Preparation And Characterization Of Flame-Retardant Nylon 6/ Hydrotalcite Composites

Nylon 6 was applied extensively in the filed of engineering plastics because of its excellent properties since its industrial preparation was invented. The output of nylon 6 was increased year by year. With the continuous innovation and development, and the more requirement on traditional materials, much more exigent work should focus on nylon 6 modification. As a maturity and effective method, filling nylon 6 with minerals has very wide foreground. Hydrotalcite(HT) is a kind of layered anionic clay with a series of excellent properties. The flame-retardant properties of the polymer/HT composites can be obtained by introduce the HT into polymer matrix. We prepared organic modified hydrotalcite with Urea Method. Nylon 6/hydrotalcite composites were prepared by in situ polymerization and melt blending. Properties including the flame retardant effect, heat decomposes performance, mechanical, dynamic mechanical, melting and crystal behaviors of composites and hydrotalcite’s dispersion in PA6 were studied, the main results as follows:(1) Crystallinity perfect and uniform grain size hydrotalcite compounds was synthesized with urea method at urea/NO3- molar ratio was 2:1. Hydrotalcite were intercalated with terephthalic acid and salicylate. The obtained suitable modification temperature was 100℃. It has been found that the interlayer distance of modified hydrotalcites was enlarged from 0.765nm to 1.47nm and 1.61 nm, respectively.(2) Nylon 6/hydrotalcite composites showed obvious flame retardant effect by situ polymerization. Comparing with pure Nylon 6, the flaming combustion time of composites decreased by 62.4%, the oxygen index improved to 21, the carbon yield ratio increased by 9 times, and the heat distortion temperature increased by 10.3℃when the composite’s mass fraction of hydrotalcite was 7%, The hydrotalcite was exfoliated and dispersed well-proportionedly in nylon 6 matrix when the contents of hydrotalcites were less than 5%.(3) Nylon 6/hydrotalcite composites were prepared by the melt blending showed obvious flame retardant effect, too. Comparing with pure Nylon 6, the oxygen index of the composites improved 40% and carbon yield ratio was increased by 28 times when hydrotalcite addition level was 30%. The flexural modulus and the bending strength of the composites were improved by 42.1% and 17.7% respectively. Heat distortion temperature increased to 13.1℃. The dynamic storage modulus of the composites and the glass transition temperature increased with the content of hydrotalcite. Hydrotalcite exfoliated and dispersed well in the matrix even the mass fraction of the hydrotalcite was 26%.(4) PA6/melamine cyanurate composites were prepared by melt blending. When the mass fraction of melamine cyanurate was 11%, flame retardant rating of the composite was improved from FV-2 to FV-0, the oxygen index increased from 20 to 24. PA6/melamine cyanurate/hydrotalcite composites were prepared by melt blending too. The oxygen index and the combustion performance of the composites were improved when the melamine cyanurate and hydrotalcite were introduced at the same time.