Synthesis Of The Single P-N Halogen-free Intumescent Flame Retardant And Its Application In PBT Resin

Flame retardant is a kind of functional agent that could improve the nonflammability and self-extinguishing of the combustible materials. It is one of important fine chemicals which is used in composite materials, it is also very important for preventing the fire hazard and protecting the safety of human being. As the development of the society, research and develop high efficient, nontoxic halogen-free flame retardants is the tendency.Thereby, based on molecule designs and synthesizes, a novel intumescent flame retardant was prepared by using chemical reaction to combine the three functional elements of the intumescent flame-retarded system in a single molecule. Then the novel flame retardant was added into poly (butylene terephthalate) (PBT), the intumescent flame-retardancy, thermal behaviors and char-forming chemistry of the flame retarded PBT resin were studied. The flame-retarded mechanism of single molecule intumescent flame retardant was preliminary studied and confirmed.The novel phosphorus-nitrogen containing intumescent flame retardant (P-N IFR) and its intermediate (PEPA) were prepared via the reaction between pentaerythritol (PER), phosphorus oxychloride and 4.4'-diamino diphenyl methane (DDM) by three steps. FTIR and NMR were used to characterize the chemical structure of the products. It was found that P-N IFR is a single molecule intumescent flame retardant where phosphorus and nitrogen elements were combined. PEPA/melamine cyanurate (MC) and P-N IFR were added into PBT respective. UL-94 test, thermogravimetry analysis (TGA), differential scanning calorimetry (DSC) and in situ infrared spectroscopy analysis (in-situ FTIR) were used to characterize the flammability, thermal degradation properties, char-forming process and flame-retarded mechanism. The results showed that PEPA/MC synergistic flame-retarded system and the P-N IFR system have excellent compatibility with PBT resin, the tensile strength and notch impact strength were much better than the traditional brominates-containing flame retarded PBT system. TGA and DTG curves demonstrated that PBT/P-N IFR composite showed outstanding char-forming action, the experiment residue was two times more than the calculated one, furthermore, the char-forming speed rate was also increased more. Char-forming chemistry of the flame-retarded PBT showed that the presence of DDM group in P-N IFR promoted the cross-linking reaction and azo processin PBT resin. In summary, the match flame-retarded elements on thermal properties and component which contain in novel single molecule intumescent flame retardant (P-N IFR) result excellent flame-retarded effect.