Study On The Compatibility Of Ethylene-Vinyl Acetate Rubber And Thermoplastic Polyurethane Elastomer Blends

The compatibility of blends of ethylene-vinyl acetate rubber and thermoplastic polyurethane elastomer was investigated in this paper. Two kinds of blends of EVM400(VA=40wt% )/TPU and EVM700(VA=70wt%)/TPU were prepared in Haake torque rheometer. The optimum mixing parameters and fillers were examined. The Universal Material Tester, FTIR, Phase Contrast Microscope, Polarizing Microscope, SEM, RPA2000 and DSC were used to examine the basic properties and compatibility of EVM400/TPU and EVM700/TPU. Two kinds of compatilizers, EVM/TPU/EVM-g-MAH and EVM/TPU/EVM-g-FME, were added in the blends and the improvement of compatibility was also studied in this paper. The results are shown as following:Filler was necessary for the blends of EVM/TPU in order to prepare qualified samples in press and make discharge of blends from the mixer easier. Compounding with 30phr silica had better mechanical properties. The optimum mixing parameters for EVM/TPU blends in Haake rheometer were mixing temperature 150℃-160℃, rotor speed 45 r/min and mixing time 10-15mins.EVM700/TPU blend had a better compatibility than EVM400/TPU which was proved by the smaller difference of the solubility parameter and a higher density than the calculated one.The phase morphology of EVM /TPU blends was the sea-island structure, in which EVM was the island (dispersed) phase and TPU was the sea (continuous) phase. The phase transition didn't appear until EVM/TPU=90/10. Comparing with EVM400/TPU, the domain of EVM700 in TPU was smaller and more uniform, which meant that EVM700/TPU had a better compatibility than EVM400/TPU. The mechanical properties of blends increased as the content of TPU increased.RPA2000 and rheological test indicated that the blends had lower viscosity as the increase of shearing rate. EVM/TPU=50/50 presented the worst dynamic mechanical properties and heat-resisting properties.In EVM400/TPU blend with compatibilizer EVM-g-MAH, the interface of two phases became fainter and the size of domain of EVM was smaller and the mechanical properties and dynamic mechanical properties were improved. The optimum content of EVM-g-MAH was between 8-12 phr; but EVM-g-MAH didn't an obvious improvement of compatibility for EVM700/TPU blends. Compatibilizer EVM-g-FME didn't improve the compatibility of EVM/TPU blends. EVM-g-MAH improved hot air aging performance of EVM400/TPU blend while it had a deleterious effect on the air aged performance of EVM700/TPU blends.