| In this paper, a novel technology, i.e., molecular complexation was established to synthesize modified melamine cyanurate (MCA), a promising halo-free flame retardant with high performance and low cost. Based on it, PA6 base materials with efficient flame retardancy and good comprehensive properties were successfully prepared, and the mechanism was studied systematically.The molecular complexation is an effective way to control the superamolecular framework of MCA while keeping its basal molecular structure. By introducing special complexer WEX into MCA superamolecular framework, the planar regularity of ME-CA self-assembly could be broken, and disturbed and restricted the growth of the hydrogen bonding network, accordingly sharply decreasing the viscosity of the system. The introduced complexer can also increase the solubility of reactants in water and accelerate the reaction without traditional alkali metal compound as catalyst. Molecular complexation technique can overcome the disadvantages of conventional preparation process such as a high system viscosity, long reaction time, complicated process and residual catalyst problems. It reduces the water/reactants ratio from 4/1 to 2/1, decreases the reaction time from 2 hours to 40 min, and the obtained products do not need wash and purification before drying and pulverization as compared to the traditional process of MCA. Therefore, the novel technique greatly simplifies the synthesis process and is an important breakthrough of MCA preparation methods.Molecular complexation technique can not only modify the MCA preparation process, but also improve its properties. Through the molecular comlexation with WEX of low melt point, the modified MCA has a melt temperature 100癈 lower than that of the traditional MCA, shows a melt phase when heated, and can be easily broken down to ultra-fine particles and even dispersed in PA6 matrix, leading to great improvement of materials performances. Complexer WEX can participate in carbonation, modify the carbon layer structure during burning, and consolidate the condensation flame retardancy, accordingly, show higher flame retardancy than traditional MCA. By using the modified MCA. high flame retardancy at small loading level for PA6 as well as glass fiber reinforced PA6 or filler filled PA6 has been realized. In addition. Modified MCA flame retarded PA6 shows high flowability, good mechanical properties, excellent wearability and basically unchanged electric insulation, is promising flame retarded engineering plastics with high-performance and muti-functions.Also, another novel technology, modified MCA encapsulating red phosphorus (RP) was established, which can overcome various shortcomings of exiting technologies of RP encapsulation, and well modify the properties of RP. Through N-P synergism effects, flame retardancy of modified MCA can be further improved. This technology provides a new approach in preparing halo-free flame retarded PA6. The study focuses on the following points:1. The synthesis mechanism and process of MCA, the influence of related factors, e.g., reaction time, viscosity and reaction temperature on ME-CA molecular comlexation2. A novel technology of molecular complexation for modified MCA and its preparationprocess as well as the influence factors, characterization of the structure and properties of modified MCA through UV, SEM, XRD, DSC, MS.3. The flame retardancy and mechanism of modified MCA to PA6, the rheological and mechanical properties, thermalstability, electrical insulation, friction and wear of modified MCA flame retarded PA64. The flame retardancy and other materials performances of glass fiber reinforced PA6 and mineral filled PA65. Development of a novel technology of modified MCA encapsulating red phosphorus (RP)and the flame retardant PA6. |
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