Sustainable plasticizer for butyl rubber cured by phenolic resin

ABSTRACT Butyl rubber (also known as isobutylene isoprene rubber, IIR) containing plasticizers and cured by phenolic resin is widely used to manufacture rubber products exposed to high temperature environments. Therefore, carbon black (CB)‐filled IIR containing a petroleum‐based plasticizer [naphthenic oil (NO)] and environmentally friendly bio‐based plasticizers [soybean oil (SO) and norbornylized soybean oil (NSO)] cured by the brominated phenolic resin were studied. The NSO was prepared through the reaction of SO and dicyclopentadiene at different ratios. Gel fraction, crosslink density, curing behavior, thermal, mechanical, and aging properties of the CB‐filled IIR containing different oils were investigated. The addition of SO and NSO increased the thermal stability and decreased the crosslink density of the IIR vulcanizates compared to that of the IIR/NO vulcanizate. This was found to be due to the reaction between the phenolic resin and the bio‐based oils. Reducing the oil level increased the crosslink density of the IIR/SO and IIR/NSO vulcanizates, which in turn increased the modulus and tensile strength. Among various vulcanizates, the IIR/NSO vulcanizates showed the best overall hot air aging resistance. Results showed that NSO in the amount less than 10 phr could be a good replacement for the petroleum‐based plasticizer in IIR cured by phenolic resins. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45500.