CONTROL OF MICROSTRUCTURE AND MOLECULAR-WEIGHT DISTRIBUTION OF CARBON-CHAIN HETEROFUNCTIONAL OLIGOPEROXIDIC CURING AGENTS

Polyreactive heterofunctional oligoperoxides (HFOPs) were synthesized by radical copolymerization of a peroxidic monomer (PM) with vinyl ace tate and butyl acrylate. In this polymerizing system, PM participates mainly in chain propagation reaction. That allows us to use the known statistical terpolymerization composition equation for description of HFOP macrochain formation. At the same time, PM not only effectively t erminates growing oligomer chains, but also reduces their total amount . Molecular weight characteristics of HFOPs were studied by gel permea tion chromatography. It is proposed that their typical bimodal molecul ar weight distribution is a result of two competitive mechanisms: a bi radical interaction termination and termination with secondary radical s formed as a result of PM transfer. The termination mechanism ratio d epends both on composition and conversion level of the monomer mixture . The main regularities of a PM containing system polymerization deter mined by us allow us to control intentionally HFOP structural and mole cular weight characteristics. The possibility of HFOP use for curing a nd modification of the castable mixtures on the basis of oligodieneure thanes and oligoacrylates has been shown. The use of such oligoperoxid es provides improved basic physicochemical properties, an increase of thermoresistance, and fatigue resistance of composite rubbers. (C) 199 8 John Wiley & Sons, Inc.