Synthesis And Copolycondensation Kinetics Of PET/PEG Copolymer

It has been a hotspot in the polyester industry to modify the polyethylene terephthalate(PET)by copolymerization to obtain a functionalized polyester product.In this paper,PET/PEG copolymers with different PEG content,different PEG molecular weight and different molecular weight of PET prepolymer have been successfully synthesized by melt copolymerization,while the chain structure and performances have been systematically studied.Firstly,the chain structure,functional group and crystal structure of the copolymers have been analyzed by Nuclear Magnetic Resonance(NMR),Fourier Transform Infrared Spectroscopy(FT-IR)and X-ray diffraction(XRD).After that,the hydrophilicity of PET/PEG copolymers was characterized by water contact angle analysis,which indicated that with the increasing of the mole content and molecular weight of PEG,as well as the molecular weight of PET prepolymer,the hydrophilicity of PET/PEG copolymers increase correspondingly.Differential Scanning Calorimetry(DSC)was used to test the non-isothermal crystallization process of PET/PEG copolymers,while the non-isothermal crystallization kinetics of PET/PEG copolymers was investigated by Jeziorny theory and Mo's method,respectively.The Avrami exponent of all the copolymers was located between 2.6 and 2.9 from Jeziorny theory while the non-isothermal crystallization parameter a obtained by the Mo's method is between 1.1 and 1.5.Both of that indicated the crystalline form of PET/PEG copolymer is consistent with PET homopolymer.The crystallization rate of PET/PEG copolymers increased at first and then decreased remarkably with the increasing of PEG content.Differently,the crystallization rate increased monotonically with increasing of the molecular weight of both PEG and PET prepolymer.Finally,copolycondensation kinetic model for PET/PEG copolymer was established based on the end-group reaction model and the corresponding kinetic experiments were carried out in the temperature range of 240?270?.The kinetic parameters were estimated by using the concentration of carboxyl end group and hydroxyl end group change with copolycondensation time.All of the results can be used to guide the melt copolycodensation process of PET/PEG copolymers.