STARCH RESIN MOISTURE LEVEL EFFECT ON INJECTION MOLDING PROCESSABILITY AND MOLDED PART MECHANICAL PROPERTIES WITH PURE STARCH RESIN AND POLYMER BLENDS

摘要

Starch has been proven to be a viable renewable resource alternative to synthetic polymer materials. Starch when solubilized with a plasticizer such as H2O becomes a thermoplastic resin known as TPS. TPS materials can be processed in pure form or as a composite with synthetic polymers to enhance mechanical properties. Moisture in the TPS causes volatilization within the polymer process melt, resulting in the creation of voids and leading to a loss of processability. This study examines the effect of moisture levels in the starch and polymer/starch materials on voids, and mechanical performance. One hundred percent TPS resin from potato starch and highdensity polyethylene (HDPE)/TPS blends were formulated, processed and tested at moisture levels up to 3 %. Moisture levels above 1.4 % showed unprocessability. Statistical analysis of moisture levels from .59 % to 1.4 % demonstrated a direct positive correlation to voids in the melt. Moisture in the TPS also showed a negative correlation to the Young's modulus of injection molded parts with a reduction of up to 25 %.