City Research Online

Abstract

Seven coatings intended to represent currently available coatings for wood were exposed to natural weathering, and the changes in them were investigated after various periods of exposure. Four of the coatings were solvent borne, and three water borne. Of the solvent borne coatings, three were based on a flexible alkyd resin, but with different pigments, and the fourth on a traditional alkyd resin. Two of the water borne paints were based on the same acrylic resin, with different pigments, and the third on an alkyd-acrylic hybrid resin.

Each paint was studied by:
differential scanning calorimetry;
dynamic mechanical scanning calorimetry;
Fourier transform infrared - photoaccoustic spectroscopy;
determination of non-volatile content;
determination of water extractable material content;
determination of dichloromethane extractable material content;
and determination of organic content.

It was found that paints with an alkyd component underwent an immediate additional cross-linking reaction, despite being allowed to cure for at least a month before being placed outside. Iron oxide was found to lower the glass transition temperature in both the autoxidation process and the photodegradation of an alkyd resin when compared with an unpigmented version.

For all coatings, the rate of degradation was dependent on seasonal changes, for alkyds being greater in the summer months, and for acrylics, a change in the polymer backbone was seen after the coating had cycled through its Tg.

Paints with an acrylic component lost material during the first four months of exposure, and this material is thought to be, at least in part, additives (e.g. thickeners).

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QD Chemistry T Technology > T Technology (General)
Departments:	School of Science & Technology > Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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