Synthesis And Characterization Of Phenol Siloxane Elastomers

Phenyl silicone rubber is formed by introducing phenyl into the main chain of dimethyl silicone rubber. In this process, the regularity of molecular chain is destroyed, the crystallization and glass transition temperature is reduced, the low temperature scope for use of polymer materials is expanded. With excellent resistance to high and low temperature, and strong resistance to oxidation, it has been widely applied in various high-tech fields, like aerospace and military users. Since the current research on synthesis of phenyl silicone rubber is inadequate and technologies for carrying out such research are confidential, and difficult to develop, this study has successfully synthesized PVMQ with different levels of phenyl, and made an attempt to find out the factors affecting molecular weight and the relation between phenyl content and the performance of silicone rubber.This paper explores the appropriate temperature and catalyst while chlorosilane hydrolysis is being conducted during the preparation of ring-phenyl siloxane. It aims to illustrate the theoretical difficulties for preparing high-phenyl silicone rubber and the difficulty to increase the molecular weight of phenyl silicone rubber, starting from the anionic ring-opening polymerization mechanism and the balance reaction of silane. The subsequent experiments are conducted to make sure the most appropriate conditions for synthesizing phenyl silicone rubber, for example, the reaction time, the reaction temperature, the amount of catalyst, the amount of blocking agent and the post-processing time. The conditions determined for the experiment are:two-hour reaction time,0.03% tetramethylammonium hydroxide as catalyst and 100℃as reaction temperature,0.1% blocking agent and three-hour post-processing time.In addition, the experiment explores the relation between the phenyl content and the performance of silicon rubber. The benzene prepared in the experiment satisfies actual production needs. Physical and mechanical properties testing shows that as phenyl content increases, it is becoming easier for the phenyl silicone rubber to extend, but more difficult to be torn, and there is little change in its hardness. It is found out that the glass transition temperature of phenyl silicone rubber ranges between-120℃and-110℃, and the glass transition temperature of silicone rubber is rising with the increase of phenyl content. dimethyl silicone rubber and low-phenyl PVMQ are crystalline silicon rubber while medium-phenyl PVMQ is non-crystalline silicon rubber. The dynamic mechanical properties tests for silicone rubber indicate that the glass transition temperature for MVQ, low-phenyl PVMQ and medium-phenyl PVMQ ranges from-125℃to-110℃, and Tg rises with the increase of phenyl content, consistent to the DSC test result. The maximum value of tan8 for MVQ is 0.21,0.63 for low-phenyl PVMQ, and 0.72 for medium-phenyl PVMQ. The introduction of phenyl significantly increases the value of tanδfor silicone rubber, achieves the expansion from damping temperature to high temperature. As the effective damping temperature increases, this result will be more prominent as phenyl content in PVMQ increases.