308 Properties of starch-poly(hydroxyester ether) composites and laminates.

J. W. LAWTON and J. L. Willett. National Center for Agricultural Utilization Research, USDA, ARS, Plant Polymer Research Unit, 1815 N. University St., Peoria, IL 61604.

Starch can be processed with synthetic polymers either in the thermoplastic state or in the dry granular state. Synthetic polymers are usually compounded with thermoplastic starch to improve the physical and mechanical properties of starch. Granular starch is usually compounded with synthetic polymers to decrease the cost and improve biodegradability of the synthetic polymer. However, mixtures of starch and synthetic polymers are uncommon because of the incompatibility of starch with most synthetic polymers. A new class of biodegradable polyesters, poly(hydroxyester ether)s (PHEEs) have an exceptional compatibility with starch. PHEE was compounded with up to 60% granular starch to give blends with tensile strengths of over 30 MPa. What is quite remarkable is not only the high tensile strength of these filled materials, but also the adhesion seen between the PHEEs and starch granules. SEMs of the fracture surfaces show that the fracture occurs through the starch granule rather than at the interface of the granule and PHEE. PHEE also shows good adhesion to thermoplastic starch. PHEE compounded with pregelatinized starch had tensile strengths over 30 MPa. Laminates of PHEE onto starch and starch-based materials could not be peeled off. Co- extruded blown films of PHEEs and starch-based materials were also produced. PHEE was difficult to peel off the supporting starch-based film. The adhesion between the PHEE and starch-based film was so strong that PHEE did not delaminate even during tensile testing. The laminated films did not disintegrate even after 8 hours in direct contact with water.