| Aramid paper has become a revolutionary material as its excellent mechanical, che mical, electrical and physical properties, which was wildly applied as the basic and structural materials in a number of fields, such as military industry, teleco mmunications, transportation and electric industry. However, strength properties mechanical including properties and dielectric properties of domestic ara mid paper are in the low-end level, so it can’t meet the requirements of high-end area in harsh environments.To solve these problems, nano-Si O2 and nano-Al2O3 were used to enhance the mechanical properties and dielec tric properties of ara mid paper. Combination dispersant and ultrasonic dispersion together to deter mine dispersion processes of nano-particles. Then the two kinds of nano-particles were added into the paper and effects of their additio n amount on the mecha nical properties, dielectric properties, crystalline and thermal performance of ara mid paper were studied. The hot pressing processes of aramid paper containing nano-particles were optimized. To improve the interface compatibility between nano-particles and aramid fibers, the nano-particles were modified by silane coupling agent, and effects of the ratio of silane coupling agent and nano-particles, amount of modified nano-particles on the perfor mance of aramid paper were studyed.The degree of dispersion of nano-particles has a significant impact on the performance of aramid paper. Combination dispersant and ultrasonic dispersion together to determine dispersion processes of nano- particles, the optimal dispersion process of nano-Si O2 was the dispersion concentration of 0.1%, the ultrasonic time 30 min, ultrasonic power 400 W, dosage of dispersant sodium dodecyl benzene sulfonate of 2%. The optimal dispersion process of nano-Al2O3 was the dispersion concentration of 0.4%, the ultrasonic time 30 min, ultrasonic p ower of 400 W, dosage of dispersant sodium polyacrylate of 2.5%.Aramid fiber and pulp were observed by optical microscopy and SEM, and the aramid pulp was analyzed by sieve analysis and Mor Fi morphological analysis. The results showed that there were groov es and folds on ara mid fiber surface, while aramid pulp was ribbon-like and with a high degree of surface fibrillation. Screening results of ara mid pulp showed that its co mposition was mainly distributed between 50-200 mesh, and pulp was relatively fine ov erall, which may be beneficial to keep the nano-particles. The number average length and weight average length of ara mid pulp were 0.466 mm and 0.609 mm respectively, which indicated that the overall length distribution of pulp was uneven.The result of effects of two nano-particles’ addition amount on the perfor mance of ara mid paper showed that, when the amount of nano-Si O2 was 15%, the tensile index of aramid paper was increased by 29.63%, the dielectric strength increased by 48.82%, but the tear inde x and tightness of paper was not changed obviously. The crystallinity of aramid paper was decreased when added so me nano-Si O2, but the ther mal properties of ara mid paper were notaffected. When the amount of nano-Al2O3 was 4%, the tensile index of ara mid paper wa s increased by 18.57%, tear index increased by 17.10%, the dielectric strengt h increased by 40.14%, but tightness was unchanged basically. In addition, the crystallinity of ara mid paper had improved when added some nano-Al2O3. Compared with paper without nano-Al2O3, the therma l decomposition temperature of ara mid paper had improved 30 ℃.TGA results showed that the addition of cationic polyacrylamide would increase the retention of nano-Si O2 in ara mid paper, but had no effect on the retention of nano-Al2O3. The aramid paper with two nan-particles and without nano-particles were measured by IR spectroscopy, and the infrared spectra results of three paper showed that there were no differences between the m, which indicated that the nano-particles and aramid fibers may be associated physically.The hot pressing processes of aramid paper contained two nano-particles were optimized. The results showed that the optimu m conditions of ara mid paper with the addition of nano-Si O2 for 15% was that the preheat time was 20 s, pressing time was 1.5 min, hot-pressure was 15 MPa and pressing temperature was 250-260℃. The optimu m conditions of aramid paper with the addition of nano-Al2O3 for 4% was that the preheat time was 40 s, pressing time was 1.0min, hot pressure was 15 MPa, hot te mperature was 260 ℃.Finally, to improve the interface compatibility betwee n nano-particles and aramid paper, both two kinds of nano-particles were modified with silicon coupling agent KH-550. After the modification, the particle size of nano-Si O2 was decreased, and its centrifugal stable dispersion degree was 3, which had increased comparing wit h nano-Si O2 unmodified. Although the particle size of modified nano-Al2O3 was decreased, the centrifugal stable dispersion degree equivalent to that of the unmodified nano-Al2O3 and the value was stable at 1. When the ratio of nano-Si O2 and silicon coupling agent KH-550 was 5g: 20 m L, and the loading of modified nano-Si O2 was 5%, the tensile strength of ara mid paper and the dielectric strength were increased by 66.24% 41.57%, respectively, while the tightness staid at the original level and tear index fluctuated around a tiny range. Whe n the ratio of nano-Al2O3 and silicon coupling agent KH-550 was 5g: 15 m L, the loading of modified nano-Al2O3 was 6%, the tensile strength of the paper was increased by 58.34%, the dielectric strength increased by 37.02%, and trends of tightness and tear index were as the same as adding modified nano-Si O2. |
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