Tensile and uniaxial fatigue behavior of poly(p-phenylene-co-3,4 '-oxydiphenylene terephthalamide) fibers: Relationship with chain orientation

This paper investigates the physical properties of poly(p-phenylene-co-3,4' -oxy-diphenylene terephthalamide) [PpPOT] fibers in comparison with poly(p- phenylene terephthalamide) (PPTA) fibers. With regard to tensile responses, the two fibers show nearly the same elastic deformation with significant m odulus increase during extension. However, they form a singular contrast wh en it comes to tensile-tensile fatigue behavior. The modulus decreases quit e rapidly after some increase for PPTA, while the decrease is much slower f or PpPOT. These observations are interpreted in correlation with the chain and crystallite movements of the polymers under load, and the influence of hydrogen bonds on slipping is also compared.