, while having the most references, is by no means comprehensive. The methods included are mostly chemical
and infrared. It is hoped that subsequent reviews will more adequately cover this area. The abbreviations recommended by ASTM Designation D1418-61T have been used ( 2 ) . They are listed in Table
I.
Table I.
BR IR CR XR IIR XBR SBR I41 EPRI
Abbreviations Recommended by ASTM (2)
Butadiene rubber Isoprene rubber, synthetic Chloroprene rubber Isoprene rubber, natural Isobutylene-isoprene rubber Nitrile-butadiene rubber Styrene-butadiene rubber Polyisobutylene Ethylene-propylene copolymer
GENERAL INFORMATION
The format of ASTM Standards has becn changed so t h a t methods dealing with rubber are now in P a r t 28 (1). In looking for ASTM Methods, one should ienieniber that there are five pertinent de4gnationy I1297 for rubber products, 1>1076 for S R latex. D1278 for crude S R , El1416 for S E R , and D1417 for SUR latex. There have been no changes in t h t v methods since the last reviea. A ne\\ edition of Scott's "Standard Methods of Cheniiral Analysis" contains a section on rubber (156), which i i essentially taken from -4STM Method\. POLYMER IDENTIFICATION
P y rol y sis-G a s C h r o m a t o g r a p h y . There seems to be no general agreement as to the best method for pyrolyzing a sample prior to gas chromatography of the pyrolyzate. It has been shown by several workers that time, temperature, and catalytic conditions, must be carefully controlled for reproducible results. A tubular furnace pac.ked with glass wool and operated a t 700' C. gave relatively few pyrolysis products and therefore simple gas chromatograms (34). Pyrolysis in a quartz capillary for 26 seconds a t 950' C. gave reproducible decomposition to small fragments (62). These conditions were applied to 150 polymers. Polyolefins including E P M were pyrolyzed at 550' C. (154). Only theuncondensable part . of the pyrolyzate was swept onto the gas chromatography column to identify X R , X B R , B R , I I R , C R , or S B R (77, 142). If a cold trap is used to retain heavy materials, styrene will be lost and SBR will be missed. The same materials were pyrolyzed a t 500' C. and identified by their gas chromatograms on squalane, dinonyl phthalate, squalane-dimethyl sulfolane, or dinonyl phthalate-dimethyl sulfolane columns (46). In another procedure, the sample F a $ pyrolyzed a t BOO" C. and only the condensed pyrolyzate was used for gas chromatography (21). Guiochon and Henniker concluded that pyrolysis followed by gas chromatography is rarely adequate for identification (64). When combined with a n infrared spectrum much more can be done. They also pointed out that polyurethanes are not adequately identified by infrared or pyrolysis and gas chromatography. Fillers affect pyrolysis by their catalytic effects. Plasticizers which are not extractable, such as polyesters and polyacrylonitrile, cannot be distinguished from the main polymer by pyrolysis and gas chromatography. The identification of silicone rubber was also reported (45). One of the seemingly simple techniques, namely. pyrolyzing the polymer
directly on a platinum coil, suffers from changes in the temperature of the platinum with each successive pyrolysis. This is due to formation of platinum carbide with a resultant increase in resistance. However, for paint it is convenient to dip a platinum coil into the sample, turn on a small current t o evaporate solvent, and then pyrolyze directly in the carrier gas stream (124). A tungsten filament can be substituted for platinum (139). This may be less prone to change in resistance. Perry has reviewed pyrolysis and gas chromatography and gives many references (115). Infrared. Two reviens o n t h e use of infrared spectra to identiiy rubber have appeared (47, 110). For ra\\ polymers, a film cast from a solution I C recommended. Cured samples are pyrolyzed with both the liquid and gaseous pyrolyzates being examined. Carbon black-filled vulcanizates were swelled in methyl cyclohexane before cutting 2-micron sections (32). Their spectra can be used to' identify both polyme: and inorganic fillers. The technique is not universally applicable. For example, CR and Y B R are not swollen by methyl cyclohexane. I t is also inapplicable to oil-extended rubber. Others workers prepared microtome sections by first freezing the sample (64, 141). A technique was described for making KBr pellets of polymers including N R - ' a n d CR (152). Attenuated total reflectance was used to identify N R , N3R, I I R , and S B R filled with clay or C a C 0 3 (70). The spectra of 13R, poly (methylbutadiene), and poly (dimethylbutadiene) have been published (30). The spectra of a number of polymers and frequency assignments for CH,, CH3, aromatic CH, S H , C=O, O H , and OOH in the 1.0- to 2.7micron region were published (51). They were all studied as films except IAI which was in carbon tetrachloride solution. The spectra of polymer filins on rock salt plates were recorded before and after exposure to ammonia, hydrogen chloride, and bromine (20). The changes can be used to identify functional groups. For example, carboxylic acids are' converted to ammonium salts and carbon-carbon double bonds are brominated. In SBR, the phenyl ring is also brominated. M a s s Spectrometry. Phillips pyrolyzed rubber in a n arc image furnace for 2 seconds a t 3300" C. (116). Under these conditions there is a high yield of monomer. The relative amounts of butadiene, acrylonitrile, styrene, and isoprene shown by the mass spectrum of the pyrolysis gas can be used to identify SBR, B R , S B R , and N R . I t is valuable to examine both the gaseous and liquid pyrolyzates by mass spectra (69). The liquid portion contains some high boiling pyrolysis products which would
be missed if only the gaseous part were used. The mechanism of polymer pyrolysis has been studied (3). POLYMER CHARACTERIZATION
General Information. T h e book edited by Ke covers infrared, optical methods, fluorescence, DT.4 (differential thermal analysis), N M R (nuclear magnetic resonance) x-ray and electron diffraction, column fractionation, and other- techniques (81). The use of infrared spect,roscopy in det,ermining tacticity and orientation was discussed (164). Slonim concluded t,hat S M R should not be used alone, but rather in conjunction with other physical and chemical methods (135). The use of KMR, infrared, and chemical reactivity in the charact,erization of stereoregular polymers (6) and the applicatim of DTA to polymers were reviewed (101). Gas chromatograms of the products of pyrolysis for 15-second intervals a t successively increasing temperatures result in a fingerprint' of the polymer ( 5 ) . I n general, block copolymers can be differentiated from random copclymers. NR and IR. Binder used polarization spectra, maleic anhydride adducts, a n d hydrogenation products t o make band assignments in t h e infrared spectra of polyisoprene (14). The infrared spectrum of polyisoprene containing 75'34 cis-1,4 and 2074 trans-1,4 structures was found to be different from that of a mixture of 80% hevea and 20% balata, which are 1 0 0 ~cis-1,4 o and 1 0 0 ~ c trans-1,4, respectively (85). The bands at 1130 and 1150 cm.-l appear only in long sequences of cis-1,4 and trans-l,4, respectively. This phenomenon may be useful in distinguishing mixtures of the two polymers from a pclymer in which the st'ructures are randomly distributed. Consequently, t'he 572 cm.-I band for determination of cis-1,4, 980 cm.-l for trans-1,4, and 888 em.-' for 3,4 are preferred for determination of overall composit'ioii. Schmalz and Geiseler, however, used the 840, 890, 910, 1130, and 1150 cm.-l bands to determine 1,2-, 3,4-, ~ i s - 1 ~ 4and , t,rans-1,4, structures (127). When the 2965 em.-' band was used for cis-1,4, t,he trans-1,4 was found by subtracting 1,2- and cis-1,4 from the total unsaturat,ion found chemically (109). The cis-1,4 is found to *37,,. After subt,racting out the contribution of the 3,4- st,ructure, found from the 890 cm.-l band, the 1415 and 1423 cm.-l bands were used to determine t ~ a n s - 1 ~and 4 cis-1,4 (31). Kinet'ics of the reaction with perbenzoic acid have been used to establish infrared calibrations (127). Chen used high resolution S M R t,o measure the shifts in the met,hyl p r o t w s and thereby to determine ~is-1~4, trans1,4,and 3,4- structures but not 1,2( 2 7 ) . These measurements can be ~
