Thermal and UV-curing behavior of phosphate diacrylate used for flame retardant coatings

• Published in: Progress in organic coatings Vol. 59; no. 4; pp. 318 - 323
• Main Authors: Chen, Xilei, Hu, Yuan, Jiao, Chuanmei, Song, Lei
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 01.07.2007; Elsevier Sequoia
• Subjects: Applied sciences; Exact sciences and technology; Flame retardant; Organic polymers; Phosphate; Physicochemistry of polymers; Polymerization; Preparation, kinetics, thermodynamics, mechanism and catalysts; Thermal degradation; UV curing; Flame retardant; UV curing; Phosphate; Thermal degradation; Coating material; Paint
• ISSN: 0300-9440; 1873-331X
• DOI: 10.1016/j.porgcoat.2007.05.002

A novel phosphorus-on-skeleton compound has been synthesized by allowing phosphorus oxychloride to react with 1-oxo-4-hydroxymethyl-2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane (PEPA) and 2-hydroxyethyl acrylate (HEA). Its structure was characterized by Fourier transformed infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance spectroscopy ( 1H NMR). The UV-curing behavior was investigated using FTIR. Results show that the conversion of the unsaturated bond of the monomer exposed to UV light for 100 s is approximately 84%. Flame-retardant effectiveness was estimated from the limiting oxygen index (LOI) and thermal stability was characterized by thermogravimetric analysis (TGA). The LOI value was 39 and the char yield was 53% at 600 °C. TG data indicate that the material undergoes degradation in three characteristic temperature stages, which may be attributed to the decomposition of the phosphate, thermal pyrolysis of aliphatic chains, and degradation of an unstable structure in char, respectively. These were further characterized by real time Fourier-transform infrared measurement. It is proposed that the flame retardant action results from decomposition of phosphate to form poly(phosphoric acid), which catalyses the breakage of bonds adjacent to carbonyl groups to form an intumescent char, preventing the sample from burning further.