The pyrolytic process and thermal degradation kinetics of UV cured multi thiol-vinyl silizane precursor was investigated by TGA-MS

FTIR

TGA-DTA.It was found that the pyrolytic processes consisted of three stages:280～430℃ (stage 1)

430～560℃ (stage 2)and above 560℃ (stage 3).In the first stage

about 20% initial weight was lost

NH3

H2 and CH4 were released by transamination

dehydrcoupling and demethylate reaction.CO2

H2S

SO2 and a little amount of thiophene and 2-methyl thiophene were evolved during the first two stages

caused by —C(=O)—O— and C—S chemical bonds decomposed.In the third stage

about 7% initial weight was lost compared with about 9% was lost in the second stage

H2 and CH4 evolved due to dehydrcoupling between C—H and C—H (or Si—H and N—H) and Si—CH3 breakage.The kinetic parameters of thermal degradation were determined by Vachuska-Voboril and Friedman methods using data of TGA-DTA with different heating rates between 5 K/min and 40 K/min under highly purity N2 atmosphere.The results showed that (i) the apparent activation energy and reaction order increased in the first stage with the increase of functionality of thiol groups

and difference of these kinetic parameters in the second stage was not obvious; (ii) the final ceramic yield and activation energies at lower degradation degree of the copolymers decreased with increasing the content of thiol compound

whereas higher activation energies were obtained at higher degradation degree; the apparent activation energies of copolymers with the molar ratio of thiol to vinyl groups 1∶3 and 2∶1 were in the range of 175～195 kJ/mol and 95～118 kJ/mol (0.05≤α≤0.65)

respectively.