VOL. 37, NO. 5, APRIL 1965
215 R
combined with N M R measurements of different types of protons (26) or infrared to get a complete structural analysis. The cis-1,4 and trans-1,4 measurements are accurate to 0.5% and the 1,2- and 3,4- to 2 to 3%. S R I R was considered to be more accurate than infrared ( 5 7 ) . As little as 0.3yG 3,4- and 1% trans-1,4 in high cis-1,4 polymer and 1% cis-1,4 in high trans-1,4 polymer could be detected. Golub, Fuqua, and Bhacca detected no cis-1,4 in balata and no trans-1,4 in hevea. Therefore, they concluded that each contains more than 99% of its nominal structure (57). Chakravarty, Hanerjee, and Sircar, on the other hand, isolated formic acid from the ozonolysis products of hevea (25), confirming the presence of 2.5yo 3,4- structure reported by Binder and Ransaw (16 ) . The amount of methanol required to cause precipitation in a carbon tetrachloride solution of polyisoprene degraded by perbenzoic acid was used to determine the 3,4- (or 1,2-) content (75). BR. Binder also assigned infrared absorption bands of B R based on polarization spectra, hydrogenated BR, maleic anhydride adducts, a n d isomerization experiments (15). One CS2 solution' was used to measure cis1,4 and 1,2- structures and another of different concentration to measure trans1,4 and 1,2- by infrared absorption ( I S ) . The 1,2- values were compared to see if the results were compatible. In this way both cis-1,4 and trans-1,4 could be measured in their optimum per cent transmission ranges regardless of the composition of the sample. The 724 em.-' band was used for cis-l,4, 967 cm.-' for trans-1,4, and 911 cm.-' for 1,2-. Results from films cast from 4Y0 solutions in benzene are less sensitive to gel content than measurements in solution ( 7 9 ) . In high cis-1,4 polymers the trans-1 ,4 was measured by the absorbance ratio of the 966 em.-' band to the 1440 cm.-' band and 1,2- was measured by the ratio of 912 em.-' to 1440 em.-' Both calibration curves were linear. Cis-1,4 was then determined by subtracting the sum of these from 100%. This avoids the errors in making a direct spectrophotometric measurement of a component a t the 95% level but introduces the assumption that the sample is composed exclusively of the three structures mentioned above. A more reliable way to avoid the dependence on a spectrophotometric measurement of a component a t the 957c level is to subtract the 1,2- and trans-1,4 content from the total unsaturation found by iodine chloride (84) or iodine bromide (93) addition. These measurements of unsaturation can be quite good if carried out with due regard to choice of solvent and corrections for splitting out and substitution ( 9 2 ) .
216 R
ANALYTICAL CHEMISTRY
Calibration for the 1,2- content can be made by kinetic studies with perbenzoic acid ( 8 4 ) . Cis-1,4 and trans-1,4 are not differentiated as their rates are nearly the same. Calibration for both 1,2-, and trans-1,4 has been made from sodium polybutadiene which contains no cis-1,4 (93). Aldehydes, ketones, 1,a-addition and trans-1,4 structure were found in butadiene popcorn polymer by its infrared spectrum in KBr pellets (106). The method of determining 1,2addition by measuring the amount of methanol required to precipitate a polymer solution after reaction with perbenzoic acid n a s also applied to B R ( 7 5 ) . The sensitivity is less than in N R and I R . SBR. T h e cis-1,4 butadiene content can be found from the absorption band a t 740 em.-' or by subtracting the 1,2- (910 em.-') and trans-1,4 (965 cm.-l) contents from total unsaturation found by iodine chloride addition ( 8 4 ) . The styrene content found from the 700 cm.-l band can be used as a check on the total unsaturation determination. K M R was used to determine styrene, 1,2- addition, and 1,4- addition (130). CCl, solutions containing (CH3)8i as internal standard were used. EPM. Infrared studies have led to general agreement on the assignment of bands in the 815 to 720 em.-' region. The 815 em.-' band is assigned to an isolated methylene group, 752 em.-' to groups of two, 733 cm.-' to groups of three, 726 em.-' to four, and 722 em.-' to five (24, 67, 68, 107, 151). Model compounds (24) and hydrogenated K R (151) have been used to establish this. These bands can be used to distinguish block copolymers from random copolymers (67, 68). Mixtures of homopolymers are like block copolymers and polyallomers. The 1154 cm.-l band is due to methyl groups on alternating carbon atoms (40, 97, 151). The absorbance ratio 752 crn.-'/1156 em.-' can lead to inferences about the catalyst system used. Trialkyl aluminum with VCl, or TiC13 gives all head to tail addition of propylene while alkyl aluminum sesquichloride with voc13 or VO(OR)s gives some tail to tail addition (151). E P M containing less than 75% ethylene leaves no residue on extraction with acetone, ether, hexane, or heptane while in mixtures of homopolymers, polyethylene is left undissolved (107). Gas chromatography of pyrolysis products gives patterns which are similar for block copolymers and mixtures of homopolymers but different from ran dom copolymers ( 5 , 6 4 ) . IM. Infrared and S M R were used to show t h a t polymer made with 13F3 catalyst has the same gem-dimethyl structure as that made by Ziegler catalysis (4). Ultraviolet and infrared spectra were used to show that irradia-
tion by 4 m.e.v. electrons produced t-butyl, 1,l-dialkyl ethylene, 1,1,2-trialkyl ethylene, 1,1,2-trialkyl ethane, and conjugated diene structures (73). NBR. T h e same bands used in B R , cis-1,4 a t 724 ern.-', trans-1,4 a t 967 em.-', and 1,2- a t 911 em.-', were used t o measure these structures in N B R (76). The need was pointed out for making the system as simple as possible extracting with ether or methanol before pyrolysis or infrared. CR. T h e cis-1,4 and trans-1,4 content was determined by means of the 1652 and 1660 em.-' bands (43). Spectra was measured in 10% solutions in CHC13 in 0.2-mm. cells. Reproducibility is *5%. Siloxane-Acetylene Polymers. An absorption band a t 2100-2150 em.-' was used to measure Si-H bands, 15951600 em.-' for vinyl, 1625-1635 cm.-l for allyl, and 3050 em.-' for unsymmetrical disubstituted ethylene (117). Piperylene Rubber. Reduction of ozonolysis products to give acetaldehyde and acetic acid made possible the calculation of 1,a-addition (161). Treatment with benzoyl peroxide to form the epoxide followed by reaction with H I to get acetaldehyde confirmed the ozonolysis results. Poly( l-Cyano-1,3-Butadiene). T h e nitrile stretching band in this polymer appears a t 2241 or 2220 cm.-' depending on whether it is attached to a saturated or unsaturated carbon atom (55). Derivatives of IR. Golub and Heller measured the degree of cyclization of polyisoprene by the absorbance ratio of the 833 to the 1380 em.-' bands (58). Lee, Scanlan, and Watson compared the perbenzoic acid, phenyl iododichloride, ozone, and IC1 methods for measuring unsaturation (91). All methods mere consistent except IC1 which gave higher results due to substitution. They preferred perbenzoic acid. The ability to correct for substitution in the IC1 method by measuring the acid produced (92) is too often overlooked. The residual unsaturation in hydrochlorinated cis-1,4 N R and I R and trans-1,4 S R and I R can be determined by high resolution N M R (59). Infrared still is a widely used tool in characterization of polymer structure, although X M R is growing. The constant signal strength of N M R for a given 5tructure gives it a decided advantage over infrared in which each band must be carefully calibrated. DETERMINATION OF POLYMERS I N POLYMER MIXTURES A N D CONSTITUENTS I N COPOLYMERS
SBR. T h e absorbance ratio of the 1639 cm.-' vinyl band and the 1601 em.-' phenyl band was used to determine from 14 to 90% styrene in Sf3R
