This study concerns the silica reinforcement of styrene-butadiene rubber compounds for passenger car tire treads, with the objective of gaining greater insight into the beneficial effects of oligomeric resins. The major tire performance factors predicted are rolling resistance and (wet) skid resistance measured on a laboratory scale. Three types of resins were tested: a polyterpene, a terpene-phenolic, and a pure vinyl-aromatic hydrocarbon resin, at various concentrations, namely, 2, 4, and 6 parts per hundred of rubber (phr). Laboratory scale dynamic mechanical analysis (DMA), Mooney viscosity, cure meter, and tensile and hardness tests were used to assess the behavior of these resins in the rubber and to characterize the processibility of the compounds. The DMA shows that the resins and rubber compounds are partially compatible for the low resin quantities used. The tan d loss factor versus temperature was used as an indication for wet skid and rolling resistance. The shift to a higher temperature in the tan d peak, due to the contribution of the tan d peak shift of the resins, is the reason for improved wet skid performance. A maximum improvement of about 35% in the wet skid region (0 8C-30 8C) is found. The improved tan d at 60 8C, indicative for rolling resistance, accounts for reduced interaction between filler particles. This is also confirmed by a decrease in the Payne effect. A maximum improvement of about 15% is found in the rolling resistance temperature range, dependent on the particular choice of the resin.

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This study concerns short-fiber reinforcement of synthetic elastomer compounds, to gain insight into the behavior of short-cut aramid (p-phenylene terephthalamide) fibers on the processability and mechanical properties. Short-fiber reinforcement of elastomers is very complex, because it depends on many mutually interacting factors: fiber concentration, fiber orientation distribution, fiber length and distribution, fiber-matrix interfacial strength and properties of the matrix. This manuscript highlights the relationship between influencing factors in a S-SBR compound by design of experiments.Two 3 mm long aramid fibers were chosen: one epoxy-amine-coated and one virgin fiber without coating. To potentially achieve fiber-matrix interaction the following coupling agents were selected: Bis-(triethoxysilylpropyl)-disulfane (TESPD), S-3-(triethoxysilylpropyl)-octanethioate (NXT), Bis-(triethoxysilylpropyl)-tetrasulfane (TESPT) and an alkylpolyether-mercapto-silane (Si 363). They are compared on equimolar basis with regard to the amount of reactive ethoxy-groups of TESPD. Processing of the still unvulcanized compounds and the vulcanized rubber properties are investigated.The results show that various factor effects, and in particular the effect of fiber-matrix interaction, are grossly overshadowed by other factors: fiber concentration and orientation, respectively effects of the vulcanization system. The effect of the coupling agent is related to the interaction with adhesion active fibers, which in turn affects either the molecular integrity of the reinforced elastomer or enhances elastomer crosslinking. For each mechanical properties response an optimization prediction is calculated and confirmed with an experimental run, showing for example a 330% potential improvement in the Young's modulus.