Study On Microwave-assisted Synthesis Of Nylon 1010 And Nylon 1212

Microwave is widely used in digestion and polymer synthesis due to its cleanliness,high efficiency,high selectivity and uniform heating.In the field of polymer synthesis,microwave as an auxiliary means can be applied to polymerization processes such as free radical polymerization,stepwise polymerization,ring-opening polymerization,etc.Its energy-saving and high-efficiency outstanding advantages have been highly valued by scholars at home and abroad.In this paper,nylon 1010 salt and nylon 1212 salt were used as polymerization monomers to study the polycondensation reaction under microwave-assisted conditions.The effects of reaction temperature and reaction time on the molecular weight and molecular weight distribution of the polymerization products were investigated.The effects of reaction conditions on the polymerization were investigated by TG and FT-IR.The crystal structure and melt crystallization behavior of microwave-assisted polymerization products were studied by WAXD and DSC.In this paper,the effects of reaction temperature and reaction time on the molecular weight and molecular weight distribution of nylon 1010 and nylon 1212 in a microwave-assisted confined environment were studied.The results show that the molecular weight increases with the increase of reaction temperature and the polymerization time,while the width of molecular weight distribution decreases.The variation range of both is from big to small.When the reaction temperature was 180?,the reaction time was 30 min,and the reaction by-product water was not excluded,the number average molecular weight measured by GPC reached 8.8×103 g/mol and 9.6 × 103 g/mol,respectively.The polymerization efficiency is much higher than the ordinary melting reaction(The ordinary melting polymerization reaches the same molecular weight needs to react at 220? for more than 4 h).Further increase the reaction temperature and prolong the reaction time,the molecular weight change is not obvious.At the same time,the molecular weight growth rate of different varieties of nylon salt is different.With the increase of reaction temperature,the molecular weight of nylon 1212 is faster than that of nylon 1010.The thermogravimetric process and infrared spectra of nylon 1010 and nylon 1212 samples with different reaction degrees were studied by TG and FT-IR.The results of TG study showed that both nylon salts were polymerized under the experimental conditions.When the reaction temperature is lower than 155?,the reaction is incomplete,and some salts are still unreacted.As the reaction temperature increases,the degree of reaction increases.When the reaction temperature is 160?,the nylon salt is completely converted into polymer;FT-IR analysis shows that the higher the polymerization temperature,the greater the degree of polymerization and the smaller the unreacted nylon salt content.When the reaction temperature was 140?,the characteristic absorption peak of the amide group appeared on the FT-IR spectrum,and the absorption peak of the nylon salt disappeared.Combined with TG and FT-IR analysis,it can be concluded that the nylon salt can be completely converted into polymer by reacting at 160? for 10 min,and the reaction temperature plays a crucial role in the polymerization reaction.The melting and crystallization behavior of the polymerization product was investigated using DSC and WAXD.The results show that the melting point and melting enthalpy of microwave-assisted polymerization of similar molecular weight are lower than those of conventional melt-polymerized samples,and the crystallization is not perfect.The results of WAXD test show that the microwave-assisted synthesis of nylon 1010 and nylon 1212 are both a-crystal.The crystallinity of nylon 1010 and nylon 1212 is 42%and 45%,respectively.The solid phase viscosification method was used to investigate the polymerization process of the polymer solid phase synthesized by microwave.The results show that with the increase of reaction temperature and the extension of reaction time,the molecular weight of the polymer increases,the increase in the early period is faster,and in the later period is slower.After a solid phase reaction at 180?for 30 h,the relative viscosity of nylon 1010 increased from 1.5 to about 2.3.After solid phase reaction at 180? for 30 h,the relative viscosity of nylon 1212 increased from 1.7 to about 2.5.It is indicated that the microwave-assisted polymerization maintains a good reactivity of the nylon end group reactive group.