Waterborne polyurethane based starch containing materials: Preparation, properties and study of degradability

摘要

New starch-containing aqueous anionic polyurethane dispersions (APU/St) were prepared by the introduction of an aqueous starch solution into an anionic oligourethane solution and by the combination of the chain extension and dispersion stages. A fundamental difference between the APU/St dispersions and mechanical mixtures of anionic polyurethane dispersions and starch (APU + St), which manifests itself in a high aggregate stability and ability to form solid films, has been proved. APU/St based films display higher tensile strength in comparison with St and are characterized by increased values of elongation at break, degree of hydrophilicity, and significantly enhanced ability to undergo an acid/ alkaline hydrolysis compared with the APU matrix. The adhesion of microorganisms Bacillus subtilis to the APU/St surface, which is the first step and determining factor of biodegradation, exceeds those of the APU matrix. The introduction of St into the APU structure resulted in the formation of amorphous polymer-polymer microdomains, i.e. an integrated system formed due to the presence of both the co-valent and the hydrogen bonds between its ingredients. This predetermines the degradation of the APU/ St systems as a whole, unlike the mixed APU + St films.