Study On Polymerization Process Of Semi-aromatic Nylon 6T/66

As a typical semi-aromatic nylon and due to its excellent high temperature resistance,solvent resistance,thermal stability and other prominent properties,PA6T/66 has in recent years become a hot research topic increase both at home and abroad.PA6T/66 has attracted a lot of attention both domestic and abroad in recent years.In this paper,the PA6T/66 is prepared through two-step process including"pre-polymerization and solid-phase copolymerization".The effects of reaction conditions on 6T/66 were studied at different stages,with the polymerization products analyzed by NMR,IR,GPC,DSC and TGA,and the results were demonstrated as follows:(1)The optimum conditions for preparation of 6T/66 pre-polymer(55/45)were determined as follows.Molar ratio of amine to acid is 1.03-1.05,and reaction temperature is set at 250?,with exhaust time of 2.0 h and stirring speed of 300 rpm.The temperature increased in gradient during the initial polymerization.At the final stage of polymerization,continuous exhaustion was applied and holding the pressure for certain period to efficiently remove the solvent water and by-product water.Triamine is the main reason of pre-polymer branching,and the apparent molecular weight of the pre-polymer and the shear viscosity increase with the increase of triamine.(2)Triamine is the main reason for pre-polymer branching,because the apparent molecular weight of the pre-polymer and the shear viscosity increase with the increase of triamine.(3)End-capping agent affects the molecular weight and the activity of following polycondensation of the pre-polymer,with no apparent influences on the melting temperature.(4)TGA and DSC analyses indicate a close correlation between thermal properties of 6T/66 pre-polymer and its structure,and the irregularity of its segments affects application performances.(5)The optimum parameters for solid-phase polycondensation are at 260? within 4.5-8 hours.As reaction time goes on,the gel-like insoluble matter would appear,which might affect performance in application.(6)The 6T/66 copolymer does not decompose under 375? according to TGA analysis,and its maximum decomposition rate is reached around 472?.(7)The fluidity of 6T/66 copolymer can be adjusted by adding diamine,which is beneficial for the application process requiring high fluidity.(8)Four char acteristics of 6T/66 copolymer,such as the tensile strength,tensile film quantity,bending strength and bending modulus,initially show gradient increase then decrease with the increment of 6T content,reaching the maximum value as 50/50(6T/66).While the impact strength decreases with the increase of 6T content.