Accession Number:

ADA232686

Title:

A Study of the Critical Factors Controlling the Synthesis of Ceramic Matrix Composites from Preceramic Polymers

Descriptive Note:

Final rept. 1 Oct 1987-15 Nov 1990

Corporate Author:

UNITED TECHNOLOGIES RESEARCH CENTER EAST HARTFORD CT

Report Date:

1990-12-15

Pagination or Media Count:

53.0

Abstract:

In this three year program, vinylmethylsilane co-polymers which were processable at ambient pressure were studied as precursors for silicon carbide matrix composites. Using measurements of curing characteristics, rheological properties, and pyrolysis kinetics, fabrication cycles for processing carbon fabric reinforced composites were identified. Composites exhibiting a range of useful mechanical properties were demonstrated. The primary shortcomings of a commercially available vinylmethylsilane polymer used in composite fabrication were identified as extreme sensitivity to oxygen contamination during processing and excess carbon in the pyrolyzed products. Analytical methods showed that 900 C pyrolysis products were amorphous ceramics consisting primarily of SiO-C complexes. The amorphous ceramic was unstable above 1200 C where CO and CO2 release initiated. Ceramic products converted at 1440 C showed increases in Beta-SiC and and SiO2 content at the expense of Si-O-C content. Polymer modifications were pursued to improve the converted ceramic thermal stability and stoichiometry. Novel methylvinylsilanes with reactive endgroups exhibited significantly reduced oxygen sensitivity and high ceramic convertibility.

Subject Categories:

  • Polymer Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE