Morphological and mechanical characterization of Pinus radiata wood treated with two organic phase change materials via vacuum impregnation

The present study examines the mechanical and morphological properties of Pinus radiata D. Don wood impregnated with two different organic phase change materials (PCM). Specifically, a paraffin-type aliphatic PCM and a fatty acid PCM were used to impregnate the samples in the tangential flow direction. The first aim is to analyze the morphological properties of wood impregnated with a fatty-acid PCM, including key anatomical features such as cell wall thickness and lumen geometry. Moreover, the research emphasizes wood’s transport properties, which quantify fluid flow perpendicular to the growth rings. These properties are correlated with the impregnation ratio. Additionally, the study focuses on how impregnation with aliphatic and fatty-acid PCMs affects the mechanical properties of wood, specifically the variation in longitudinal Young’s modulus. The Young’s modulus was measured using the impulse excitation technique, following ASTM E1876. Experiments were conducted at three manometric pressures (55, 70, and 85 kPa) and at two constant temperatures (30 C and 70 C). The longitudinal Young’s modulus increased by up to 29.99%. Microscopic observations showed that PCM was distributed throughout the cellular microstructure, primarily occupying the luminal spaces of wood cells. These findings suggest that PCM impregnation alters the mechanical properties of Pinus radiata wood by increasing stiffness, which is associated with the occupation of luminal spaces observed in the microstructural analysis and the consequent reduction in porosity, supporting its potential application in passive thermal conditioning systems.