Improvement On Crystallization Property Of PET

In this paper,dibasic acids(butanedioic acid,adipic acid,sebacic acid),powders(zirconium dioxide,magnesium sulfate,magnesium carbonate),homemade dibasic acid sodium salt(sodium succinate,sodium adipic acid,sodium sebacate),ethylene glycol metal compound(sodium ethylene glycol,zinc ethylene glycol,magnesium ethylene glycol)and stearic acid salt(lithium stearate,sodium stearate,potassium stearate,magnesium stearate)were used as modifiers.A series of PET samples were prepared by copolycondenzation and blending.Their thermal properties and crystallization behaviors were characterized by DSC,XRD,Optical Depolarization methods.By in-situ polymerization powders(zirconium dioxide,magnesium sulfate,magnesium carbonate),dibasic acids(butanedioic acid,adipic acid,sebacic acid),and their mixture were used as modifiers for PET synthesis.The esterification reaction dynamics and the influence of the kinds and quantities of the additives on the activation energies and reaction time were systematically studied.The intrinsic viscosity,the transition temperatures,and isothermal crystallization kinetics have been characterized.The results have shown that esterification time and esterification reaction activation energy was reduced by adding dibasic acids and powders(except ZrO2 treated by sodium stearate).The intrinsic viscosity was decreased by adding dibasic acids and increased by adding powders(except MgSO4).The influence of dibasic acids and powders on the crystallization rate was obviously different.The Avrami index(n)of PET was very complicated.In the blending modification,dibasic acid salts(sodium succinate,sodium adipic acid,sodium sebacic),ethylene glycol metal compounds(sodium ethylene glycol,zinc ethylene glycol,magnesium ethylene glycol)and stearic acid salts(lithium stearate,sodium stearate,potassium stearate,magnesium stearate)were used as modifiers for PET.Their intrinsic viscosity,thermal transition temperature and crystallization properties were characterized.The results have shown that the intrinsic viscosity was increased by adding powders.The melt crystallization temperature and crystallization rate have improved obviously by adding dibasic acids salts.The isothermal crystallization kinetics results indicated that the Avrami index(n)of PET have also become complicated.Meanwhile,different quantities of sodium succinate,sodium adipic acid,sodium sebacic and sodium stearate were used as modifiers for PET.The samples was cooled down with different cooling rates in DSC measurement.The influence of quantities of the additives and cooling rates on crystallization temperature was studied,and non-isothermal crystallization kinetics have been characterized by Mo equation.The results have shown that the intrinsic viscosity was decreased by adding powders,but the change tendency was different.The influence tendency of sodium succinate and sodium adipic acid on transition temperatures was the same,while the influence tendency of sodium sebacic and sodium stearate was opposed to sodium succinate and sodium adipic acid.The non-isothermal crystallization kinetics of PET could be characterized by Mo equation.