Natural and Synthetic Rubbers F. 1. Linnig, Max Tryon, and E. 1. Parks National Bureau of Standards, Washington 25, D.
T
H I S i. tiic, ninth of n sl7ric.s of rc~vimlarticalt’s on tcst mothods for n:itiir:il and synthetic rubbers. It covers hoth thc clicniical and physical methods rt’1 ~ i r t i in d t’li[,iitcrnture during thc pvriod .iuc,cb th(t prc,vious rcvicw (8)U!I to Octoljcxr 1960. As in the. c a w of proviou- rrvic~n-s (1-8) trst mi~thocis ap1,lictl to compounding ingrcdicnts Iinvc, 1 ) t ~ i oniittctl i esccspt for tliose involTing their c1ri:ilitntivc or qu:irititati\.cs tlctcrniirintion in rubhibr. Siniilarlj-.mvthotl; d(’visc’t1to tcst thc raw in:itc’ri:ily uswl in thi- in:inufncturc of ~yntlii~tie rnlibcrs 1i:ivo nlso bccn oniittcd. S o attchmpt ha.? l x ~ ~r i ina d c ~to inclutics artic.1t.s nith oiiiy potentid application of clastomc~rs. Old procedures hnve bccn included only if modifictl or iiiiprovcd. liccnux of thc, Inrg-cx volume of pu1)Iishixl work, it ha5 not b ( ~ , i i1)ossihle to make an ~sIi:iustivt.1y ciinip1ttc~rclvicn-, The litcrnturc citctl hos b ~ e ntlivided into sithjc.ct classes for convenic~nw. ~
GENERAL INFORMATION
A nuinher of books of general intcwst liavo :ipplarc%dsince the last review. There :iw the annual reports on the progress of rubbpr technology edited by Drakeley (8.4, gAi) for 19% and 19.59. Ipetifieations (an incrcme of about 20 over thc previous edition) including two items unt1c.r a new heading--Effc.cts of Radiation. “-45TlI Standards on Plastics,” (5-1) sponsored by ComniitteP D-20, also illeludes sonic spc,cifications and test mixthods for rubber and rubberlike materials. In anothcr A4S’rlI publication, Potts (16.1) discusses the application of infrarcd spxtroscopy to the characterization of po1ymc.r structure. Of gcncral intcrc,st are the “Procecdings of the International Rubber ConE(wnce” (lcS.l:~ Iiitld i n \\ C‘.;in 1959, :iiitI the, “Procctdings of the First 1ntc~rnation:il Skid Prevention Confrrenw” (17. I ) held in Charlottesville, Va., in 1959. Burger (7-1) has written a coiiiprehensive rcvicl\v on the analysis of rubber rovcring such topics as tiw idcmtification and determinatioii of elnstomers; total. f r w , :ind coniljiiitd sulfur; accelerators; antiosid:int:: ; antl activators. Smith (21.1 i ri,vieived the analysis of organoiiiwii compounds, including silicorw c~lnstomcrs. Atlung (6.1) has rci,ic~\vtdthc ti’.-ting of plustics and vu1c:iriiztd rul>licr> including mechanical. thc~rni~il.and chemical Lukoniskaya and Rc’zproperties. nikovskii (1.5.1) niadt a comprishensive survey of Russian and other mcthods and apparatus used in the dynamic testing of rubbcr. Tcst mc~thotlsand standards are included in R rclvicw of rubber and plastic, inwlation by Palinchak and Hamilton (15.1). Shively (2&4) surveyed the use of eiwtronic measuring instruments in various types of testing in the rubber a n d plastic industry. The Research Association of British Rubber hIanufncturers. Shawbury, Shrewbury, Shropshire, England, publishes monthly Rubber Abstracts, which covers the rubber literature generally and inclutles test methods.
