Study On Preparation And Properties Of PP/POE/MVQ Thermoplastic Vulcanizate

Thermoplastic vulcanizate is that rubber phase under high temperature and high shear, dynamic vulcanizated in the molten plastic phase, and meanwhile cut to sulfide particles of micron, dispersed uniformly in the plastic phase, and formed the "Sea-Island" structure of rubber and plastic two-phase system.In this paper,polypropylene(PP) / ethylene octene co-polymer(POE) / methyl vinyl silicone rubber(MVQ) thermoplastic vulcanizate was prepared by dynamic vulcanization.First the influence of blending ratio, feeding sequence, dynamic vulcanization process on the mechanical properties, surface tension, melt flow rate(MFR) of PP/POE/MVQ thermoplastic vulcanizate was discussed.And we used some environmentally-friendly halogen-free flame retardant with different ratio and improve the flame retardant properties of the TPV. The structure of Ethylene Propylene Diane Terpolymer(EPDM) is similar with POE,they have good compatibility, so EPDM was used to improve the compatibility of the TPV.The results showed that the thermoplastic vulcanizate prepared by blending PP/MVQ with different proportions, with the increase of the amount of MVQ, the crosslinked particles formed by dynamic vulcanization became larger and the curing rate increased.The mechanical properties of the TPV decreased with the increase of the amount of MVQ, the hardness was decreased, the elasticity was improved, and the compression permanent deformation decreased firstly and then increased.The contact angle between TPV and water increased gradually,the surface tension reduced gradually, and the hydrophobic was improved.The Vicat softening temperature of the TPV decreased, the melt flow rate becomes faster, the processing mobility of the TPV has improved.POE has good compatibility with PP,and it is commonly used to toughening PP,the structure of POE is similar to the structure of rubber, so in this experiment POE was used to increase the compatibility of PP/MVQ blends. Firstly,the optimum blending ratio of 100:50:50 was determined by the mechanical properties, hardness and surface tension of PP/POE/MVQ. For the blending sequence, POE/MVQ was prepared under high temperature and high shear by dynamic vulcanization into thermoplastic vulcanizate based on POE(PMTPV) firstly,and then melting blended with PP, the properties of the TPV were better than the three blended simultaneously.Therefore, in subsequent experiments, POE and MVQ were prepared by dynamic vulcanization into PMTPV firstly, and then blended with PP. With larger shear stress, the rubber particles in the TPV prepared by dynamic vulcanization through the double screw extruder were smaller and dispersed more evenly,and its mechanical properties were better than the PMTPV prepared by dynamic vulcanization through the torque Rheometer. Using the PMTPV prepared to modify the PP, with the increase of the amount of PMTPV, the tensile strength,tearing strength, tensile stress and other mechanical properties of the TPV did not decrease obviously, but the hardness of the TPV was improved.The processing flow properties of the material was improved obviously, the surface tension was decreased, and the hydrophobicity was improved.When the blending ratio of PP/PMTPV was 1:2, the elastic modulus of the TPV was the lowest, the elasticity was the best, and the elastic modulus of the TPV was the most stable when the temperature and strain changed.The experiment was made to improve the flame retardant properties of the TPV with some environmentally-friendly halogen-free flame retardant. Al(OH)3, fly ash, APP and PER,ZnB4O7,these four halogen-free flame retardant improved the flame retardant properties of TPV in different degree.The mechanical properties and oxygen index of the TPV were considered, and the selection of Al(OH) 3 was better.The combination of Al(OH)3 with DMMP( a high efficiency flame retardant)of different ratio improved the oxygen index of the TPV further. When the combination of Al(OH)3, DMMP, EG-200 three kinds of halogen-free flame retardant, and the amount of EG-200 was 10 phr, the mechanical property of the TPV was best, and oxygen index increased to 32%, reach the level of the fireproof material.The structure of EPDM is similar to POE, and their compatibility is good,so the experiment considered to use EPDM to increase the compatibility of the TPV.EPDM and PMTPV was blending with different proportions, with the increase of the amount of PMTPV, the mechanical properties of EPDM/PMTPV blends increased gradually, and the best blending ratio was 40/60. PMTPV improved the electrical insulating properties of EPDM/PMTPV blends, which made the volume resistivity of the blends increased by an order of magnitude.With the increase of the amount of PMTPV, the aging resistance of EPDM/PMTPV blends under the conditions of 160℃×24h increased gradually, and the oil resistance at room temperature increased. The SEM photos showed that, with the compatibilization of EPDM, the TPV had a dense structure and had no obvious phase interface, the compatibility of the PP/POE/MVQ blends had been further improved.