Synthesis And Flame Retardant Mechanism Of Polyphosphate Acrylate Oligomer

The present thesis was aimed on the synthesis of two new kinds of polyphosphate acrylate oligomers, and the study on their photopolymerization kinetics, thermal degradation behavior, flame retardance and flame retardant mechanisms as well as applications in UV curable coatings. The detailed outline is elaborated as follows:Poly(bisphenol A acryloxyethyl phosphate) (BPAAEP) being used for UV curable flame retardant coatings and adhesives, was synthesized from phosphorus oxychloride, hydroxylethyl acrylate and bisphenol A as raw materials, and characterized using ¹³C NMR, ³¹P NMR, FTIR, MS and GPC measurements. The photo-polymerization rate, which was monitored by Photo-DSC, increased along with the temperature, then decreased after reaching the maximum value at 70℃. The thermal degradation mechanism was studied by thermogravimetric analysis, in-situ Fourier-transform infrared and direct pyrolysis/mass spectrometry measurements. The obtained results showed that the degradation of UV cured BPAAEP film can be divided into three steps. The first stage can be assigned to the decomposition of phosphate and acrylate, whereas the second is due to the thermal pyrolysis of alkyl chains. The third stage is attributed to the decomposition of some aromatic structures and the formation of poly(phosphoric acid).A series of formulations with different ratios of BPAAEP to urethane acrylate were prepared to obtain flame retardant resins. Both phosphorus and nitrogen contributed to the flame retardance, and had a synergistic effect to form an intumescent system, especially for the formulation with 1.5 wt% of phosphorus was presented, corresponding to the maximum LOI value of 32.0. The good miscibility between BPAAEP and urethane acrylate was observed from the dynamic mechanical thermal analysis. The kinetics of thermal decomposition was evaluated by Kissinger, Friedman, Flynn-Wall, Horowitz-Metzger and Ozawa method, respectively. The degradation behaviours of urethane acrylate blended with BPAAEP were found to be greatly changed. The results showed that the activation energy at lower degree of the degradation decreased by the incorporation of BPAAEP, while increased at higher degree of the degradation.Through Michael addition from piperazine as an A₂ monomer and tri(acryloyloxyethyl) phosphate (TAEP) as a B₃ monomer, a novel hyperbranched polyphosphate acrylate (HPPA) was synthesized via the "A₂+B₃" approach. HPPA was blended with TAEP in different ratios to obtain a series of UV curable intumescent flame retardant resins. Their degradation process was monitored by thermogravimetric analysis and in-situ Fourier-transform infrared spectroscopy. The morphologic structures of the formed chars were also investigated by scanning electron microscopy. It was found that the flame retardancy of TAEP was mainly acting in the gas phase, whereas HPPA mainly acting in the condensed phase, and the gas phase mechanism held the dominant effect as their blends were burning. Moreover, their photo-curing properties, dynamic mechanical thermal properties and mechanical properties were also investigated. The mechanical data showed that the toughness of TAEP was improved by the addition of HPPA. Less than 20% HPPA addition improved both the tensile strength and elongation at break without damaging the modulus. The HPPA₂₀TAEP₈₀ film has the highest tensile strength of 31.7 MPa and an elongation at break two times of that for cured TAEP.A nitrogen-containing methacrylate monomer (DHMP) was synthesized and blended with HPPA in different ratios to obtain UV curable flame retardant resins. It was found that the viscosity of the resins greatly reduced by the addition of DHMP, whereas their photopolymerization rates increased. The thermal behavior, flammability, dynamic mechanical thermal property and mechanical behavior of the UV cured films were also investigated.