Study On Aramid Paper-based Functional Materials And Its Reinforcement Technology

The para-aramid paper-based functional materials based on PPTA fiber, alsonamed Korex paper, had exceptional mechanical properties, excellent dielectricproperties, stable chemistry performance and flexibility of designing. Because ofthese favorable properties, the aramid paper had such diverse applications ashoneycomb structure materials, high-temperature insulating materials and highperformance electronic equipment, etc. Compared with Nomex paper, as theexisting of surface inertia of PPTA fiber, the combination of the fiber mat wasvery poor. So this paper-based material could not entirely realize the propertiesof the fiber itself, such as high mechanical strength, dimensional stability andheat resistance. Some special enhancement processing was applying to it.In this paper, chemical-mechanical method of the traditional papermakingprocess was used to produce fibrillated PPTA-pulp in laboratory. By using thecharacterization method of plant fiber combined with modern material analysismethods, the structure and properties of PPTA-pulp were characterized. Based onthis, the effect of different technics on the performance of all para-aramidpaper-based material was systematically investigated. What’s more, in order toimprove the property of para-aramid paper composite, a kind of new high-performance fiber called Y and some kinds of modified phenolic resin wereapplied to the reinforcement of this material. Both of the producing andenhancement processing technology was obtained.First of all, the fiber morphology, chemical structure, thermal performanceand papermaking properties of both PPTA short fiber and PPTA-pulp werecharacterized, by using multimedia microscope, scanning electron microscopy(SEM), fiber quality analysis (FQA) and Bauer screening analysis, infrared spectrum(IR), X-ray diffraction (XRD), thermal analysis (TG), etc.A kind of new high-performance dispersant called S was produced in lab.And it was applied to the preparation of all para-aramid paper-based material toimprove the dispersion property of PPTA short fiber and PPTA-pulp. The keytechnologies of all para-aramid paper composite were systematically investigated,such as the ratio of PPTA-pulp and PPTA-fiber, beating degree of PPTA-pulp,length of PPTA-fiber, etc. The appropriate technology of all para-aramidpaper-based material was achieved. When the beating degree of PPTA-pulp was35°SR, length of PPTA-fiber was5mm and the ratio of PPTA-pulp andPPTA-fiber was70%to30%, the aramid paper’s tensile strength, tearing strength,elongation and dielectric strength was68.17N·m/g,20.95mN·m2/g,1.36%and19.51KV/mm, respectively.The hot pressing of para-aramid paper composite enhanced bythermoplastic fiber Y was optimized by orthogonal experiment. Also, therelevant factors and level affecting the performance of para-aramid papercomposite were analyzed. It showed that the preheat temperature was the mainfactor of paper sheet, and hot pressing pressure and pressure roller speed was thesecondary factors while the influence of hot pressing time was relativelyignorable. The optimized hot pressing process were: preheat temperature180℃,hot pressing pressure14MPa, pressing1time, pressure roller speed1r/min.When the addition of Y fiber is10%, the sample obtained showed the bestenhancement effect, and the tensile strength, tearing strength, elongation anddielectric strength of which was77.03N·m/g,24.10mN·m2/g,1.75%and16.33KV/mm, respectively. And the paper sheet’s hot weightlessness was9.01%under300℃.Finally, the modified phenolic resin was applied to enhance the para-aramidpaper composite. The effect of resin properties, impregnation method and curingprocess on the performance of para-aramid paper composite was discussed. Theappropriate technology para-aramid paper composite enhanced by resin wasachieved. The original aramid sheet was immersed in phenolic resin to get theresin-impregnated sheet. Then it was hot pressed in three different continuousstages. Each stage lasted for10min. The hot pressure and temperature in eachstage was5MPa and120℃,10MPa and180℃,15MPa and260℃, respectively. During the pressing process, there’re short-time pressures releasing two to threetimes to let some small molecules of byproducts volatize effectively. Theperformance of samples obtained under the optimized condition was: tensilestrength109.75N·m/g, tearing strength25.38mN·m2/g, elongation1.91%, anddielectric strength21.15KV/mm.