Interphase Compatibility And Properties Of Non-halogen Flame Retarded GF/PA66

Glass fiber (GF) reinforced nylon has been widely used in many fields such as electric, electronic, automobile, etc, so the study and expoitation of non-halogen flame retardant glass fiber reinforced nylon new materials is very important. Especially RollS enforcement was delivered on the 1 st July 2006. The RollS Directive stands for "the restriction of the use of certain hazardous substances in electrical and electronic equipment". It makes many countries take remarkable consideration of the non-halogen materials and the demands of product's market are more imminence.The whole properties of composites relate to not only reinforcement phase and matrix phase, but also the interface between these two phases. Interface is a very important micro- structure of composites. As the bridge between reinforcement fiber and matrix, the interface has an important effect on the physical, chemical and mechanical properties of composites. However, the interface between fiber and matrix is the weak area in composites which are reinforced by fiber, therefore the improvement of interfacial adhesion, as the hotspot in composite research, is of great significance.In this paper, aiming at solving the problem of interface and flame retardancy, on the base of our previous work, we prepared the flame retardant through the reaction of melamine and polyphosphoric acid. FTIR, XRD, DSC, DMA and SEM were used to characterize the interface and properties. Upon the addition of 25%MPP, 25%GF, 7%MA-EPDM, 1% additives, the flame retarded GF reinforced PA66 reached UL 94 V-O rating at 1.6mm thickness, and possessed good mechanical properties, tensile strength more than 140MPa, flexural strength more than 210 MPa and impact strength 8.5 kJ.m^-2. We also got the screw configuration, processing parameters, injection parameters, etc.The effect of MPP on the isothermal crystallization and melting behavior of PA66 was investigated by differential scanning calorimetry (DSC). The Avrami equation was used to describe the isothermal crystallization kinetics. It is indicated that the MPP act as effective heterogeneous nucleating agents, the crystallization rate of PA 66 in the composites is thus increased. However the MPP inhinders the motion of PA66 chains, thus reduce the crystal spherulite radius of PA66. The flame retarded composites exhibit double melting endotherms during researched crystallization temperature. The multiple melting endotherms are mainly caused by the recrystallization of PA66 spherulites with different crystal sizes and imperfection during heating. The MPP have little effect on the crystalline structure of PA66 under isothermal condition, which can be proved by XRD.The non-isothermal crystallization and melting behavior of PA66 and its composites were investigated by DSC. The Avrami, Kissinger, Ozawa equations are used to describe the non- isothermal crystallization kinetics. The results show that those equations can all describe the nonisothermal crystallization process. The addition of MPP into PA66 has an effect on the mechanism of nucleation and the growth of PA66 crystallites. The MPP and glass fiber all act as nucleating agents, but MPP hinders the motion of PA66 chains which resulted in the decrease of crystallization rate. The result is different from the isothermal process, indicating the complexity of non-isothermal crystallization. A combination of DSC, XRD and polarized microscopy (POM) was used to investigate the effect of MPP on the crystallization structure of PA66, the results showed the phenomena of multi-crystalline.The mechaniacal properties of PA66 composites were investigated. It is found that MPP cause the tensile strength, flexural strength, storage modulus, glass transiton temperature (Tg) and relaxation activation energy to increase. The better properties of the composites result from the stronger interfacial adhesion between GF and PA66.The thermal degradation behavior of GF/PA66/MPP composites was studied using thermogravimetric analysis (TGA). The presence of MPP decreased the thermal stability of PA66, which showed that MPP accelerated the formation of char of nylon 66 reinforced with glass fiber and enhanced the flame retardancy.From the rheology properties study, PA66 exhibited Newtonian fluid behavior, and the composites exhibited the shear thinning behavior. The introduction of MPP increased the viscosity and flow activation energy of GF/PA66 composites. The research of activation energy showed that the processing temperature fitted in the industrial production is at 275℃for GF/PA66/MPP. The stronger rheological effect of MPP results from stronger matrix-fillers interactions.In all, MPP improves the compatibility between the GF and PA66, resulting in stronger interfacial adhesion.