Study On Preparation And Properties Of Waster Rubber Based Thermoplastic Elastomer

Waste rubber based thermal plastic elastomer(W-TPE) is composite mainly made from recycled rubber,(such as rubber particles) and thermoplastic matrix. The production of W-TPE realize the utilization of rubber powder(RP) as material resources and consume a large amount of RP, which is an important way to solve the so-called "black pollution" of waste rubber.In the experiment, the RP/ polypropylene(PP) thermoplastic elastomer was prepared by using Haake torque rheometer, and many modern analysis methods and equipment such as scanning electron microscopy(SEM), capillary rheometer, differential scanning calorimetry(DSC), dynamic mechanical analyzer(DMA) were employed to systematically study the influence of raw materials(PP matrix, RP, in-situ compatibilization agent and sulfur), formulation, compounding parameters(temperature, rotation speed and time) on the mixing characteristics, rheology,mechanical properties, crystallization of PP matrix and dynamic properties of RP/PP thermoplastic elastomers, the mechanism of in-situ compatibilization during melt blending of RP/PP blends and its effect on microstructure and mechanical properties of RP/PP blends was thoroughly discussed.The results show that interaction between RP and PP phase of simple blended RP/PP blends is wake, thus the compatibility of RP and PP is rather poor. The mechanical properties, especially the tensile elongation of RP/PP blends are very low, so they cannot be used as thermoplastic elastomer.Peroxide can initiate in-situ chemical reaction between RP and PP matrix during melt blending process, which improve the compatibility and interaction between RP and PP phase and thus improve mechanical properties of RP/PP blends significantly. Sulfur can initiate crosslinking reaction, inhibit the degradation of PP matrix and further improve the mechanical properties of RP/PP thermoplastic elastomers. The elongation at break of RP/PP blends with RP content of 50%-80% is rather high,which is close to ordinary thermoplastic elastomer. There RP particle size(from 40 to 100 mesh) has almost no effect on the main performance of RP/PP blends. The optimized RP/PP formulation and processing parameters are shown as follow: RP particle size 40-100 mesh, RP content 60%- 70%, DHBP content 2-4%, sulfur content 0.5%; mixing temperature 160-170 oC, mixing time 7-9min, rotor speed 50-70 rpm. Under this condition, the tensile strength of RP/PP thermoplastic elastomer is 16 MPa, elongation at break is higher than 200%.Non-isothermal crystallization kinetics study shows that peroxide in-situ compatibilization lowered the crystallization temperature and decrease the crystallization rate of PP matrix. The in-situ compatibilization decreases the molecular mass of PP and thus reduce the crystallization temperature of PP; at the same time, insitu compatibilization enhances the interaction between PR and PP and thus reduce the crystallization rate of PP.