Super polyolefin blends achieved via dynamic packing injection molding: Tensile strength

The tensile strength of some polyolefin blends, HDPE/PP, HDPE/LDPE, HDPE/ LLDPE, and PP/LLDPE, achieved by dynamic packing injection molding have been investigated as a function of composition and melt temperature. Molecular architecture and phase behavior play an important role in chain orientation, hence the tensile strength. For HDPE, which has a linear structure, the highest enhancement of tensile strength is obtained. LDPE, which has a highly branched structure, the smallest enhancement is seen. PP and LLDPE lie in between. Super polyolefin blends with high tensile strength and high elongation have been obtained by this method. The shear‐induced morphologies with core in the center, oriented zone surrounding the core and skin layer were observed in the cross‐section areas of the samples. The tensile strength was found to be directly proportional to the area of the oriented zone. When the area of oriented zone is less than 35%, the tensile strength is not only the orientation dependency but the blending components dependency as well. When the area of oriented zone is more than 35%, however, our new finding is that the orientation will be the dominating parameter to determine the tensile strength of the blends, independent of the components, the composition, molecular architecture, phase behavior, and crystal morphology. The maximum tensile strength for all the polyolefin blends is extrapolated as to 230MPa, as the area of oriented zone reaches to 100%.