Shrinkage of polymer coatings on wood veneers in aircraft structure: understanding the causes of the problem and possible solution

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A common problem in aircraft cabinetry is deterioration in the appearance of "wet-look" or high gloss finishes that causes them to eventually resemble the surfaces of orange peels (giving the so-called "orange-peel look"). This is attributed to some kind of dimensional instability (or shrinkage) in the varnish covering the cabinetry veneers. Possible sources of the problem include the nature of the varnish, its interactions with the wood and the ways in which they evolve over time, as well as the different environmental conditions (particularly temperature and humidity) to which the aircraft cabinetry are exposed during their manufacturing and usage (when landed, the aircraft doors are opened to widely varying climates, like hot and dry desert climate, hot and humid coastal climate, and cold and dry "siberian" climate). The problem causes significant loss of time and money to companies like Bombardier Aerospace, because they must frequently rework the cabinetry surfaces in the face of customer complaints and to meet the expectations of their customers. The high cost of the regional and business aircraft sold by Bombardier Aerospace provides an opportunity to try to get to the bottom of this problem, and thereby help Bombardier maintain a competitive edge internationally. The implication of 3M Canada is their interest in understanding the underlying factors that give rise to the present problems in order to help identify solutions. Therefore, in this project, we will try to understand in detail the reasons for the problem by analyzing both the varnish and veneer properties and interactions, and their evolution over time when exposed to different temperatures and levels of humidity, using a large variety of appropriate scientific techniques that involve both chemists and wood scientists. With the information gained, we hope to supply Bombardier and 3M Canada with possible solutions that we will also test. We anticipate that the information gained will also be useful generally for veneer varnishes, and thus benefit a wide range of Canadian industry.