Table 2.

Main PU functions and their principal degradation types.

Functions/Polymer	Main degradation types
Ester/Polyester	Hydrolytic [61], enzymatic [62,64]
Ether/Polyether	Oxidative [61], enzymatic, physical [61]
Carbonate/Polycarbonate	Enzymatic [62,64], hydrolytic [61] a
Polyamine	Oxidative [61]
Urethane HS/Polyurethane	Enzymatic [62,64], hydrolytic [61] a
Urea HS/Polyurea or Polyurethane-urea	Enzymatic [62,64]

^aLower than ester functions but higher than ether.