Polymer-Oxygen Compatibility Testing: Effect of Oxygen Aging on Ignition and Combustion Properties

摘要

The oxygen (O_2) compatibility of six polymers used in O_2 service was evaluated after 48 h exposures at 121 °C (250 °C) to O_2 pressures of 620 and 6200 kPa (90 and 900 psia). Three elastomers were tested: chloroprene rubber (C873-70), fluorocarbon rubber (Viton~((~R)3) A), and silicone rubber (MVQ type); and three thermoplastics were tested: polyhexamethylene adipamide (Zytel~((~R)3) 42), polytetrafluoroethylene (PTFE Teflon~((~R)3) 500A), and polychlorotrifluoroethylene (Neoflon~((~R)3) CTFE M400H). Post-aged changes in mass, dimensions, tensile strength, elongation at break, durometer hardness, and thermomechanical properties were evaluated. For selected materials, gaseous nitrogen-(GN_2-) aged controls were used to ascertain the effect of thermal versus oxidative degradation. Finally, -the effect of O_2 aging on selected ignition (AIT) and combustion (ΔH_C) properties was determined. As expected, aged polymers were less ignitable and combustible. Special attention was given to Neoflon CTFE; namely, the possible effect of percent crystallinity (quick- versus slow-quenched) on the aging, ignition, and combustion behavior was evaluated.