Study On The Preparation And Properties Of Semi-aromatic Nylon MXD6/6 Co-polyamide

Semi-aromatic nylon poly(m-xylene diamide)(MXD6)shows great development potential and market prospects for its excellent barrier performance in high barrier functional packaging materials,but its toughness and processing performance are poor.In addition,the production technology of its main raw material,m-phthalate,is monopolized by foreign countries,which limits the application and promotion of nylon MXD6.Therefore it is urgent to improve its toughness,processing performance,and to reduce its cost.The commonly used blending modification method is suitable for nylon MXD6 as structural material,but it is restricted by the size of additives,matrix compatibility and other factors when it is used as packaging film material,which limits its popularization and application.Copolymerization modification can achieve a certain degree of performance adjustability and make up for the shortcomings of blending modification.In this study,the intermediate of nylon MXD6 was synthesized first,also the semi-aromatic MXD6/6 co-polyamide was prepared by introducing nylon 6 segment into the MXD6 matrix via polycondensation method in high temperature and pressure,while the relevant properties of copolymerized nylon MXD6/6 prepared with different caprolactam feed ratios were also studied.Then the nylon MXD6/6 film material was prepared by calendaring method.The influence of nylon 6 segment on the copolymerization system was investigated.The main contents of this study are as follows:1.Using m-phenylamine,adipic acid and water as raw materials,the important intermediate of nylon MXD6,m-phenylamine adipate salt(nylon MXD6 salt),was synthesized.The synthetic conditions of nylon MXD6 salt were explored and optimized.The structure and purity of the product were determined by FTIR and ~1HNMR spectra.TG and DSC tests showed that synthesized nylon MXD6 salt began to polymerize at203?and the maximum decomposition rate temperature is 401?,it can meet the needs of polymerization process.2.Nylon MXD6/6 co-polyamide with different caprolactam feeding ratios were prepared by using nylon MXD6 salt and caprolactam as raw materials via polycondensation method in high temperature and pressure.The synthetic conditions were investigated and optimized,while the basic properties of MXD6/6 co-polyamide were characterized.The results show that the introduction of nylon 6 segment will destroy the regularity of nylon MXD6 molecular chain,make the worse crystallinity,reduce the melting point and glass transition temperature of nylon MXD6 and improve the toughness and processing properties of nylon MXD6,but damage a certain mechanical strength and thermal stability.When the ratio of caprolactam is 10%,elongation at break and impact strength of the copolymer MXD6/6 increased by 104.86%and 68%,respectively,while the tensile strength and bending strength decreased by 5.87%and17.42%,the glass transition temperature reduced by 7%,the melting point reduced by 23%,and the heat deflection temperature reduced by6.4%.And with the increase of caprolactam feeding ratio,the ranges of increase or decrease mentioned above were amplified.3.MXD6/6 co-polyamide films were prepared by calendering method.The oxygen barrier,elongation at break,transmittance and haze of the films were characterized.The results show that the introduction of nylon 6 segment would reduce the barrier,tensile properties and haze of nylon MXD6,but improve its elongation at break and transmittance.