CHEMICAL ANALYSIS
Polymer Identification and Analysis. i i i a gi’nJTilli:imson (?7B) rorisi(Ii~r~~i1 e r d n-ny the qunlitativc :ini1 (1u:iiitit:itive characterization of polynicw. iiicluding natural antl syntlic’tics rublwrs. Clevcrlcy and Himiniin j20R/ imployeil a mcthod for klrntitying c1:t.trrmors by means of tht: inlrarml 5yctr:i of tlioir pyrolyzates obtaincil i i m l v r proprly controllid contlition., :i11(1 freed of atlditiws. Infrarcil s p c t~r:i w r e also used for the iiientific,ntioir of pw:i tvtl ai It lit i m s , $mi tll I on a stxining twliiiiqui~ in which tn-o dye solutions ~ v t i~i wi l~ ~ n u m l m of polyiiitw inral elastomc,rs. Im p u i d Chcniic.al Industries, Lttl. iS!/B). tic,scrilxd sim~ilcvisu:il anti 11~:ttingtcds for idvntifying a numbi~r of ( ,1,i.‘ qonicrs. ‘I’hc 13ritish Stant t i m ( 1 {B)publishd 13. 1311 and 1312. rrlatcd to thcl cl(~tc~rniinatiori of total rubber hydroc:irhii i n natural rub1x.r. anti h t y l m t l lxitadim! styronc rulilwrs; nitropin i r i nitrile rubhcrs; and chlorincs i n chIi)riipri~nt~ polyrncrs and copolymers. 1I:ino ( . i l B ) idtJntified polyisoprenc in i>uri)c! anti uncurcd rompounds by dctcctirig its osidation product. actitic< :wid, by iiiean~of a. siinplc color reartion or papcr rhroriiatography. E3posito i36B) r l ~ ~ s cribed a method for dptcc,tiiig and analyzing chlorosulfonatid piyct hylene. Cunneen, Higgins, and Katson ( 2 0 3 ) describcd an infrared nit,thod for the analysis of cis and trans double bonds in polyisoprene, and Corish (29B) attacked the same problem b y tlic us(’ of the near-infrared region. Kasritkina (4SB) analyzed for 1,4; 3 , 4 ; anti 1,2 linkages in synthetic polyisol)rcncls by comparing rates of ositlat,ioii of ‘the rubbers in bmzoyl hydroperi~side tvith those of morlcl compounds; li:iliubcliik and Filatova (79B) applic~la similar technique to sodium 1)ut:dient) rulber. Several articles (&B, 67B,69B) have appeared in which infrared spectroscopy has been cniployeil in the tletermination of urisaturation iri hutadiene polymers. The proportions of 1:2 and 1,4 side chains in sodium butadiene rubber were studied by Yakubchik, Zykova, anti Goncharuk (SOB) using the ozonolysis technique VOL. 33, NO. 5, APRIL 1961
127 R
and separating the mixture of products chromatographically. Smith and hIcHard (70B) reviewed the application of a variety of spectroscopic techniques to the identification of organosilicone compounds, including polymers. Lady and coworkers (47B) used infrared spectroscopy in the determination of the ratio of met,hyl to phenyl groups in silicone polymers. Baumann and Steingiser (1B) have described a colorimetric test for distinguishing polyester- and polyetherbased urethane polymers. Corish (22B) developed qualitative and quantitative methods for the analysis of polyurethane rubbers by infrared techniques. Hilton, Sewell, and Tolsma (35B) . presented a method for the deterniination of bound styrene which involves measurement of the ultraviolet absorption of the neutralized p-nitrobenzoic acid formed on nitration and oxidation of the polymer with nitric acid. Hilton (34B) dem-ibed a streamlined version of this method which eliminates several ether extractions. Wood, Madorsky, and Paulson (78B) described in detail the precise combustion analysis for carbon and hydrogen necessary to determine accurately the composition of styrene-butadiene copolymers. Burleigh, hIcKinney, and Barker (18B) have developed methods for determining vinylpyridine, acrylonitrile, and acrylic acid units in elastomers. Sterling and coworkers (7SB) presented an infrared procedure for analyzing a terpolymer of methyl isopropenyl ketone, butadiene , and acrylonitrile. Ethylene-propylene copolymers have been analyzed using an ultrasonic procedure by Kabin and Cs’yarov (42B), a method involving mass spectrometric analysis of the polymer pyrolyzates by Bua and Slanarcsi (ITB), and an infrared technique by Kei (76B) employing films. Hummel (3;B) employed infrared spectroscopy for the identification of raw rubber, and soft and hard vulcanized rubber. The method is applicable to a u-ide range of synthetic rubbers as well as to natural rubber. Gresler, Pyrkov, and Frenkel (10B) used ultracentrifugation in n density gradient to analyzr the composition arid molecular weight distribution of block and graft polymers. Milliken and Linnig (5SB) indicated that certain antioxidants interfere in the IC1 addition method for the determination of low polymer in SBR. Three articles (8B, GIB, ,‘7B) irere concerned with infrared techniques including preparation of polymer samples for analysis. Sulfur and Related Analyses. T h r w articles (2%) 6B, 29B) reported methods for the analysis of total sulfur. Ivashova, Fedoseev, and coworkers 128 R
