Effect of flow field on structure and properties for polycarbonate blends

Abstract

Flow-induced segregation and phase-mixing behaviors of polymer blends comprising polycarbonate (PC) and another polymer with low molecular weight, such as poly(methyl methacrylate) (PMMA) and polystyrene (PS), are studied. Although PMMA with low molecular weight is miscible with PC, the PMMA fraction in an injection-molded plate is found to be rich at the surface, suggesting that PMMA is segregated to the surface region under pressure-driven flow in the mold. The high concentration of the PMMA fraction at surface will provide enhanced surface hardness of a product. Furthermore, the PS addition is found to decrease the apparent shear viscosity greatly especially in the high shear rate region at capillary extrusion, which will be responsible for a long spiral flow length at injection-molding. The decrease in the shear viscosity is attributed to the flow-induced phase-mixing, which occurs only in the surface region.Flow-induced segregation and phase-mixing behaviors of polymer blends comprising polycarbonate (PC) and another polymer with low molecular weight, such as poly(methyl methacrylate) (PMMA) and polystyrene (PS), are studied. Although PMMA with low molecular weight is miscible with PC, the PMMA fraction in an injection-molded plate is found to be rich at the surface, suggesting that PMMA is segregated to the surface region under pressure-driven flow in the mold. The high concentration of the PMMA fraction at surface will provide enhanced surface hardness of a product. Furthermore, the PS addition is found to decrease the apparent shear viscosity greatly especially in the high shear rate region at capillary extrusion, which will be responsible for a long spiral flow length at injection-molding. The decrease in the shear viscosity is attributed to the flow-induced phase-mixing, which occurs only in the surface region.