INDUSTRIAL AND ENGINEERING CHEMISTRY
976
\vas not possible with standard GR-S because t h e master batchrLa were d r y and crumbly and not so easy t o handle on the Banbury mill. BETTERADHESIOSOF CALESDERC O ~ TO T S O L L ~ T I O SF.uED R I C BEFORE ~ULCASIZITIOS. This enabled tire factories to increase calender efficiency 10-137 by permitting skim and friction coating :it higher speed. It also reduced "peeling" of the calcnder coat in t h e cutting and building operations and, a s a result. reduced fabric scrap and product, building labor. In ;Iddition it reduced the number of r a w t i l e s to he repaired because of scpar:itions occurring during the tire-shaping operation. GREATERTACKINESS FOR I J . ~ M I S A T I S G .4XD ~ P L I L ' I S C-, PARTICULARLY FOR COUPOUXDS COSTAIXISGSOMESATLXLI, RUBBER. T h e addition of a small quantity of natural rubber to GR-S 10 compounds enhances the tackiness for fabricating purposes t o a greater extent than does a n equivalent, addition t o corresponding standard GR-Scompounds. BETTERPLY-SEPARATION Ras1sT.4XcE. The much iniproved ply-separation resistance of GR-S 10 carcass compounds is indicated b y the rating given in Table I1 for a n indoor wheel test, made b y our Detroit. tire plant. This is typical of the results obtained by several performance evaluations, both indoor and highway.
TXBLE
11.
I S D O O R IVHEEI,
Elastomer In carcass Ply-separation rating Heat-break rating
TWT(DETROIT P R O J C C T 8540 gtandard GR-' 100 100
GR-s i n 156 126
Vol. 38, No. 9
In hose friction compounds it g i w s the advantage of easier calendering and greater tackiness for product building. Performance quality in equal t o or slightly better than t h a t of eorre.spending standard GR-S compounds. Our mechanical goo& plant has realized a saving of as much as 18% in the building time of suction and fire hoses through the use of rosin polymer. I n shoe soling it of'fcrs the advantage of slightly better :)braaion resistance and higher tensile st'rength, v-ithout s:icrifice nE resilience, tear resistunce, ur other important, cured propt'rties. I n power transmission and conveyor beltings the replacement oi atandard GR-S with GR-S 10 nould increase calendering eficiency, improve adhesion of coatings, give greater tackiness for laminating, and improve service life. p;irticularly in high s p e d applications. X-273 GR-S
5-273 GR-S is a nondiscoloring, nonstaining variatioii of C;I!-S 10; it is specially made for use in white and light-colored compounds xvhich are required t.o retain their brilliance throughout life, and for all compounds which are required t o be free from the tendency to stain paper, paint, cnbmel, or lacquer surf:ices with which they may come in contact during service. Its .similarity to GR-S 10 in properties and freedom from discoloring and staining tendencies indicates advantage in the compounding of white shoe soles and heels, mottled floor tile, lightcolored electric lamp cord, and white sidewall tires. This is a relatively new variation, and as yet the production of this polymer is low in volume; b u t it is expected t o increase when t h r evaluations now in progress have been completed. X-272 GR-S
HIGHERHEAT-BREAKRESISTBNCE. The improvenwnt, ill heat-break resistance realized from the replacement of standard GR-S bvith GR-S 10 in carcass compounds is about 2 5 7 (Table 11). POSSIBLY BETTERABRASIOX ASD CUT-GROFTH RESISTAWE. T h e results of road tests completed t o date have been inconclusive; additional tests are being made to fis these points. The disadvantages are few and are easily offset by niiiioi changes in compounding and processing. The four diff ercncw requiring consideration follow : M O R E T7~scousT H A S STANDARD GR-S. The viscosity til which GR-S 10 is made is the result of a compromise b e t m e n t h r desire for performance quality and t h e need for processibility. GR-S 10 as current,ly made requires slightly more masticatinn than standard GR-S t o obtain t h e same processibility. SLIGHTLY ~ I O R"SCORCHY". E If part' or all of the greatei ma*tication requirement is denied, processing temperatures are higher and the tendency for scorching is increased. If production schedules permit part of t,he saving in Banbury and mill tinir realized from the use of concentrated master batches to be applied t o polymer mastication, the compounds should be as safe as those made with standard GR-S. SLOWERCURINGTHAN STAXDARD GR-S. T h e differc~firei r l rate of vulcanization can be corrected by an adjustmcnt of the accelerator ratio aqd the addit,ion of 1.0 t.o 1.5 parts of fatty acid TENDESCY TO STICK ON MILL AND CALESDER.This can br overcome b y t.he use of standard GR-S OI natur:il rubbei as part of the elastomer in the cbmpound. The addition of 1.0 to 1.5 parts of fatt,y acid is generally sufficient t o c o m c t for tliis tcndency. If natural rubber is used as part of the cla.tomcr in thcz compound, no sticking should be experienced. iilthough emphasis has been placed on the perforniaiice v i GR-S 10 in tire compounds, its value is not limited t o tircc. It offers advantages in the compounding of many products, .rich :I.. hoses, shoe soles, poner transmission and conveyor belts, ctc., in which nonblack fillers or low loadings of black fillers must be uscat1 to obtain required appearance or performance charactPristics.
Itosin polymer is also available in a third form under the Rubber Reserve designation X-272 GR-S. This modification made its first appearance a s X-40 GR-S on December 28, 1943, when the Xaugatuck polymer plant, completed t h e production of two batches. Since t h a t time 1,132,000 pounds have been produced for use in t h e compounding of adhesives and pressure-sensitive tapes. I n these applications X-272 GR-S is definitely superior to standard GR-Sand it,s variations. M V C H HIGHERR A W STREXGTH.High raw strength or cohesiveness is necessary t o prevent transfer to the adhesive from one surface t o another, and t o give bonds which will not break when subjected t o continuous l o x stresses. S o FATTY ACID COSTEST TO CRYSTALLIZE IXTERSALLY OR BLOOMTO SURFACE. Since surface tackiness and t'he performance quality of the product are reduced by crystalliZation and blooming, this is a matter of much concern t o t,ape and adhesives manufacturers. SOSDISCOLORIXG TESDESCY.T h e stabilizer in X-272 GR-S is low in discoloring tendency and docs not darken appreciably during exposure t'o light. This is of importance in transparentback tapes, stationery adhesives, etc. Lev- I N WATER-SOLUBLE MATTER. This is a n important COIIsidemtion in tapes made for electrical applications in IT hich the adhesive !Till contact metal surfaces. X-272 GR-S is low in soluble soap and ash nhich Jvould cause corrosion. X-272 is slightly less soluble in common solvents than Standard ' GR-S or GR-S 10, but its solubility is sufficient t o permit processing in the normal n i a ~ i i i ~ r . i C K N O W LEDGXIEST
Tlie I~"l?.mc.rizativn n-ork reported ip this pnper XIS part oi the government synthetic rubber research and devclopmcnt program. PREaEsTF.U before the Division of R u b b e r Chemistry a t t h e IO!Jtll l i e e t i n g the AXFRICASCHEVICAI. SocIeTr. .itlantic City, W. J.
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