Synthesis Of A DOPO-based Phosphorus-and Silicon-containing Flame Retardant And Its Flame-Retardant Application In Epoxy And Polyurea Resins

The polymeric materials are widely used in our life and the quantity demanded of polymer commodity polymer such as plastic, rubbers, fiber, coating and adhesive are large all over the world.Despite having a number of benefits in applications, those polymeric materials also have drawbacks; the main drawback is due to their flammability, which hinders their applications in some areas, especially for the places require the fire safety. In this dissertation, a novel organic-inorganic hybrid flame retardant containing phosphorus and silicon were synthesized by the way of molecular design. Meanwhile, the novel organic-inorganic flame retardant was incorporated into polymeric matrix through the sol-gel and thermal curing processes to improve the flame retardancy of polymeric materials. Novel technologies such as sol-gel technology and "nano" technology are adopted, with the aim of further improving the flame retardant efficiency of the polymeric materials. The research work of this dissertation is composed of the following parts:1. A novel liquid monomer containing phosphorus and silicon was synthesized by the way of molecular design. The sol-gel, UV-curing and thermo-curing technologies are employed to incorporate the flame retardants into the structures of epoxy acrylates and epoxy resins, resulting in the formation of organic-inorganic hybrid materials. The flame retardant performances of the organic-inorganic FRs/EP and organic-inorganic FRs/EA are compared and the flame retardant mechanisms are also discussed. The high content of phosphorus and silicon contribute a good flame retardancy to epoxy acrylates and epoxy resinswhich can be confirmed by the LOI and heat release results. The FRs/EP composites exhibit high flame retardant efficiency compared with EA/FRs composites:the FRs/EP can reach the UL-94VO ratio at the loading of15wt.%and has higher char residues at high temperature. From the DP-MS analysis, it can be found that the degradation of FRs in the FRs/EA matrix only occurs at low temperature. However, as for the FRs/EP composites. DOPO and its derivates are released at low temperature as well as high temperature. As a result, it can be concluded that the organic-inorganic FRs can play its flame retardant roles during the thermal degradation process of EP. Thus, the organic-inorganic flame retardants could impart great flame retardant efficiency to EP. which is worth depthly study.2. A novel organic-inorganic FRs containing phosphorus, nitrogen and silicon was prepared through the sol-gel process and incorporated the flame retardants into epoxy resins. The organic-inorganic networks were formed and the organic-inorganic FRs has good water resistance. The flame retardant properties of the composites are investigated. The heat release results showed that the inclusion of EP-N1can significantly decrease the pHRR and THR ofEP compared with other composites, exhibiting the synergistic effect between phosphorus and nitrogen. Interestingly, at the same addition level. EP-N1exhibited much better flame retardancy (LOI and UL-94) and thermal stability (TGA, air). The SEM. FTIR. XPS and the TGA-FTIR results indicates that the strategy of organic-inorganic FRs combines condensed phase and gases phase flame retardant strategies.3. A novel flame retardant (FRs-rGO) containing exfoliated graphene via in suit sol-gel process and incorporated the flame retardants into epoxy resins. With the incorporation of FRs-rGO into EP. a significant improvement in thermal stability is achieved in both air atmosphere and nitrogen atmosphere. The results indicate that the FRs-rGO could significantly improve the char residues at high temperature. Thus, satisfactory flame retardant grade was obtained when5wt.%of FRs-rGO was incorporated into the epoxy resins, indicating the great improvement.4. The organic-inorganic nanoparticles (FRs-nanoparticles) containing organophosphorus and silicon were synthesized through the sol-gel process by the way of molecular design. Then FRs-nanoparticles were incorporated into the polyurea in different ratio via in situ polymerizationand the flame retardant properties and the mechanism are investigated. The TGA results indicated that FRs-nanoparticles could significantly postpone the initial decomposition temperature of the nanocomposites in air atmosphere. The peakheat release rate (pHRR) of the materials was significantly reduced due to the incorporation of FRs-nanoparticles. The RTIR results indicated that FRs-nanoparticles could catalyze the formation of benzene and its derived structure or improve thermal stability of benzene in the polyurea matrix. Furthermore, the tensile testing demonstrated that FRs-nanoparticles could also enhance the mechanical properties of polyurea.5. The rGO was decorated with organic-inorganic nanoparticles (DOPO-VTS) through sol-gel process and the thickness of the nanoparticles-rGO can be varied by changing the additive amount of DOPO-VTS. Then, the nanoparticles-rGO was incorporated into polyurea in different rations via in situ polymerization. The thermal stability and the fire safety of the composites are investigated. Compared with the untreated rGO. the nanoparticles-rGO could significantly improve the thermal stability of polyurea and combustion properties, implying that the good dispersion of nanoparticles-rGO and thefunctional groups on the surface of rGO had the significant effect on the thermal stability of polyurea in air atmosphere. Moreover, the tensile and dynamic mechanical properties showed that the tensile strength and storage modulus of the nanocomposites could be obviously improved by incorporation of nanoparticles-rGO at low contents. The heart release results indicate that the0.5wt.%loading of nanoparticles-rGO has the same effect with the5wt.%loading of nanoparticles. indicating the advancement of layered nanotechnology.