Synthesis Of Flame Retardant UV Curable Phosphoramide And Study On Thermal Degradation And Properties Of The Coating

Recently, UV curable coatings have attracted increasingly attention due to their many advantages, such as energy saving, environmental friendly and excellent coating properties. And they have gained acceptance in a number of life areas and industrial applications. However, most of UV curable coatings are combustible. To reduce the fire hazard, flame retardant coatings or fireproofing functional coatings are expected to have broad prospects for development. The present thesis focused on the synthesis of two kinds of UV curable phosphoramide monomers (N-PBAAP and EBAAP) containing acid and gas sources in one and the preparation of UV curable coating systems by blending the phophoramides with commercial polyurethane acrylate and epoxy acrylate repectively. The flame retardancy, thermal degradation behaviour of the two phosphoramide cured films were compared and studied. And the properties of the flame retardant polyurethane acrylate system and the epoxy acrylate systems were also investigated. The detailed outline is elaborated as follows:1. Piperazine-N,N'-bis(acryloxyethylaryl- phosphoramidate) (N-PBAAP) as flame retardant bifunctional monomer used for UV curable systems has been synthesized using phenyl dichlorophosphate, piperazine anhydrous and hydroxyethyl acrylate. And ethylene-bis (acryloxyethylaryl-phosphoramidate) (EBAAP) was synthesized as above except for replacing piperazine with ethylenediamine. The thermal stability of the two kinds of phosphoramidate cured films was monitored by TGA. It showed that EBAAP shows better thermal stability at elevated temperature with higher char yeilds compared with N-PBAAP, but the later has higher char stability during high temperature region. The thermal degradation behavior of N-PBAAP cured film was examined by RT-FTIR and TG-FTIR, and possible degradation mechanism was proposed. The thermal degradation of N-PBAAP film takes place initially along the side chain attributing to the scission of unstable P-O-C bond, and the eventual char residue consists of various kinds of phosphorus-rich compounds and polyaromatic molecules. Raman and XPS results show that there is more graphite in the char residue of EBAAP. But as for N-PBAAP, more phosphorus and nitrogen are conserved in the solid phase, thus resulting in the higher stability of char.2. N-PBAAP, used as reactive flame retardant monomer, was blended with a commercial polyurethane acrylate (PUA) to obtain a series of UV curable coatings. The thermal degradation behavior, combustion property, dynamic mechanic thermal property, photopolymerization kinetic and other physical properties of the cured films were studied. TGA result showed that the addition of N-PBAAP can obviously enhance the char residues of PUA coatings. MCC test suggested that N-PBAAP is an effective flame retardant for the PUA coatings and it can reduce the potential combustion risk of the resins. The results of MCC showed that the peak heat release rate (pHRR) of PUA cured film containing wt50% N-PBAAP was reduced to 142.5W/g, comparing with the 275.3 W/g of pure PUA film. In addition, according to the RT-FTIR analysis, different flame retarding mechanisms were proposed for N-PBAAP when incorporated in the PUA films at different ratios. With low N-PBAAP loading (10 wt%) in the coating formulation, the flame retardant mainly act in the gas phase. While the content of N-PBAAP is high (50 wt%) , a soild phase mechanism holds the dominant effect. From the DMA analysis, the incorporation of N-PBAAP in the PUA films results in a significant increase of Tg. And photopolymerization kinetics study show that the photopolymerization rate and the unsaturation convertion increased with the increasing amount of N-PBAAP. Other physical property tests showed that the incorporation of N-PBAAP can increase the hardness and decrease the swelling ratio of the PUA films, but N-PBAAP had no great influence on the coatings.3. N-PBAAP, EBAAP were blended with Epoxy acrylate repectively. The thermal stability, combustion property and the degradation kinetics of the two flame retardant EA systems were studied. TGA result implied that EBAAP is more efficient than N-PBAAP when applied to EA coatings. MCC data show that both of the two flame retardant can greatly decrease the pHRR of the EA coatings. The kinetics of thermal degradation was investigated based on five UV curable systems, which were EA, EBAAP,N-PBAAP,EBAAP0.3,N-PBAAP0.3. Kissinger and Flynn-Wall-Ozawa methods were used in this study. The obtained results of activation energies suggested that the thermal stability of the blends at elevated temperature was improved due to the addition of phosphoramides EBAAP and N-PBAAP.