Abstract
AbstractThe 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(ε‐caprolactone), PCL) viscosity decreased (lower molecular weight), starch melt viscosity increased (lower moisture) and feedblock/die temperature increased. Peel strengths were 1 to 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.
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