New Degradation Technology Of Waste Polyurethane Foam And Its Life Cycle Assessment

Polyurethane is a widely used polymer material,and its waste treatment and effective recycling have become one of the major difficulties in the field of resource recovery.In this paper,we develop a new recycling technology for the preparation of recycled polyol by non-catalytic solvent thermal liquefaction of waste rigid polyurethane,which is further processed into recycled polyurethane rigid foam;and based on the principles and requirements stipulated in ISO 14040,ISO 14044,GB/T 24040-2008 and GB/T 24044-2008,the life cycle assessment of recycled polyol and recycled polyurethane was carried out.The main research results are as follows:（1）A new process for the preparation of recycled polyol by non-catalytic solvent thermal degradation of waste polyurethane rigid foam was developed.Through orthogonal experiments,the influence of liquefying agent type,reaction temperature,reaction time,mass ratio of raw material to liquefying agent and other conditions on the physical properties of the recycled polyol was discussed.Through the extreme difference analysis,it was found that the type of liquefying agent had the greatest influence on the physical properties of the recycled polyol.（2）The comprehensive analysis showed that Diethylene glycol（DEG）degradation system was the best.The optimized process parameters were:liquefaction time of 3 h,reaction temperature of 200℃,and mass ratio of waste polyurethane to DEG of 1/2.The DEG-based recycled polyol has a viscosity of 650 cps,a number average molecular weight of 1670,a hydroxyl value of 465 mg KOH/g,and a water content of 0.05%.（3）Through the evaluation of the comprehensive performance of the recycled rigid polyurethane foam prepared by 50%replacement of virgin polyol by EG-based,DEG-based,TEG-based and PG-based recycled polyol,it was found that the DEG-based recycled rigid polyurethane foam had the best comprehensive performance in appearance,microstructure,compression strength,specific strength,thermal conductivity and thermal stability.The DEG-based recycled PURF was white in color,with dense and uniform pores,compressive strength of 1050 k Pa,specific strength of 11.36 k N·m/kg,and thermal conductivity of 0.046 W/（m·K）.（4）To evaluate the comprehensive environmental impact of the process,a life cycle assessment of the process was conducted.Life cycle assessment was conducted for the preparation of recycled polyol by non-catalytic solvent thermal liquefaction of waste polyurethane rigid foam and the preparation of recycled polyurethane rigid foam by replacing 50%of virgin polyol with high percentage of recycled polyol.The results showed that 1 ton of recycled polyol induced global warming（GWP）of 1.98E+03 kg CO₂eq;1 ton of recycled polyurethane rigid foam caused global warming（GWP）of 3.69E+03kg CO₂eq.（5）Finally,the results of life cycle assessment of recycled polyol and recycled polyurethane rigid foam were compared with those of virgin polyol and virgin polyurethane rigid foam,respectively,and the results showed that recycled polyol had less impact on abiotic resource depletion-fossil fuel（ADPF）,global warming（GWP）,terrestrial ecotoxicity（TE）,photochemical ozone synthesis（POCP）,acidification（AP）,eutrophication（EP）,etc.The effects in terms of GWP are less than those of virgin polyol,in which,the recycled polyol reduces 46.05%than virgin polyol in terms of GWP,while the recycled polyurethane rigid foam reduces 16.52%and 10.65%than virgin polyurethane rigid foam（Ecoinvent database）and virgin polyurethane rigid foam（water-blown foam）in terms of GWP,respectively.The research results show that this waste polyurethane resource recovery process is not only technically feasible,but also environmentally sustainable.