UV Curable Intumescent Flame-retardant: Preparation And Its Flame-retardant Mechanism Studied

The present thesis was aimed on the synthesis of novel circular UV curablephosphorus-containing acrylate oligomers (ANP). ANP, MAPM, EM235 were used asoligomers to prepare UV curable intumescent flame retardant coatings. Then the flameretardance, thermal stability and physical properties of their cured films were studied.Moreover, the thermal degradation mechanism and their intumescent properties duringburning were discussed. The detailed outline is elaborated as follows:ANP was synthesized from neopentyl glycol, phosphorus oxychloride,hydroxyethyl acrylate, which was characterized by Fourior-transformed infraredspectroscopy (FT-IR) and 1H nuclear magnetic resonance (1H-NMR). The resultsindicated the successful synthesis of the production.Then ANP, MAPM and EM235 were used as oligomers to prepare a series of UVcurable intumescent flame retardant coatings. The results showed that the flameretardancy of UV cured coatings without ANP were poor, and the limiting oxygenindex (LOI) values of UV cured coatings were greatly improved with ANP addition.The LOI value increased from 23.5 to 29.5 with increasing ANP content. Bothphosphorus and nitrogen contributed to the flame retardance, and showed a synergisticeffect to form an intumescent system. The formulation of35%ANP-25%MAPM-40%EM235 had the maximum LOI value of 29.5 and the bestflame retardancy among all samples. All samples with MAPM addition showedeffective intumescent behavior during burning. The LOI value and intumescentbehavior during heating results indicated a distinct synergistic effect between ANP,MAPM and EM235.The degradation process of the UV cured films of ANP, EM235/GMA andANP/MAPM/EM235 system were studied used by thermogravimetric analysis (TGA),the differential weight loss (DTG) and FT-IR. The results indicated that: thedegradation of the UV cured ANPfilms could be divided into three steps. From 160℃to 270℃, the degradation is mainly attributed to the fast degradation of phosphate groups. From 270℃to 350℃, poly( phosphoric acid) is formed, which catalyses thebreakage of carbonyl groups to form polynuclear aromatic structures. From 350℃to500℃,the structures hadn't obviously changed. When raising the temperature over500℃, some unstable structures in the char are decomposed, resulting in the formationof phosphorus oxides and some volatile aromatic molecules. The low temperaturestability was decreased to form stable char with increasing ANP content, and the hightemperature stabilitywas improved.During degradation of the UV cured EM235/GMAfilm, ester degradation is slowdegraded with alkyl chain to generate thick ring. At the higher temperatures, thecharring layer was farther degraded to form volatile aromatic compounds.The degradation of the UV cured ANP/MAPM/EM235 films can be divided intothree steps. From 160℃to 270℃, the degradation is mainly attributed to the fastdegradation of phosphate groups. From 270℃to 380℃, poly(phosphoric acid) isformed, which catalyses the breakage of carbonyl groups to form polynuclear aromaticstructures. From 380℃to 500℃,the structures hadn't obviously changed. Whenraising the temperature over 500℃, some unstable structures in the char aredecomposed, resulting in the formation of phosphorus oxides and some volatilearomatic molecules.The expansion degrees, char layer intensity values and fire resistance and photosof the UV cured ANP, ANP/MAPM/EM235 films after burnt were studied. The resultsshowed that ANP, MAPM and EM235 had a synergistic effect to form an intumescentsystem. In all tested samples, 0.35ANP-0.25MAPM-0.4EM235 had better expansiondegrees (7.76), the best char layer intensity values (2.2) and the highest fire resistance.At 100℃, fire resistance increased from 7.08 seconds to 37.29 seconds, and at 350℃,fire resistance increased from 93.26 seconds to 340.04 seconds, which all indicates that0.35ANP-0.25MAPM-0.4EM235 has the best intumescent flame retardant properties.