Study On EVA-g-PU/OMMT/SBR Nanocomposites

Ethylene-vinyl acetate copolymer (EVA) is a sort of thermoplastic elastomer plastic. In EVA molecule, due to the existence of vinyl acetate (VAc), regularity and degree of crystallinity of the PE chain decreased, internal rotation movement ability of molecule chain in thermo-movement and flexibility of molecule chain were improved greatly. In macroscopic view, it represents performing high elasticity. EVA contained 12%～30% VAc can be used to produce the independent microporous foam material. For excellent insulation, flexibility, elasticity and weather resistance, the EVA foam was widely used in industry, construction, aquaculture, especially in shoe materials. However, there are some defects for EVA, such as poor adhesion, wetting, printing, gas permeability and material compatibility, and these defects confined its further application. This research is aiming at combination the chemical graft modification and physical blend modification and wishes to prepare a novel EVA based nanocomposites with excellent properties and can be applied in shoes industry. Meanwhile, the foam properties and friction mechanism of nanocomposites is studied.In alkalescence situation, there is a saponification hydrolysis reaction of EVA and free hydroxy can be created. The reaction condition was optimized and the products were characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and Nuclear Magnetic Resonance (NMR). The structure character was analyzed. Sequence structure of the saponified EVA was studied by C-NMR. There were three sequence structures of free hydroxy of EVAL. Polyurethane prepolymer (PU prepolymer) was produced with Diphenyl-methane-diisocyanate (MDI) and Polytetrahydrofuran glycol (PTMG). The PU prepolymer was terminated with -NCO. The structure of PU prepolymer was characterized by FT-IR and the effect of reaction time and reaction temperature and moisture content on properties of PU prepolymer were analyzed. Dynamics equation of PU prepolymer was explored. FT-IR suggested that PU prepolymer was terminted by -NCO.A new type of graft copolymer EVA-g-PU was synthesized via melt grafting reaction. FTIR and ¹³C-NMR testing showed that the PU prepolymer was grafted on EVA main chains successfully. Mechanical testing showed that the tensile strength and elongation at break of EVA-g-PU were far superior to pure EVA. The enhanced storage modulus of EVA-g-PU was characterized by dynamic mechanical thermal analysis (DMA). The enhanced degree in the storage modulus of EVA-g-PU increased with the increase of PU prepolymer content. The thermal stabilities of EVA-g-PU were also studied by thermal gravimetric analysis (TGA).EVA-g-PU/OMMT nanocomposites were prepared by two different methods. Combining the analysis of X-ray Diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM), it can be knew that the distributing state of OMMT was intercalated in composites prepared by the method of one step and the distributing state of OMMT was exploited in composites prepared by the method of two steps. Mechanical properties of nanocomposites prepared by method of two steps were superior to the nanocomposites prepared by method of one step. Mechanical testing showed that the tensile strength and Tear strength of EVA-g-PU/OMMT nanocomposites were far superior to pure EVA. When the mass fraction of OMMT was 3%, mechanics properties of nanocomposites were the best. The storage modulus of EVA-g-PU/OMMT nanocomposites was characterized by dynamic mechanical thermal analysis (DMTA). Along with the increase of OMMT content, the storage modulus of nanocomposites was increased and the Tanδwas decreasing. The thermal stabilities of nanocomposites were also studied by thermal gravimetric analysis (TGA). The thermal stabilities of nanocomposites were more superior to pure EVA.EVA-g-PU/OMMT/SBR nanocomposites were prepared by the method of melt blend with SBR (styrene-butadiene rubber) and EVA-g-PU/OMMT nanocomposites prepared by method two steps. Through the study of mechanical and friction properties of nanocomposites, we knew when the mass fraction of OMMT and SBR were 3% and 15%, mechanics and friction properties of nanocomposites were the best.EVA-g-PU/OMMT/SBR nanocomposites were applied to foam experiment. Through the optimized experiment of vesicant content and crosshnking agent content and foam temperature and foam time, the optimized techniques of EVA-g-PU/OMMT/SBR nanocomposites were: vesicant content of AC was 6%, crosshnking agent of DCP was 0.7%, foam time was 15 min, foam temperature was 130℃, and foam pressure was 10MPa. The foams made by EVA-g-PU/OMMT/SBR nanocomposites were applied in Jihua 3515 leather & leather shoes Co., Ltd and were recognized by the company.