Effect of extended outdoor exposure on surface quality and mechanical properties of Malaysian hardwood species

Abstract

Tropical hardwoods, often used as outdoor wood products, are frequently exposed to the hot and humid conditions in Malaysia. This has led to many studies attempting to develop suitable coatings and establishing maintenance cycles so that product service life can be extended. The objective of this study was to evaluate the surface quality and mechanical properties of both uncoated and coated three Malaysian hardwood species, namely dark red meranti (Shorea spp.), keruing (Dipterocarpus spp.) and keranji (Dialium spp.) after exposure to outdoor condition at different time spans. Surface quality of uncoated and coated with exterior transparent alkyd finished of the samples was evaluated visually as well as employing a profilometer-type equipment. Bending characteristics of outdoor exposed samples were also tested. The results showed that the surface of all coated samples degraded after 48 months of exposure. In addition, after 48 months of outdoor exposure, the modulus of rupture (MOR) values for dark red meranti, keruing and keranji decreased by more than 15% while the modulus of elasticity (MOE) values decreased by approximately 20% for both uncoated and coated samples. Generally, refinishing and maintenance should be performed within 2 years, and the cost of the maintenance should be calculated to ensure that the condition of the wood remains suitable for use as a building material in Malaysia’s climate conditions.