Preparation and properties of biodegradable foams from starch acetate and poly(tetramethylene adipate-co-terephthalate)

Biodegradable composite foams were prepared by extruding starch acetate, with degree of substitution (DS) 1.78, with poly(tetramethylene adipate-co-terephthalate) (EBC). The foams' chemical structures, thermal behaviors, and microstructures were investigated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). By measuring these properties, it was found that low EBC contents in the blends favored the miscibility of the two polymers, as characterized by (1) disappearance of EBC carbonyl peak and appearance of hydrogen-bonded EBC carbonyl groups in FTIR spectra; (2) an increase in T_g of starch acetate and the decreases in T_m values of starch acetate and EBC in DSC thermograms; and (3) formation of a homogeneous morphology in SEM. However, large amounts of EBC decreased the miscibility of these two polymers, as reflected by the foams' physical and mechanical properties. With a small amount of EBC, the foams had high radial expansion ratios (RER) and spring indices (SI) and low unit densities and compressibilities. Biodegradation rates of the composite foams decreased with the addition of EBC to starch acetate.