Biopolymers from polylactic acid and milk proteins

AGRO 196

Charles Onwulata, and Peggy M Tomasula, Dairy Processing and Products Research Unit, USDA-Agricultural Research Service, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038
Polylactic acid (PLA) is a commercially-available biodegradable polymer derived from lactic acid and is used in many products as an alternative to petrochemical-derived polymers. However, the physical properties limit its use in many applications. Using dairy proteins to substitute for portions of PLA in a formulation may extend its use and prevent shortages of PLA. This work reports on the mechanical and thermal properties of composites made from PLA substituted with starch-whey concentrates and casein blends (DPB). The blends were extruded under the following conditions: mass flow rates (27 to 102 g/min), solids feed rates (0.43 to 2.85 g/sec), moisture (30 to 75%); extrusion melt profiles were: 75, 90, 100, 100, 90, 80C; and molding conditions at 200C and 12,000 psi. The physical properties of the extruded DBP were moisture 14-18%, peak tensile strength 4.5 mPa, thickness 3.9 mm, elongation at break 45%, and storage modulus 5.0 mPa. Injection molded product peak melt temperature shifted down in order: PLA 132.8C, DBP/PLA (10/90%) 149.4/130.3C, DBP/PLA (20/80%) 148.8/128.2C, indicating softening of PLA when combined with DBP. Dairy proteins, whey and casein, may provide an advantage by lowering the peak molding temperature of PLA allowing for more biomaterials to be used. Further work is needed to improve the extrusion compounding and miscibility of this high-temperature melting PLA and high-temperature burning-DBP blend.

Agricultural Biomass, Biobased Products, and Biofuels
8:30 AM-12:10 PM, Thursday, March 29, 2007 McCormick Place South -- Room S103D, Level 1, Oral

Division of Agrochemicals

The 233rd ACS National Meeting, Chicago, IL, March 25-29, 2007