| Summary: | 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.
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