|St Lawrence, Sterling|
Submitted to: Polymer Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2001
Publication Date: N/A
Interpretive Summary: There has been a considerable effort made to develop biodegradable plastics in order to reduce the amount of material in landfills. Unfortunately, these materials are usually too expensive and, therefore, not widely used. To reduce their cost, they are often combined with a cheap filler, such as corn starch, but the resulting materials typically have poor mechanical properties. The plastic studied in this investigation is, however, a promising candidate, but before it can be used, it's mechanical properties must be fully characterized, including the effect of moisture. The purpose of this investigation was, therefore, to understand how absorbed water affected the mechanical properties of this plastic. This information is necessary if this plastic is to be used in combination with starch to make biodegradable consumer products such as cutlery or plant pots. The development of which would create additional markets for corn starch and, therefore, benefit the farmer.
Technical Abstract: The effects of moisture and strain rate on the tensile properties of poly (hydroxy ester ether)(PHEE) were investigated. Water was shown to act as a plasticiser which lowered the room temperature tensile strength and modulus. The strain at failure increased with increasing water content and a change in the mode of failure was observed. Brittle failure occurred when the moisture content was low, however, as the sorbed water content increased, the samples necked and extensive plastic deformation resulted. The samples deformed in a quasi-homogeneous manner at testing temperatures close to the glass transition temperature. The yield stress was found to be dependent on the water content and the strain rate. For samples which deformed in a ductile manner, the variation in the yield stress with strain rate was well described using the Eyring model. The effect of water content on the yield stress was shown to be analoguous to the effect of temperature.