Studies On Structure And Properties Of Polypropylene And Polypropylene Blends Effected By Ultrasonic Wave

The effects of ultrasonic irradiation on extrusion processing of polypropylene (PP), PP/ethylene-propylene-diene monomer terpolymer (EPDM) blends and crystallization behavior of PP in different PP/nucleators system are studied. During extrusion of PP, die pressure and apparent viscosity prominently decrease, and die temperature increase with ultrasonic treatment. Ultrasonic effects also contribute to the increase of output, reduction of die swell and smoother appearance of PP. Special effects can be induced by ultrasound, which suppress nucleation of PP as well accelerate the growth of crystals, particular the growth of p-crystals.Ultrasonic wave can also improve the processing of PP/EPDM through decreasing apparent viscosity and increasing throughout. Ultrasonic vibration can enhance interfacial interactions and improves the dispersion and distribution of EPDM particles in PP matrix. When the content of EPDM is more than 20%, ultrasound presents toughening effects on PP/EPDM. The maximum impact strength is in the PP/EPDM (80/20) samples affected by ultrasonic power of 200W. With ultrasonic treatment, young's modulus and yield strength remain little change except PP/EPDM (95/5) blending.By applying ultrasonic wave to different PP/nucleators system, crystalline structures of PP are changed. Appropriate ultrasonic irradiation has beneficial effectson reduction of d-spacing and lattice parameter of PP added with Talc, which has poor dispersion in PP. Definite ultrasonic irradiation induce the formation of P-crystals in pure PP and PP/NaBz, as well make preferential growth in some crystal face in PP/Talc, PP/Talc(KH) and PP/Mica. However, PP/MHS, PP/NC-4, PP/TM-1 do not present such effects under ultrasonic irradiation. Both the formation of (3-crystals and preferential growth of crystal face are manifestation of high order of crystal phase, so at the corresponding ultrasonic intensity, crystallite sizes (LhkJ) increase otherwise decrease. Moreover, the crystallinity of PP and PP/nucleators are reduced by ultrasonic irradiation.