POLY(P-PHENYLENEBENZOBISOXAZOLE) FIBER WITH POLYPHENYLENE SULFIDE PENDENT GROUPS

Poly(p-phenylenebenzobisoxazole) (PBO) fiber with polyphenylene sulfid e (PPS) pendent groups was made to improve PBO fiber compressive stren gth by crosslinking. PPS moieties allowed the polymeric network to cro sslink at heat-treatment temperatures at which PBO does not thermally degrade. PBO-PPS fiber heat-treated for 30 s at 600-degrees-C did not dissolve or break up in methanesulfonic acid. Compressive strength of crosslinked fiber was about 20% better than that of unmodified PBO fib er. In another experiment, 10 mol % of 2,5-diphenylsulfideterephthalic acid was incorporated into PBO fiber. The side chain of one phenyl su lfide unit was too short to enhance crosslinking, and the fiber had ab out the same compressive strength as unmodified PBO fiber. (C) 1995 Jo hn Wiley & Sons, Inc.