(157). The succe5s of the method depends on the constant 20% 1,2- addition in emulsion polymerization of but'adiene over a wide range of temperature and but,adiene content. Analysis of polymers made by other methods will require other calibration data. Systems with low 1,2- content would require use of another band for t,he butadiene component. E P M . T h e absorbance ratio of t h e 1150 and 720 em.-' bands was used to determine the et,hylene-propylene ratio (40). According t,o Lomonte, t'he 1154 em.-' band is due to methyl groups on alternate backbone carbon atoms and is applicable to block copolymers and mixtures of polyethylene and polypropylene but not to random copolymers (97). The intensit,y of the 720 em.-' band in a film of fixed thickness a t 180' C. is proportional to ethylene content ( 9 8 ) . The elevated t,emperature eliminates crystallinity effects. The absorbance ratio of the 720 em.-' band to the 1041 rni.-' band was preferred by others (68). The overtone region permits t,he use of thicker films which are easier to handle. The absorbance rat'io of the methyl band a t 1.692 microns to the methylene band a t 1.764 microns is proportional t,o ethylene,/propylene ratio ( 2 3 ) . Corish and Tunnicliffe made a thorough study of several absorbance ratios and found that the ratio of the 1380 em.-' and 1460 em.-' bands in a film a t 120" C. is the best general purpose method for composition (33). The accuracy is il% in the region of 50% ethylene. The method is applicable to random copolymers, block copolymers, and mixt,ures of homopolymers. Samples which are soluble in CCI, can be analyzed by means of the 1380 cm.-l met,hyl band (107). The calibration was done with atact,ic polypropylene. The liquid phase of the pyrolyzate has a vinyl band at, 909 cni.-' and a vinylidene band a t 889 em.-' Their absorbance ratio was used to determine 10 to XI^^ propylene with a standard deviation of 1.35 mole 70( 2 2 ) . The calibrat,ion was based on the nominal compositions of commercial samples, which is a risky foundation on which to base a n analytical method. The pyrolyzate can also be subjected to gas chromatography. Vsing peak height ratios, blends of polyethylene and polypropylene were analyzed to =t370 (62, 154). Ethylenepropylene copolymers give chromatograms different from homopolymer blends of the same overall composition (62). EPM of known composit'ion was made by decomposing known amounts of diazomethane and diazpropane together (SO). This met,hod of synthesis should be useful for making calibration samples. NBR. T h e acrylonitrile content was determined by means of the nitrile band a t 2237 cm.-' with precision of +IyG( 7 6 ) . It, is important to ext,ract
the sample before making the determination. The nitrile content of NBR or t,he XUR cont.ent of polymer mixtures can be found from t'he nit,rogen content determined by the Kjeldahl or Dumas method ( 7 6 ) . In the latter application, the nitrile content of the K B R must be known. Of course, other nitrogen-cont,aining materials must be absent, or removed by extraction. Polyurethanes. Polyester urethanes were broken down by saponification (128)). The sodium salt was converted to free acid on an ion exchange column and the acid was titrated. The poly01 was determined by the periodate or permanganate method. The amines were converted to diazonium salts and measured colorimetrically. Trimethylol propane was isolated by treatment of the polyurethane with phenet'hyl amine, converted t'o the triacetate, and measured by gas chromatography with precision of 1 3 % relative a t the 1% level (159).
Butadiene-1,3-Pentadiene
Co-
polymers. Infrared spectra of carbon tetrachloride solutions have bands a t 1377 em.-' due t,o 1,2-pentadiene addition, 1371 cm.-' due to 1,4-pentadiene addit,ioii, and at' 1355 em.-' due to 1,4butadiene (I 19). Analysis by means of these bands agrees with radioactivity measurements on copolymers cont'aining 0-40 mole % tagged 1,3-pent'adiene. 1 - Pentene - 4 - Methyl - 1 - Pent e n e Copolymers. This polymer gives only a low yield of the starting monomers upon pyrolysis. However, mass spect,ra of the pyrolyzate can be used to determine the composit'ion (155). S B R / N R . Further s t u d y (94) of pyrolysis followed by infrared measurement (148) showed that the absorbance ratio of bands at' 889 and 909 em. was a function of the vulcanization recipe when pyrolysis was done a t 550' C. However, when t h e temperature was increased to 950" C., six different curing systems gave variations of only i1.3% ( 9 4 ) . The liquid and gaseous portions of the pyrolyzate obtained a t 600' C. were combined in cyclohexane and the absorbance was measured a t 697 em.-' to find the SBR content (44). An attempted calibration by mixing varied proportions of pyrolyzates of t.he two pure homopolymers gave results too high for SI3R by 10%. When calibration was based on pyrolysis of known mixtures results were accurate to +2% in the range from 5 to 95% S B R . The gaseous portion of the pyrolyzate obt,ained in a n arc image furnace was analyzed by mass spectrometry (116). The ratio of the sum of the heights of the 53 and 54 mass number peaks to t,he sum of the heights of the peaks a t 68 and 104 was correlated with composition. This method also was applied to 13R/ S R and S B R / E R mixtures.
NR;NBR. This mixture in a cured, filled covulcanizate was analyzed for total polymer by subtracting the sum of acetone, CHCl,, a n d alcoholic K O H extracts, sulfur, ash, a n d carbon black from 100% according t,o .%3TX4 D297-61T ( 1 , 53). The Y R was then found by chromic acid oxidation ( I ) . The N B R remaining was accurate t o 2y0. From the nitrogen content the acrylonitrile, but'adiene ratio of the S I < R can be found. DETERMINATION OF RUBBER
S R in hevea brasiliensis leaves was determined by measuring the unsaturation of the benzene extract (102). The extract was treated with bromine generated from KBr, Kh'Oa, and HC1, then the excess was measured by adding KI and S a 2 S 2 0 3and backtitrating with iodine. The amount of rubber was calculated with a n empirical factor. The coefficient of variation was 1.53%. Interferences can be removed rapidly by extractions with ethanol and water (104). Rubber in rubber-bit,umen mixtures was determined from the iodine value of the acetone-insoluble portion (144). A sample of the unrubberized bit,umen must' be available to est'ablish a correct,ion factor for its iodine value. I N in cured, filled stocks was det'ermined by solubilizing the polymer wit'h nitric acid (19). The polymer was then extracted with prt'roleuni ether and CHCl,, precipitated with ether, dried, and weighed. This is similar to the method of Kress (86). UNSATURATION
The unsaturation in the side chains of 1,2- units in piperylene rubber was calculated from the amounts of acetic acid and acetaldehyde in the ozonolysis products (161). Ozonization was carried out in CHC13 a t -40' C. and reduction was conducted catalytically with P d on CaC03. In a n alternative method, acetaldehyde was obtained by reacting an epoxide of piperylene rubber with HI. The epoxide was formed by the oxidation of the rubber with benzoyl peroxide. Good agreement of the results is claimed. Ozonolysis was applied to B R to determine the amounts of 1,2- and 1,4units (160), and it was also used to determine the unsaturation of S B R (138). Ozonolysis of I I R was carried out in the presence of dibutyl sulfide to prevent attack on carbon-carbon single bonds (100). Unsaturation in E P M containing cyclooctadiene was determined by ozonization of the double bonds and spectrophotometric measurement of the active oyygen (55). The ozonized solution was treated with the leuco base of malachite green to form the corresponding dye, or VOL. 37, NO. 5, APRIL 1965
217R
'
treated with for subsequent determination of free iodine. Halogenation a i t h IC1 mas used to determine unsaturation in NBR (76) and in high impact polystyrene ( 3 5 ) . The samples were treated with CHC13 and IC1 and the excess IC1 was determined. Unsaturation below 0.5 mole Yo in I I R was investigated successfully by the use of radioactive chlorine (99). Two atoms of chlorine were incorporated in the polymer for each double bond originally present. CC1, was used as the solvent.
