| Aramid has wide application prospects in aerospace,high-speed trains and high-performance electric and electronic industry,due to their high heat resistance,excellent high strength,high modulus,superior heat resistance,corrosion resistance and insulation properties.However,there is still a great gap in mechanical property and insulation performance between the domestic aramid paper and Nomex paper.The problems of the domestic aramid paper can be attributed to the low quality of raw materials,poor dispersion of the fibers and its low-tech wet-process technology and equipments.In particular,imperfections about the hot pressing process and the interface adhesion between the fibers have not solved yet.In addition,it still needs concerning that Nomex papers are applied to the low-end field,but the high performance appears superfluous.The hybrid fiber technique provides an effective method to prepare various aramid papers with better integrated performance through the completary advantages of different raw papers.In this work,high performance hybrid fiber papers were prepared by para-aramid fiber?PPTA?,meta-aramid fiber?PMIA?,baodelun fiber?POD?,aromatic sulfonamide fiber?PSA?,polyester fiber?PET?and meta aramid pulp?PMIA?.Based on the comprehensive understanding of the structure and properties of different types of fibers,the application potential of high-performance hybrid fiber paper made from different types of chopped fibers and meta-aramid pulp was discussed.Different types of fiber reinforced paper-based composites were prepared by mixing single-component chopped fibers,two-component chopped fibers and meta-aramid pulp,and the hot pressing process was also optimized.Influences of the interaction and interface bonding properties on chopped fibers and fibrids during hot-pressing process were also studied.According to the structure and performance requirements of product,adjusting the fiber type,ratio,hybrid,forming methods,other processing parameters and preparation technology,a series of cost-effective functional composite materials with controllable design and preparation were synthized.The above research results can help to expand the range of raw materials and lay foundation of further study for aramid paper-based materials.Different types of chopped fiber were all with cylindrical rod-like structure and large thickness difference.The length of the fibers was around 5mm;surface of the PMIA-fiber was rough with large amount gully-like wrinkles,but surfaces of the PPTA-fiber,POD-fiber,PSA-fiber and PET-fiber were smooth.PMIA-pulp was a kind of soft fine fibrid with ribbon-like shape.It was beneficial for the wetting forming process owning to its high surface area.The crystallinity of PPTA-fiber,POD-fiber and PET-fiber were relatively higher,followed by PMIA-fiber,while crystallinity of PSA-fiber was the lowest.PMIA pulp is amorphous structure with larger amorphous degree.Different types of fibers have different heat resistance,PPTA-fiber and POD-fiber were relatively higher,PMIA-fiber,PSA-fiber and PMIA-slurry were junior,and the thermal stability of PET-fiber was the worst.Single-component mixed fiber paper was prepared by five type chopped fibers and PMIA-pulp.The results showed that under the optimum hot pressing conditions,the tensile index of PPTA-paper were 212.6N·m· g-1,which was about twice of that of Nomex T410 paper(111.1N· m· g-1).The tensile indexes of PMIA-paper and POD-paper between 95100N· m· g-1 were slightly less than that of Nomex T410 paper,PSA-paper and PET-paper between 8090N· m· g-1 were relatively poorer.The dielectric strengths of PPTA-paper,PMIA-paper,POD-paper,PSA-paper between 1417.0kV· mm-1,PET-paper were relatively high 22.0kV· mm-1,but still remained a big gap with Nomex T410 paper(27.0kV· mm-1).The high hot pressing temperature was beneficial to improve the crystallinity of the paper.PPTA-paper,PMIA-paper,POD-paper,PSA-paper heat resistance are similar,PET-paper heat resistance was poorer,but it still had a stable heat resistance.The two-component mixed paper was prepared by mixing PPTA-fiber,POD-fiber,PSA-fiber,PET-fiber and PMIA-pulp,and the optimum chopped fiber ratio and hot-pressing process were also discussed.The results showed that under the optimum chopped fiber ratio and hot pressing process condition: the tensile index PPTA/PMIA-paper was 130.4N· m· g-1,the dielectric strength was 26.0kV· mm-1,comprehensive performance better than Nomex T410 paper.But the POD/PMIA-paper,PSA/PMIA-paper,PET/PMIA-paper comprehensive performance were quite different from Nomex T410 paper.High crystallinity bulk fiber was beneficial to the improvement of the crystallinity of different chopped fiber hybrid paper.Compared with the heat-resistant properties of the paper,the self-made paper has relatively stable heat resistance.The PPTA/PMIA-paper,POD/PMIA-paper and PSA/PMIA-paper have similar heat resistance,while the thermal performance of PET/PMIA-paper is relatively poorer.It can be concluded that the PPTA-paper has effectively improved its composite properties,alignment structure and high strength property with paper forming advantages.And the PET-paper can successfully enhace its electrical properties owing to its alignment structure.Based on previous results,the high cost-performance ratio hybrid fiber paper-based materials were further prepared,and the high cost PPTA-fiber with remarkable effect on the mechanical properties of PMIA-paper was selected and the low-cost PET chopped fiber was used to enhance the electrical insulation performance.The results showed that mechanical properties,insulation properties,crystallinity and heat resistance of the paper were similar to those of Nomex T410 paper when the mixing ratio of PPTA/PET chopped fiber was 1: 3.And through the adjustment and selection of different types,the relative content of different fibers,different hybrid methods,the products with cost-effective paper-based functional composite materials can be controlled designed.Consequently,it has laid good foundations for the expanded choice of raw materials and further study. |
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