Study On Thermal Degradation Kinetics And Melt Transport Simulation Of PBT

Due to its excellent elasticity,soft hand and easy dyeing properties,PBT fiber is aroused general concern,which is widely used in apparel,home textiles and other fields.At present,PBT fiber can only be spun by PBT chips,while melt direct spinning for PBT has not yet been achieved,which limits the production and application of PBT fiber.In order to provide a theoretical basis for melt direct spinning of PBT,in this paper,the melt conveying model is programmed by Matlab,and the melt conveying model of PBT is established to simulate the transport process.Firstly,in order to establish the PBT melt conveying model accurately,various physical parameters of PBT need to be obtained.In this paper,the thermal degradation kinetics equations of two intrinsic viscosity PBT chips were obtained with five thermal degradation kinetics analysis methods,and the thermal degradation mechanism of PBT was known as phase boundary control type.The specific heat capacity of PBT melt was determined by DSC method.It was found that the specific heat capacity of PBT melt increased with the rise of temperature,showing a good linear relationship,and the relationship between specific heat capacity and temperature was obtained by linear fitting.The capillary rheometer was used to investigate the flow condition of PBT melt in the capillary,and the viscous flow activation energy ?Ea of the melt was obtained,providing a reference for the adjustment of the melt conveying and spinning temperature of PBT.In addition,within a certain range of temperature and intrinsic viscosity,the flow viscosity of the PBT melt showed a linear relationship with the temperature by the test of rotary rheometer.Finally,in order to conclude the PBT melt viscosity drop formula,the Mark-Houwink parameters of PBT were determined by measuring the intrinsic viscosity and molecular weight of the sample.Secondly,according to the process of direct spinning of polyester melt,the PBT melt transfer model was established,including the melt transfer pipe model,booster and metering pump model,melt filter model and spinning component model.In the case of the given melt transport parameters,the related model was compiled with Matlab software.The melt transport process of PBT was simulated and calculated,and the change of melt temperature,melt pressure,melt characteristic viscosity and residence time in each tube section was analyzed.After analysis,it was known that the melt temperature rise was more obvious when the melt in the pipe section with large flow resistance,such as booster pump,melt filter and metering pump.The increase of melt pressure were mainly provided by booster pump and metering pump,while the pressure drop occurs mainly in the spinning component.The intrinsic viscosity drop of the melt mainly occurs in the melt conveying pipe and the spinning assembly,where the melt temperature was higher andthe residence time was longer.Finally,combined with the simulated results of Matlab software and the pilot test of the enterprise,the PBT melt conveying and melt direct spinning were introduced in this paper,and two different melt conveying processes were investigated.After the test of the enterprise,it was found that the PBT elastic filament spun by the high temperature and high viscosity melt was similar to that of filament spun,meeting the requirements of relevant quality indexes,and the PBT melt direct spinning elastic filament was successfully realized.Compared with the actual production of the enterprise,the data gotten by using the software to simulate the melt conveying process has a high degree of match,providing a reference for the melt conveying test in the factory,but some of the data were also biased,and the model needs to be modified so that simulation results are closer to actual test results.