Submitted to: Rheologica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 27, 2000
Publication Date: N/A
Interpretive Summary: Synthetic non-degradable polymers are extensively used as packing materials. They are causing serious environmental problems. Synthetic biodegradable polymers are costly to produce. To integrate cheap and renewable resources like starch into synthetic polyesters shows promise in developing cost effective biodegradable products. Viscosity of highly starch-filled polyester composites determines the composite processability in extrusion equipment. Knowledge of the temperature dependence of the composite viscosity is a necessity for the design of the extrusion equipment. In this paper, several models are verified to correlate the temperature dependence of the composite viscosity. This work would 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 equipment. Scientists sboth in industry and in academia in developing and testing biodegradable polymeric materials would also benefit. This research was conducted under Cooperative Research & Development Agreement (CRADA) #58-3K95-8-0635 between ARS and Biotechnology Research Development Consortium (BRDC).
Technical Abstract: This research focuses on how flow behavior of highly starch-filled poly (hydroxy ester ether) (PHEE) biodegradable composites. In this paper, the temperature dependence of the vicosity is presented. Corn starch (Buffalo 3401)/PHEE (Dow Chemical) materials were extruded using a Leitritz twin- screw extruder with starch volume fractions from 0.27 to 0.66. Dynamic strain sweep measurements were carried out using an ARES Rheometer (Rheometric Scientific) at 10 rad/s and at 6 different temperatures from 100 to 150 deg C. Correlation equations (Arrhenius, WLF) were applied to describe the temperature dependence of the melt viscosity. The average activation energy for flow in the Arrhenius equation was found to be 62.44 kJ/mol for pure PHEE and composites with starch volume fraction smaller than 0.46. Deviation from the correlations at high starch concentration was explored from different aspects (yield stress and non-linearity). The non-linearity of the rheological behavior that occurred at high starch concentration is considered as the main reason from strain (stress) dependence of the melt viscosity. This research was conducted under CRADA number 58-3K95-8-0635 between ARS and Biotechnology Research Development Corporation.