Preparation of Methylphenylvinyl Raw Rubber by Bulk Polymerization and Ring-Opening Polymerization Methods

Abstract

Methylphenylvinyl raw rubber (MPVRR) is one of the important materials for preparation of phenyl-containing additive molding liquid silicone rubber (AMLSR). Two methods, bulk polymerization (BP) and ring-opening polymerization (ROP), were used to prepare MPVRR. The effects of formulation, temperature and water content on MPVRR properties for BP method were investigated and the product was characterized by Fourier Infrared Spectrometer. The effects of formulation, end capping reagent dosage, feeding sequence, reaction temperature and time on MPVRR properties for ROP method were discussed and the product was characterized by Double Beam UV-visible Spectrophotometer. The results showed that BP method could only prepare low phenyl content of MPVRR with phenyl mass percentage of 3.4%-5.2%, but ROP method could prepare both low phenyl content of MPVRR with phenyl mass percentage of 9.2% and middle phenyl content of MPVRR with phenyl mass percentage of 16.4%, which were nearly close to the theoretical values of 12% and 21.5%, respectively. The samples prepared using the two methods were proved to be MPVRR materials by the instrument analysis, respectively. Introduction Methylphenylvinyl raw rubber (MPVRR), also called as vinyl-terminated polymethylphenylsiloxane, is one of the main components of additive molding liquid silicone rubber (AMLSR). The AMLSR consists of MPVRR, hydrogen silicone, oil-containing crosslinking agent, catalyst, etc. High quality MPVRR is needed to meet the requirement of AMLSR preparation because the vulcanization of ethylene with silicon hydrogen bases depends on the molar ratio of ethylene/silicon hydrogen base in ACLSR preparation. If some byproducts are formed in MPVRR preparation, it will affect the performance of AMLSR.The synthesis of phenyl-containing silicone polymer is similar to that of normal organic silicon polymer. The methods include bulk polymerization, solvent polymerization, emulsion polymerization, suspension polymerization and ring-opening polymerization, among which, bulk polymerization (BP) and ring-opening polymerization(ROP) methods are usually used. BP, generally consisting of monomer synthesis, separation and hydrolysis, de-polymerization and ring opening polymerization of hydrolysate, can be directly conducted by the action of benzene-containing silane and ring siloxane with the help of end capping reagent, catalyst, chain transfer agent and stabilizer. BP method has some advantages such as simple technique, short process, less equipment, low investment and easy operation. Ring-opening polymerization is a process in which the cyclic monomers are opened to form linear polymers under the action of initiator or catalyst. The characteristics of ROP are different from addition polymerization and polycondensation, but similar to them in some aspects. The catalysts used for ROP are divided into the alkaline and acidic. The ROP with acidic catalyst or alkaline catalyst are called cationic ROP or anionic ROP, respectively. Under International Conference on Material Science and Application (ICMSA 2015) © 2015. The authors Published by Atlantis Press 330 most conditions, the anionic ROP method is used due to its more convenience and effectiveness than cationic ROP. The cationic ROP is only used when alkaline catalyst cannot be used for the polymerization. So far, only a few of articles reported the preparation of hydroxyl-terminated poly methyl phenyl siloxane [1-2], however, no reports on the preparation of vinyl-terminated poly methyl phenylsiloxane by BP and ROP methods were found in literature. In this paper, the two methods above were used to prepare MPVRR and compared in operation procedure, technical parameters and product properties.