Abstract
Abstract The main objective of this work was to establish a correlation between natural aging with artificial aging in medium density particleboards produced with polyurethane resin of castor oil and Pinus sp. For such correlation, climatological parameters at São Carlos city, São Paulo state Brazil were used. The established correlation was that 20 cycles would be proportional to the same degradation of two months of exposure under natural aging. The relation between physical and mechanical properties with the effects provided by number of months (M) on the natural aging with number of cycles (Nc) on the artificial aging was obtained with cubical polynomial regression models. In general, for physical properties, 20 Nc represents 7 to 8 months and for mechanical properties, 11 to 12 months, with exception to internal bonding, with 8 months of natural aging. The equations which best represent the relation between Nc and M were thickness swelling at 2h and water absorption at 2 h and 24 h, with R² above 93%.
Highlights
Wood panels, when exposed to weathering, undergo changes on physical and mechanical properties due to their production and exposure conditions
Of the total energy of the solar spectrum calculated from one year, approximately 4% is derived from ultraviolet radiation, as described on Atlas (ATLAS..., 2001) and Silva (2008)
To calculate the equivalence between artificial aging and natural aging was following the methodology described in the Weathering Testing Guidebook (EMPRESA..., 2017)
Summary
Wood panels, when exposed to weathering, undergo changes on physical and mechanical properties due to their production and exposure conditions. It is possible to submit particleboards to natural and artificial weathering. UV light, which causes chemical changes on wood, is controlled in laboratory, as well as temperature and moisture content, leading to a well-controlled process. For natural weathering, sunlight, temperature and humidity follows the local climate where the panels are located. The variations on particleboards are caused by combinations of several effects like moisture, sunlight, oxygen, atmosphere pollutants and microorganisms. When the sunlight and oxygen reach the wood, it leads to hemicellulose and lignin oxidation and cellulose depolymerisation (LIONETTO et al, 2012)
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