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Abstract
Two scries of copolymers, siloxane-urethane and imide-containing siloxane-urethane copolymers (SiU and SiUI copolymers), were synthesized from 4,4'-diphenylmethane diisocyanate (MDI), OH-terminated polydimethylsiloxane (PDMS) and chain extender 1,4-butanediol (1,4-BD) or pyromellitic dianhydride (PMDA) in one-step process. SiU copolymer had four stages of degradation. The degradation in the first, second, third and fourth stage were caused by the decomposition of urethane resulted from MDI and 1,4-BD at 250∼320 °C, urethane resulted from MDI and PDMS at 320∼420 °C, linear PDMS at 420∼550 °C, and macro-cyclics PDMS at 550∼620 °C, respectively. SiUI copolymer had three stages of degradation caused by decomposition of urethane resulted from MDI and PDMS, linear PDMS, and PMDA. The imide group and content greatly affected the degradation behavior of copolymer. The influence of components, hard and soft contents on degradation characterization and thermal stability of copolymer at 220 °C and 450 °C were investigated by the isothermal degradation measurements.
Published Version
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