Effect of structure of nonisocyanate condensation polyurethanes based on benzoic acid on its susceptibility to biodegrad
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Effect of structure of nonisocyanate condensation polyurethanes based on benzoic acid on its susceptibility to biodegradation Mohamed Bakar1 · Anita Białkowska1 · Barbora Hanulikova2 · Milan Masař2 · Iwona Zarzyka3 Received: 9 July 2020 / Accepted: 17 November 2020 © The Polymer Society, Taipei 2020
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. Keywords Nonisocyanate polyurethanes · Biodegradation · Mechanical properties · Structure
Introduction During the last few decades, various research groups around the world have shown great interest in biodegradable conventional polyurethanes (PURs). The investigations concerned mainly the biodegradation of isocyanate based polyaddition PURs [1, 2, 3, 4, 5, 6, 7, 8, 9]. Due to their versatile structure and characteristic performance properties, PURs belong to the most popular group of polymeric materials which are used in applications such as rigid and flexible foams, coatings and biomaterials. Their wide use makes recycling and biodegradability of great importance. Several conducted studies have shown that the biodegradation process of polymeric materials depends on biological * Mohamed Bakar [email protected] 1
University of Technology and Humanities, Radom, Poland
2
Centre of Polymer Systems, University Institute, Tomas Bata University in Zlín, Zlin, Czech Republic
3
Rzeszów University of Technology, Rzeszów, Poland
factors, such as bacteria, fungi and enzymes. It is also influenced by environmental factors such as humidity, the presence of oxygen, pH, temperature and the presence of minerals that can affect degradation activity of microorganisms [1, 2, 3, 4, 5 , 6, 7, 8, 9]. Biodegrad
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