Preparation, Structure And Properties Of Nylon6/Modified MCA Halogen-free Flame Retardant Composites

Graphene oxides(GO), organic modified GO (OGO), GO sol modified melaminecyanurate (GO-MCA), OGO/PA6nanocomposites and GO-MCA/pentaerythritol（PER）/PA6halogen-free composites were prepared, the structures and properties ofthe resultant materials were characterized and some results were obtained, as wereshowed as fellows:GO were prepared by improved Hummers method and fewer layers GO wereprepared by ultrasonic processing. The resultant materials were characterized byFT-IR, XRD, SEM, TEM, AFM and TGA. The results show that the thick of GO isabout1nm; the chemical structures of both the pre-and post treated GO are almostthe same, many oxygen-containing groups were found in GO, the physical structuresof post-treated GO were irregularity for the treatment, and four thermaldecomposition stages were found from the TG curves.GO was modified by cetyl trimethyl ammonium bromide (CTAB). The resultantmaterials were characterized by FT-IR and TG, the results shows that CTAB iscombined to GO by hydrogen bond or chemical bonds, the hydrophobicity isimproved, and the thermal stability of modified GO is improved too as thetemperature is lower than300℃.Several kinds modified MCA flame retardants were prepared by changing thecontent of GO sol, added time of GO, the reaction temperature, PH and reaction time.The resultant materials were characterized by FT-IR, SEM, XRD, TGA, verticalflame test and the oxygen index tests. The results shows that modified MCA particlessizes are controlled by GO, which is β-crystalline, and around200～500nm longand the diameter is around20～50nm. As the GO content is3wt%, the mol ratio is1:1.05, the reaction system is weak acid, the temperature is95～98℃, the totalreaction time is4hours and the addition time is zero or60minutes, the flameretardant properties of modified MCA are the optimized, which dispersed in PA6matrix evenly. As the content is15wt%the flame retardant property of PA6composites is UL94V-0grade.OGO/PA6nano-composites were prepared by solution-blending firstly and thenmelt-blending method. The resultant materials were characterized by electronicuniversal testing machine, SEM, XRD, TGA, DSC, and ARES rheometer. Theresults shows that as the OGO content is0.3wt%, the mechanical properties ofcomposites are optimized, the tensile strength increases5%, the elongation at break reduces little, flexural strength, flexural modulus and rockwell hardness increases15.1%,10.7%and13.1%respectively. The crystallization degree of compositesreduce for the presence fo OGO, the thermal stability of composites were improved,OGO is helpful to the charring. The steady and dynamic rheological behaviors showsthat the composites are pseudo plastic fluid, the lowest viscosity is found as the OGOcontent is0.6wt%, there is strong interactions between PA6and OGO, which areaffected by temperature.Halogen-free flame retardant PA6composites were prepared by melt blendingwith PA6, PRE, and modified MCA (modified with3wt%,5wt%,10wt%and15wt%GO sol respectively). The resultant materials were characterized by electronicuniversal testing machine, SEM, XRD, TGA, DSC, vertical flame test and theoxygen index tests. The results shows that the modified MCA particles are verysmall and dispersed evenly in PA6matrix. As the content of modified MCA(modified by3wt%GO) is10.2wt%, the flame retardant property of the compositesare optimized. the valve of LOI is29, the tensile strength, flexural strength andflexural modulus increases to10.8%,29.3%and33.5%respectively. However, whilethe GO-MCA content increasing the LOI and vertical combustion property ofcomposites decrease, it maybe due to the wick effect caused by GO. The resultsobtained from the burning phenomena, the chars and the thermal decompositionprocesses of flame retardant PA6composites show that the presence of modifiedMCA enhancing the charring, forming the dense char and suppressing flaming drips.