Synthesis and characterization of a rigid-rod dihydroxy poly(p-phenylene benzobisoxazole) fiber with excellent surface and axial compression properties

A series of dihydroxy poly(p-phenylene benzobisoxazole) (DHPBO) were prepared by introducing binary hydroxyl polar groups into poly(p-phenylene benzoxazole) PBO macromolecular chains and the effects of hydroxyl polar groups on surface wettability, interfacial adhesion and axial compression property of PBO fiber were investigated. Contact angle measurement showed that the wetting process both for water and for ethanol on DHPBO fibers were obviously shorter than that on PBO fibers, implying DHPBO fibers have a higher surface free energy. Meanwhile, single fiber pull-out test showed that DHPBO fibers had higher interfacial shear strength than that of PBO fibers. Scanning electron microscope proved that there was more resin remained on the surface of DHPBO fibers than on PBO fibers after pull-out test. Furthermore, axial compression bending test showed that the introduction of binary hydroxyl groups into macromolecular chains apparently improved the equivalent bending modulus of DHPBO fibers.