Properties of the fatty acid esters of amylose

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Abstract
To help establish the suitability of esters of amylose and fatty acids as dip‐coating materials, esters of the evennumbered, saturated fatty acids, acetic through stearic, and of oleic and cottonseed oil fatty acids were prepared, and their properties were determined.The various esters generally were prepared by the interaction of acid chlorides with the amylose suspended in a suitable mixture of solvents. Analyses for content of free fatty acid groups indicated that high proportions of the hydroxyl groups were esterified. Intrinsic viscosity decreased as the chain length of the acyl group increased, a reflection of the changing nature of the products rather than a decrease in the degree of polymerization of the amylose.As the chain length of the saturated fatty acid group increased the softening point at first decreased and then increased, the minimum being obtained with the myristate. The stearate softened at 56.2ŶC. The stearate had a hardness index of 139, which was about equal to the index of 140 for completely hydrogenated cottonseed oil. Densities were greater than those of the corresponding triglycerides and decreased as the chain length of the fatty acid group increased. Permeability to water vapor also decreased as the chain length increased, the index being 620ȕ10蜢12 for the acetate and 15ȕ10蜢12 for the stearate. The acetate possessed the highest tensile strength, about 4.40 kg./sq. mm., while the palmitate had a tensile strength of about 0.49 kg./sq. mm. Elongation at the break point varied widely, being 632% for the caprate and 0.95% for the stearate.

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