ANALYTICAL CHEMISTRY
described two methods (40B, j I B ) for sulfur in organic substances, including vulcanized rubber. Hummcl and Bertram (38B) used vanadium pentoxide and quartz as a catalyst to aid in achieving complete combustion of the vulcanized sample, but found that alkali earth sulfates were not completely dccomposed. Mocker and Luft (67B) claimed a rapid method for determining elemental sulfur in rubber-sulfur mixes, and Strassburg (?@) dcvelopcd a scmimicro method for free sulfur in cured rubber. Both these methods are based on the standard technique employing sodium sulfite followed by the iodometric titration of the resulting sodium thiosulfate. Rozaci (64B)claimed to have improved the method of Proske and others by using a different medium for the polarographic determination of free sulfur in vulcanized rubbcr. Studebaker and Kabors (75B) described trchniqucs for sulfur group analysis in natural rubber vulcanizstes. ICirittwu and Ceamis (46s)chose paper impregnated with a hot saturated solution of lead acetate as the most semitire indicator papw for the identification anti approximate determination of hydrogen sulfide in rubber articles. Metals, Metal Oxides, and Halogens. The British Standards Inst it u t ion ha s published A men ti m en t s 2 and 3 to B.S. 1673, Part 2 ( I I B , I @ ) . relating to the determination of manganese and copper in raw and unvulcanized compounded rubber. This organization has also issued Part E l f of B.S.903 (I5B) dercribing a colorimet,ric proccdurc using zinc diethyldithiocarbamate as reagent in the determination of copper in vulcanizcd rubber. The Deutscher Normenausschuss has reported a draft of specification DIS‘ 53569 ( M B ) relating to the determination of copper and manganese in crude rubber and latex. Pohl (63B) proposed lead dietliyl~litliiocarbamate in place of the zinc salt in the above specification for copper and describtd means for eliminating sinall organic residues, after ashing, xhich intcrfere i n the permanganate ositiation in the manganese procedure. Madan (COB) claimed a quick anid sensitiyc method for copper using zinc dibcnzyldithiocarbmiate. Fader1 (27B) presented a rapid simple method for determining as little as 0.02 p.p.m. of copper iusing Fast (fray R h as the reagent. S a g s (COB) described colorimetric methods for copper for use in the rubber intiustry. Two Kussian articles (!+@, SSBj presented spectrographic methods oi anaiysis for a number of metallic c~irmerit~ in rubber, including quantitative determinations for magnesium, zinc, calcium, and barium. Copper, manganese, and zinc were determined
in ran- and vulcanized rubber by Belitskaya (4B) using a polarographic trchniquc. IJogina and lfartyukhina (SB) used nitroso-R salt for the photocolorimetric determination of cobalt in rubber, a test in which it was claimed other metals do not interfere. Laning, Vagner, and Sellers ( @ B ) employed x-ray diffraction techniques in a rapid nondestructive method for determining zinc oxide in vulranizatps with a relative error of less than *lo%. The Schoniger combustion technique has been applied in two articles (27QB, SIB) to the determination of chlorine in polymeric materials, and Haslam, Hamilton, and Squirrel1 (31B ) described attempts to improve Schoniger’s original procedure. In this last article the only polymc,ric application was to polyinyl chloride. Uogina and IIartyukhina (7B) used a combustion technique in the analysis of vhlorine and broniine in polymers. Ychroder and Waurick (66B)claimed