Submitted to: Journal of Polymer Science Part B: Polymer Physics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2002
Publication Date: N/A
Interpretive Summary: Finding new uses for agricultural commodities is essential for overcoming the current slump in commodity prices. Currently, a large number of consumer and industrial products are manufactured from petroleum-based raw materials. Successful replacement of these petroleum-based materials will open new value-added markets for agricultural commodities and lessen the United States dependence on foreign oil. Many of these new materials will comprise blends of ag-based products such as starch and proteins from wheat and soybeans, with one or more synthetic materials. In order to produce blends with acceptable properties, good compatibility between blend components is required. In the work reported herein, initial studies on the compatibility of an experimental biodegradable material, polylactic acid, with a petroleum-based material are reported. These studies are part of an ongoing effort to address the lack of knowledge, which inhibits presenting the development of new ag-based materials.
Technical Abstract: Polylactic acid (PLA) is a biodegradable synthetic polyester with unique properties that make it an excellent candidate for biomaterial blends. It provides improved moisture resistance to blends with biopolymers and biodegradability/biocompatibility to blends with synthetic polymers, without impairing the useful properties of blend components. Successful development of materials from blends of PLA requires understanding of the factors affecting the interfacial properties of such blends. In this work, the effect of temperature on the interfacial tension (IT) of polylactic acid/polystyrene (PLA/PS) blends were measured at 170-200 deg C using the imbedded fiber retraction (IFR) method. The IFR allows for direct measurement of the IT of blends with high molecular weight and/or high viscosity components. In the temperature range studied, the IT of PLA/PS was independent of temperature and had a value of 5.4 +/ 1.3 dyn/cm. IT was also calculated from the surface energies of PLA and PS using geometric mean (GM), harmonic mean (HM), and Antonoff's eqns; and from solubility parameters using the procedure of Luciani, et al. IFR measured values were similar to those predicted by the procedure of Luciani, et al. and Antonoff's eqns., which gave 4.4 and 3.0 +/ 1.4 dyn/cm, respectively. The GM and HM methods predicted much lower values of 1.1 +/ 0.2 and 1.7 +/ 1.1 dyn/cm, respectively.