Investigating the drying characteristics and curing behavior of bamboo scrimber base unit: Phenolic resin impregnated heat-treated bamboo bundles

Abstract

The PHB serves as the fundamental unit of bamboo scrimber, with its drying rate, moisture content (MC) distribution, and post-drying curing degree being crucial factors for enhancing production efficiency, ensuring high-quality hot pressing, and optimizing the physical-mechanical properties of bamboo scrimber. This study investigated the impact of drying temperatures (50 ℃, 60 ℃, 70 ℃, 80 ℃) and stacking patterns (P₁, P₃, P₆, P₁₂) on the drying rate and MC distribution uniformity in PHB. Additionally, the curing behavior of PHB was examined using the differential scanning calorimetry (DSC) method. The results revealed that both the drying temperature and stacking patterns had a significant effect on the drying rate and MC distribution uniformity in PHB (P < 0.001). The MC of PHB exhibited significant variations at different locations during low-temperature drying, whereas increasing the temperature not only improved the uniformity in MC distribution. The greater number of layers made it easier for PHB to intertwine with each other, thereby reducing the flow channels for dry media and impeding heat/mass exchange. Consequently, this resulted in a decrease in both drying rate and MC distribution uniformity. Compared to PF resin (155.95 kJ/mol), the apparent activation energy of PHB decreased (104.78 kJ/mol) and the curing reaction rate increased. Within the temperature range of 50 ℃ to 80 ℃, under identical conditions, PHB exhibited a significantly higher degree of curing compared to PF resin. The differences in final curing degrees between them were 0.47, 0.31, 0.10, and 0.01 respectively. This indicated that PHB was more susceptible to undergoing a curing reaction during the drying process. Therefore, it is recommended to maintain the drying temperature at 60 ℃ and employ the P₃ stacking pattern. The findings of this paper hold great significance in informing the design and optimization of the PHB drying process.