The Preparation And Characterization Of Polyamide 6-Polyamide 6T Copolymers And Fibers

Polyamide PA6,also known as nylon 6,has excellent abrasion resistance,light weight,high elastic recovery,and high breaking strength.However,nylon 6 fiber has smaller bending rigidity and initial modulus,and it is easier to deform in use.The clothes made of nylon are not as good as polyester and wool.Polyamide 6T is a representative of semi-aromatic nylon.The introduction of aromatic ring structure can increase the rigidity of the molecular chain and significantly improve the mechanical properties of nylon 6 fiber.Therefore,polyamide 6T was copolymerized with polyamide 6,and benzene ring was introduced into nylon 6 chain to synthesize a modified nylon 6 with high stiffness and high strength.The modified nylon 6 POY was prepared by melt spinning,and the rigidity of nylon 6 fiber was improved.In this paper,polyamide 6-polyamide 6T copolymer with 5 wt%,9 wt%,15 wt% and 20 wt% was successfully prepared by direct copolymerization.It is found that the addition of 6T salt lowers the reaction speed and improves the melt viscosity of products.With the addition of 6T salt,the polymerization time was prolonged.The relative viscosity of polyamide 6-polyamide 6T series copolymer can be improved by controlling polymerization time.The polyamide 6-polyamide 6T series copolymers were tested and characterized.The results of 1HNMR,FT-IR,GPC,and end groups indicate that the copolymer contains both the characteristic peaks of PA6 and PA6 T,which proves that PA6 and PA6 T have been copolymerized,and the relative molecular weight of the copolymer is about 17000.The results of DSC and XRD show that the addition of a benzene ring leads to slower migration of the molecular chains,which tends to result in the formation of crystals with less crystallinity and less perfect crystallinity.With the increase of 6T salt content,the melting temperature and crystallization peak temperature of the copolymer decreased,the crystal form remained the same ? and ? crystal form as PA6,but the proportion of ? crystal form increased.The results of non-isothermal crystallization showed that the addition of 6T salt increased the copolymer's half-crystallization time t1/2 and the crystallization rate decreased.The crystallization peak temperature Tp moves to low temperature with the increase of the cooling rate,and the crystallization peak width ?Tc broadens as the cooling rate increases.From the results of TGA,melt index,and relative viscosity,it can be seen that the amount of 6T salt added increases,the relative viscosity of the copolymer increases,and the fluidity of the solution decreases.The copolymer has good thermal stability and completely meets the processing requirements of spinning or injection molding.The tensile test results showed that the initial modulus and tensile strength of the copolymer increased with the introduction of benzene ring.Polyamide 6-polyamide 6T copolymer chips with good mechanical properties were melt-spun,and the properties of the modified nylon 6 fibers with different drafting times were characterized.The results of bending and tensile properties show that the introduction of benzene rings on macromolecular chains can significantly improve the flexural rigidity and elastic modulus of nylon 6 fibers.The properties of modified nylon 6 fiber are the best when the amount of addition is 9wt% and the drafting ratio is 3.7.The results of XRD showed that the main ? crystal form is mainly in the modified nylon 6 fiber.The increase of 6T salt content is beneficial to the formation of ? crystal form.The increase of the drafting ratio is beneficial to the phase transition of the ? crystal to the ? crystal.The results of boiling water shrinkage and heat shrinkage showed that the amount of 6T salt added increased the boiling water shrinkage and thermal shrinkage of the modified nylon 6 fiber.