Enzymatic degradation of polyurethane coatings

The purpose of these studies was the evaluation of susceptibility of polyurethane coatings obtaining via polyaddition of polycarbonate diol (Desmophen (R) C2200 Bayer) or polyesterether polyols with different branching degrees (Desmophen (R) 1150, Desmophen (R) 1200 Bayer), trimethyl-1,6-hexamethylene diisocyanate (TMDI) in the presence of 1,4-butanediol (BD) as a chain extender, on enzymatic degradation. Polyurethane coatings were synthesized by step growth polymerization in bulk or with using N, N-dimethylacetamide (DMAC) as a solvent. Such obtained polyurethane coatings were treated by lipase from Candida antarctica (Novozym 735, CALB L), from Aspergillus (Novozym 51032), lipase from Rhizomucor miehei (Pallatase 20000 L) or lipase from z Thermomyces lanuginosus (Lipozyme TL 100 L) to generate enzymatic degradation. In all cases process was realized in optimal conditions of pH and temperature, which are characteristic for each of lipase. The time of degradation, chemical structure, the manner of synthesis and the type of enzyme influenced on biodegradability. Loss of mass of the samples which were treated by enzymes, growing amount of total organic carbon in the solutions after degradation, difference in the free surface energy (SEP) confirmed biodegradation of the samples. The changes in the morphology of the samples were visualized by optical microscopy - after treating by enzyme some characteristic cracks, craters and rows appeared. The enhanced degradability of polyurethane coatings which were obtained by bulk polymerization compared to samples synthesized in the solution of DMAC is due to their higher degree of polydispersity and the higher free surface energy.