Preparation And Properties Investigation Of Liquid Crystalline Polyester-imide/Phenol Formaldehyde Resin Composition

Liquid crystalline polyester-imide (TLCP) is a novel kind of liquid crystalline polymers,it has been widely used in the aerospace、fiber optics、electronic、LCD and laser fields, so ithas attracted people’s considerable research interest. In this paper, four kinds of liquidcrystalline polyester-imide was designed and systhesized. The structure and properties of theliquid crystalline polymers were studied. The liquid crystal polyester polyimide(TLCP)/phenolic resin (PF) composites were prepared by blending and melt extrusionmethod. Effects of TLCP on the morphology of phenolic resin blends and the structure andproperties of TLCP/PF composites were studied.Based on the developed Higashi’s direct polycondensation method, tri-copolymer withPHQ、tri-copolymer with DHBP、tetra-copolymer with HQ and tetra-copolymer with BP weresynthesized derived from N, N’-hexane-1,6-diybis (tri-millitimides)(IA6), p-hydroxylbenzoic acid (PHB) and different diphenols. FTIR, DSC, TGA, POM and WAXD et al wereused to study the structure and properties of the TLCPs. Results showed that characteristicpeaks of both methylene and imide bond were appeared. Due to the mesogenic proportion oftri-copolymer with PHQ is higher, therefore its melting point higher34oC than that oftri-copolymer with DHBP. Compared with two kinds of tetra-copolymers and tri-copolymerwith DHBP, duo to added different diphenols, the melting point and clear point of two kindsof tetra-copolymers are reduced more than10oC. The TLCPs exhibited nematic phase withthreaded texture and had wide mesophase temperature range. the decomposition temperatureof the TLCPs were＞380oC.The blends of TLCP/PF resin were prepared by one-step and two-step processes. POM、WAXD and TGA were used to study the inference of adding methods、temperature、TLCPcontent and curing time to the morphology and thermal properties of the blends. Resultsshowed that two-step blending method to blend TLCP with PF is better than one-stepblending method,230-240oC is the ideal blending temperature range; When the content ofTLCP is7.5%, the initial decomposition temperature of blends increased by32.58oC than thepure PF, the initial decomposition temperature of two-step blends increased by24.88oC thanthat of one-step blends.Differential Scanning Calorimetry (DSC) was used to study the curing kinetics ofThermotropic liquid crystalline polyester-imide (TLCP)/phenol formaldehyde resin (PF)blends with different content of TLCP and curing agent. The results show that the activationenergy calculated by Kissinger model in agreement with that by Ozawa. Strong dependencyof activation energy on apparent conversion has been observed for all blends by KAS model. The presence of TLCP accelerates the addition reaction in the curing process of PF andreduces the activation energy. The apparent activation energy of TLCP/PF blends has thelowest value when the loading of TLCP was3%, the minimum of the apparent activationenergy is140.0kJ/mol (Ozawa model) and127.8kJ/mol (Kissinger model). The presence ofcuring agent involved in the curing process of PF, The apparent activation energy ofTLCP/PF blends has the lowest value when the content of curing agent was6%., theminimum of the apparent activation energy is136.3kJ/mol (Ozawa model) and123.8kJ/mol(Kissinger model).Thermotropic liquid crystal polyester-imide (TLCP)/Phenol-formaldehyde resin (PF)composites were prepared. Effects of TLCP contents on mechanical properties and thermalproperties were studied. Results showed that the addition of TLCP, the mechanical propertiesand thermal properties of TLCP/PF composites was improved. The impact strength, bendingstrength, the decomposition temperature of TLCP/PF composites was increased by23.77%,26.99%and25oC respectively.