MATSUMOTO KozoDepartment of Biological and Environmental Chemistry Professor |
Polymerization promotors of benzoxazine-alicyclic epoxy resin mixtures were investigated aiming to achieve their complete curing at 150 ℃ within 3 hours, and their polymerization bahaviors and thermal properties of the cured materials were examined. As a result, it was found that addition of 0.1mol% Tb(OTf)3 lowered the polymerization temperature about 20 ℃ and exhibited the maximum promotion effect on the benzoxazine polymerization at 150 ℃ for 3 hours.
Various arylmethylpyridinium tetrakis(pentafluorophenyl)borates were synthesized and their properties as cationic thermally-latent curing agents for epoxy resins were studied. Arylmethylpyridinium chlorides were prepared by reaction of arylmethylchlorides with cyanopyridines. The desired arylmethylpridinium borates were obtained by the successive ionexchange of these salts with sodium tetrakis(pentafluorophenyl)borate. Catalytic activity of the pyridinium borates toward bisphenol A diglycidyl ether (BAGE) and difunctional alicyclic epoxy resin (Celoxide) were examined by differential scanning calorimetry (DSC). Storage stability of the epoxy resins/salt mixture at room temperature for one month was examined by 1H-NMR measurements. We found that p-methoxybenzyl-3-cyanopyridimium tetrakis(pentafluorophenyl) borate (pMB3CPB) has high curing activity with good storage stability toward epoxy resins. We also found that the cured BAGE possessed higher glass transition temperatures and higher adhesion strength to stainless steel than the resin cured with a conventional sulfonium antimonate.
Binary mixture materials were prepared by mixing cross-linked polystyrene and liquid polybutadiene by several methods and their shapes and thermal phase transition behaviors were examined. Evaporating dichloromethane of crosslinked polystyrene and polybutadiene (1/1 wt/wt) solution in dichloromethane at 40 ℃ under reduced pressure gave solid/liquid two-phase-separated materials. Differential scanning calorimetry (DSC) of the materials showed that they had two glass transition temperature (Tg)s, one was Tg(-91.0 ℃) attributed to polybutadiene and the other was Tg (103.1 ℃) attributed to polystyrene. They coincided well with those of original polybutadiene and cross-linked polystyrene, respectively. On the other hand, freeze-drying of the cross-linked polystyrene and polybutadiene (1/1 wt/wt) solution in 1,4-dioxane gave powdered solid materials. DSC analysis of these materials revealed higher temperature shift of polybutadiene Tg (-88.8 ℃) along with lower temperature shift of polystyrene Tg (97.8 ℃). These observations indicated that binary materials with quite different shapes and properties can be prepared by varying the mixing methods.