Preparation And Properities Of Flame Retardant Polyamide6and Fibers

Polyamide6(PA6) fibers have been widely used in civil, industrial fields andothers because of its excellent abrasion resistance, superior resilience and high tensilestrength. However, PA6fibers have low limiting oxygen index (LOI) and burningwith many melting drops, thus seriously restricts its application. Therefore,modification of flame retardant to PA6fiber has great significance.In this paper, melamine cyanurate (MCA) and aluminum diethylphosphinate(AlPi) were chosen to prepare flame retardant PA6by in-situ polymerizationrespectively, and MCA and AlPi were synergistically added into PA6to prepare. Thenthe flame retardant PA6(FRPA6) fibers were prepared with FRPA6resins bymelt-spinning. The detailed content is described as follow:Firstly, MCA and AlPi were introduced into the melt ε-caprolactam respectively,and then synthetize the FRPA6by hydrolytic polymerization. Their molecular weightwere measured by Gel permeation chromatography(GPC) and relative viscositymethod. The molecular weight of PA6decreased as a result of the introduction ofMCA and AlPi, and the AlPi have a greater impact on PA6than MCA. The structuresand properties of MCA/PA6and AlPi/PA6were characterized by FT-IR, scanningelectron microscopy, X-ray diffraction, differential scanning calorimetry, andthermogravimetric analysis. SEM shows that the two flame retardants coulddisperse uniformly in PA6. The decomposition temperature of MCA and AlPi are allabove300°C that can satisfy the requirements of the subsequent process and meltingspinning, and the decomposition temperature of AlPi closed to PA6, so its thermalstability is better than MCA. At the same contents of MCA and AlPi, the flameretardant property of AlPi/PA6is superior to MCA/PA6, but the mechanical propertieslower than MCA/PA6through their limit oxygen index test, the flame retardant levelof vertical combustion and mechanical properties.Secondly, in order to reduce the contents of flame retardants and improve the flame retardancy of PA6, MCA and AlPi were introduced synergistically into PA6toprepare MCA/AlPi/PA6which was compared with MCA/PA6system andMCA/Sb2O3/PA6system, the result indicates that synergistic flame retardancy isbetter than the single flame retardant because adding AlPi can enhance the effect ofcondensed phase flame retardancy of PA6, promoting char formation, and associatewith the vapor phase of MCA makes the flame retardancy of MCA/AlPi/PA6superiorto MCA/PA6and MCA/Sb2O3/PA6.Finally, the fire retardant PA6fibers were prepared with FRPA6resins bymelt-spinning, and the morphology, degree of orientation and crystalline propertieswere characterized. The results show that: flame retardants uniformly dispersed inPA6fibers, and have a good compatibility with the matrix. γ crystalline of PA6fibersis fewer than PA6resins, but the introduction of MCA and AlPi promotes theformation of γ crystalline. The tensile strength of the flame retardant PA6fibersdecreased owing to the loss of molecular weight and stress concentration of flameretardants, but it still meet the general requirements of fibers for textile use. Theapplication of MCA/AlPi synergistic flame retardant in PA6fibers shows excellentflame retardancy under a simple vertical burning test.