| Polyethylene terephthalate(PET)is a semi crystalline linear thermoplastic polyester,which has excellent performance,good transparency,tasteless and non-toxic.It can still maintain excellent physical and mechanical properties in a wide temperature range,as one of the important members of packaging waste,it is widely used.However,its waste is difficult to degrade in the natural environment,resulting in white pollution with great harm.In view of the huge pressure on the environment caused by waste PET,this study uses alcoholic's method to degrade waste PET with different alcoholysis agents,which can be used as chemical raw materials to reduce the pressure on the environment caused by waste PET.In this paper,the waste PET was treated by chemical degradation to realize the recycling of packaging waste PET.Firstly,different molecular weight of polypropylene glycol(PPG)was used to alcoholize the waste PET at different temperatures.By means of FTIR,1H-NMR and MALDI-TOF,the influence of molecular weight of alcoholysis agent and alcoholysis reaction temperature on the structure of alcoholysis product was analyzed,and the possible low content of the waste PET product was found.The polymer and monomer structures were analyzed in depth.Thermogravimetry(TG)and differential scanning calorimetry(DSC)were used to characterize the thermal properties of alcoholysis products,and the products with good shelf stability were obtained.Secondly,DPG and NPG were used as alcoholysis agents to alcoholize waste PET.The effects of alcoholysis temperature and reaction time on the products of brittle PET were investigated,and the structure and morphology of brittle PET were characterized.The thermal properties of the products were analyzed,and the best alcoholysis technology for the preparation of brittle PET products was explored,Finally,the two alcoholysis products were used as chemical raw materials in the synthesis of waterborne polyurethane,which improved the heat resistance of polyurethane.The results show that,for the degradation of waste PET,when PPG is used as alcoholysis agent to degrade waste PET,alcoholysis products with similar structure can be obtained at different temperatures.PPG as alcoholysis agent,low temperature degradation can effectively reduce the energy consumption cost of recycling waste PET.With the increase of PPG molecular weight,the overall molecular weight of alcoholysis products is larger,and the product structure is less different.A small amount of BHET is formed.When the temperature of alcoholysis increases,the activity of alcoholysis reaction can be increased,which is beneficial to the formation of oligomers.The smallest molecule is ethanol.The results showed that the optimum reaction conditions were as follows:temperature 160-180?,reaction time 3 h.The yield of degradation product was about 93.3%.After carbonizing the solid products at high temperature,carbon nanofibers with good electrical conductivity were obtained,which can realize the high-efficiency recycling of waste PET.In this paper,different alcoholysis products were used in the synthesis of waterborne polyurethane,and the differences between polyurethane samples were analyzed.When DPG/NPG alcoholysis product is introduced into WPU as hard segment,the structure of hard segment and soft segment will be balanced,and WPU with better performance can be obtained with lower degree of phase separation. |
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