Effects Of Heat And Ultraviolet Treatemnt Onthe Structure And Properties Of PIPD Fibers

In last ten years, poly(pyridobisimiazole)(PIPD) fibers have gained more and more attentions because of its excellent properties, so it’s meaningful to study PIPD fibers to improve its properties, as well as extending its using field. In this study, the PIPD fibers were treated with heating and ultraviolet light shining,followed by the discussions about the change of fibers structure and the properties.In order to study the influence on the structure and the properties of the heat treatment, temperature, times, and tension were changed during the heat processor,analysis the function of these three elements on the properties of fibers. The properties of the fibers were studies after the best treated conditions were concluded. The time of fibers exposed to the ultraviolet ranged to measure the variation tendency of the fibers structure and properties.The surface morphology of PIPD fibers were observed using Scanning Electron Microscope. FTIR was used to discuss changes of characteristic peaks and the surface elements composition was analyzed by XPS. At the same time, the crystal structure was detected by XRD. Thermogravimetry was used to test the thermal properties after the treatment. The mechanical properties were reflected through tension strength and interface shear strength.The results of the data shows that, heat treatment processor smoothen the fiber surface and compacted the internal structure. IR and XPS explained functional groups changed barely after the heat treatment. Degree of crystallinity increased on a large margin. The TG curves show the thermo-stability promoted,the quality increased 10%. The tension strength reached 2.0609 GPa, which is52.39% increased to the as-spun fibers. The interface shear strength is 55.063 MPa,increased by 18.6%. The optimum heat conditions were as follows: 480℃ for the temperature, 20 g for the tension and the time is 600 s.The ultra-violet processor caused a serious damage to the fiber surface, which was proved by IR and XPS and XRD. From the IR and XPS, polymer chains were broken and new functional groups(-NO2 and C=O) was born. On the other hand,XRD analysis showed the size of the crystalline grain decreased remarkable. The tension strength decreased gradually varied from the time exposed to ultraviolet ray. The tensile strength retention of HT-PIPD was 56% after the ultra-violet processor, which was 13% higher than that of the AS-PIPD fibers. The interfacial shear strength shows a feature which increased first then decreased.Comprehensive considered the decrease extent of the strength and new functionalgroups occurred in the IR and the XPS analysis, reaction formula was speculated.