Synthesis And Abrasion Resistance Modification Of Polyimides

Polyimides have excellent thermal properties, mechanical properties, corrosion resistance and abrasion resistance, and have great application value in the fields of faerospace,microelectronic and automotive. But most of polyimides are insoluble,not melting and shows a poor processing performance, then their widespread application was limited. Therefor,synthesis of new type polyimides with excellent thermal properties and processability was one of research hotspot in these filed.A series of thermosetting polyimides were successfully synthesized from the dianhydride monomers 2,3,3’,4’-biphenyltetracarboxylic dianhydride (a-BPDA), 2,3,3’,4’-diphenyl ether tetracarboxylic acid dianhydride (a-ODPA) and 4,4’-(hexafluoroisopropylidene)diphthalic anhydride (6-FDA) with different diamine monomers 4,4’-diaminodiphenylmethane (MDA),p-phenylenediamine (p-PDA) and m-phenylenediamine (m-PDA) using 4-phenylethynylphthalic anhydride (4-PEPA) as an end-capping agent. The structure of polyimide resins were characterized by IR, and the melt rheological properties and thermal properties of polyimides were investigated by rheometer, TGA and DMA, The results indicate that all polyimides have excellent thermal performance. The polyimide (PI-1) exhibits a high glass transition temperature of 368 ℃ and excellent thermal stability that the 5% weight loss temperatures reached 550 ℃ in N2,the lowest melt viscosity was 14.5 Pa.s, This polyimide has excellent processability and thermal properties, and has a broad application prospect in aerospace field.In this paper, the kinetics of the curing reaction of resin PI-1 was studied by the method of non-isothermal DSC. Kissinger method and Ozawa method showed that the activation energy (Ea) of PI-1 was 142.96 kJ/mol and 146.36 kJ/mol, respectively. This curing reaction was considered as a first order reaction. This curing reaction kinetics equation of resin PI-1 was dα/dt= 2.44×109 exp(-17400/T)(1-a)0.9399 . The theoretical curing process of PI-1 was 304 ℃/1h + 357 ℃/1h + 401 ℃/1h.In this paper, using molybdenum disulfide (MoS2),silicon dioxide (SiO2) and silicon nitride (Si3N4) as abrasion resistance modifier, and researching abrasion resistance of modified polyimide resins. The friction and wear performance and wear surface of polyimide resins were tested and analyzed by friction testing machine and SEM. The results indicate that the abrasion resistance of polyimide resin modified with MoS2 was the best, when MoS2 filling quantity of 15%, the friction coefficient of polyimide resin reduced to 0.121 from 0.212,the wear mass loss was decreased by 53%.