Design Of High Efficiency Curing System Of Phthalonitrile Resin And Performance Study

Phthalonitrile resin is a class of high performance thermosetting resins with the structure of phthalonitrile at the end of the molecular chain.This type of resin has excellent comprehensive properties,which has a broad application prospect in aerospace,electronics,ship,automobile,machinery and other high-tech fields.However,the major problem of currently limiting the widespread application and development of phthalonitrile resin is the harsh and complex curing process.In order to reduce the curing temperature of phthalonitrile resin and broaden its processing window,this thesis designed experiments from new resin precursors and novel curing agents.The main contents are as follows:Melamine-zinc chloride?ME-ZnCl₂?complex curing agent was constructed.ME is a trifunctional monomer with a stable heterocyclic structure?triazine ring?.It could be combined with Lewis acid curing agent ZnCl₂ to obtain a new curing agent,which was more effective in promoting the curing of phthalonitrile resin than single curing agent.The activation energy and initial curing temperature of resorcinol-based phthalonitrile resin?DPPH?system cured by ME-ZnCl₂ decreased from 130.7 kJ/mol and 256.7 ^oC in the ZnCl₂ system to 99.9 kJ/mol and198.3 ^oC,respectively.The glass transition temperature?T_g?of DPPH resin cured with ME-ZnCl₂ was higher than the T_g of the resin cured with the single curing agent,especially when the post-curing temperature was lower.The T_gs of DPPH resins cured with the single curing agents ME and ZnCl₂ were 270 ^oC and 285 ^oC after 300 ^oC post-curing,while the resin cured by ME-ZnCl₂ had no obvious glass transition peak?T_g was higher than 380 ^oC?within the test temperature range.At the same time,the DPPH resins cured with ME-ZnCl₂ showed outstanding thermo-oxidative stability and lower water absorption.The self-curing TPPA-based phthalonitrile resin precursor?TPPA-Ph?was designed and synthesized.The precursor had low melting point?less than 100 ^oC?and low melting viscosity,which could be self-cured in the absence of additional curing reagent,and the self-cured TPPA-Ph resin had excellent thermal stability.TPPA-Ph precursor contains amount of phenolic hydroxyl and cyano groups which could also be used to optimize other phthalonitrile resins as curing agent so as to improve the processing performance of phthalonitrile resin.The results showed that the cured DPPH resin with various amount of TPPA-Ph had outstanding thermal stability,thermo-oxidative stability and processing fluidity:the highest 5%weight loss temperature of the resin could reach 547 ^oC,T_gs of the resins were higher than the highest test temperature 380 ^oC and the lowest viscosity of the melt ranged from 0.1 to 0.3 Pa·s.Amino-terminated phthalazinone poly?phthalazinone ether ketone?oligomer A-PPEK was prepared and its feasibility of curing DPPH resin was explored.TGA results showed that the 5%weight loss temperature of A-PPEK was 69.3 ^oC higher than the commonly small molecule curing agent 4,4'-diaminodiphenyl sulfone?DDS?.Different from the rapid sublimation of DDS at 400 ^oC,A-PPEK still retained more than 95%weight at the same temperature,which proved that A-PPEK could solve the resin defects caused by the decomposition of small molecular curing agent at high temperature.A series of tests showed that DPPH resins cured with different content of A-PPEK had outstanding heat resistance and processing fluidity:the highest 5%weight loss temperature of the resin could reach 553.2 ^oC,T_gs of the resins were higher than the highest test temperature 380 ^oC and the lowest viscosity could reach 0.2 Pa·s.