| High temperature resistant polyamides have broad application prospects and can be used in automotive,aerospace,electronic and electrical fields and semi-aromatic polyamides have obvious advantages in dimensional stability,heat resistance and processability.They can be used in heat-resistant parts such as automobile engine and circuit board.PA6T?polyterephthaloyl p-phenylenediamine?,as a kind of material widely used in semi-aromatic polyamide,has attracted much attention,and the process of preparing this material abroad has been mature,and the domestic is still in the exploratory stage.PA6T is not suitable for melt processing because its melting temperature?370??is higher than decomposition temperature?350??.Its properties can be improved by copolymerization with aliphatic polyamide,one of the hot materials is PA6T/66.In this paper,high temperature resistant PA6T/66,was prepared by one-step melt polymerization and its crystallization properties,solvent resistance,thermal properties and crystallization kinetics were studied.Firstly,PA6T salt was synthesized with water as solvent,and its infrared spectrum analysis was carried out,and the prepolymerization temperature of PA6T salt was determined by measuring the melting point of the synthesized salt.Then PA6T/66,was prepared by one-step melting polymerization in the reactor,and the structure of PA6T/66 was determined by infrared spectroscopy,and the intrinsic viscosity of the product was tested.The crystallization properties and solvent resistance of PA6T/66 were tested.It was found that PA6T/66 had many fine microcrystals,and its crystal forms with different proportions remained unchanged.Through the test of solvent resistance of PA6T/66,it was found that its solvent resistance was better.Only concentrated sulfuric acid was dissolved in several common solvents tested.The thermal properties of PA6T/66 were tested.It was found that the thermal deformation temperature and melting temperature decrease gradually with the increase of PA66 content.The thermal degradation process of PA6T/66 may be a one-step degradation process of random broken chain,and the average activation energy of thermal degradation of PA6T/66?45/55?is 227.381 kJ·mol-1,the thermal degradation process in nitrogen atmosphere may follow the F3 mechanism in the deceleration curve.That is,the random nucleation,is three nuclei per particle.Through the analysis of crystallization kinetics of the samples,it is concluded that the growth mode of polymer under isothermal crystallization condition may be two-dimensional flake growth,and the growth mode of polymer under non-isothermal crystallization condition is two-dimensional flake growth.With the increase of PA66 content,the crystallization rate of the polymer increased at first and then decreased. |
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