Synthesis of Flame Retardant Acrylate Monomer/Oligomer and Study on Thermal Degradation Mechanism and Properties of the Coating
|School||University of Science and Technology of China|
|Course||Safety Technology and Engineering|
|Keywords||flame retardant mechanism acrylate thermal degradation transparent coatings UV-curable|
The thesis was aimed on the synthesis of bis（2-acryloxyethyl） 2.6.7-trioxa-1-phosphabicyclo[2.2.2.]octane-methylol-1-oxide（BTP）containing acid and carbon source,and the study on its thermal degradation and flame retardant mechanisms as well as applications in UV curable coatings together with epoxy acrylate and polyurethane acrylate.Then,the thesis was focused on the syntheses of an acrylate monomer containing phosphorus,nitrogen and silicon（DGTH）and a star acrylated melamine oligomer（SPUA）.The thermal degradation mechanism and the flame retardant properties of the cured DGTH and SPUA films have been also investigated.The thermal degradation mechanism and combustion behaviours of the intumescent flame retardant resins by blending star acrylated melamine oligomer （SPUA）with DGTH and tri（acryloyloxyethyl）phosphate（TAEP）in different ratios have also been investigated.Based on the selected several coating systems,the fire protection of the Chinese fir wood has also been investigated.The detailed outline is elaborated as follows:1.Bis（2-acryloxyethyl）2.6.7-trioxa- 1-phosphabicyclo[2.2.2.]octane-methylol-1-oxide （BTP）as flame retardant multifunctional monomer used for UV curable systems has been synthesized using phosphorus oxychloride,pentaerythritol and hydroxylethyl acrylate.Its thermal degradation mechanism has been studied using thermogravimetric analysis,in-situ Fourier-transform infrared and direct pyrolysis/mass spectrometry measurements.The BTP cured film has high char residue in the thermogravimetric analysis test,and the residual weight is about 36%at 800℃.The flame retardant mechanism is proposed that the degraded products of phosphate formed poly（phosphoric acid）at the temperature of 160℃to 270℃, which further catalyzes the breakage of carbonyl groups to form an intumescent char for preventing the samples from further burning.A lot of water and carbon dioxide are released at the temperature of 300℃to 400℃.As the temperature is raised to 500℃,there are some phosphorus oxides such as P2O5 and P4O10formed.There is graphite-like structure in char residue using XRD,SEM and Raman measurements.2.BTP has been used as reactive-type flame retardant diluent monomer for commercial epoxy acrylate（EA）and polyurethane acrylate（PUA）oligomers in UV curable resins.It has been found that the addition of BTP obviously increases the photopolymerization rates and the flame retardance.The thermal degradation results showed that the phosphate in BTP decomposes to form poly（phosphoric acid）at low temperature,which catalyze EA and PUA carbonization,and increase the thermal stability at high temperature.The LOI,UL 94,HRR and MLR results showed that BTP effectively improve the flame retardance of EA and PUA.The UL 94 rating can raise to V-0 with the addition of 50 wt.%BTP for EA,however,it can pass V-0 for PUA with only 30 wt.%BTP loading.The LOI of EA and PUA can increase 18.0 to 28.0 and 19.0 to 30.5,the heat release rate decreases by 58.9%and 66.0%, respectively with the addition of 30 wt.%BTP.There is obviously distinct synergistic flame retardant effect between BTP and PUA.3.An acrylate monomer containing phosphorus,nitrogen and silicon（DGTH）as flame retardant multifunctional monomers used for UV/moisture curable systems has been synthesized using 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide （DOPO）,3-Glycidoxypropyltrimethoxysilane（GPTMS）,2,4-Toluene diisocyanate （TDI）and hydroxylethyl acrylate（HEA）.Its thermal degradation mechanism has been studied using thermogravimetric analysis,in-situ Fourier-transform infrared and direct pyrolysis/mass spectrometry measurements.The cured DGTH film showed high thermal stability with the initial decomposition temperature of 273℃.And the residue is as high as 38%at 600℃.The process of thermal degradation of the cured DGTH film can be mainly divided into three parts.DOPO structure units firstly degrade to form aromatic compounds containing phosphorus,and then catalyze the adjacent ester groups to decomposition.Acrylate units mainly occurs depolymerization,and then form acetone or acrolein compound under the catalyst phosphide.Polyurethane waits generate depolymerization to polyol and isocyanate, and the isocyanates generate polyurea structure with the release of carbon dioxide.4.Star aerylated melamine oligomer（SPUA）as a flame retardant multifunctional oligomer used for UV curable systems has been synthesized.The thermal degradation mechanism of SPUA cured film was characterized using thermogravimetric analysis and in-situ FTIR.DGTH and TAEP were blended with SPUA in different ratios to obtain a series of UV curable intumescent flame retardant resins.There is a distinct synergistic flame retardant effect in DGTH/SPUA and TAEP/SPUA systems.The sample containing 37.5 wt.%SPUA in DGTH/SPUA systems showed the highest LOI value of 41 and the lowest heat release rate among all resins.The degradation mechanism suggested that phosphate group in DGTH first degraded to form Aromatic compounds containing phosphorus,which further catalyze the degradation of the material to form char with the emission of nitrogen volatiles from SPUA,leading to the formation of expanding char.The degradation mechanism suggested that phosphate group in TAEP first degraded to form poly（phosphoric acid）s,which further catalyze the degradation of the material to form char with the emission of nitrogen volatiles from SPUA,leading to the formation of expanding char.The sample containing 50 wt.%SPUA in TAEP/SPUA systems showed lowest heat release rate and total heal release among all resins.There is a better synergistic flame retardant effect between TAEP and SPUA.5.BTP,DGTH/SPUA and TAEP/SPUA protective fire coatings has been prepared on the Chinese fir wood.The cone calorimeter results showed that BTP and DGTH/SPUA systems have better protective effect among the all the samples.The reason may be that BTP can form high char residue,that BTP can catalyze wood to carbonization,and SPUA/DGTH can form compact char residue with high intensity.