Biodegradation mechanism of polyurethanes

Polyurethane is widely used in various fields, such as the manufacture of plastic foams, cushions, rubber goods, synthetic leathers, adhesives, paints, and fibers. Conventional polyurethane is produced using toxic diisocyanate, which is derived from the even more toxic phosgene, and it is generally resistant to biodegradation (Tokiwa, 2003b Howard, 2002). This may be ascribed both to the complexity of the molecular structures and lack of enzymatically cleavable linkages in the polymer chain. 

18 Proposed degradation scheme of urethane model compound (adapted from Owen eta ., 1996). 

It is easy to understand that poly(ester-urethane) is susceptible to hydrolysis by an enzyme, such as lipase and esterase. The poly(ester-urethane) was hydrolyzed by Rhizopus delemar lipase at the polyester moiety of poly(ester-urethane) (Tokiwa et al, 1988). Santerre et al (1994) and Wang et al (1997) reported that cholesterol esterase degraded poly(ester-urethane), synthesized from TDI, polycaprolactonediol and ethylene diamine, and released the hard-segment components. 

79 Enzymatic synthesis and chemical recycling of biodegradable poly(ester/carbonate urethane) (adapted from Soeda eta ., 2004, 2005). 

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Christenson EM, Anderson JM, Hiltner A. Biodegradation mechanisms of polyurethane elastomers. Corros Eng Sci Technol 2007 42(4) 312—23. 

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