The Study Of Preparation And Properties Of Imide-Based Copolymer Foam Plastic

With the development of modern economy,the strength,stiffness and heat resistance of traditional foam such as PE,PS,PU and PVC have not met the special requirements of high-tech fields such as aerospace and high-speed trains.Therefore,foam research has shifted from the general-purpose to high performance.Polymethacrylimide(PMI)foam is a new type of highperformance foam with a rigid six-membered imide ring in the main chain and 100% closed cell structure which giving it excellent overall performance,mainly used in aerospace,high-speed trains and wind power and other fields.Many preliminary studies showed that EMA/AM copolymer could be synthesized by free radical copolymerization,and the copolymer foam was prepared through high temperature foaming by using ethyl methacrylate(EMA)and acrylamide(AM)as main monomers.The research contents of this paper mainly include the following three aspects: the theory analysis of EMA and AM copolymerization process,by means of fourier transform infrared spectral analysis(FTIR),differential scanning calorimetry(DSC),thermogravimetric analysis(TGA),optical microscope and mechanical property test,the effects of system composition and proportion on the structure and properties of copolymer were studied in detail.The foaming process of EMA/AM copolymer foamed plastics was studied,the effects of foaming process of EMA/AM copolymer foam on the structure and properties of EMA/AM copolymer foam foaming agent,including type,amount and ratio,foaming temperature and foaming time were investigated.Meanwhile,the molecular structure changes in the process of high temperature foaming were further researched.The results show that the molar ratio of EMA and AM has a significant impact on the structure and property of EMA/AM copolymer.When the ratio of the two monomers is between 0.5 to 2,the appearances of the copolymers are transparent and uniform.With the decrease of the mole ratio of EMA/AM,there are more AM unit in the molecular chains of EMA/AM copolymer,and the thermal stability of EMA/AM copolymer is better.However,the residual amount of AM in the copolymer are also increased or even cause phase separation.The uniform EMA/AM foam plastics could be prepared when using formamide and tert-butanol composite foaming agent at the mass ratio of 1:3.Furtherly,the content of composite foaming agent affect the property of EMA/AM copolymer foam plastics significantly.With the content of foaming agents increases,the density and compression performance of EMA/AM copolymers are reduced.Moreover,with the foaming temperature and time increase,the foaming degree of the copolymer foam tends to be perfect.Unfortunately,the bubble holes of EMA/AM copolymer foam will break up when the foaming temperature exceeds 200? and the time exceeds 45 min.During the high-temperature foaming process,the molecular structure of EMA / AM changes.The cross-linking and cyclization reaction between EMA and AM chain in the copolymer generates the intermolecular imide cross-linked and the hexanoyl imine ring structure.High-temperature foaming process also has a greater impact on the degree of crosslinking and cyclization reaction of EMA/AM copolymer,the higher the foaming temperature or foaming time,the crosslinking and cyclization reaction are more fully,the degree of crosslinking and cyclization of EMA / AM copolymer are also higher.