Long-Term Hygroscopic Thickness Swelling Rate of Hydrothermally Treated Beech Wood / Polypropylene Composites

Abstract

Long-term hygroscopic thickness swelling rate of polypropylene (PP) composites filled with thermally treated wood flour was investigated. The beech wood chips were heat treated at 120 °C, 150 °C or 180 °C for 30 or 120 min using saturated steam in a digester. The composites based on PP, beech wood flour (BF), and coupling agents (PP-g-MA) were made by melt compounding and injection molding. The weight ratio of BF to PP was controlled at 50/47 for all blends. The amount of coupling agent was fixed at 3 wt.% for all formulations. Further study was conducted to model thickness swelling of the composites, a swelling rate parameter (KSR). The thickness swelling of thermally-treated samples at 120 ºC for 30 min and at 150 ºC for 30 min were lower than that of control samples, followed by thermally-treated samples at 180 ºC for 120 min, at 180 ºC for 30 min, at 120 ºC for 120 min, and at 150 ºC for 120 min, respectively. Furthermore, the thickness swelling of the BF/PP composites decreased with increasing time and temperature of the thermal-treatment. In addition, at 120 ºC for 30 min, the composites showed a lower swelling rate than control samples. The KSR of the composites was influenced both by the time and temperature of thermal treatment.

Effect of fungal infection on physico-mechanical resistance of WPC made from thermally treated wood/PP

“…The density and EMC values of the control specimens were higher than the heattreated samples. Arwinfar et al (2016) and Hosseinihashemi et al (2022) discuss the mechanical properties and long-term hygroscopic thickness swelling rate of heat-treated wood particle WPCs in different conditions; they found that the acceptable treatment to make the WPC was 150 °C for 30 minutes for mechanical strength; 120 °C for 30 min and 150 °C for 30 minutes for long-term hygroscopic thickness swelling rate. Moreover, the micromorphology images of the composites produced from the wood heated at the aforementioned conditions showed that there are considerably fewer pores and so broken fiber ends embedded in the matrix of polymer.…”