Covulcanization of elastomer blends with special reference to NR/EPDM blends

Attempts have been made to attain satisfactory\nnetwork structures in each of the phases of a rubber blend\nby minimising the cure rate imbalance by employing methods\nsuch as grafting of accelerators to the slow curing rubber,\nchemically bonding the crosslinking agents to the rubber in\nwhich it has lower solubility, functionalisation of the slow\ncuring rubber, masterbatching of the curing agents\nto the slow curing rubber etc. Functionalisation of\nthe slow curing constituents of NR/IIR and NR/EIPDM blends\nis tried using novel reagents as the first part of this\nstudy. However, the crux of the present study is a more\ndirect approach to attaining a covulcanized state in NR/IIR\nand NR/EPDM blends: Precuring the slow curing rubber (IIR\nor EPDM) to a low level when it can still blend with NR and\nthen to ck) the final curing after blending with NR. TNM3\nprecuring is also likely to minimise the viscosity mismatch.\nSince a low level of resmmal crosslink density is likely to\nbe present lJ1 reclaimed rubbers, blending heat resistant\nreclaimed rubber such as butyl reclaim with NR may also have\nthe same effect of precuring IIR, and then blending with NR.\nHence use of IIR reclaim for developing blends with NR is\nalso proposed to be investigated in this study