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Effect of high‐pressure carbon dioxide on thermal conversion process of polydimethylsilane to Si–C backbone polymers
Author(s) -
Narisawa Masaki,
Yamada Kouya,
Sakura Ukyo,
Inoue Hirofumi
Publication year - 2019
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.16637
Subject(s) - inert gas , yield (engineering) , polymer , bar (unit) , condensation , ceramic , carbon dioxide , volatilisation , atmosphere (unit) , materials science , chemical engineering , viscosity , partial pressure , inert , chemistry , analytical chemistry (journal) , polymer chemistry , organic chemistry , composite material , thermodynamics , physics , meteorology , oxygen , engineering
Polycarbosilane (PCS) is synthesized from polydimethylsilane (PDMS) by thermal condensation reaction in an inert atmosphere. In the new process described in this article, CO 2 at high pressure (2–10 bar) was introduced into the system before the condensation reaction of PDMS. Si – C backbone formation process was accelerated at 340‐360ºC, and brown “PCS” liquid was obtained at 380ºC. Polymer recovery increased from 60% (in a pressure vessel with a N 2 atmosphere) to >95% in CO 2 atmosphere at 10 bar. The apparent viscosity also increased at high CO 2 pressures. Spectrum analysis indicates the existence of the Si – CH 2 – Si, Si – O – Si bridges, and Si – H bonds in the heat‐treated product. The viscous liquid “PCS” obtained at 380ºC is stable up to 200ºC. However, at temperatures of 200–600ºC, the volatilization of macromolecular species proceeded, and the resulting ceramic yield at 1000ºC was 29 mass%. In the CO 2 treatment, product solidified at 420ºC and ceramic yield increased to 56%. The volatilization of macromolecules, however, proceeded in two steps at 200–400ºC and 600–800ºC. When the product was heated beyond 400ºC, it probably contained infinite PCS network with shorter chains.