Recycling of waste materials was classified in general and recycling technologies of polyurethanes (PU) were described based on literature data,mainly on proceedings of conferences and congresses of 1991-1997 and on work performed at the Polymer Institute,University of Detroit Mercy.In particular,physical and chemical recycling methods of PU were described;the recovery of energy was only mentioned.The physical methods of recycling include separation,granulation,densification and/or disintegration operations,and then reusing powdered material for the production process of PU.These methods are applicable for flexible and rigid PU foams,as well as for RIM products.Amongst chemical recycling methods the following processes were considered:pyrolysis,hydrolysis,glycolysis,recovery with alkanolamines,and petrochemical feedstock processing.In particular,the glycolysis process was described and mechanisms of chemical reactions were presented.
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