Using phase change materials (PCMs) is an efficient solution for reducing energy consumption in buildings. These materials have a large capacity for storing thermal energy, making them an appealing option for energy management purposes. Phase change materials have been successfully incorporated into various construction materials such as concrete, brick, or plaster. The primary objective of this review is to examine previous studies conducted on the application of PCMs in wood. The initial section presents an overview of the direct impregnation techniques utilized for wooden materials. This is followed by a discussion on the implementation of macroencapsulated PCMs in wooden structures that are typically present in residential buildings. In addition, the use of shape-stabilized PCM/wood composites, preventing potential leaks during the phase change transition, is explored. Finally, patents related to the use of PCMs in wood are described. Future challenges include the incorporation of PCMs into wood composites to improve their thermal properties. This literature review shows that there is a gap in knowledge regarding the utilization of phase change materials in wood-based panels such as oriented strandboards, fiberboards, and particleboards. This provides an opportunity for future research to improve the performance of the products manufactured by the wood-based panels industry.

The wood-based panel industry is experiencing an excessive accumulation of solid residues from the production of medium-density fiberboard (MDF) panels and moldings. It is possible to create new MDF products with acceptable physical and mechanical properties by revaluing MDF residues. Additionally, those products’ thermal properties can be improved by incorporating phase change materials (PCMs). This study aims to develop a wood-based fiberboard made of MDF residues, capable of storing thermal energy. Two types of PCMs (liquid and microencapsulated), two PCM ratios (2% and 6%), and two types of adhesives (urea-formaldehyde and phenol-formaldehyde) were used to produce eight different types of panels. The vertical density profile, thickness swelling, water absorption, internal bond (IB), and static bending properties—modulus of elasticity (MOE) and modulus of rupture (MOR)—were determined for each panel type. The specific heat of the panels was also determined. The results show the panels’ densities were greater than 700 kg/m³. Thickness swelling in water improved by 23% compared to the reference value of the control panel PCMs after PCM incorporation. The highest IB value was 1.30 MPa, which is almost three times the minimum required by regulation standards. The incorporation of PCMs reduced the panels’ bending properties compared to the properties of the control panels. Even though the values obtained are sufficient to comply with the minimum values set out in ANSI standard A208.2 with an MOE value of 2072.4 MPa and the values obtained are sufficient to comply with the minimum standards with an MOE value of 2072.4 MPa and an MOR value of 16.4 MPa, when microencapsulated PCM is used, the specific heat of the panels is increased by more than 100% over that of the control panels. This study developed fiberboards with adequate physical and mechanical properties and capable of storing thermal energy.

The wood-based panel industry generates a significant amount of solid residues in its production activities, including medium-density fiberboard (MDF) molding manufacturing. These residues consist of fine fibers measuring between 0.15 mm and 1.19 mm in length. A large proportion of them currently needs to be utilized, mainly due to the problem of excessive accumulation. They can be reused as raw material for manufacturing new products by adopting a circular economy approach. Their thermal properties can also be enhanced by impregnating them with phase change materials (PCMs). This research aims to develop a process for impregnating MDF panel residues (R) with PCMs to obtain shape-stabilized compounds capable of storing thermal energy. Three different commercially available PCMs were used. They were incorporated in the MDF residues by vacuum impregnation. The morphology, chemical structure, thermal stability, and phase change properties of the compounds obtained were studied by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectrometry, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), respectively. The SEM images indicated the PCM filled the empty spaces in the porous surface of the residue fibers to form shape-stabilized compounds. The FTIR spectrometry results indicated the compounds still exhibited characteristic peaks corresponding to both the MDF residues and the PCMs. No chemical reaction was observed between the two components. Moreover, according to the TGA results, the compounds produced exhibit high thermal stability. The R+PCM1 compound had the highest latent heat capacity of all the compounds developed in this study, reaching a maximum of 57.8 J⋅g⁻¹, and a phase change temperature comparable to that of PCM1. This better thermal performance could be attributed to the compounds having a higher encapsulation ratio (31.4%) than the other compounds developed. Furthermore, the R+PCM1 compound had an absorption capacity of 142.8%. This study, therefore, unveiled a promising alternative for storing thermal energy and valorizing solid MDF residues.

