Study On The Auxiliaries For Making Polyimide/Aramid Fiber Paper

Polyimide fiber has excellent mechanical properties,the fracture strength can reach 6.4Gpa,high temperature and low temperature resistance,the initial decomposition temperature is greater than 500℃,can not be quended in liquid helium,and the thermal expansion coefficient is small,the dielectric performance is outstanding.But polyimide fibers are rigid,smooth,and lack of active groups.The aramid fiber also has good strength and thermal stability,the aramid pulp obtained after the fibronzing treatment can greatly improve the interweaving force between the fibers,and the polyimide fiber can improve the initial strength of the paper.But,because of the poor hydrophilic and excessive length of polyimide fiber,and the high curvature of aramid pulp,the pulp is easy to gather after molding,lead to poor paper evenness and loose structure.So the study focusing on choosing appropriate forming additives to improve the dispersion characteristics of the thick liquid material,improve the evenness of paper,at the same time,the strength cannot reach the requirements,so it is necessary to further improve the strength and barrier properties of the paper by using maceration processing.Firstly,the paper forming process of polyimide fiber paper was studied by observing the fiber morphology,analyzing the properties of paper structure,so as to determine the necessity way and order of using auxiliaries.The results show that:（1）Fiber bundles can be removed by a trough beater.（2）The heat resistance of the paper becomes worse coordinated with plant fiber.The length of aramid pulp is 0.7 mm,width is greater than 20 microns,suitable for coordinating（coordinating with 30%,fiber total quality meter）,but need to add some additives.（3）Wet-pressing can not significantly improve the wet strength and dry strength of polyimide fiber paper,and the use of auxiliaries is importance.（4）The strength of polyimide fiber paper was still low after the aramid pulp was coordinated.（5）Hot pressing treatment after impregnation of paper can greatly improve the performance of the paper.Secondly,the paper studied the influence of wet chemical control.Results showed that:（1）PEO（60w molecular weight）and cetyl trimethyl ammonium bromide can obviously improve the paper evenness and strength,PEO（0.1 g/L）compounded with hexadecyl trimethyl ammonium bromide(0.1 x10^-3 mol/L)can obtain good effect,adding suitable amount of Lamepon can reduce paper electrostatic.（2）In the selected wet strength agent,cationic polyacrylamide has a significant humidification effect,and can simultaneously improve the dry strength of the paper.（3）Water-soluble epoxy resin can obviously improve the dry strength of paper,but is not suitable for pulp addition.Then,the properties of several resins were compared by analysing chemical structure,thermodynamic performance and morphology,the resins were synthesized and modified according to the needs.The results showed that:（1）polyimide resin has the best heat resistance,epoxy resin has strong adhesion,methyl phenyl silicone resin and vinyl silicone resin have good flexibility.（2）Among the synthetic phenolic resins,the mass loss temperature of 5%of the resin rose to 295℃and the carbon residue rate increased to 73%.（3）using vinyl silicone modified（dosage of 30%）,after curing the resin system toughness and crosslinking density were improved.（4）The 5%mass loss temperature of alloy resin was increased to339.2℃after adding 5%polyimide resin to the modified epoxy resin.Finally,the polyimide fiber paper matrix composites were impregnated with the resin,and the mechanical properties and morphology of the paper were analyzed.Results showed that（1）The epoxy resin impregnation volume 30%,the paper tensile index can reach 46.6N·m/g,but the strength declined obviously at 200℃.（2）Synthetic phenolic resin has good curing performance,tensile index can reach 52.1 N·m/g dipping 30%phenolic 1#,and remain 35 N·m/g at 200℃.（3）Strength of paper impregnated with epoxy resin modified by methyl phenyl silicone resin decreased obviously at high temperature,tensile index can reach 30.24 N·m/g dipping by 30%vinyl silicone modified epoxy resin at 200℃,at the same temperature the tensile index can reach 33.91 N·m/g impregnated by alloy resin,fiber combined closely when paper impregnated by vinyl silicone modified epoxy resin,and with surface has good hydrophobic properties.