Systematic investigations on the biological degradability of packing material III. New polyvinylalcohol-starch-acetal films [German]

摘要

Based upon earlier investigations [1-3] on the biodegradability of polyvinylalcohols (PVAL) and so-called biodegradable films [4, 5], new acetals of selected PVALs of low molecular weight with starch derivatives have been synthesized and tested with respect to their biodegradation. Acetalization of PVAL with starch and starch derivatives has been performed in aqueous solution and by reaction extrusion at low water contents, affording up to 50% of the theoretical possible degree of acetalization in the former case and up to 93% in the latter one. Low molecular weight PVALs are not suitable for the manufacturing of films of sufficiant tensile strength for practical use as packing material. Nevertheless, they show improved biodegradability, probably due to a mechanism similar to the beta-oxidation of fatty acids which mechanism becomes significant at very low degrees of polymerization [3]. The acetals of such PVALs with starch derivatives show acceptable tensile strengths and significantly improved biodegradability compared to conventional films of similar mechanical properties. [References: 26]