CREEP RESISTANCE AND HIGH-TEMPERATURE STRENGTH OF POLY(PARA-XYLYLENE) FIBERS

High-strength and high-modulus poly(p-xylylene) (PPX) fibers show no creep at room temperature and retain at 200-degrees-C, in air or in nitrogen atmosphere, still 50 to 60 % of their tensile strengths at room temperature, whereas the modulus does not change. In stress relaxation experiments PPX fibers have relaxed after 17.4 hours less than 4 % of the initial stress whereas during the same period of time polyethylene fibers relax over 75 % of the initial stress.