Diacetylene-siloxane-carborane thermosets and ceramic precursors

Abstract

Thermosets and ceramic chars were prepared and characterized from a diacetylene–siloxane–carborane polymer, DSCS, and a diacetylene–siloxane polymer, DS. The goal was to incorporate the known thermo‐oxidative stability found in the siloxane–carborane elastomers into high‐performance thermosets and ceramic chars. The DSCS thermoset had excellent thermo‐oxidative stability as determined by a low weight loss and tough residue after annealing for 100 h in air at 300 °C, but it had a low glass transition temperature (94 °C). The DS thermoset did not undergo a glass transition below 350 °C and had a low weight loss on thermo‐oxidative aging, but the residue was quite brittle. Two random copolymers were made to optimize the thermo‐oxidative stability and toughness of the DSCS thermoset and the higher glass transition of the DS thermoset. Significantly, the 50:50 DSCS/DS random copolymer when cured to a thermoset did not undergo a glass transition below 350 °C, yet retained much of the strength, toughness and thermo‐oxidative stability of the DSCS thermoset. Heat treatment of the poly‐DSCS to elevated temperatures resulted in a ceramic material with improved properties relative to the ceramic derived from poly‐DS. Both polymers had similar char yields to 800 °C, but the poly‐DSCS solidified to a 15% denser ceramic. Copyright © 2000 John Wiley & Sons, Ltd.

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Preparation, characterization and properties of fiber reinforced composites using silicon-containing hybrid polymers

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