Preparation And Modification Of BMA/AM Copolymer

Polymethacrylimide (PMI) foams are lightweight and total of closed-cells, which haveexcellent thermal mechanical properties and chemical durability. When the densities are identical,PMI foams possess the highest strength and rigidity of all existing polymer foams in the world.As the sandwich composites, PMI foams are used in electronics, aviation, marine, sporting goodsand so on.In most of the existing literature, PMI foams are prepared with acrylonitrile andmethacrylonitrile, which achieve the prominent achievements and industrialization successfully.However, the polymerization process is difficult to control and the implosion phenomenon cannot completely eliminate when acrylonitrile or methacrylonitrile is used as the main comonomers.Meanwhile, it is different to obtain homogeneous and transparent copolymers. Therefore, thecopolymers are prone to reject or leftover material, which lead to material wasting.In this paper, the financial support from the National Science Foundation (51103134) andZhejiang Provincial Natural Science Foundation (Y4110360). Moreover, Butyl methacrylate(BMA) and Acrylamide (AM) that are low toxicity and inexpensive are used as comonomers toprepare PMI foams. This paper focuses on the mutual influence of the preparation, molecularstructure and properties of BMA/AM copolymers, which can lay the foundation for preparationthe high-performance PMI foams. The results were listed as follows:(1) The BMA/AM copolymers were prepared via two steps bulk copolymerization that thefirst step was conducted at a higher temperature. Moreover, the reaction system was transferredto a lower temperature (the second step) when the conversion monomer was up to a certain rate.The effects of polymerization temperature, the different types of initiator (BPO, AIBN) and theamount of initiator (0.1~1.2%) on the BMA/AM copolymerization process were studied. Theresults showed that, in order to prepare the homogeneous BMA/AM copolymers, the first stepwas conduced at70~100℃and the second step was at40~70℃. Meanwhile, BPO was used asthe initiator and the content of BPO was between0.4%and1.0%. Moreover, the molar ratio ofBMA/AM was between0.5and2.(2) Effect of monomer ratios on the structure and properties of butyl methacrylate/acrylamide copolymers. With the theoretical research of radical copolymerization via Q-eequation, the structure and properties of BMA/AM copolymers were characterized by infraredadsorption spectra (FTIR-ATR), differential scanning calorimetry (DSC), thermogravimeter(TGA) and universal material testing machine. The results indicated that the content of the AMunites in the BMA/AM copolymer molecular chain increased when the ratios of BMA/AM decreased. Besides, thermal stability and compression property of BMA/AM copolymers wouldimprove. When the molar ratio of BMA and AM was1:1, the content of the AM unites in thecopolymer molecular chain was the highest. The BMA/AM copolymer had residual monomerswhen the ratios were1:1and0.5:1, which would influence the compression property.(3) Effects of the polar molecule on copolymerization of butyl methacrylate/acrylamide. Thecyclohexanol was added into the BMA/AM copolymerization system. Effects of cyclohexanol onthe monomer conversion and the intrinsic viscosity of BMA/AM copolymers were investigated.With the amount of cyclohexanol rising, the content of AM which dissolved in the reactionsystem increased, so the total conversion of the comonomers augmented. Meanwhile, theintrinsic viscosity of BMA/AM copolymer had a peak value. Effects of cyclohexanol on thestructure and properties of BMA/AM copolymer were investigated through FTIR,13CNMR,DMA, DSC and TGA. The results showed AM only participated in the copolymerizationreaction with BMA. With the amount of cyclohexanol increasing, the proportion of BMA/AMcopolymer would be increased. Therefore the degree of imidization reaction would be the higherduring the subsequent foaming stage, which induced more contents of the imide ring in themolecular chains. As a result, the properties of BMA/AM copolymer would be evidentlyimproved. A high-performance polymethacrylimide (PMI) foam materials could be expected.（4）Effect of cross-linking agents on mechanical properties of BMA/AM copolymers. Theresults showed that the mechanical properties of BMA/AM copolymers were evidently improvedwith the rise of the content of cross-linking agents. With adding multiple cross-linking agentwhich was made up of acrylic acid and Mg(OH)2, the compressive properties of BMA/AMcopolymers were increased with the decrease of the molar rate of acrylic acid and Mg(OH)2.