Effect of structure of nonisocyanate condensation polyurethanes based on benzoic acid on its susceptibility to biodegradation

Abstract

The present study investigates the effect of the biodegradation time on the properties of condensation segmented nonisocyanate polyurethanes (NIPUs) using the aerobic strain of Gordonia alkanivorans. Polyurethane samples were prepared from phenolsulfonic acid, benzoic acid, polytetramethylene glycol (PTMG 1000) or oligooxypropylene triol (G 1000) and different amounts of formaldehyde. The emulsifying activity, protein concentration, pH, tensile strength and strain at break were evaluated as function of biodegradation time and formaldehyde content. The existence of a segmented structure was confirmed by the existence of two phase transitions in the glass transition temperatures of flexible segments and melting temperatures of hard segments. The tensile strength (TS) of NIPUs based on PTMG 1000 and 50% excess of formaldehyde decreased by about 20%, 60% and 95% after 10, 21 and 90 days of biodegradation. TS decrease was less pronounced for NIPUs prepared from G1000. The 21 days biodegradation caused the most significant changes in the pH, emulsifying activity and protein concentration. The highest degree of cross-linking induced by an excess of formaldehyde led to the highest resistance of NIPU to Gordonia alkanivorans. The DSC, FTIR, SEM and element concentration analyses demonstrated that biodegradation occurred mainly in hydrolysis sensitive hard segments and, to a lesser extent, in flexible oligomerol segments.