propane, or cyclohexanone and injecting the solution into a gas chromatograph (158). The first t u o reagents remove the water by reacting with it. Free styrene or a-methyl styrene in copolymers with butadiene was determined with accuracy of +47, by measuring the ultraviolet spectrum of the isooctane, octane, heptane, or petroleum ether extract (39). CURING AGENTS
Sulfenamide accelerators in extract's of vulcanizates were identified by exdraction of the rubber with a mixture of The free sulfur content of SBR latex CCla and methanol, treatment of the was determined by reaction of sulfur extract with chlorine water to form with Na2S03and by iodine titration of amine hydrochlorides, paper chromathe Na2S203 formed (83). Accuracy tography of the amine hydrochlorides is 0,02y0 on a 0.05-g. sample. -4 using acet.ic acid-water solution as the method developed for the determination eluent, and identification of the various of sulfides present in vulcanized rubber amine hydrochlorides (72). The compounds consists of treatment of the met,fiod was applied to extracts of rubber with HC1 in a COS atmosphere vulcanizates cont.aining t'he sulfenato liberate H2S, absorption of the H2S mides of morpholine, diethyl amine, in cadmium acetate, treatment with cpclohexyl amine, t-octyl amine, iodine, and back-titration with iYa2SL03 and t-butyl amine. Rubber accelera(90). The free sulfur content of C R \\as tors of the t'hiurani series were also obtained by measuring the polarogram identified by paper chromatography of the acetone extract in a solution of (118). sodium acetate in 1 : l methanol and Tetramethyl and tetraethyl t,hiuram acetic acid (146). In another method, mono- and disulfides alone and in mixcathode ray polarography was applied tures in amounts of 3 to 5 fig. were to ethyl acetate and isopropyl alcohol ex- determined by paper st,rip and circular tracts of rubber, as well as to rubber paper chromatography using acetic acidsolutions prepared with CHC13 (150). water solut,ion as the mobile phase. Methanol was used as the base electro- Spots of mercapt'obenzothiazole in paper lyte. The mean value of 10 measure- chroniat'ograms of acetone extracts were ments was 0.3070, with a standard developed with saturated 13i(S03)3 deviation of 0.01%. solution, cut out, and weighed for Alterations in unsaturation during quantitative measurements (141). cure of cis-IR were followed by changes Benzothiazyl disulfide was determined in the infrared absorption spectra (38). by reduction 60 mercaptobenzothiazole Decrease in the intensity of absorption prior to the chromatographic ~~rocess. a t 840 em.-' was interpreted as de- The average errors were 15 and 207& crease in unsaturation during cure. The respectively. resulting sulfide bonds were investiQuantitative chromatographic sepgated from data in the ultraviolet region. aration of sulfur from dimorpholinyl The mechanism of sulfur-rubber reac- disulfide and tetramethylthiuram dition during vulcanization of cis-IR and sulfide accelerators in vulcanizates was -BR was investigated by studying the carried out by toluene elution of tagged infrared spectra of vulcanizates (133). sulfur from a column of alumina (114). The occurrence of absorption a t 962 The radioactive fraction was measured cm.-l was attributed to the formation of by scintillat,ion counting with accuracy cyclic sulfides and ne\% conjugated of 157,. Acet'one extracts were also double bonds. The determination of separated on silica gel columns (37). the free sulfur content of natural rubber The fract.ions were examined under ult,ravulcanizates was carried out by measur- violet radiation or by chemical tests. ing the luminescence intensity of vulEthanol extrack of S R , SUR, S B R , canizates as a function of the time of CR, and IIR containing diazoaminocure (122). benzene, benzothiazyl disulfide, tetraReplica electron microscopy was used methylthiuram disulfide, and mercaptofor the examination of the fracture sur- benzot,hiazole were analyzed in the face of compounded synthetic rubbers ult,raviolet, region (132). The content to identify sulfur and other compound- of the ingredient's was determined by ing ingredients (120). comiiarinz suect'ra of extracts of uncured rubber mixes and their vulcanRESIDUAL MONOMERS izates. Mercai)tobenzothiazole and -1general method for residual mono- benzothiazolesulfenamides were detected mers in latex involves dissolving the by comparing the spectra of untreated latex in acetic anhydride, 2,2-dimethouy- rubber extracts with those treated with SULFUR A N D SULFIDES
I
21 8 R
ANALYTICAL CHEMISTRY
L
A
KH3 and hydrogen, respectively (96). Sulfur was identified by comparing the spectra of extracts treated with Sa13H4 and NH8. Examinat'ion of the fracture surface of compounded, unvulcanized rubber stocks by electron microscopy provides information on distinctive crystal habits of major compounding materials. The method was used to identify benzothiazyl disulfide, cyclohexyl benzothiazyl sulfenamide, and sulfur in SI3R (120). Mercaptobenzothiazole was determined by titrating the extract of a vulcanizate or a n uncured rubber mix with iodine or .igS03 to an ampero-' metric end point (61). Titration with dg?;Os was conducted by adding a n excess to the est,ract and back-titrat,ing the unreacted silver with a solution of XaC1. This prevent,ed the adsorption of mercaptobenzothiazole on the precipitate. STABILIZERS
Identification. The superiority of separating an extract before attempting to identify stabilizers was poinbed out by Fiorenza, Ijonomi, and Piacentini (48). The additional dat,um of a n R value from a chromatographic separation plus the availability of a relatively pure sample makes the effort worthwhile. The high absorptivities in the ultraviolet region make possible the examination of small amounts of matmerial. This is an advantage over infrared in stabilizer ident,ification. p - Phenylenediamine and several of its alkyl and aryl derivat8iveswere identified by paper chromatography of extracts (71). Fractions eluted from alumina or silica gel columns were examined by fluorescence under ultraviolet irradiation or chemical tests for identification (37). Paper elkctrophoresis was used to separate the azo dyes formed by treating the acetone extract of a vulcanizate with diazotized sulfanilic acid (125, 126). hldehyde-amine accelerators interfere. Some phenolic stabilizers are not' separat,ed by this method. The visible spectra of 23 stabilizers treated with 3methyl-2-benzothiazolone hydrazone hydrochloride and FeC13 were published for use in identificat.ion (87). Paper chromatography is also helpful, although many of the derivatives have the same R , value (88). If the stabilizers expected can be restricted to a limited number as in raw SBR, rapid color tests can be used. iYPhenyl-2-naphthylaniine, acetone-diphenylamine condensation product, styrenat,ed phenol, alkylated diphenylamine, and tris(nonylpheny1) phosphite can be distinguished in 15 minutes (113). Color t,ests are not very selective and the results should not be considered infallible.
