Study On The Chemical Recycling Technology Of The Post-consumer Polyester And Polyester Cotton Blend Fabrics

According to―The Uniform Management Regulations‖issued by the central militarycommittee, retired soldiers must turn and submit their uniforms to the PLA to prevent the useduniforms from flowing into the society. It is reported that the annual returned uniforms exceedtens of thousands of tons which exerts great pressure onto the uniform storages. Therefore, theresearch on the recycling of the polyester or polyester/cotton blend uniform fabrics is of greattheoretical and practical significances.In this work, polyester textile waste of low bulk density were firstly thermal condensedand the glycolysis process of the condensed textile waste was carried out using ethyleneglycol (EG) as degradation agent. Systematic studies were carried out by changing suchparameters as mass ratio of PET to EG, reaction time and reaction temperature, catalyst typeand concentration. The extent of reaction was studied by determining the amount of BHETpresent in reaction mixture. The monomer was characterized by differential scanningcalorimetry (DSC) and nuclear magnetic resonance (NMR). The structure and properties ofcotton fiber separated from the blend fabric which undergone the glycolysis process was alsotested.The results showed that thermal condensation by solid phase extrusion could increase thebulk density and had no obvious change in the properties and structure of the fabric. Theglycolytic degree was increased along with the increase of the mass ratio of PET to EG,reaction time and reaction temperature, reaching to certain value and no obvious change wasfound beyond. The optimal reaction time was1hr, temperature was196℃, mass ratio ofEG/PET was2.5and amount of catalyst was0.3%of PET. Among the four degradation catalysts namely zinc acetate, sodium carbonate, potassium acetate, magnesium chloride,sodium carbonate was the best. The values of the activation energy62.85KJ/mol (teryleneZnAC2),82.06KJ/mol (terylene Na2CO3),55.2KJ/mol(polyester-cotton ZnAC2) were derived.The glycolysis products were analysed by different techniques, such as1H NMR and DSC. Itwas found that the glycolysis products consist mainly of BHET monomer. After being treatedby the glycolysis process, the surface of cotton fiber in blend fabric become rough and itsmechanical properties showed a large decline.In this thesis, PET thermal condensed uniform waste was used as raw materials and the―partial-degradation-polymerization process PDPP‖was studied by adding EG with lessamount than required for complete PET degradation and then re-polymerization. Systematicexperiments were conducted by changing the parameters such as mass ratio of PET/EG,reaction time and reaction temperature. The intrinsic viscosity, diethylene glycol (DEG),carboxyl end group and thermal properties such as Tg, Tm of the prepared PET were testedby ubbelohde viscometer, gas chromatography, potentiometric titration and DSC respectively.The results showed that, the final PET with higher intrinsic viscosity and good thermalperformance was prepared when the mass ratio of PET:EG was10:1. The optimal reactiontemperature was265℃, the degree of side reaction will increase when temperature beyondthis value. It is suggested that the reaction time should be short if the quality of the productare assured. Exceeded reaction time did not help to increasing the molecular weight and theaddition of Zn containing catalyst tended to accelerate the reversed reaction, which isunfavorable to the polymerization reaction.