Research Of Anionic Polymerization Of Caprolactam In Polyamide 6 Melt

Polyamide 6(PA6) is a widely used polymer material. It is mainly used in textile fiber, tire cord etc. As one of the five major engineering plastics, it is mainly used in the fields of machinery, chemical industry, communication and so on. The polymerization mechanism of PA6 includes the hydrolytic ring-open polymerization and anionic ring-open polymerization. Hydrolysis polymerization belongs to the gradual polymerization and uses water as a ring-open agent. Anionic polymerization belongs to the chain polymerization and the content of water and acid should be strictly controlled. The molecular chain of the hydrolysis product has no active center. Anionic polymerization has the characteristics of fast reaction rate and high molecular weight. In this paper, the hydrolytic ring-open polymerization and anionic ring-open polymerization are combined to prepare composite materials via the method of adding CL and catalyst in the PA6 melt. In order to determine the dosage of initiator and activator, and the suitable reaction temperature and time, static casting and dynamic mixing, conventional casting temperature and high temperature of pure anionic polymerization experiments were explored.The experimental results show that PA6 products are successfully obtained in conventional casting temperature(160 oС) and relatively high temperature(220 oС). FT-IR, TGA and DSC test results show that this anion catalyst system is also suitable for higher reaction temperature. Thermal stability test show that small molecules weight loss percentage of the product of CL/C10/C20(100/2.0/2.0) is the lowest. At the same time, a small amount of heat loss of the catalyst may occur during the dynamic mixing process. Therefore, 100/2.5/2.5 also is a suitable proportion.The torque rheometer is used as a dynamic mixed reaction sites to prepare anionic PA6 of two kinds of additives, four kinds of reaction temperature by a one-step charging method. The FT-IR test result shows that the products have typical polyamide characteristic peaks. Extract content test show that the conversion of caprolactam is about 90%. The thermal performance test show that the products containing different polymerization degree of components. Products of 100/2.5/2.5 proportion have a high degree of crystallization and less surplus monomer. The reaction temperature will affect the melt flow and the crosslinking degree. Therefore, 230 oС is chosen as the reaction temperatureAccording to the established additives ratio and temperature, HPA6/APA6 composite is prepared by a one-step charging method. The torque rheometer is also used as a dynamic mixed reaction sites. FT-IR tests show that the mixed product keep characteristic peaks of polyamide. DSC tests show that with the increase of the initial content, the crystallinity of the composite decreased, the crystallization peak turn from narrow to wide, the melting temperature decreased. The TGA test show that there are three obvious heat loss when the system has a high initial content of caprolactam and also prove the occurrence of the anionic polymerization of caprolactam. Extractable content test show that with the decrease of the initial caprolactam content, the conversion rate is rising and the highest one is close to 50%. The viscosity test showed that except the sample which has the highest conversion rate, the relative viscosity of the remaining samples are less than or equal to that of blank sample.Severe thermal degradation is speculated to occur during the reaction. End group content test show that the carboxyl content increased after the reaction. The degradation products influenced the reaction which could have a higher degree of anionic polymerization. Linear low density polyethylene is used as a reference. The PA6 without the industrial extraction is also used as a reference. The test results show that high degree of polymerization does not exist when there is thermal degradation in the system. The conversion rate of the system of the PA6 without the industrial extraction is lower than the system of PA6 with the industrial extraction, which confirms that the thermal degradation of polymer has an effect on the degree of polymerization of caprolactam.