a simplified method for determining fluorine in high polymers. Antioxidants and Accelerators. Hilton has used p-nitroaniline in n colorimetric procedure employiug a spectrophotometer for the qualitative identification and qusiititative estimation of amine antiosidants (33B) and phenolic antiosidants !32B;. Collins, Goethel, and Hci (21B) cietermined di-o-to1ylgu:tnidine dicatechol borate in ru!iber compounds qualitatively and semiquantitatiwly by coupling the antiosidaiit with diazobcnzene sulfanilic avid. Shcherbacheva Land Tar:isova, in a Russian serial pamphlet on inspection methods in the rubber industry (5WB)>analyzed nitrile rubbers for cliniethylphenyl p-crpsol. Kingstay 100 has been determined by the C h m ical Division of Goodyear Tire arid Rubber Co., Inc. (SUB), using btnzoyl peroxide as rcagcnt and measuring the intensity of the amber color produced a t G O mp. The accelerator mercaptobmzothiazole was determined colorinietrictilly by Sttpanova (72B) using the C O ~ I ~ I J ~ X formed with cobalt oleas?. f3enzoihiazyl disulfide w s dctermiIied iu the same way following reduction to nicrcaptobenzothiszole. 13elitskaya and natural rubber vulcanizatcs. Roth ( S J ) reported results of indentation hardness measurements of several rubber compounds over a range of indentaNo tion times and temperatures. unique rclation was apparent for charact'erizing all the vulranizates. Gardincr, Jordon, and Adams ( 6 J ) described a Ticat-typP penetration testcr for evaluating hardncss and elastic recovery in i)olynieric materials from 125- to O.i-mil thicnkncss. F ~ d y u kin, Zyryanov, and Korotkova (57) illustrntcd :in app:tratus and dcsrribed a method for hardness testing of sponge articlw by a penetration procedure. ABRASIO N
Abrasion tests based on rate of wear of the specimen in contact with an abrasive surface was the major approach to the problem of the evaluation of abrasion resistanre of rubbers. .-lbbat (fK)described a 3-minute test procedure for plastics and rubbers using a revolving drum carrying an a paper. The paper was stand by the use of a standard rubber. Kakahara, Xagao, and 0gan.a ( 5 K ) mcasured abrasion loss a t different vclocities on a new machine. This machine also allowed the measurement of the power consumed and offcred control of the slip velocity. The U.S.S.R. Standards Organization (8K) used the volumetric loss of a specimen clamped against a revolving abrasive disk as the means for determining abrasion resistance of rubbers on a Grasselli-type machine. Martin-Gras and Prat (4K) reported on the influence of variations of abrasive paper used n i t h the Du Pont-Grasselli machine. They concluded that constant results should be possible using a strictly specified paper. SakhnovskiI and coworkers ( 6 K ) suggest a method of laboratory testing intended to ensure better correlation between laboratory and operational tests than is usually possible. Toth ( 7 K ) constructed a machine designed to overcome the difficulties of comparison between the resistance to abrasion of leather and rubber using the same machine for both materials. Vclasquez-Sanchez and Prat ( Q K ) described a machine for abrasion measurements in which the speed of the abrasive n-heel, loading on the sample, and the friction can be varied to approximate the factors influencing road wear. Gelinas and Storey ( 3 K ) devised a test device for estimating road wear of rubber compounds that consists of a test jig to be towed behind a car. l h i s apparatus is so designed that a n estimate of the road wear performance
132 R
ANALYTICAL CHEMISTRY
a t different severity levels may be obtained from a 6-ounce sample. Brodskii and Reznikovskii (LK) described a method for measuring the electrostatic potentials formed on the surface of a specimen during friction and abrasion. ADHESION A N D TACK
