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 modulus increase during extension. However, they form a singular contrast when it comes to tensile-tensile fatigue behavior. The modulus decreases quite rapidly after some increase for PPTA, while the decrease is much slower for 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.