Polymerization Kinetics And Modeling Of Poly (Ethylene Furandicarboxylate)

Poly(ethylene furandicarboxylate)(PEF)is a bio-based polymer with great potential to replace polyethylene terephthalate(PET),exhibiting better gas barrier properties,glass transition temperature and processing temperature than that of PET.Currently,the PEF monomer purification and synthesis technologies are becoming mature.Large scale manufacturing of PEF has been put on the agenda.Therefore,it is necessary to investigate the reaction kinetics and establish kinetic models for understanding the reaction mechanism and developing pilot and industrial production technologies.The synthesis of PEF is generally divided into two stages.First,the transesterification product or esterification product is obtained by transesterification or esterification,and then the final product is obtained by polycondensation.The kinetics of transesterification and esterification are significantly different,while the subsequent polycondensation process is basically the same.Therefore,the transesterification,esterification and polycondensation are studied separately in this paper.The kinetics of the transesterification reaction between dimethyl 2,5furandicarboxylate(DMFD)and ethylene glycol(EG)was studied by kinetic experiments.The 1H NMR method was established to determine the concentration of each component,and the equilibrium constant of the polycondensation reaction was obtained.The constant K3 is 0.456.The temperature of the transesterification process is measured,and it is found that the transesterification reaction is a temperature-changing process rather than a constant temperature process.An exponential function describing the temperature change with time is established.The kinetic model including transesterification reaction and polycondensation reaction was established.The rate constant and activation energy were obtained by "variable temperature" fitting.The kinetic model can well describe the experimental results of transesterification kinetics.The kinetics of the esterification reaction between 2,5-furandicarboxylic acid(FDCA)and EG was experimentally studied.The concentration of each component before and after the clearing point and the solubility of FDCA,that is,the liquid phase concentration of FDCA before the clearing point,were obtained by 1H NMR.The equilibrium constant of the polycondensation was calculated from the concentration quotient.It is found that the reaction equilibrium constant is close to the polycondensation equilibrium constant at the transesterification stage.It was found that with the increase of the reaction temperature,the reaction reached the clearing point earlier,and the esterification rate at the clearing point decreased slightly.The esterification kinetic model including esterification reaction and polycondensation reaction was established.The rate constant and activation energy were obtained by the"variable temperature" fitting of experimental data.The kinetic model can well describe the experimental results of esterification kinetics.For the PEF polycondensation stage,the kinetic experiment was studied by the pressure relief sampling method,and a method for calculating the number average molecular weight and end group concentration of PEF by measuring the intrinsic viscosity was established.The second-order kinetic model of the PEF poly condensation process was established.The "variable temperature" fitting of the experimental results of polycondensation kinetics yields the reaction rate constant and activation energy of polycondensation.The kinetic model can well describe the experimental results of polycondensation kinetics.