Skip to main content
ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Plant Polymer Research » Research » Publications at this Location » Publication #99297
Title: PREPARATION AND PROPERTIES OF THERMOPLASTIC STARCH-POLYESTER LAMINATE SHEETS BY COEXTRUSION

Author
item WANG, LINFU - RAYONIERE, INC.
item Shogren, Randal
item Carriere, Craig

Submitted to: Polymer Engineering & Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: There has been increasing public demand recently for disposable plastic articles made from biodegradable, environmentally friendly materials. Starch from corn or wheat can be melted and processed into plastic-like articles such as films and foams but suffers from poor water resistance. This research showed that it is feasible to prepare water resistant starch sheets by laminating them with a thin layer of a biodegradable polyester o each side. The preparation of starch sheet and lamination were carried out in a single step without the use of solvents or hazardous chemicals. The adhesion of the polyester coating on the starch was surprisingly high and was due to roughness of the interface. Even though biodegradable polyesters are much more expensive than starch, very little was used (<5% by weight) so the composite should be very economical. This work should be of interest to companies involved in making single use items such as disposable plates, clammshells, and compost bags, as well as those making starches and biodegradable polyesters. Researchers in universities and government laboratories working on biodegradable materials for industrial and medical applications should also benefit.

Technical Abstract: The effects of extrusion and formulation variables on the structure and properties of starch-polyester laminates were examined. Three-layer polyester/starch/polyester sheets were prepared using a twin-screw extruder for the starch/water center layer, a single screw extruder for the outer polyester layers, and a feedblock and coathanger type sheet die. Overall sheet and coating thicknesses were more uniform as coating polymer (poly (epsilon-caprolactone), PCL) viscosity decreased (lower molecular weight), starch melt viscosity increased (lower moisture), and feedblock/die temperature increased. Peel strengths were 1-2 orders of magnitude larger for high than low molecular weight PCL. High peel strengths were associated with rough, wavy interfaces (interfacial instability). Addition of plasticizer such as glycerol and sorbitol to the starch decreased peel strengths. Peel strengths varied little with type of polyester coating, except perhaps for polylactic acid and polyesteramide, which were more difficult to peel. Some possible applications of laminated starch sheets include food packaging and controlled release of drugs, pesticides, insect diets, etc.