Abstract: Polypropylene (PP) composite for outer-cap ring of plastic infusion containers was prepared via melt extrusion blending of polyethylene (PE), elastomer, PP, and other additives. The ratio of PP, PE, and elastomer was optimized by orthogonal factorial design. The mechanical properties of the composite and the open force of outer-cap ring were studied. It showed that the most important factor affecting the mechanical properties and the open force of outer-cap ring was the content of elastomer. The impact strength of the composite increased first and then decreased, the tensile strength and open force of outer cap ring decreased with increasing elastomer. SEM observations revealed that elastomer was finelydistributed in composite when the content of elastomer was less than 25 mass%. It could be concluded that the optimized recipe was: PP 65 mass%, PE 20 mass%, elastomer 25 mass%, and antioxidant and other additives 5%.

Key words: tougheness, polypropylene, influsion container, combinational closure, uter cap, open force