Submitted to: Polymer Engineering & Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 8, 2000
Publication Date: N/A
Interpretive Summary: Synthetic polymers, or plastics, are extensively used in disposable, one- use applications. Their disposal is a serious environmental concern. Synthetic biodegradable plastics are costly to produce. Integration of a low-cost, renewable resource like starch into synthetic plastics shows promise in developing cost-effective biodegradable products. Knowledge of the flow properties, or viscosity, of starch-filled plastic materials is necessary for the understanding of their behavior in processing equipment. In this paper, the effect of starch content on the composite viscosity was investigated. Several models are examined to describe the effect of starch content on the composite viscosity. This work could benefit producers of starch-based biodegradable products by providing useful information for predicting process conditions of starch-based polyester composites and for the design of extrusion/injection molding equipment. Scientists both in industry and in academia developing and testing biodegradable polymeric materials would also benefit. The results also are of interest to researchers concerned with highly-filled materials, such as dispersions and suspensions.
Technical Abstract: The effect of starch volume fraction on starch-filled poly(hydroxy ester ether) (PHEE)biodegradable composites was analyzed using Mooney, Thomas, Maron & Pierce, and Frankel & Acrivos equations. Corn starch/PHEE materials were extruded using a twin screw extruder with starch volume fractions from 0.27 to 0.66. The starch was dried to a moisture content of 0.7% to minimize moisture effect on composite rheology. Dynamic frequency sweep measurements were carried out at 120 deg C and 1% strain. Maron & Pierce, Thomas, and Frankel & Acrivos' equation can be used to describe the experimental data. It is found that the relative viscosity at the same shear stress increases with increasing shear stress. The possible existence of yield stress at high starch concentrations was examined using Casson plot.