Reinforcement And Modification Of Rubber Composites By Sorbic Acid And Its Salts

Unsaturated metal carboxylates such as zinc dimethacrylate (ZDMA) and magnesium dimethacrylate (MDMA) have exhibited a significantly reinforcing effect on rubbers. In the present study, we used a nontoxic and cheap sorbic acid (SA) to substitute the corrosive and irritative (meth)acrylic acid for in situ synthesis of unsaturated metal carboxylates. We studied the reinforcement of in situ formed metal sorbates on nitrile rubber (NBR), and explored SA and its salt as the interfacial modifier for styrene-butadiene rubber (SBR)/inorganic fillers composites. The preparation, structure, properties, reinforcement and modification mechanisms of the above composites systems were systematically investigated.A basic salt was formed by the reaction of SA and zinc oxide (ZnO) under an appropriate temperature and further converted to neutral salt zinc disorbate (ZDS). The in situ formed ZDS was polymerized during rubber vulcanization, and formed the ionic bonding in the composites. Analysis on vulcanization characteristics indicated that the incorporation of ZDS enhanced the crosslink density of the composites and accelerated the vulcanization. The nano-dispersion structure of the poly-ZDS in the NBR matrix was confirmed by transmission electron microscopy (TEM). Composites with excellent mechanical properties and good aging resistance were achieved by the reinforcement of in situ formed ZDS on NBR, and the tensile strength, 100% modulus and tear strength of the composites were eight to nine folds of those for the neat NBR vulcanizate. The in situ formed magnesium disorbate (MDS) also exhibited significantly reinforcing effects on NBR.SBR/halloysite (HNTs) nanocomposites were in situ modified by SA. With suitable SA content, the compound had higher curing rate and crosslink density. SA bond SBR and HNTs through grafting copolymerization/hydrogen bonding mechanism. Significantly improved dispersion of HNTs and strong interfacial bonding between HNTs and rubber matrix were resulted, and the mechanical properties of SBR/HNTs nanocomposites were greatly enhanced consequently. We further used HNTs and ZDS as dual fillers and prepared highly filled SBR/HNTs/ZDS hybrids. The hybrids had excellent room temperature mechanical properties and good high temperature properties. Good dispersion of HNTs in the matrix and strong interfacial bond were confirmed by scanning electron microscopy (SEM) and TEM.SA was used to improve the performance of SBR/silica composites by direct blending. ZDS was in situ formed during compounding and polymerized during vulcanization, and influenced the vulcanization characteristics of the composites. The hydrogen bonding between SA and silica improved the dispersion of silica in rubber matrix and enhanced the interfacial bonding, and the bound rubber content was also increased. The interfacial modified SBR/silica composites exhibited remarkably improved abrasion resistance and mechanical properties.