Preparation And Properties Of Low-viscosity And Low-melting PET Copolyester

Low-melting PET copolyester is a kind of PET copolyester with a lower melting point obtained by copolymerizing or blending.The melting point of low-melting PET copolyester is generally between 100°C and 240°C.It is often used as hot melt adhesives or masterbatch for the preparation of non-woven fabrics or coatings.Therefore,its fluidity and dispersibility during melting are very important.However,the fluidity of the most commonly used iso-benzene series low-melting PET copolyesters in melting is still not very satisfactory,it is necessary to further improve the fluidity of low-melting PET copolyesters.For this reason,in this paper,1,2-butanediol（1,2-BDO）and diethylene glycol（DEG）were used as modified components to prepare a series of low-viscosity and low-melting PET copolyesters.A series of PET copolyesters modified by DMIP and DEG with the same content as the PET copolyesters modified by 1,2-BDO and DEG,a kind of PET copolyester modified only by DEG and the PET polyester were prepared at the same time for comparison.The contents of the research were as follows:1.Combined with the ~1H-NMR spectrum and the infrared spectrogram,it was proved that each modified component had been successfully introduced into PET polyesters.It was discovered that the actual chemical component ratio of each sample was similar to the raw material ratio at the time of feeding.2.When modified components were added into PET polyester,the glass transition temperature and melting point would be reduced.However,with the increase of the content of1,2-BDO or DMIP,the melting point of the PET copolyester modified by 1,2-BDO decreased slightly lower than that of the PET copolyester modified by DMIP.In terms of thermal degradation performance,there was little effect on the thermal stability of copolyester when DEG and DMIP were added to PET polyester.While with the introduction of 1,2-BDO,there would be a decrease in thermal stability.Even so,the thermal stability of the PET copolyesters modified by1,2-BDO still met the processing requirement in production.3.The crystallinity of PET polyester would reduce with the increase of DMIP content.But for the PET copolyester modified by 1,2-BDO,there was no obvious downward trend in its crystallinity with the increase of 1,2-BDO content.4.Each modified PET copolyester melt and the PET polyester melt were pseudoplastic fluids and the higher the temperature was,the lower the apparent viscosity became.Besides,the fluidity of each modified PET copolyester melt was better than that of the PET polyester melt.The apparent viscosity of the PET copolyester melt modified by 1,2-BDO was lower than that of the PET copolyester modified melt by DMIP at the same shear rate.In other ways,for the PET copolyester melt modified by 1,2-BDO,its non-Newtonian exponent was higher and its activation energy of viscous flow was smaller than the PET copolyester modified melt by DMIP.5.The low-melting PET copolyesters were tested by neutral hydrolysis for studying theirs hydrolysis resistance.The results showed that the changes of the hydroxyl group peak,the carboxyl carbonyl peak and the ester carbonyl peak of the PET copolyesters modified by DMIP after hydrolysis were more drastic than the PET copolyesters modified by 1,2-BDO.At the same time,the glass transition temperature and melting point of the PET copolyesters modified by DMIP after hydrolysis decreased more than that of the PET copolyesters modified by 1,2-BDO.In summary,the hydrolysis resistance of the PET copolyesters modified by 1,2-BDO was better than that of the PET copolyesters modified by DMIP.