Problems of testing adhesion were rcvicwed by Julien ( 5 L ) . The author emphasized the importance of dynamic effects such as impacts on the evaluation of this property. Painter (9L, fOL)described a new method for testing rubber-to-metal bonds by using a conical specimen. The conical specimen ensures failure at the bond by introducing a strain concentration a t the bond surface. JIorozova (6L) dizcwsed a method for the determination of the adhesion of polymers to various surfaces using a roller adheqiometer Krotovd, Morozova. and Sokolina (6L) described a comples adheroinctrr in n hith the speed IS selected and the stresses are recorded. Voyutskii and S'akula ( I I L ) reported a method for the determination of the adhesion of s! nthetic and natural rubber to various substrates such as cellophanc, polj ethylene, pols isobutylene, polyamide film, and others. Guyot ( jL) discussed various methods for measuring the adhesion of rubber to textiles. Eagles and Norman (SL) showed the importance of measuring instantaneous load on the test piece; the conventional tensile test is insensitive to transient peak loads. They also showed that a standard moving-coil milliammeter is too slow to detect the fluctuations important in evaluation of ply adhesion. A cathoderay oscillograph was found to be 'satisfactory by the authors. The British, Standards Institution (1L) has specified a test procedure for the determination of rubber-to-fabric adhesion in which a requirement for the machine to be used is that it be of a type having the shortest possible time contrast. Xillard (7L) defined and classifled the properties most desired in pressuresensitive adhesive products. Test methods were reviewed and suggestions made to cover properties not presently specified. Brunt (2%) described a n instrument capable of measuring the various parameters determining tackiness. ELECTRICAL TESTING
.A review of the measurement of electrical properties of high polymers was presented by Norman ( 4 M ) . He considered the measurement of the direct current resistivity of nonconducting rubbers and the circuits used for such measurements, eltctrical breakdown under high voltage. and the meas-
urement of the dielectric properties of rubber. J h l l e r and Huff (3M) described measurements and discussed the results of the alteration of the dielectric relaxation spectrum of rubber on stretching. Norman (5M) defined the terms conductive and antistatic rubbcrs and described methods of testing conductive rubbers. Gooding (2M) JIas anarded a U. S. patient for an apparatus dcqigned to test electric cable insulation by progressively submerging thr cable in a gas of high dielectric strength while in contact nith an annular electrode connected to a high voltage sourw Rollinson (6.11) used d i s h of rubber for testing the longtime electric brcakdon n of common insulating mntcrinls such as Neoprene, silicone, nitrile, wnd natural rubbers. Tests for the voltage endurance and resistance to corona discharge of silicone rubber insiilation were described by Bartos (IJIi. LOW TEMPERATURE TESTS
A% simplified method for determining the glass transition temperature of elastomers as reported by Trick ( 7 N ) uses a correlation betn een dilatometer measurements and the Gehman low temperature torsion fleu test. Lichtman, bdler, and Hanok ( 5 S j found a tensile stress dccay apl)aratus more satisfactory for the e\ alnation of stress decay of elastomers a t lon temperatures than a compression apparatus. Sinnott (SLY)developed a torsion pendulum apparatus for the measurement of shear modulus and internal friction between 4.2' and 100' K. Boor et aZ. ( I N ) published the results of a cool erative study of the extent to nhwh the superposition principles are applicable to analysis of elastomeric materials. The British Standards Institution ( S N ) has issued a specification method for the determination of the resistance of vulcanized rubber to low temperatures. Braun (ZX) recommended using prolonged exposure tests over a range of low temperatures in a study of the rheology of silicone elastomers a t low temperatures. The Czechoslovakian Standards Institute ( 4 N ) has adopted a springloaded impact test on cooled specimens as a test procedure for measuring the low temperature flexing brittleness of vulcanized rubber. TIRE TESTING
The jet age has posed new problems to the tire manufacturer. High accelerations and speeds beyond anything even thought possible a few years ago have been attained and tires ca-
