Influência do revestimento nas propriedades de painéis compensados não-estruturais de uso exterior submetidos à câmara de intemperismo acelerado

Abstract

Plywood panels are widely used in civil construction as forms for concrete, being produced, for the most part, by veneers of Pinus spp. and adhesive based on phenol formaldehyde resin. However, after several reuses, the panels tend to lose their original strength and stiffness characteristics due to continuous exposure to weather, water from the concrete composition and sunlight. The objective of the study was to evaluate the influence of coatings on the technological properties of non-structural plywood for outdoor use of Pinus spp., after exposure to adverse conditions of radiation, precipitation and condensation in an accelerated aging chamber. Twenty 18 mm thick commercial panels were used, divided into 5 groups according to the surface: (i) uncoated (control), (ii) oil, (iii) melamine resin, (iv) melamine film and, (v) tego film. From each group, 80 specimens were removed, of which each subgroup of 20 was subjected to 0, 10, 30 and 50 cycles of radiation, precipitation and condensation in an accelerated aging chamber, according to the procedures described in ASTM G154 (2006). After completion of the cycles, the determination of density, moisture content, strength and stiffness to static bending, and strength in bonding line shear was performed. Data were evaluated in a multifactorial way in parametric statistics through analysis of variance and Tukey's test at 95% probability of success, considering 5 factors (coatings) and four levels (0, 10, 30 and 50 cycles). The results demonstrated thar the panels of all treatments met the parameters recommended by the Brazilian Association of Mechanically Processed Wood (ABIMCI) up to 50 cycles, that is, the coatings applied and the exposure time to radiation, precipitation and condensation variables did not adversely affect the panels in terms of strength and stiffness.