IMPROVEMENTS IN OR RELATING TO THE PRE-OXIDATION OF THERMALLY RESISTANT AROMATIC POLYMERS

摘要

1,236,282. Polyamide filaments. MONSANTO CO. 15 July, 1968, No. 33726/68. Heading B5B. [Also in Divisions B5 and C3] Thermally resistant wholly aromatic polyamides in the form of films, fibres, fabrics, webs, foams and other shaped articles having similarly high surface: volume ratio are pre-oxidized by heating in air from room temperature to a temperature between 350‹ and 500‹ C. but below that at which structural identity and strength are lost over a period between 45 and 60 minutes and maintaining the polyamide at that temperature for up to 12 hours. Various polyamide, some of which contain heterocyclic rings, are mentioned. The treated articles may be used for flameproof applications, e.g. heat shields, high temperature and electrical insulation, protective clothing and curtains, hot filtration media and supports for ablative materials; they may also be used as precursors for carbon and graphite fibres. In examples poly-mphenylenebis (m-benzamido) terephthalamide and polymers having the repeat unit are treated in the form of fabric or yarn.