pable of viithstanding these stringent requirements have been made. Testing of these t,ires poses a probleni in itself and several tire nianufacturing companies hsve designed and constructed apparatus for this purpose (5P-P). The problem of testing more conventional tires under more conventional conditions is still one which has not been completely resolved. Several papers have appeared (4.P, lSP, i4P, 1SP) in which attempts to construct test apparatus designrd to simulate a road test under controlled conditions have been described. In general, correlations of laboratory test,s, even with such complex devices and controls, with actual road tests are somewhat less than good. Perkins ( I 7 P ) said that complete tire evaluation depends on a wide variety of tests including laboratory testing of raw materials as ell as road tests and consumer use experience. Roberts ( I Q P ) described a machine for measuring tire poirer losses under driving or braking conditions, while H:irrin ( I I P ) discussed nppnratus designed for making force measurements while operating tires on wet surfaces. A method used to measure th.e deformations of elements of a tire was reported by Biderman and coworkers (SF'). Tickers and Robinson (ZOP) devised equipment to trace the movern(>:lts of tread clement? in rolling contac C with a slipping surface. Hanneil (IOPj described laboratory crown-in:pact-endurance tests for evaluating new fibers for tire cords. 13ergc.r And North ill') described attempts to build a machine capable of giving a quantitative rstinintc of "tire ride. ' A U.S. patent was granted to H u h wit, Elliott, and Gulp (I2Pj for a deviw designed for determining the tendenry of tires to produce "thump." Esiwio and Lleo (6P) wported on an a p p m t u s for measuring skid resistance. Lanib (I5Pl described romplex testing machines for aircraft tires in which s?ininiy tests, drop tests, and coniplete larding gcar assembly tcsting may be in :t c i e . \-nvn1ioi'sAii, Evstraitov, anii 1,evia ) detailed laboratory methods used iniuitaneousiy measuring the temperat'ure in five zones of a tire. Hitiernian ( 2 P ! explaincd a short.F., Tchromov, AI. K., Vostroknutov, I. C., l r u d y .~auch.-Iss!edoi~atel'. Inst. Shinnoi
139,711 (1950). (22H) Volodin, .'1 P., Kuvshinskii, E. V., Pribory i l'ekh. E k s p t . Xo. 5, 86 (1957); Research rissoc. Brit. Rubher hffrs. Translation 698, Sh:iwlmri, 1959. (23H) T'olterra, E., Barton, C. P'.,Proc. Soc. Erptl. Stress .4r~al. 16, 157 11958); Pockaping A bntr. 16,ahs. 1396 (1959).
Hardness
(1J) Rartenrv, G. )I., Zakharchenko, N. V.. Knttchzik i Rezina 17. Nn. I . 10
(imj.
(25) Bennett, F. N. B., Proc. I n s f . Rubber I n d . 6,29 (1959). 13J) British Standards Institution. Lon' don. Spec. B.S. 903,Part ,420, 1{,59 (4J) Ente Nazionnle Italian0 Di 'I-nificazionr, UTI 4046, hlilan, 1058. (5J) F'rdyukin, I>. L., Zyryanov, R. A , , Korotkova, .4. A , , Kniichuk i Rrzina 17. S o . 11. 36 1958). (6J) 'Gnrtiin&. K. IT., Jordan, T. F , Atlnnis. F. JT,, .ZSTM Bull. S o 246,
38. 1080 ( 7 5 ) 'nhei-to. S IRef lX.1, p 162 i8J) Hoth, F T,,, Rubber Tf'orld 139, 406 1 lo,%) (9J'i proit, J R Poden, A I , , Fef M A , p 170; Trarui: Inst. Riibber Ind. 36, 1 (1r)AO). Ritbber C h m and Twhnol. 33, 876 11060)
(31,) Eagles, A. E., Korman, R . H., Rubber J . and Intern. Plastics 135, 189 (1958). (4L) Guyot, R., Rev. gin. caouichouc 35, 13-10 (1958). (5L) Julicn, R I . .4., Ibid., 35, 1359 (1958). (rj1,) Iirotova, h-.A., hlorozova, L. P., Sokolina, 6. A., Dok[ady i l k a d . S a u k . S.S.S.R. 127, KO, 2, 302 (1959); Rei,. Current Lit. Paint, (lolour, Varnish (idAliied 1nds 32,821 f 1959). (71,) hIillard, J. F., Inst. Rubber Ind. and Plastics Inst. Joint Corif. London Swtions on .4dhesion, Londun, April 17, 1958. Morozova, L. P., .~aiich.-Isslcdocatel’. l’rudy, lsenlral. haitch.-Isslrdo~aiel’. I n s f . Korhwenno-0bui:noi. Prom. Sborn i k , S o . 28, 119 (1957). (91,) Painter, G. W., Rztbber Age 86, 262 i195!1), (10L) Painter, G. TI-., -4dhesiz’es Age 3, :38 (1960). ( 1 11,) Voyutskir, 8.
S.,Vakula, V. L.,
1~!i.~okonioiekulynrnye Soedineniya 2, 51 1i w ) .
1OP) Hannell, J. \V., -4SlIE Publ. 5% SA48, 1959. 11P) Harrin, E. S . , I n d m Aero. 15, abs. 280/15/2 (1959))l Nat. Advisory Comm. Aeronaut., lech. Kotea: KO. 4406, 195S. I2P) Hulswit. TY. H., Jr., Elliott, D. ii., Culp, E. H. ( t o United States ltuhber co.),U. 8. Patent 2,920,481(1960). 131’) Hungary, Academy of Sciences, hlanufacturing 5hterpri.e I’or Research Equipment; J. I?arlrns, Rubber J . and Intern. Plastics 136, 430 (1959). (14P) Iiulliiian~, K., Institiit 1;ranCais du Caouttmhouc. Tire Syniposium, Paris, 1959. ( 1 5 ~ )I ~ I I ) rr. , P., Ref. M A , p. o l .
(16P) Kuvopol’skii, V. I., Erstrutov, V. F’., Levin, S. I,., !L‘rztd!/ .\‘ouch.-
(21(i:Hair~es, I{. C., Gould, E , G,, I’roc. I d . Rubber Ind. 6, No. 3, 85 (1959;. (25Q) JanAiek, J., Cheiii. Pr.;irnysI 8, -1% (195s). (2GQ Kadiec, F., Thoman, R., Rubber Age 87, 81 (1‘360); Rubber W o r l d 142, 105 (1960). (27Q) Ice, B., J . i’olymer Sci. 42, No. 129$ 12 (1960i.
(2SQj Iieskkul:i, B.,Iluiiber A y e 84, 1003 ( l p ) ; Kztbbcr W o r l d 139,8\15 (1959). (29Q) I i e s k k u h , H,, Sorton, J. Tl-., Jr., J . f l p p l . P o i p e r Sci. 2, KO.8, 280 (1909).
(30Q) Kiizek, Y,,II>.linikar. F.,Ploslr ! I . Koictschrtk 6, 113 (l!l5!l). (3lQ) Larigton, S. H., Sti’phenq, M., Plasti(.s fLojidon) 23, 381, 388, 4%2
Issicdosatel’. Inst. Shinnol Proni Sbornik.
3, 106 (1957). (17P) Perkins, \T. F., Rubber W o r l d 139,
412 (1958). (1SP) Ilichey, G. G., hlandrl. J., Ptiehler, R . D., Ref. lSAjp. 10-4. (19P) Roherts, G. B., Ref. ;+I, p. 5 7 . (20P) Vickers, H . H., Robinson, P. B., KPf. 1&4, p. 128.
Electrical Testing
(111) Ihrtos, D. N., Ricbb~rAge 86, 6SO i11160). (211) Gooding, F. H. (to Okonite Co.), I-.S.Patent 2,900,597(1959). (3hI) l l u l l r r , F. H., Huff, K., Kaiiischuk i t . (;iimmi 1 1 , W T 278 (1958). (4311 Kormnn, R. H., Rubber J . and Inic7-71. Plastics. 136, 122 (1959). (511) lbid.,242, 250. (651) Rollinson, \V., Metropoliian-Tlickers Gazette 28, 286 (1957).
Miscellaneous Topics and Techniques
l o w Temperature Tests
( 1 s ) Boor, L., Hanok, A I . , Conant, F. 8..S‘coville. W.E.,, Jr.., ASTM Bull.
KO, 246, 25, iosu. (2K) Braun, D. R., Rubber Age 87, 80 (1960); Rubber World 142, 104 (1960).
(3K)British Standards Institution, London, Spec. B. $. 903, Part A13, 1960. ( 4 I i ) Czechoslovakia, Crad Pro Kormalisari. CSS 621554, Prague, 1956.
(5K) Li‘chtman, J. %., Adler, G., Hanok, ?IT.. U. P. Office Naval Research Srmposium Rept. ACR-4, 2, 66 (1956). “ (6K) Sinnott, K. hl., J . A p p l . Phvs. 29,
1623 (19581 (47Q) Rosenthal, 1,. A , , Atidis, G. I.? S P E Joiirnal 15, KO.I , 97 (1959). 148Q) 5andomirslii, 1). >I., Fogel, 1.. 0 , . 3Iaizelis. 13. A , . Kcriichiik i I?etina 18,
1433 (1958).
(7N)Trick, G. S., J . A p p l . Polymer Sci. 3, No. 8, 253 (1960).
3-0,1.1 3 8,1!).5
