Degradation of paint films. III.:IR Spectral change of drying oil films on out door exposing
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概要
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Authors investigated the out door degradation of the films of linseed oil and polymerized chinese tung oil. These oils were coated on polyethylene film (20μ thickness) at the thickness of about 25μ, then dried in door for 1 week. The films were exposed for 8 weeks, then IR spectra of the films were measured at the following intervals : The coated film is set in the position of sample cell, and another polyethylene film (not coated) is set in the position of compensate cell of a double beam type IR spectrophotometer. Then the spectra of the oil film were written.<BR>Changes of the weight, hardness and luster were also measured from films coated on glass plate and exposed.<BR>Results : Degradation of these films was very quickly happened, especially linseed oil film was extremely degradated, which thinned gradually, almost no oil film was remained on the polyethylene after 8 weeks. Main absorption changes of IR spectra of linseed oil film were as follows : <BR>3420cm<SUP>-</SUP> : OH or OOH, not decreased so much.<BR>2930, 2855cm<SUP>-</SUP> : CH<SUB>2</SUB> and CH<SUB>3</SUB>, decreased very quickly, its decreasing speed was very much more than that of CO (1740cm<SUP>-</SUP>).<BR>1740cm<SUP>-</SUP> : Ester CO, this band expanded to both higher and lower frequency side, and the absorption peak moved to 1730-1705 cm<SUP>-</SUP> after 2 weeks exposing. This is believed as that many kinds of carbonyl compound formed on exposing.<BR>1460cm<SUP>-</SUP> : CH2, this absorption disappeared after 1 week, which also indicates quick decrease of CH<SUB>2</SUB>.<BR>1175cm<SUP>-</SUP> : Ester CO, which decreased slowly.<BR>1050cm<SUP>-</SUP> : New absorption grew on this frepuency, that was broad band. It seems to be due to the appearance of many kinds of OH groups.<BR>Almost the same results was obtained for the case of polymerized chinese tung oil, but the rapidity of these spectral change in this case was much slower than that of linseed oil.<BR>Weight of both films decreased with hardness increased, gradually in both, but luster rapidly decreased down to about 20% after 1 month exposing.<BR>As a result, the authors could conclude that the feature of degradation is the quick disappearance of methylene part of the film. This part is oxidized to carbonyl radical and carbinol part, then the rupture of chain or the polymerization occures successively. Low molecular weight compounds thus formed seemed to be vapourized or dissolved to rain water, and polymerization would be the cause of hardening nf the film.
- Japan Society of Colour Materialの論文