Preparation And Modification Of Butyl Methacrylate/Acrylamide Copolymer Foam Plastics

With the rapid development of new fields such as the space navigations, high speed trains and microelectronics industries, the traditional foam plastics such as the PP, PS and PU have been restricted to apply to these fields because of the inferior mechanical properties and thermal stability. Therefore, the emphasis was shifted to high functional materials from traditional universal materials. Polymethacrylimide(PMI) foam plastics, used in many fields, have excellent mechanical property and thermal stability because of the particular rigid imide ring structure. PMI foam plastics have an unaffordable price, which are difficult access to obtain due to the limited supply provided by the Degussa of Germany and SEKISUI of Japan. It is the very time to make a breakthrough in this field to implement the self-determination production of the PMI foam plastics.The BMA/AM copolymer foam plastics, having similar structure to the PMI foams, were prepared with the major monomers of the methylbutyl acrylate(BMA)and acrylamide(AM) through the free radical bulk polymerization, which had been demonstrated by the investigations in our lab based on the previous researches. The preparation of the BMA/AM copolymer foam plastics includes the preparation of BMA/AM copolymer at a lower temperature and foaming at a higher temperature.The contents of this paper include three aspects. Firstly, the molecular structures of the BMA/AM copolymers were controlled by modulating the pre-polymerization temperatures and the feeding modes. Secondly, the process of foaming of BMA/AM copolymer foam plastics have been investigated including the type, proportion and content of foaming agents. Thirdly, the effect of crosslinking agents on the structure and properties of copolymer foams was investigated by selecting ethylene glycol dimethacrylate(EGDMA), allyl methacrylate(AMA) and triallyl isocyanurat(TAIC)as crosslinking agents, respectively. The Structure and properties of the BMA/AMcopolymers and the foams were investigated by 13 C NMR, FTIR, DSC, TGA, DMA,optical microscope and mechanical property tests.The results of pre-polymerization process show that pre-polymerization temperature and feeding methods would greatly influence the molecular structure and properties of the BMA/AM copolymers. The conversion ratio of AM would increase by batch feeding or at a higher pre-polymerization temperature, which would result in a higher content of AM unit in the BMA/AM copolymers. It would increase the degree of the imidization reactions, which would further increase the comprehensive properties and thermal stability of BMA/AM copolymer foam plastics.The results of foaming processing show that, the uniform cells of the BMA/AM copolymer plastics could be obtained by selecting the foaming agents of formamide and tertiary butyl alcohol with the ratio of 1:3. With the increase of the contents of foaming agents, the density and comprehensive properties of foams decreased.Moreover, imide reactions happened to the BMA/AM copolymers during the process of foaming.The results of crosslinking modification show that, the crosslinking agents had a great influence on the thermal stability and comprehensive properties of the BMA/AM copolymer foam plastics. With the increase of the contents of crosslinking agents, the density of the foams increased, and the thermal stability and comprehensive properties were also improved. EGDMA and AMA had greater influences on the density, heat resistance and comprehensive properties of BMA/AM copolymer foams.