New stabilizers are appearing constantly and, for positive ident,ification, the unknown must be isolated and comp r c d with a known saniljle, preferably by inore t>han one physic-a1 property. Color tests for .\--i)henyl-2-naphthy1amine; 1~oly(2,2,4-trimethyl-1,2-dihydroquinoline) ; S-cyclohexyl-S'-ljheri~-lI.'-l)henylc~nedianiine;niercaptobenzoiinidazole; styrenated phenol; nonylated cresol : and acetone-diphenylamine condensation product Ivere also reported (131). I-ltraviolet sljectra of extract's were also used for identification (132). .Again. the lack of l)reliminary separation can result in missing const,ituents of mixtures. Ident,ificat'ion of stabilizers in oil-pstended rubber without separation from t,he oil is out' of t,he question ( 52) . Determination. Fluorescence a n d phosljhorescence were used to determine 0.01 %, ,Y-phenyl-2-napht~hylamine; ]joIy(2,2,4 - trimethyl - 1,2 - dihydroquirio line) ; and 2 2 '-dimet hy1-5,5'-di-tbut>-1 - 4,4' - dihydroxy - disulfide in 7,polymer (41). cements containing 5 This method is also applicable to t,hin films. It is rapid, for no ext,ract,ion is needed. .Y>.\-' - Diphenyl - p - phenylenediamin? and -Y-phenyll-2-napht,hylamine werc determined in the presence of each ot,her by the visible spectra of their 3methyl-2-benzothiazolone hydrazone hydrochlorides (87). The derivatives made by coupling st,abilizers with diazotized p-nitroaniline were measured colorinietricall>- (64). This method is satisfartory for determination if the identity of the stabilizer is known, but the spectra are not' specific enough for identification. Couljling with the diazonium salt of sulfanilic acid was also used to form colored products (162). Tris(nony1phenyl) phosphite was det,ermined by and measurement' a t 296 nifi e and neut,ral media (131). This is similar to the method of Y a w konski (108). Free radicals generat'ed from 2,4,6tri-t-butyl phenol were used to titrate 2,6 - di - t - butyl - CY - dimethylaminop-cresol and 2,3-dimethyl tetramethylene-4',4''-dipyrocatechol (111). This method should be generally applicable to determination of stabilizers. FREE C A R B O N
A factor was determined to correct the error caused by the presence of residual ash, carbonization of the polymer, and dry diqtillation of organic matter in the combustion method, eliminating the need for concurrent use of a standard sample (146). Carbon black in vulcanized I I R i\as determined by decomposing the rubber, extracting the polynier, drying and igniting the residue, and
weighing before and after ignition (29). Quantitative determination of carbon black in rubber was also done by measuring the luminescence intensity of a crude rubber mixture as a function of its carbon black content (114). A review was presented on published information about quantitative determination of carbon black in vulcanized and unvulcanized rubber stocks which included a discussion of the most commonly used methods-i.e., pyrolysis, nitric acid, high-boiling solvents, and p-dichlorobenzene (49). METALS
EDTA Titration. T h e convenience of EIlT.1 [ (ethylenedinitrilotraacetic acid) ] titration combined with preliminary separation has continued to produce improved methods for metals. This is exemplified by t h e work of Blenkin, who devised a scheme for Ca, X g , Zn present as ZnO, Zn pre\ent as ZnS, Fe, and E a , all by titration with E D T A ( 1 7 ) . T h e sample was first ashed, a t a temperature lower than 600" C. to avoid conversion of ZnS to ZnO. The ash was treated a i t h N acetic acid to dissolve out Ca and h l g not present as silicates, and Zn present as ZnO. One aliquot was titrated a t p H 6.8 for Zn present as ZnO, then the p H was increased to titrate the sum of Ca and Mg. Another aliquot was titrated a t p H 11.5 for Ca only. Xlg was calculated by difference. The residue insoluble in S acetic acid was treated with H202to dissolve ZnS and convert it to ZnS0,. The Zn in this portion was then titrated a t p H 10. The remaining insoluble residue was fused in KaOH and the fusion mass was dissolved in HC1. I n one aliquot, Fe was titrated a t p H 4.5. Excess E D T h \vas then added and back-titrated with A1 to measure X1. Other aliquots of this solution were then titrated as before t o find the Ca and 1 I g which didn't dissolve in Ar acetic acid because they were present as silicates. F e and ill were masked with triethanolamine in the Ca plus M g and Ca titrations. A fresh portion of ash was dissolved in concentrated H&04 and poured into water to precipitate Ba as BaS04. The precipitate was dissolved in excess ammonium salt of E D T A and the excess was back-titrated with M g a t p H 10. Care must be exercised in this method, for success is based on selective dissolution of various groups of materials from the ash. Occlusion could cause some materials to be missed or t o appear in the wrong place. I n another approach the ash is treated with hot 1 : 1 HC1 to dissolve i l l , Fe, Ca, Xlg, and Zn (153). A1 and F e are precipitated with N H 4 0 H . The filtrate is made 2 5 in HC1 to put Zn into the tetrachlorozincate anion. T h e solution
is then passed through a polyamine anion exchange column where Zn is retained while Ca and M g pass through. Ca plus M g are titrated a t p H 10 and C a a t pH 12, as above. Zn is then eluted with water and titrated at p H 10. The ",OH precipitate is dissolved in HC1 and F e is titrated at p H 1.0. Excess EDTA\ is added t'o complex X1, the p H is adjusted to 4.8 to 6, and the excess E D T A is back-titrated with Fe. If much AI and F e are present the S H , O H precipitation is avoided to prevent loss of Zn, Ca, and h l g by coprecipitation. Then, after Zn is removed on the anion exchange column, A1 and F e are masked with triethanolamine during titration of Ca plus Mg. Ca alone is titrated in sugar solution. d l and F e are titrated in the presence of Ca and M g by the procedure outlined above. Ca and M g do not interfere a t t h e low pH. An alternative route, after removal of the S H 4 0 H precipitate, is to titrate a n aliquot for Zn plus Ca plus M g at p H 10. Then Zn is precipitated as the sulfide in another aliquot (18). After that, Ca plus 1 I g and Ca are titrated as above. The S H 4 0 H precipitate is dissolved in HCl and titrated in strongly acid solution for Fe. Excess E D T A is added to complex -ill t h e p H is increased t o 4.8, and the excess is back-titrated with F e to measure Al. This method gave good agreement with the oxalate method for Ca, the magnesium ammonium phosphate method for M g , and the ferrocyanide method for Zn. T h e titration of Zn in the presence of Fe was accomplished a t pH 4.5 by masking F e mit'h fluoride (205). F e alone, Ca alone, or XIg alone did not interfere. Films of carboxylated rubber were dissolved in oleic acid and t h e metal attached to the carboxyl group was extracted with boiling 3 S HC1 (89). Then Ca, M g j h l , C r ( I I I ) , or Ba was titrated with E D T A . Other Titrimetric Methods. T h e silica filler in silicone rubber can be selectively dissolved by HF, K F , and HC1 at 50" C. (163). K2SiF6 is then precipitated by adding ethanol and the precipitate is titrated with 0 . 5 S KOH. I n another method, total silicon is precipitated as quinoline molybdosilicate, which is titrated with S a O H ( 1 7 ) . Colorimetric Methods. EPM was analyzed for vanadium by the 3,3'-diaminobenzidine method (133, which agreed with neutron activation analysis. Silicone polymers were treated with HClO, and HF to remove Si ( 5 2 ) . illiquots of the resulting solution were analyzed for Fe with 2,2'-bipyridine and for A1 with 8-hydroxyquinoline. T h e leaves of Hevea brasiliensis were digested with H S O I , H2S04,and HClO, (103). The p H was adjust'ed to 2.8 to 3.0 and the iron (111) 8-hydroxyquinolate was extracted into CHC1, leaving AI in the aqueous phase. F e was measured VOL. 37, NO. 5, APRIL 1965