Acid hydrolysis can be more efficient than water hydrolysis, particularly in breaking down cured adhesives found in waste panels within a shorter reaction time, which could benefit large-scale industrial processes. This study evaluates the effects of various acid hydrolysis conditions on the thermal, physical, and chemical properties of recycled particles intended for particleboard production. Particleboards were recycled using oxalic acid and ammonium chloride at different concentrations and reaction times at 122 °C. The thermal stability of the particles was determined by thermogravimetric analysis. Particle size distribution, particle morphology, nitrogen content, pH and acid/base buffer capacity were analyzed. The effect of the recycled particles on the urea-formaldehyde (UF) curing was assessed using differential scanning calorimetry and the gel time method. The recycled particles exhibited a higher thermal degradation beyond 200 °C, indicating their thermal stability for manufacturing new panels. The acid treatments did not damage the anatomical structure of the particles, preserving the prosenchymatous elements. The nitrogen content of recycled particles decreased by up to 90% when oxalic acid was used, compared to raw board particles. Recycled particles exhibited a lower pH, with a maximum reduction of 44%. They also showed a decreased acid buffer capacity and an increased base buffer capacity compared to raw board particles. This effect was particularly pronounced in treatments that included ammonium chloride. The recycled particles did not significantly affect the peak polymerization temperature of the UF adhesive. However, some treatments affected the gel time of the adhesive, particularly those using 30% ammonium chloride. The results indicate that particleboards can be effectively recycled through acid hydrolysis, mainly with oxalic acid, which provides better results than hydrolysis using water alone. Oxalic acid showed increased selectivity in eliminating the cured UF adhesive, resulting in recycled particles suitable for manufacturing new panels.

Acid hydrolysis can be more efficient than water hydrolysis, particularly in breaking down cured adhesives found in waste panels within a shorter reaction time that could benefit large-scale industrial processes. This study evaluates the effects of various acid hydrolysis conditions on the thermal, physical, and chemical properties of recycled particles intended for particleboard production. Particleboards were recycled using oxalic acid and ammonium chloride at different concentrations and reaction times at 122 °C. The thermal stability of the particles was determined by thermogravimetric analysis. Particle size distribution, particle morphology, nitrogen content, pH and acid/base buffer capacity were analyzed. The effect of the recycled particles on the urea-formaldehyde (UF) curing was assessed using differential scanning calorimetry and the gel time method. The recycled particles exhibited a higher thermal degradation beyond 200 °C, indicating their thermal stability for manufacturing new panels. The acid treatments did not damage the anatomical structure of the particles. The nitrogen content of recycled particles decreased by up to 90% when oxalic acid was used, compared to raw board particles. Recycled particles had a lower pH, a lower acid buffer capacity, and a higher base buffer capacity than those of raw board particles. The recycled particles did not significantly affect the peak polymerization temperature of the UF adhesive. However, some treatments affected the gel time of the adhesive. The results indicate that particleboards can be effectively recycled through acid hydrolysis, mainly with oxalic acid, which gives better results than hydrolysis using water alone. Oxalic acid showed increased selectivity in eliminating the cured UF adhesive, resulting in recycled particles suitable for manufacturing new panels.

The growing global demand for particleboards has generated large quantities of waste in recent years. This waste mainly arises from manufacturing processes, furniture industry offcuts, and end-of-life disposal. In response to waste management challenges, recycling and reuse technologies have advanced significantly. In this context, this study evaluates the feasibility of producing new particleboards using recycled particles obtained from laminated particleboard waste treated with oxalic acid hydrolysis. Three-layer panels were manufactured with varying proportions of recycled particles (0%, 25%, 50%, 75%, and 100%) in the core layer. Their average density, vertical density profile, physical and mechanical properties, as well as their formaldehyde emissions, were assessed. The results showed that the inclusion of recycled particles did not significantly impact the average density or the vertical density profiles of the panels. Thickness swelling and water absorption after 24 h immersion were similar across all panels, indicating good dimensional stability. Internal bond (IB) strength showed no consistent trend with increasing recycled particle content, and panels with 75% recycled particles achieved the highest IB strength (0.48 MPa). In contrast, bending properties decreased when the proportion of recycled particles exceeded 25%. All panels satisfied the requirements of the LD-2 Grade for low-density particleboards specified by the ANSI A208.1-2022 standard. Although formaldehyde emissions increased in panels with more than 25% recycled particles, they remained within acceptable limits up to 75% recycled material. These findings indicate that particleboards can incorporate up to 75% recycled particles in the core, while maintaining physical and mechanical properties comparable to those of the control panels.