Injection molding technology limitations

Another proposed process employed injection molding in which starch and limited amounts of plasticizing water are heated under pressure to temperatures above the Tg and Tm to transform the native starch into a homogenous, destructured, thermoplastic melt. The process melt is then cooled to below the Tg of the system before pressure release to maintain the moisture content. Additives include natural and synthetic polymers, plasticizers and lubricants.136-139 159 160 The technology has been used to prepare pharmaceutical capsules and shaped objects, such as disposable cutlery, straws and pens. 

Many reasons such as lack of familiarity and the current, limited availability have so far prevented large-scale penetration of these materials into broader injection-molded markets. However, double-digit growth is still expected as large companies enter the market and technological advances are made [32]. 

These improvement possibilities do not only apply to injection molds. In addition to mold cavities for thermoplastics, thermoset and elastomer processing, also extrusion dies, sliders and jaws, ejector systems, melt control systems, no return valves, and cooling channels are treated with success. Also with regard to the treatable mold materials the limits have been further extended in recent years. In addition to typical mold steels, nonferrous metals such as aluminum or various copper alloys can also be optimized by surface and coating technologies. 

Structural RIM (SRIM) is a relatively new process that involves a combination of Uaditional RIM technology with the use of a preformed reinforcement that is placed in the mold prior to injection. The introduction of a reinforcing preform into the mold addresses the traditional stiffness limitations that are associated with unfilled or RRIM systems, and offers a significant structural improvement over the use of glass fiber or flake. The RIM material impregnates the preform and forms a skin around it, providing a composite part that can be then removed from the mold. 

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