Microwave-assisted Polymerization And Characterization Of PA11T?PA12T

Semi-aromatic polyamides have attracted extensive attention from domestic andinternational scholars and are used in electronic appliances,automobiles,rail transit,and special equipment,due to their excellent mechanical strength,heat resistance and solvent resistance.However,the traditional polymerization has many technical problems,such as long preparation period and wide molecular weight distribution,which cannot be effectively solved within a long time.In recent years,the microwave has attracted wide attention in the field of polymer synthesis because of its high efficiency,green and targeted heating.In this paper,the odd and even carbon chain semi-aromatic polyamides PA 11T and PA 12T were prepared by microwave-assisted polymerization,the polymerized monomers are the nylon 11T salt and nylon 12T salt which are obtained from the neutralization reaction of C11 and C12 binary amines with p-terephthalic acid,respectively.The effects among polymerization conditions and the odd and even carbon atomic number of binary amines on the polymerization process the structure,properties of the products were investigated.The main conclusions are as follows:(1)In this paper,high temperature resistant semi-aromatic polyamides PA 11T and PA12T were prepared under microwave assisted conditions for the first time.The effects of the amount of water,reaction temperature,reaction time and microwave power on the viscosity of the polymeric product were studied under closed condition.The results showed that when the water dosage was 0.17 m L(reaction volume was 30m L),the reaction temperature was 210?,and the reaction time was 60 min,the product viscosity reached the maximum.If the heating rate is low,the viscosity of PA11T is lower than that of PA12T,on the contrary,the viscosity of PA11T is high.The melting point of PA11T salt is lower than that of PA12T salt and the vapor pressure of C11amine is lower than that of C12 amine were referred to as the main factors of the above phenomenon.The results of solid phase post-polymerization showed that the prepolymer maintained good reactivity and the product with higher viscosity could be obtained at 230?.(2)In this paper,a microwave reaction device with controllable reactor pressure was designed to implement the one-step synthesis of PA 11T and PA 12T by microwave-assisted polymerization.The results show that the reaction time of the one-step polymerization process is significantly shorter than that of the pre-polymerization+solid-phase post-polymerization process when the molecular weight of the products is similar.(3)The initial decomposition temperatures of PA 11T and PA 12T obtained by microwave-assisted polymerization were higher than those of the traditional polymerization products,indicating that the proportion of oligomers in the products was lower under microwave conditions.The molecular weight distribution of the microwave-assisted polymerization product was determined by gel penetration chromatography(GPC),and the results show that the molecular weight distribution is mean.(4)PA11T and PA12T showed significant differences in physical properties.PA 11T is soluble in hexafluoroisopropanol and PA 12T is insoluble.The melting point(T_m)and?H_m of PA 11T are lower than that of PA 12T;PA 11T tends to form?crystal,while PA 12T tends to form?crystal.Meanwhile,PA 11T and PA 12T did not exhibit the Brill transition like commonly aliphatic polyamides.