| The weight of waste PET is increasing quickly with the rapid development of polyester industry. So, how to reuse waste PET is an important subject that is ungently dealed with to keep rapid development of polyester industry. Waste PET and its products, especially the second waste from reusing process, unfit to reuse directly because lower instrinsic viscosity number. It's a good case of making new polymer material by glycolysis and modifies waste PET. When waste PET can replace part of raw material, it's a costless and meaningful thing to develop and utilize PET waste and protect environment.Hot-melting adhesive fibers, a fiber-like thermoplastic polymer, has been widely used for non-woven fabric non-collodion, solid-quality cotton and interlining. With the rapid development of composite fiber indusrty, it's urgent to develop a variety of low melting point copolyester used for hot-melting adhesive fibers.In this article, the glycolysis and budanediolysis of waste PET were studied, and then added some modifiers into the glyxolysis product for making low melting point copolyesters, the relationship between copolyesters' physical properties and chemical structures were also investigated. The results show that: glycolysis procedure glycolysis temperature glycolysis time and catalyst were found to have drasticlyeffect on depolymerization of waste PET. The reactions will be accelerated with the refluxing dinstilling procedure, so the glycolysis times shorten. The glycolysis product is mainly bis-hydroxyethyl terephthalate, but the budanediolysis product is mainly dimer. All the glycolysis reactions reach equilibriums after PET oligomer fragments disappeared. There are about 5.5mol% DEG segments will add to macromolecular chain of regenerative PET, while the chain has 5.7mol% ET segments in waste PET with butanediolysis and then condensation.The copolyesters which regenerate from waste PET by glycolysized and modified with EPA, AA, will have lower glass transition temperature and melt point. With the involvement of PEI, the copolyesters become less crystallizable and evenamorphous when PEI content is reach 40mol%. In PEAT, crystallization is weaker with moer AA involvement. A series of copolyeste'r were also obtained by butanediolysis and modifying with IPA and AA. The results show that: with the involvement of AA and IPA, the melting point and glass transition temperature of copolyester decrease. The effect of the compositions on the glass transition temperature and melt transition temperature was interesting. The glass transion temperature was found to be dependent mainly on the content of AA. As the content of AA increased, the glass transition decreased. The melt transitions of copolyesters were obvious decreasing with addition of IPA and AA. With the relative contents of IPA and AA changing, the melt temperature of copolyesters did not follow a simple rule. After enough time to crystalize, PBET-BA-BI in the DSC scan performed multiple endotherms. The results indicated that there are different perfective crystals. It need long time to form crystallization field, such anormalous behavior is ascribed to a very low crystallization rate low crystallinity and imperfect crystal(or defective crystal). With the cotent of AA increasing, the crystallization accelerated. The crystal rate of copolyesters dependents on crystal growth rate.Multi-conponent low melting point copolyesters were synthesized when waste PET use for basic raw materials. Better preliminary trial result obtained when the copolyesters were applied in hot melt composite fibers and hot-melt adhesives. The results indicated that the copolyesters have promising application perspectives.To sum up, the process of waste PET under glycolysis esterification co-condensation to make low melting point copolyester is feasible. It is a useful approach to recycle waste PET and prepare new polymer materials. |
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