Modification Mechanism Of Sebs On Transparent Polypropylene

Today, the subject of improved transparent polypropylene composition has attracted great scientific and industrial attention, and great effort continues to be devoted to this area of research. The research is mainly focus on the addition of nucleating agents. Polymer blend is the other way to improve the transparency of PP, which is limited by compatibility and refractive index, and little related research is found, especially for the mechanism.In recent years, as dynamic viscoelasticity of polymer melt is sensitive to the change of phase structure, rheology is used to study the morphology of polymer blend. In the paper, the mechanism of improving transparency of PP was studied by means of rheological behavior.The blends consisting of PP/POE,PP/EVA,PP/EPDM,PP/SEBS were prepared by melt blending. It was found that SEBS could improve the transparency of PP. When its content was 40%, light transmittance changed from 81% to 84%, and haze also reduced from 76% to 50%. It was because SEBS could reduce the light scattering within PP.From WAXD and PLM, it showed that SEBS not only reduced the degree of crystallinity, but also undermined the formation of crystal structure. The amorphous region in blend increases as the content of SEBS increasing, for which light scattering decreased and haze was reduced.Studies on dynamic rheology showed that with the SEBS content increased, the particle size of dispersed phase decreased, and the structure of PP/SEBS blends was changed from the sea-island structure to the two-continuous phase structure. PP/SEBS blends conformed to the characteristics of crystalline haze area, and haze reduced with the melt elasticity increased.Thermal properties analysis showed that, SEBS could hinder the crystallization of polypropylene, and decrease the crystallization temperature at the same time. And thermal stability of polypropylene was reduced with the increase of SEBS.Mechanical properties showed that as the content of SEBS increasing, the tensile strength of PP/SEBS blends was reduced, while the low-temperature impact strength and elongation at break were increased.In summary, when the content of SEBS reached to 40%, the transmittance was 84%, tensile strength was 22.1MPa, and impact strength became 3.9KJ/m2. Optical properties and mechanical properties got to a better balance.