Kinetics of peroxide crosslinking process of rubber is studied in this paper. A formula is proposed to analyze this kinetics. The formula shows the relation between the rate of crosslinking and the initial peroxide concentration,
V=A√<[I]₀>+B[I]₀
where V is the rate of crosslinking measured by oscillating rheometer, [I]₀ is the initial peroxide concentration, and A and B are coefficients.
The rate of crosslinking is determined from the gradient of the torque curve measured by a oscillating rheometer. The first term of this equation represents that the rate of crosslinking between a double bond on a polymer chain and a carbon radical on other polymer chains, the rate of additional reaction, is propotional to the root of the initial peroxide concentration. The second term of this equation represents that the rate of crosslinking between two carbon radicals on polymer chains, the rate of radical terminations, are proportional to the initial peroxide concentration.
Calculated values of A/B for SBR, BR, NBR, and HNBR by varying peroxide concentration clarified that mechanism of crosslinking differed depending on the kinds of rubbers. SBR and BR were mainly crosslinked by the addition reaction, while NBR and HNBR were mainly crosslinked by the radical termination.

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Direct adhesion between natural rubber (NR) and nickel plated steel cords (nickel cords) during vulcanization has been investigated to develop new type steel cord for tire. Nickel plated cords were not adhered with NR compounds composed of sulfur and sulfenamide type accelerators. The NR compound was adhered to nickel cords treated with the monosodium salt of triazine trithiol. The highest pull-out strength and rubber coverage in NR-nickel adherends were obtained when nickel cords were treated with 0.4% TTN aqueous solution at 80°C for 15min. Pull-out strength and rubber coverage in the adherends were influenced by TTN concentration, treating time and temperature, the amount and kind of accelerators, sulfur concentration, and Co salt concentration. The water resistance of the adherends were influenced by sulfur concentration, accelerators, and Co salt. Particularly, the presence of Co salt in vulcanizates decreased markedly the pull-out strength and rubber coverage of NR-nickel adherends.

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