Preparation Of Graphene Hybrid Materials And Nanotubes And Investigation On Thermal Stability And Flame Retardancy For Their Polymer Composites

Graphene, as a two-dimensional nano material, has many excellent properties, and grapheme/polymer nanocomposites are also applied to various fields of material science. Grapheme and its derivatives could affect the flame retardant properties of polymer matrixes. The flame retardancy of graphene-nickel oxide hybrid material, and the synergistic effect of graphene-NiO combined with carbon nanotubes or TiO2 nanotubes and ZnO nanotubes was investigated. Meanwhile, the dispersion of nanofillers in polymer matrixes (EP, PP and PS) has been studied, as well as the thermal stability and flame retardancy of polymer nanocomposites. The detailed contents are listed as follows:1. GNS-NiO hybrid material, synthesized by co-precipitation method; titania nanotube (TNT) and zinc oxide nanotubes (ZNT) was prepared via hydrothermal method. The acidified carbon nanotubes was obtained by chemical modification method. The nano fillers were then added to the epoxy matrix through a solution blended process. As a contrast, the same content of different formulations of the nanocomposites were prepared. The morphology, structure of GNS-NiO and nanotubes as well as their dispersion in polymer matrix were characterized by XRD, TEM, SEM, etc. The results showed that NiO on the surface of graphene can improve the peel degree of graphene layers and prevent them agglomeration, which can improve the dispersion property in polymer matrix. The good dispersion of nano materials and the strong interfacial interaction can improve the mechanical properties of the composites, which is also benefit for promoting the thermal stability and flame retardancy. The addition of single nanofillers and hybrids or both of them into polymer matrix are conducive to improving the thermal stabilities. As for synergic compound system, the maximum decomposition temperature of GNS-NiO/CNT/EP is 379℃, which is higher than that of GNS-NiO/EP and CNT/EP, indicating that synergetic effect exists between the two nanofillers. Compared to other fillers, the introduction of ZNT to polymer matrix could increase char residue significantly, more than 12%. The cone results showed that GNS-NiO can reduce PHRR and THR values of EP composites by 40% and 29%, respectively. This is due to the char forming function of nickel oxide. While PHRR and THR value of synergetic system for GNS-NiO and TNT decreased by 61% and 41%, suggesting GNS-NiO and TNT played a synergistic effect.2. PP nanocomposites were prepared by solution blended process, and the dispersion of nanofillers in PP matrix was analyzed by SEM. The thermal stability, flame retardancy of nanocomposites were characterized by TGA and cone. From the characterization we can know that the nanofillers dispersed well in PP composites. The NiO can prevent the agglomeration of graphene layers. The TGA data showed that, there are synergistic effect between GNS-NiO and CNT, the synergistic compound system can get better result than others. And for GNS-NiO/TNT/PP and GNS-NiO/ZNT/PP nanocomposites, their synergistic effect are not obviously. From the cone result, it confirmed that either just added graphene hybrid or nanotubes or add the compound system, can reduce the heat release rate and improve the fire safety of PP. However, the compound system can reach the better result, which indicated that the system can improve the flame retardancy effectively.3. We used the solution blended process to prepare PS nanocomposites. SEM were applied to get fraction images of PS composites in liquid nitrogen. The dispersibility of the nanofillers in PS matrax was studied. The result showed that GNS-NiO hybrid and nanotube materials diepersed well in the composites. And the nanotube on the surface of the fraction can act as a reinforcement in PS composites. The TGA and Cone were used to characterize the thermal stability and flame retardancy. The result showed that the CNT can improve the thermal stability of the PS matrix, and TNT and ZNT act the same effect as CNT. Focus on the char residue, TNT can catalyze the carbonization to form the char layer. And introduce of ZNT into PS get the lower maximum mass loss rate than pure PS. The GNS-NiO/ZNT system has the better thermal stability result than just added ZNT, the char residue improved to 3.94%,it is much higher than pure PS, indicated that GNS-NiO hybrid and ZNT have synergistic effect in enhancing the char residue. Compare to add nanotubes only, the compound system obtained lower PHRR and THR. Among them, the GNS-NiO/CNT/PS sample reached the lowest PHRR value, reduced more than 26% than pure PS. Although the GNS-NiO and nanotube synergistic compound system not always get the best effect, the synergistic effect can make the system more efficient and can reduce the PHRR and THR obviously.