The Mechanism of the Alcoholysis of High Temperature Vulcanized Silicone Rubber

• Main Authors: Huang, Kao-Cheng, 黃國徵
• Other Authors: Chang Cheng-Liang
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/56309764068050450655

碩士 === 淡江大學 === 化學工程學系 === 85 === The objective of this reserch was to investigate the reaction mechanism of alcoholysis of HTV silicone rubber. Careful examination of the strong base enhanced alcoholysis of model compound revealed that the gas product was ethylene as was identified by GC- MASS analysis and the liquid products were PDMS terminated by -OMe and -OEt groups as were confirmed by 1H-NMR analysis. This result indicated a mechanism of alcoholysis that involved the β-elimination reaction. Subsequently, HTV silicone rubber was prepared via the hydrosilylation reaction of vinyl silicone fluid and silicone hydride fluid, dissolved in an alcohol solution. A large amount of gas bubbles appeared in the alcoholysis system. This gaseous byproduct was found to be ethylene as was analysed by passing it through a potassium permangnate solution. This confirmed the occurrence of β- elimination reaction demonstrated in the cracking system. Furthermore, when HTV silicone rubber was dissolved in the amine solution, the degradation of HTV silicone rubber was found to complete within 15 minutes , much faster than the degradation rate of RTV silicone rubber. When THF was employed as the solvent ,the main products became D5, D4 and a minute amount of MD2M. The terminal groups of the obtained polymers were -OH and -OEt. This suggested that the cyclization reaction due to the back-bitting effect was influenced by the solvent polarity. The aminolysis reaction of commercial HTV silicone rubber was also studied in this reserch. The performance of the degradation of commercial HTV silicone rubber was similar to that of the synthesized rubber. It could therefore be concluded the nucleophilic reaction had happened in the aminolysis process, which we have developed. As different solvents in this case , THF or toluene were empolyed as the carrier, the yields of the aminolysis reactions and the molecular weight of the polymer products changed depending upon the rate of the back- bitting step.