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SBR (sol)

BR

CB

Silica

Oil

TESPT

ZnO

Stearic acid

Wax (AO)

6PPD

Process additives

DPG

CBS

Sulfur

Typical Formula

70 30 6 80 33 6.4 2.5 2 1.5 1.9 ~3 1.5 2 1.1

The rubber industry bases the formula’s on 100 parts of rubber. This formula was taken out of the patent literature. The styrene butadiene rubber we use is a Duradene from Firestone Polymer. These are usually oil extended and are specified by viscosity, styrene content, and vinyl groups. The high cis butadiene rubber is from Lanxess. The bulk of our work is with Degussa’s Ultrasil 7000 GR. The carbon black (CB) is in the tire grade series. Some of work we’ve done looks at varying the levels of CB to silica and then the silane is kept at the same % of the silica surface. The silane level here is 8% but lower ranges are also used. The ZnO and stearic acid react during compounding and are considered to be activators for the cure. The microcrystalline wax and the phenylene diamine protect the rubber from ozone attack. The diphenyl guanidine, cyclohexyl benzathazole sulfenamide, and sulfur are part of the cure system and added in the last pass where the temperature and time is maintained to prevent any precuring. The process additives will be added at 2-5 parts some place early in the mix. These process additives are not in any of the early patents but are gaining acceptance as processing problems are being identified. Several additives have been developed that improve the processing of these compounds. Struktol HT254(from our European office) is a zinc free lubricant blend and Struktol JV 46F contains zinc based surfactants.

STP0260

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