Preparation And Characterization Of Phenolic Resin/Attapulgite Nanocomposites And Phenolic Resin/Polyacrylonitrile Pre-oxidized Fibers

In this paper, phenolic resin(PF)/attapulgite(AT) nanocomposites were prepared by solution blending. The purified and acid activated of AT were introduced and the structure and properties of PF/AT nanocomposites were studied by scanning electron microscope (SEM), dynamic mechanical properties (DMA), thermogravimetric analysis (TGA), mechanical test. Moreover, PF/Polyacrylonitrile (PAN) composite fibers were fabricated by wet spinning based on the characteristics of heating curing of PF, which result in the formation of semi-interpenetrating polymer network with PAN during pre-oxidation. Then the composite fibers were pre-oxidated. The ratio of PAN and PF, pre-oxidation temperature and pre-oxidation time were studied.The resulting nanocomposites exhibited increases in the toughness and heat resistance. SEM results indicated that the cross-section of PF/AT nanocomposites were rough and uneven, showing ductile fracture characteristics. The tensile strength of the nanocomposites reached 45.86 MPa and the impact strength was 10.80 KJ*M-2 when the AT content was 1 wt%. DMA results showed that the storage modulus of PF/AT nanocomposites has significantly increased compare to the pure PF. The storage modulus decreased at first and increased as the temperature increasd. The glass transition temperature was 218℃, which increased by 81℃when the AT content was 2wt%. After the post-curing, the storage modulus curves of PF/AT nanocomposites became more flat, confirming the previous increase of DMA storage modulus was caused by the post-curing. The TGA results showed that the thermal degradation of PF/AT nanocomposites can be divided into three stages, and the decomposition temperature of the nanocomposites were higher than that of pure PF. It was found that decomposition of PF/AT nanocomposites required higher activation energy from the kinetic study of TGA data. The three stages of thermal decomposition of PF/AT nanocomposites were studied in detail by TG-FTIR. And the results showed that AT can effcetively prevent the volatile substances during the degradation process, thereby enhancing the thermal stability of PF/AT nanocomposites.PF/PAN pre-oxidized fibers were characterized by DMA, TGA and mechanical test. DMA results showed there was a single peak, which meant the good compatibility between PF and PAN. The glass transition temperature (Tg) of PF/PAN were enhanced with increasing of PF content and reached maximum when PF content was 10% by DMA. TGA results showed that PF was post-cured during the thermal degradation, which led to a more comprehensive network structure. The PF/PAN pre-oxidized fiber exhibited improved mechanical properties. The fracture strength of pre-oxidized fiber reached 8.75cN*dex-1 when PF content was 10%.