Injection molding material containing starch and plant protein

Abstract

An injection molding material that includes a renewable resin containing a combination of renewable polymers (e.g., starch and plant protein) and a plasticizer is provided. Although such compounds are normally difficult to process into thermoplastics, the present inventors have discovered that injection molding materials may nevertheless be formed by melt blending the renewable resin with a synthetic resin (e.g., polyolefin) while selectively controlling the nature of the resins and their relative concentrations. In this manner, a morphology may be achieved in which the renewable resin is present as a discontinuous phase that is dispersed within a continuous phase of the synthetic resin (e.g., 'island-in-the-sea' morphology). The discontinuous and continuous phases may each constitute from about 30 vol. % to about 70 vol. %, and in some embodiments, from about 40 vol. % to about 60 vol. %. With such a morphology, the continuity of the synthetic resin can minimize the aggregate properties of the renewable resin such that the molding material possesses melt properties similar to that of the synthetic resin. Further, this morphology may also minimize the need to use different molding tools as the shrinkage properties of the overall composition may be substantially similar to that of the synthetic resin.