Effects of NO₂ gas concentration on the degradation of polyphenylene sulfide non-woven bag filter at high temperature

The influence of NO₂ concentration and exposure time on the degradation of polyphenylene sulfide (PPS) fabric filter at high temperature was investigated in detail. PPS fiber damage in the filter became more severe with increasing NO₂ concentration and exposure time. The elastic modulus of the PPS filter increased rapidly during the initial stage of exposure, and then increased more slowly to reach an almost constant value, nearly independent of NO₂ concentration. The tensile strength also decreased significantly during the initial stage, gradually attaining a constant value with increasing exposure time. Higher NO₂ concentrations resulted in rapid reducing of the tensile strength. Short exposure time to lower NO₂ concentrations caused the oxidation of S atoms in PPS to [sbnd]SO[sbnd] and O[dbnd]S[dbnd]O, whereas oxidation of benzene rings in PPS were induced only with longer exposure times and higher NO₂ concentrations. The model proposed in our previous paper accurately expresses the change in PPS conversion and reaction rate for every NO₂ concentration. An improved model that successfully estimated the degradation of tensile strength in both the machine direction and transverse direction, regardless of NO₂ concentration, was also proposed.