DEHYDRATION OF BARIUM METHACRYLATE IN AIR

Barium methacrylate has been shown to crystallize from aqueous solution as the monohydrate. The isothermal rates of dehydration have been measured in air in the temperature range 40-100°, giving Ea = 33 kcal/mol. There was no effect due to particle size at 70° over the range 50-500 μ. At low temperatures tailing, or retention, occurred over a substantial part of the reaction. Differential thermal analysis and X-ray diffraction showed that the dehydration occurs in two stages. The first is a phase transition to a second crystalline form (that of the anhydrate) and the second is dehydration (effectively desorption). Ea for the second stage from DTA was 15 kcal/mol. During dynamic thermogravimetric analysis, dehydration occurred over the range 65-140°. Decomposition started at 210° and became catastrophic at 400°. Analysis of the TGA dehydration curves gave Ea ≈ 17 kcal/mol.