Study On The Preparation And Properties Of Polyurethane Elastomer For Waste PET

Packaging polyethylene terephthalate(PET)loses its original packaging properties after a single use and is discarded.The accumulation of packaging waste PET in nature causes serious environmental pollution and waste of resources.Chemical recycling is the key to solving this pain point,as the effective use of waste PET for up-cycling has been a hot topic of research.Most of the current research only uses the small molecule monomers or oligomers produced by the degradation of PET as raw materials,but the waste from the degradation process is not effectively treated,which creates more pollution and defeats the purpose of the chemical cycle,so the effective use of degradation products is a key part of the chemical cycle.In response to the above problems,this study proposes for the first time the use of degradation liquid(GOPL)from waste PET as a chain extender for the preparation of polyurethane,and the corresponding high value technology for polyurethane.The details of the work and the main findings are as follows:A home-made waste PET degradation product(GOPL)was used as a raw material for the synthesis of polyurethane elastomers in the laboratory.Polyurethane elastomers were successfully produced by the prepolymerisation method,setting different GOPL additions,and the results show a shift from polyurethane elastomers to polyurethane adhesives when the addition exceeds 8 wt%.Infrared analysis shows that GOPL is successfully incorporated into the polyurethane chain segments;mechanically,the addition of GOPL changes the orderliness of the molecular chains and forms more amorphous regions compared to polyurethane elastomers without GOPL,increasing the strain elongation by 943% from the original base;it also has good low temperature rigidity and thermal stability up to 289 °C;the light transmission rate increases with GOPL content The light transmission rate increases with increasing GOPL content.The best overall performance of the polyurethane elastomer was obtained with the 6 wt%addition,and the 6% GPUE was chosen as the base material for the subsequent work.The combined results show that the preparation of polyurethane elastomers using GOPL is feasible.To broaden the scope of application of GPUE,a molecular chain design was carried out to introduce tannic acid(TA)with dynamic covalent bonding of phenol to prepare GPUE with dynamic covalent bonding of phenol(TA-GPUE).The addition of TA alters the spatial structure of the polyurethane molecular chain,allowing TA-GPUE to be rapidly dissolved by polar solutions for repeated recycling;the thermal stability and strain elongation of the polyurethane are improved by regulating and controlling the content of dynamic bonds of phenol carbamates in the polyurethane backbone.The appearance of the characteristic peak of TA in IR indicates the successful incorporation of TA into the GPUE skeleton.The low-temperature rigidity was enhanced by the introduction of a structurally complex and multifunctional TA as a rigid element.Under ambient conditions TA-GPUE in N-dimethylformamide(DMF)is able to form a homogeneous polymer solution within 50 min and still forms a TA-GPUE film after drying,therefore TA-GPUE can be used as a linker for conductive substances.GPUE is used as a flexible substrate,and TA-GPUE and carbon nanotubes are used as a conductive composite layer to build a flexible electronic sensor.The conductive composite layer has good abrasion resistance.After 20 round trips on 600 grit sandpaper,the composite layer does not peel off,the adhesion reaches IOS 1 level,the scratch force between the composite coating and the substrate reaches 36.8 N,and has good water resistance.In terms of sensing applications,it has good durability and stability and can withstand 1500 stretch-release cycles without change.It can effectively monitor human activities such as fast press,slow press,light-heavy shift press,finger flexion,triple quick click and double quick click,confirming the feasibility of the sensor assembled by the waste.In summary,the GOPL-based polyurethane elastomer(GPUE)with high flexibility,mechanical strength and thermal stability was prepared in this paper.The introduction of TA successfully improved the solubility of GPUE,while confirming the feasibility of GPUE and TA-GPUE in the field of flexible sensors,and this study provides new ideas for the preparation of polyurethane from packaging waste PET and its high value utilization.