2.3 Copolymerized flame retardant modification method

The flame retardant components of the materials prepared by the copolymerized flame retardant modification method are uniformly dispersed in the matrix, and at the same time, in the polymerization process, only one polymerization molding is required, and the resulting degradation is avoided, so as to maintain the stability of the basic properties of the materials and the strong reprocessability.

The hydrogen of the amide group in the polyamide 66 molecular chain can be replaced, which has certain reactivity, and can react with the reactive flame retardant, so as to introduce the flame retardant structure into the polyamide 66 macromolecular chain, and the flame retardant copolymer polyamide 66 can be prepared. At present, this method has become a research hotspot of flame retardancy of polyamide 66.

Using CEMPO as flame retardant monomer, RIDGWAY prepared CEM?PO flame retardant copolymer polyamide 66 with certain flame retardant properties by co-polycondensation with polyamide 66 salt. The introduction of CEMPO flame retardant monomer into polyamide 66 macromolecular chain was discussed. Influence on melting point, water absorption, thermal stability, tensile strength and other properties. The results show that when the mass fraction of CEMPO reaches 30%~40%, the crystallization property and orientation of polyamide 66 will be greatly affected.

Li Qiaolin et al. prepared a new halogen-free flame retardant copolymer polyamide 66 by using self-made double (p-carboxyphenyl) phenyl phosphine oxide (BCPPO) and polyamide 66 salt as raw materials through two-step co-condensation polymerization. The molecular structure, thermal stability and flame retardant properties of flame retardant copolymer polyamide 66 were studied and analyzed. The results showed that, With the introduction of BCPPO, the thermal stability and carbon forming properties of flame-retardant copolyamide 66 were improved. At the same time, the flame retardancy of the material has been improved to a certain extent by copolymerized flame retardancy modification.

Li Xia et al. developed a reactive flame retardant BCPPO and prepared intrinsically flame retardant polyamide 66 by reaction method. The test results showed that the flame retardant performance of flame retardant polyamide 66 was significantly improved and it had high thermal stability. The tensile strength and impact strength of flame-retardant polyamide 66 decreased only slightly, and the mechanical properties were good. The comprehensive analysis of various properties of flame retardant polyamide 66 shows that when the mass fraction of flame retardant is 3%, the comprehensive performance of flame retardant polyamide 66 is the best. However, the preparation process of BCPPO is complicated and the cost is huge, which is not conducive to industrial application.

3. Development trend

At present, the development trend of flame-retardant polyamide 66 mainly has the following aspects.

① Environmental protection and green. With the progress of industry technology and the continuous improvement of people's awareness of their own health and environmental protection, brominated flame retardant polyamide 66 will gradually be replaced by more environmentally friendly and safe materials, so in the future, high-performance halogen-free flame retardant polyamide 66 will be the focus of market development.

② High efficiency. With the continuous development and maturity of flame-retardant polyamide 66, higher flame retardant grade, lower addition amount, better performance retention rate, are the direction of product development, while coating, microencapsulation, masterbatch and other technical means continue to enrich, high efficiency will become the development trend of flame retardants, which also needs to continue to refine, improve technology, improve competitiveness.

③ Functionalization. Product design for polyamide flame retardant materials continue to put forward new requirements, such as better electrical properties, laser marking, welding, wear resistance, etc., how to maintain and improve the performance of existing products at the same time, meet these new functional indicators, so that products meet the full range of requirements is our research direction.

④ Differentiation. Different categories of flame retardant polyamide 66 due to the differences in flame retardants, in the mechanical properties of materials, electrical properties, appearance of color, processing characteristics, environmental protection and safety aspects have advantages and disadvantages.

⑤ Color. With the improvement of living standards and the rapid development of material technology, in addition to the continuous improvement of the inherent properties of electronic and electrical products materials, people also put forward the demand for the aesthetic and colorization of flame-retardant polyamide 66.

⑥ Increase quantization. With the continuous improvement of safety requirements, the market demand for flame retardant products is greatly increased, so many common products are also put forward flame retardant requirements.

4. Conclusion

Flame retardant polyamide 66 has experienced three milestone stages of blending, polymer molecular chain modification and molecular chain direct polymeric flame retardant structure, which opens up a wider range of application prospects for flame retardant polyamide 66, especially from the molecular structure design, increase the flame retardant structure, making the application of flame retardant polyamide 66 has a qualitative leap. With the further study of the flame retardant structure of direct polymerization on molecular chains, the future dosage of flame retardant polyamide 66 will continue to rise.

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