219 R
at 470 mp with accuracy of 1.0%. The p H of the aqueous solution was then increased to 5.5 and the A1 %hydroxyquinolate was extracted into CHCl,. was measured a t 385 mp with accuracy of 1.4%. Ti was determined by dissolving t h e ash in HzS04 and measuring its peroxide complex colorimetrically ( 17 ) . Activation Analysis. This method avoids the laborious task of decomposing the organic part of the sample by ashing or wet digestion. I n addition, very high sensitivity is obtained. For example, short-lived nuclides were used to determine Ti to 5 p.p.b., A1 to 1 p.p.b., and CI to 10 p.p.b. in rubber made with Ziegler catalyst (29,63). X-Ray Fluorescence. Ziegler catalyst residues were also determined by x-ray fluorescence (137). The precision a t levels of less than 150 p.1i.m. was 4 p.p.m, for Ti, 9 p.p.m. for A1, 40 p.p.m. for C1, and 2 p.1i.m. for Fe. Emission Spectrometry. T h e ash of rubber samples was dissolved in HCl or HC1 and H S 0 3 and t h e acid was subjected to spark excitation (66). Fe wa5 determined to *O.Ol% in the range 0.01 t o 0.25%, RIn to O . O O S ~ Oin the range 0.008 to O.lyO, and Cu to 0.01% in the range 0.01 to 0.15%. Polarography. T h e ash of the rubber sample was leached with water, and S a , K, or Li was determined polarographically using (CH?)&I as the supporting electrolyte (143). Ultrasound Adsorption. TiOn was determined by exposing the sample to ultrasound and measuring the heat rise of the sample (4.2). Gravimetry. Total silicon in silicone rubber was determined by acid digestion of the sample followed by precipitation and weighing of Si02 (163). Alternatively, the precipitate can be weighed in P t , treated with HF, and the residue reweighed to correct for materials other than SiOn in the precipitate. If TI is present, (NH&S04 must be added during digestion to prevent contamination of the precipitate by TiO?. HALOGENS
TWOmethods were developed for determining the fluorine content of polymers (66). In one, complexing of fluoride ion by a standard solution of aluminum was followed by potentiometric titration of t h e excess aluminum ion with S a F using aluminum-nichrome electrodes. In the other, HF was formed as a result of ion exchange with a strongly acid resin and titrated with alkali, The accuracy of determination by both methods is +0.4yc in the range 35-7576. ORGANIC ACIDS
A procedure used to determine free stearic acid in sodium BR and in SBR comprises extraction of the rubber with 220R
ANALYTICAL CHEMISTRY
acetone and polarographic analysis of the extract in LiCl (221). Relative accuracy of the method is +8%. Determination of free methacrylic adid in butadiene-styrene-methacrylic acid terpolymer latex was conducted by subjecting the latex to polarographic analysis in a n aqueous solution of (CHa)&I (121). Carboxylic acid and carboxylate groups in polymers were detected by comparing the infrared spectra of untreated films of the polymer with those exposed to vapors of NH3 and HC1, respectively (20). Colorimetric determination of sodium dibutylnaphthalene sulfonate in S13R was done by extraction of the rubber with ethanol or CHCL and formation of color with methylene blue (78). WATER
Moisture content of polycarbonates, polyesters, and polyurethanes was determined in a vacuum system by condensing the moisture and volatiles in a liquid nitrogen trap, re-evaporating, and measuring the pressure. Water was removed by absorption in CaH2,the pressure was remeasured, and water was calculated from the drop in pressure (36). EXTRACTION
A variety of raw polymers and cured stocks were extracted with 18 solvents to select one satisfactory for use in the analysis of unknown elastomers (74). Ethanol was the most effective in preventing solubilization of the polymers and in simplifying analysis of the extract. Extraction of plasticizers, accelerators, free sulfur, and stearic acid from I I R was carried out with a n azeotropic 3: 1 mixture of methyl ethyl ketone and ethanol (50). GEL
The gel content of BR, SBR,IR, and N R was determined by dissolving the polymer in benzene, separating the gel from the solution by centrifugation, and weighing the solids isolated from the supernatant liquid (123). LATEX
Latex was treated with monofunctional carbonyl reagents, such as hydroxylamine or 5,5’-dimethyl cyclohexane-1,3-dione to determine the carbonyl content (129). OTHERS
Determination of oxygen in natural and synthetic rubber was carried out with accuracy of 2.8Oj, by nuclear activation (28). Phenyl-aniline-formaldehyde resin in reinforced SBR was determined by extracting the free resin with acetone
and weighing the dried residual rubber (82). Esters were detected by obtaining spectra of a polymer film before and after treatment with K O H in methanol (20). LITERATURE CITED
( l ) , A m . Soc. for Testing and Materials, 1964 Book of ASTM Standards, Part 28,” Philadelphia, 1964. ( 2 ) Zbid., p. 717. (3) Anderson, H. C., J . Polymer Sci., Pt. B 2. 115 11964). (4) Bicskai,‘ R., ’Lapporte, S. J., Ibid., Pt. A 1, 2225 (1963). (5) Barlow, A., Lehrle, R. S.,Robb, J. C., “Tech. of Polymer Sci., No. 17,” p. 267, Gordon and Breach Science Publishers. Inc., New York, 1963. (6} Bawn, C. E. H., Ibid., p. 251. ( 7 ) Bekkedahl, N., ANAL.CHEM.22, 253 (1950). (8) Zbid., 23, 243 (1951). (9) Zbid., 24, 279 (1952). (10) Zbid.. 25. 54 (19533. (11) Bekkedahl, N.: Stiehler, R. D., Zbid., 21,266 (1949). (12) Bekkedahl, N., Tryon, M., Zbid., 27, 589 (1955). (13) Berger, AI., Buckley, D. J., J. Polymer Sci., Pt. A 1, 2945 (1963); Rubber Chem. Technol. 37. 169 (1964). (14) Binder, J. L., J . Polymer Sci.~,Pt. A 1, 37 (1963’1. (15) Ihid.,-p. 47. (16) Binder, J. L., Ransaw, H. C., ANAL. CHEU.29,503 (1957). (17) Blenkin, J., Trans. Inst. Rubber Znd. 40. T123 (1964). (18) ’Bogina,~L. L., Martyukhina, I. P., Kauchuk i Rezdna 20 (lo), 34 (1961); Soviet Rubber Technol. (Eng. transl.) 20 ( l o ) , 27 (1961). (19) Zbid., 22 (12), 50 (1963); C.A. 60, 9447.5 (1964). (20) Brako, F. D., Wexler, A. S.,ANAL. CHEM.35, 1944 (1963). (21) Braun, D., Farbp Lack 69,820 (1963); C.A. 60, 6929d (1964). (22) Brown, J. E., Tryon, RI., Mandel, J., AKAL.CHEM.35, 2172 (1963). (23) Bucci, G., Simonazzi, T., Chim Znd. ( M i l a n ) 44, 262 (1962). (24) Bucci, G., Simonazzi, T., J . Polymer Sci., Pt. C 1964 (7), p. 203. (25) Chakravarty, S. M., Banerjee, D., Sircar, A. K., Trans. Inst. Rubber Ind. 38, T226 (1962). (26) Chen, H. Y., ANAL.CHEM.34, 1134 (1962). (27) Ibid., p. 1793. (28) Chepel. L. V., Chapyzhnikov, B. A., Viting, B. I., Zh. Analit. Khim. 18, 865 (1963); C A 59, 9326e (1963). (29) Chinaplia, B., Ciuffolotti, L., Fasolo, G. B., Malvano, R., Energia h’ucl. (Milan) 9, 503 (1962); C.A. 58, 1901a (1962). (30) Ciampelli, F., Manovicia, I., Gazz. Chim. Ital. 91, 1045 (1961); C . A . 57, 998g (1962): (31) Ciampelh, F., Morero, D., Cambini, hl., Makromol. Chem. 61, 250 (1963). (32) Corish, P. J., J . A p p l . Polymer Sci. 7, 727 (1963). (33) Corish, P. J., Tunnicliffe, 31. E., J . Polymer Sci., Pt. C 1964 (7), p. 187. (34) Cox, B. C., Ellis, B., ANAL. CHEM. 36, 90 (1964). (35) Crompton, T., J . Polymer Sci., Pt. A 1, 347 (1963). (36’1 David. 11. J.. Baumann. G. F.. Steingiser, S., S P E (SOC. P1ast;cs Eng7s.j P. 2. 231 (19621.
