Optimization of Tensile Strength and Shrinkage of Talc-Filled Polypropylene as a Packaging Material in Injection Molding

Abstract

Polypropylene (PP), as a rigid and low-cost packaging material, has been used to make many packaging products such as containers, tubs, buckets, and various closures, etc. The addition of talc in PP brings many benefits such as enhanced stiffness, lower coefficient of thermal expansion, reduced water vapor and oxygen transmission, etc. Thus, talc-filled polypropylene (TFPP) has been widely used in packaging and automotive industry. For injection-molded TFPP packaging products, tensile strength and dimensional accuracy are two important quality characteristics. Both are heavily influenced by the molding conditions. One molding window for enhancing the tensile strength may not be favorable to shrinkage control and dimensional accuracy. This paper presents a Taguchi-based design approach, developed for multi-objective optimization, with the combined goals of maximizing the tensile strength and minimizing the shrinkage of injection-molded TFPP parts under the same molding condition. With the Taguchi optimization approach, it turned out that the tensile strength was increased from 22.07 to 24.40 MPa and the shrinkage was reduced from 3.25 to 2.28%. The optimizing approach and the tensile and shrinkage behaviors of TFPP can be used in other manufacturing processes, wherein two or more quality objectives are to be optimized.