Accession Number : AD0442329


Title :   THE WATER ABSORPTION AND WATER VAPOR PERMEABILITY OF CLEAR ORGANIC COATINGS,


Corporate Author : NATIONAL RESEARCH COUNCIL OF CANADA OTTAWA (ONTARIO) DIV OF BUILDING RESEARCH


Personal Author(s) : Ashton,H E


Report Date : Apr 1964


Pagination or Media Count : 13


Abstract : The three factors which degrade a clear coating or the wood substrate are light, water, and oxygen. The paper covers the transmission and absorption by clear organic coatings of one of the agents--water. The range of materials tested include pure phenolic varnishes, air-drying alkyds, cold-cured epoxies, and two types of urethanes. Absorption was found not to vary with composition and was extremely low for all the unpigmented materials. Both wet and dry cup permeabilities were measured. At equal film thickness permeability was not affected by the number of coats. Permeability correlated very well with composition and increased with increasing oil content of phenolic varnishes and alkyd resins. It decreased with increasing molecular weight of a series of varnishes. There was, however, no correlation between permeability and durability. An amidecured epoxy which had the lowest permeability also had a low durability rating. Tung oil-p. phenyl phenolic varnishes which gave the best exterior exposures were intermediate in permeability. The ratio of wet cup to dry cup permeability was close to one indicating the materials are not water sorbing. The results show that permeability and water absorption are not related. (Author)


Descriptors :   *PERMEABILITY , ORGANIC COATINGS , ORGANIC COATINGS , WATER VAPOR , PAINT THINNERS , PLASTIC PAINTS , PLASTIC COATINGS , EPOXY RESINS , PHENOLIC PLASTICS , THICKNESS , VARNISHES , WATER , CANADA


Distribution Statement : APPROVED FOR PUBLIC RELEASE