Analit. Khim. dkad. .Vauk S S S R , Inst. Geokhim. i Analit. Khim. 13, 191 (1963); C A 59, 7737h (1963). (38) Dogadkin, B. A,, Pavlov, N. N., Rubber Chem. Technol. 36, 262 (1963). (39) Drugov, Y. S., Kauchuk i Rezina 23, ( l ) ,51 (1964); C.A.60, 13417e (1964). (40) Drushel, H. V., Iddings, F. A., ANAL. CHEM.35, 28 (1963). (41) Drushel, H. V., Sommers, A. L., Ibid., 36, 836 (1964). (42) Faerman, V. T., USSR Patent 160,359 (Jan. 16, 1964); C.A. 61, 5806h 11964).
(43) Ferguson, R. C., ANAL. CHEM.36,
2204 (1964). (44) Feuerberg, H., Gross, D., Zimmer, H., Kautschuk Gummi 16,199(1963). (45) Feuerberg, H., Weigel, H., Z. Anal. Chem. 199, 121 (1964); C.A. 60, 5 6 4 1 ~ (1964). (46) Fiorenza, A,, Bonomi, G., Rass. Chim. 15 (5), 197 (1963); C . A . 60,9447d (1964). (47) Fiorenza, A., Bonomi, G., Rubber Chem. Technol. 36.1129 i1963). (48) Fioreriza, A,, Bonomi, G., Piacentini, R., Ibid., p. 1119. (49) Fiorenza, A., Rizzardini, L., Ind. Gomma 7 ( 4 ) , 23 (1963). (50) Ibid., (11), 35(1963). (51) Foster, G. N., Row, S. B., Griskey, R. G., J . Appl. Polymer Sci. 8, 1357 i1964’1. (52) Fujiwara, S.,Narasaki, H., ANAL. CHEM.36,206 (1964). (53) Ganguli, K . K., Chakravarti, A. P., Balakrishna, K . J., J . Sei. Ind. Res. ( I n d i a ) 21 D (2), 58 (1962); C.A. 57, 2384h (1962). (54)Ghosh. A. K.. Sircar. A . K.. J . Indian ‘ Chem. Soc. 39, 60 (1962). (55) Giaririini, U.,Cambini, >I., Cassata, A,, Makromol. Chem. 61, 246 (1963). (56) Giuffre, L., Cassani, F., Chim. Ind. ( N i l a n j 45, 806 (1963); C.A. 59, 7733b (1963). (57) Golub, M.A,, Fuqua, S. A., Bhacca, N. S., J . 4 m . Chem. S O C .84, 4981 (1962). (58; Golub, M. A., Heller, J., Can. J . Chem. 41, 937 (1963). (59) Golub, AT. A., Heller, J., J . Polymer Sei., Pt. 5 2, 723 (1964). (60) Goodyear Tire and Rubber Co., Rubber World 146 (4), 66 (1962). (61) Gordon, B. E., Melamed, E. A . , Belova, N. A,, Kauchuk i Rezina 21 ( 8 ) , 53 (1962); Soviet Rubber Technol. (Eng. transl.) 21 ( 8 ) , 46 (1962). (62) Groten, B., ANAL. CHEM.36, 1206 (1964). (63) Guinn, V. P., Prod. Use Short-Lived Radioisotoaes Reactors. Proc. Seminar, Vienna, 1‘962 2, 3 (1963); C.A. 59, 69729 (1963). (64) Guiochon, G., Henniker, J., Brit. Plastics 37 (2), 74 (1964). (65) (;ulimov, V. N., JIartyukhina, I. P., KaiLchuk i Rezina 22 (101, 54, (1963); C.A. 60, 5715e (1964). (66) Giirvich, 1). B., Balandina, V. A . , Soviet Plastics (Eng. transl.) 1962 (6) p. 49. ( 6 7 ) Hagemeyer, H. J., Jr., Mod. Plastics 39 ( l o ) , 157 (1962). (68) Hagemeyer, H. J., Jr., Edwards, 51. B., J . Polymer Sei., Pt. C 1963 (4)p. 731. (69) H a m . G. P.. Maier, I>. P., ANAL. ‘ CHEM:36, 1678 ’( 1964). ’ (70) Harris, R. L., Bull. Parenteral Drug Assoc. 17 (4), l ( 1 9 6 3 ) ; C . A . 60, 5719d (1964). (71) Herr, I., Plaste Kautschuk 10, 98 (1963j. (72) Ibid., p. 737. (73) Higgins, G, SI. C., Turner, D. T., J . Polymer Sei., Pt. A 2, 1713 (1964). 174) Hilton. C . L.. Rubber d o e ( N . Y . ) 91. ‘ 068 (1962).
(75) Hoffman, &I., Makromol. Chem. 57, 96 (1962). (76) Hofmann, W., Rubber Chem. Technol. Pt. 2 37 (2) 1 (1964). ( 7 7 ) Hulot. H.. Lebel. P.. Rev. Gen. Caoutchohc 40, 969 ’ (1963); Rubber Chem. Technol. (Eng. transl.) 37, 297 (1964). (78) Isakova, N. A , , Rakhmanina, A . SI., Orlova, Z. N., Kauchuk i Rezina 21 (4), 48 (1962); Soviet Rubber Technol. (Eng. transl.) 21 (4), 42 (1962). (79) Kastorskii, I,. P., lkdnikova, I. S . , Ibid., 22 (3), 55 (1963); Soviet Rubber Technol. (Eng. transl.) 22 (3), 46 (1963). (80) Ke, B., J . Polymer Sei. 61,47 (1962). (81) Ke, B., “Newer Methods of Polymer Characterization,” Iiiterscience, New York, 1964. ( 8 “ ) Khoroshaya, E. S., Kovrigina, G. I., Dinzburg, B. N., Safrai, B. A , , Soviet Plastics (Eng. transl. j 1962 (2), p. 60. (83) Khoroshaya, E. S., Kovrigina, G. I., Narinskaya, A . P., Pisarenko, A . P., Kauchuk i Rezina 20 ( l a ) , 40 (1.961); Soviet Rubber Technol. (Eng. transl.) 20 (12), 39 (1961). (84) Kimmer, W., Schmalz, ‘ E . O., Kairtschuk Gummi 16,606 (1963). (85) Kossler, I., Vodehnal, J., J . Polymer Sci., Pt. 5 1,415 (1963). ( 8 6 ) Kress, K . E., ANAL.CHEX 30, 287 (1958). (87) Kubota, T., Kuribayashi, S., Fnruhama, T., ,Vippon Gomu Kyokaishi 35, 662 (1962); C.A. 58, 14265h (1963). (88) Ibid., p. 669; C . A . 58, 14266~(1963). (89) Kiiznetsov, A. R., hrbuzov, G. A,, Ezhova, T. I., Kairchuk i Rezina 22 (5), 51 (1963); Soviet Rubber Technol. (Engl. Transl.) 22 (ti), 36 (1963). (90) Lazarescu, I., Jilavii, )I., Ind. I-soma (Bucharest) 10 (3), 101 (1963); C.A. 59, 1299ld (1963 j . (91) Lee, 1). F., Scanlan, J., U‘atson, W. F., Proc. Roy. SOC.(London)Ser. A 273, 345 (1963). 192) Lee. T. S.. Kolthoff. I. AI.., 11Znirs. ~ - , AI. A., J . Polymer Sci. 3 , 6 6 (1948). (93) Leonova, N. I., Tikhomirov, B. I., Yakubchik, A . I., Polumer Sei. r - S S R (Eng. transl.) 4, 953 (1963). (94) Lerner, >I., Gilbert. R. C.. h . 4 ~ . CHEM.36. 1382 11964). (95) Linnig,’F. J., Tryon, AI.>Parks, E. J., Ibid., 33, 127R (1961). (96) Lloyd, 1). G., Photoelec. Spectrome t r y Group Bull. 1962 (141, p . 395; C.A. 58, 5863b (1962). (97) Lomonte, J. N., J . Polymer Sei.. Pt. 5 1, 645 (1963). 198) Lomonte. J. N.. Tiroak. G. A , ,. .I. Polymer Sci:, Pt. A 2 , 705 (1964). (99) 11cNeil1, I. C., Polymer 4, 15 (1963). (100) SIaillard, A4., Deluzarche, A., Dole Robbe, J. P., Bull. SOC.Chim. France 1963,p. 549; C.A. 59, 4143h (1963). (101) SIanley, T. R., “Tech. of Polymer Sci., X o . 17,” p. 175, Gordon arid Breach, Science Publishers, Inc., New York, 1963. (102) IIiddleton, K. R., Analyst 88, 368 (1963). (103) Ibid., 89, 421 (1964). (104) AIiddleton, K. R . , Westgarth, D. R., [hid., 88, 544 (1963). (105) Sliksch, R., Hinteneder, L., Kautschuk Gummi 15, W T 358 (1962). (106) >Tiller, G. H., Larson, V. R., Pritchard, G. O., J . Polymer Sci. 61, 475 (1962). 07) Natta, G., Crespi, G., l’alvassori, A . , Sartori, G., Rubber Chem. Technol. 36, 1583 (1963). 08) Nawakowski, A. C., ANAL.CHEM. 30, 1868 (1958). 09) Nel’son, K. V., Skripova, L. S., Kozlova, X. V., Zavodsk. Lab. 29, 704 (1963); C . A . 59, 895lb (1963). ~
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(110) Nikitin, T.’. N., Volchek, B. Z., Intern. Chem. Eng. 2,486 (1962). ( 111) Paris, J. P., Gorsuch, J. D., Hercules, L). 11., h X , 4 L . CHEM. 36, 13:I., Horowitz, E., llandel, J., J . Res. S a t . Bur. Std. 55, 219 (1955). (140) Trvon. AI.. Linniz. F. J.. ASAI,. CHEM.”31,767(19%). (150) Lllbrechtova, V., Kresta. J., Chem. L z s t y 57, 1282 (1963); C.A. 60, 57159 (1964). (151) VaiiSchooten, J., Mostert, S., Polymer 4 , 135 (1963). ~
