フェノール・エポキシ系樹脂塗料の硬化反応-13-
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概要
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Thermosetting mechanism of ammoniacal resol type phenolic resin and bisphenol-A type epoxy resin system was studied. The thermosetting condition studied was from 3 sec to 50 min and at temperatures of 150°C to 300°C. Gel fraction of cured film was determined by solvent extraction to follow the thermosetting reaction. Chloroform was used as the solvent to extract from cured enamel because of solubility for phenolic and epoxy resin. Extracts by chloroform from cured enamel contained the materials of lower average molecular weight than bi-molecular condensate of the prepolymer.<BR>The ratio of phenolic and epoxy components in the extracts was quantitatively analyzed, using by NMR spectra. These components were discriminated by the signal of proton. of methyl group in phenolic resin component, p-cresol, 2.25 ppm and that in epoxy resin. component, bisphenol-A, 1.65 ppm, respectively. By analyzing this ratio with thermosetting condition, the thermosetting mechanism was discussed.<BR>In all cases of thermosetting condition studied, the gelation of phenolic component alone by their methylol group was found at initial stage. Then the reaction between epoxide in epoxy resin and phenolic hydroxyl group in phenolic resin would arise.<BR>Temperature dependency of thermosetting properties of phenolic component was more strict than that of epoxy component; phenolic component gelled slower than epoxy resin at 150°C, meanwhile faster above 200°C.<BR>By these results, the thermosetting model of this resin system was considered as follows. Condensation reaction of phenolic resin by its methylol group arises at first and forms primary chain, then epoxide in epoxy resin adducts to hydroxyl group in phenolic resin. and hydroxyl group produced from epoxide also reacts on other epoxide group. On the other hand, methylol group in phenolic resin reacts with the secondary hydroxyl group in epoxy resin. Thus crosslinking reaction would proceed.<BR>However, the contribution of the resin to the thermosetting reaction differs depending upon the temperature. When the gel fraction was the same, phenolic resin was more contributive at high temperature curing and epoxy resin was more contributive at low temperature curing.
- 色材協会の論文
色材協会 | 論文
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