Kinetics of thermal depolymerization of trimethylsiloxy end-blocked polydimethylsiloxane and polydimethylsiloxane-N-phenylsilazane copolymer

摘要: Abstract The thermal degradation of Me3SiO end-blocked polydimethylsiloxane (eb-PDMS) and polydimethylsiloxane-N-phenylsilazane (eb-PDMS-NPhSz) copolymer was studied. For both polymers, relative degree polymerization( DP / 0 ) as a function conversion (C = 1 − W/W0) data were obtained. eb-PDMS with three different molecular weights, the results consistent mechanism involving rate-determining random siloxane bond cleavage initiation step followed by rapid complete depropagation active fragments evolving volatile cyclic oligomers. Rate constants for obtained at four temperatures from plots −1 vs. time M n 6.83 × 10 4 . An Arrhenius activation energy ∼ is SiOSi scission transition state. eb-PDMS-NPhSz appears to follow same depolymerization process Although C suggest cleavage-complete mechanism, an plot suggests more complex mechanism. role impurities catalysts discussed.