Research On Heat-resistant Property Of PEEK Resin Modified By A Thermoplastic Polyimide

Specialized engineering plastics, also known as high-performance engineeringplastics, are mainly used in high-tech fields, with excellent overall performance,long-term use under temperature higher than150oC. Specialized engineering plasticswhich have excellent characteristics of high specific strength, high heat-resistantgrade are the third generation of advanced polymer materials after common plastics,general engineering plastics. In recent years, the study of specialized engineeringplastics has been rapidly developed and a wide variety of specialized engineeringplastics are industrialized, The main varieties are: polyimides (PI), polyaromatic etherketone(PAEK), etc. More and more research attention has been focused on specializedengineering plastics as they are widely used in the cutting-edge industry for theiroutstanding combined properties.Polyether ether ketone (PEEK)，having excellent overall performance, is themost typical materials in polyaryletherketone (PAEK), which can be substituted withother materials in many fields and significantly enhance the products’ performance.But PEEK has a low glass transition temperature (Tg) and heat distortion temperature,therefore the mechanical properties decreased rapidly in high temperature. Meltviscosity is not sensitive to temperature changes lead to processing difficulties, Highcost of PEEK restrict its application. So PEEK modified becomes a research hotspotin recent years, chemical modification and filling modification is usually used toimprove the performance of PEEK in high temperature.Polyimide (PI) has excellent mechanical properties, heat resistance, dimensionalstability and weather resistance, etc., its products are widely used in a number of areasand countries. But polyimide usually has a high melting point/softening temperature,therefore it has poor melt processing properties. From the analysis of chemicalstructure, the rigidity of the molecular chains, force between the molecular chains, crystallization, and other factors cause the polyimide molecular chain to packedclosely,so it has a high melting/softening temperature and poor dissolutionproperties. Therefore, from molecular design perspective, changing the repeatingunits of molecular chain can improve the processing properties of the TPI which canbe used as a modifier for PEEK.In the study, we use the isomer blend comprising non-planar structure ofdianhydride monomer (s-BPDA, a-BPDA, i-BPDA) and a thermoplastic polyimidewas obtained by random copolymerization reaction with4,4’-ODA, and the TPI’sproperties were studied. Thermal and mechanical were evaluated and the resultsshowed that this type of TPI had good thermal and mechanical properties, with a glasstransiton temperature of320oC, dynamic mechanical analysis showed that thepolyimide chains were highly active during glass transition for the storage modulusunderwent decrease of three-order magnitude, implying a high degree of thermalplasticity. Melt viscosity results showed that this type of polyimide had a relativelylow melt viscosity and stability of the melt fluidity when melted, showing that meltprocessing can be conducted to this TPI, which layed the foundation of melt blendingwith PEEK as a modifier.Modified PEEK resins were obtained by mechanical blending method,amorphous films and the crystalline form films were obtained through different heattreatment method. TGA analysis showed good thermal stability of the resin, DSCresults implied composition an incompatible system. Melt viscosity tests showed thatthe modified resin had good melt stability, and melt viscosity can be controlled by themolecular weight of the PI and the component of the resin, DMA analysis gave theimpression of incompatibility again and, the retention of storage modulus at hightemperature ranges increased as the modifier component increased, Dimensionalstability was also enhanced as the modifier was incorporated，especially for theamorphous samples. As the TPI increasing, the mechanical properties of the resinunder the normal temperature conditions was slightly reduced, but were significantlyincreased in the high temperature, it still had a certain mechanical properties even at 300oC，indicating the high-temperature performance of the resin was improvedcompared to that of pure PEEK.