(152) Visapaa, A., Valtion l‘ek. Tutkimuslaitos, Tiedotus 4 (42), (1962); C.A. 57, 7447e (1962). (153) Vit’alskaya,N. 11.)Pantaeva, N. F., Kauchuk i Rezina 21 (6), 53 (1962); Soaiet Rubber Technol. (Eng. transl.) 21 (6), 45 (1962). (154) i’oigt, J., Kunststoje 54, 2 (1964). (155) Wanless, G. C., J. Polymer Sci. 62, 263 (1962). (156) Welcher, F. J., ed., “Standard Methods of Chem. Anal.,” 6th ed., Pt. R, p. 2146, Van Nostrand, New York, 1963. (157) Wexler, 4. S.,ANAL. CHEM.36, 1829 (1964). (158) Wilkinsori, L. B., Norman, C. W., Buettner, J. P., Ibid., p. 1759. (159) Wittendorfer, R. E., Ibid., p. 930. (160) Yakubchik, A . I., Shostatskaya,
I. D., Shikheeva, L. \-., Vlasova, V. H., Zh. Prikl. Khirn. 35, 876 (1962); J. Appl. Chem. USSR (Eng. transl.) 35, 844 (1962). (161) Yakubchik, A. I., Smirnova, 1:. K., Ibid., p. 159; J . A p p l . Chem. USSR (Eng. transl.) 35, 141 (1962). (162) Yamaji, I., Sawada, AI. Yamashina, T., ,Vippon Gomu Kyokaishi 35, 774 (1962); C.A. 59, 4143a (1963). (163) Zadorozhnaya, Z. S., Ka aseva, N. P., Kauchuk i Rezina 21 (6), 51 (1962); Soaiet Rubber Technol. (Eng. fransl.) 2 1 (6), 44 (1962). (164) Zbinden, R., “Infrared Spectroscopy of High Polymers,” Academic Press, Yew York, 1964. Contribution S o . 306 from the Research Division, 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 o f the Interior, Pittsburgh, Pa.
E
reviews have been made in this series on testing methods used in the evaluation of solid and gaseous fuels. The period covered in this review is October 1962 to September 1964 inclusive, and follows a format similar to the last review. IGHT PREVIOUS
SOLID FUELS
This section reports on studies on methods of sampling, analyzing, and testing coal, coke, and related materials. The greater part of the investigations reported are related to present standard methods of evaluation and are proposed to improve accuracy and reduce cost and time of analysis. Several references to investigations on nonstandard tests are given in the miscellaneous tests section. I t is believed that some of these will develop into tests to measure properties of solid fuels not now covered by standard procedures. Sampling. Visman (9A) reported terms and quantities easy to measure t h a t are common to all sampling experiments. Ghosal (3.4) proposes a theory to show how the factors of sampling variance differ between individual and bulk sampling. Chandra ( 1 A ) points out the importance of standard methods of sampling by geologists in appraising coal deposits. 4 procedure is specified in detail from the selection of the sampling site to the submission of the subsample to the laboratory. Hall ( 5 A ) developed a method of determining the bias of samples taken mechanically from a belt conveyor. He also gave conditions necessary to take accurate samples from washed and raw coal. 222 R
ANALYTICAL CHEMISTRY
Nikolaev et al. ( 7 , l ) described a mechanism that positions the coal cars on the track, extracts increments from various locations of the car, and composites them in the hopper of the sample preparation unit. The preparation device crushes, mixes, and divides the sample. The entire unit can be operated partly or fully automatically. Gorelov ( 4 A ) devised a multiple sample divider consisting of a square vertical tube containing several sets of riffles. Each riffle was positioned a t a right angle to the one immediately above. The discarded half from each riffle was fed back into a chute leading to the storage bin. The laboratory sample was collected in a cup a t the end of the tube. Test results for ash and volatile matter agreed with the values obtained by the national standard method of sampling. Semisalov ( 8 A ) evaluated the arcswinging-bucket, cut-off, and horizontally moving-bucket types of coke samplers. The first two types of samplers gave a distorted size consist increment, the first one required a structural modification, and the second one required a change of operation. The third type was judged to be of the best design, but it was concluded that the bucket should start the cut on the side of the stream containing the smaller material in order that it would act as a cushion for the larger pieces of coke. In a preliminary study Das Gupta et al. (211) found that in sampling runof-oven coke a 50-pound sample was required for a proximate analysis. Ash percentages in the different size fractions showed small variations. Later work on coke sampling by Menon, Das, and Das Gupta (6‘4) and Das Gupta et al. (2d) discuss the
influence of size, location in ovens, and manner of discharge on the physical properties of the coke. An alternate bias-free method of sample collection for physical testing is proposed. Proximate Analysis. T h e proximate analysis is sometimes erroneously referred to as “approximate” analysis, as if t h e determinations were only approxim ations. T h e proximate analysis consists of accurately determined groups consisting of moisture, ash, volatile matter, and fixed carbon. The latter item is calculated by subtracting the sum of the first 3 items from 100. MOISTURE. Abernethy, Tarpley, and Drogowski (1B) reported the effect of a number of processing variables on the determined moisture in coal by three gravimetric methods. Small and consistently lower values for moisture were obtained when air is used in place of nitrogen in the moisture determination. Other variables such as temperature, air flow, time, and atmosphere have pronounced effects on the final result. Bull (3B)and Burns and Swaine (4B) reported that the minimum free-space oven is acceptable under certain specified modifications for the determination of moisture in brown coals. Goldinov, Lukhovitskii, and Srubinskaya (14B) modified the C a H 2 method by heating both the sample and CaH2 to 550” to 600” C. Identical results were obtained with those by weight-loss method for hydrated salts. Schmidt and Telling (34B) examined the Dorr-Wage, xylol, and the Feuma rapid drier methods for moisture in coal. The xylol method is recommended if the required sample is available.
