Iranian Journal of Wood and Paper Industries

Iranian Journal of Wood and Paper Industries

Investigation of physical and mechanical properties of wood plastic composite after steaming and adding recycled polymer

Document Type : Research Paper

Authors
Sanaz Parvizi 1
Habibollah Khademieslam 2
1 Islamic Azad University, Science and Research Brananch . Tehran
2 : Department of Wood and Paper Science and Technology, Faculty of Natural Resources and Environment, Science and Research Branch, Islamic Azad University, Tehran, Iran
10.22034/ijwp.2025.2067804.1720
Abstract
Problem definition and objectives: Wood-plastic composites (WPCs) are a suitable alternative for reducing environmental pollution and managing waste due to their utilization of wood and polymeric residues. While the use of raw cellulosic fibers reduces compatibility with non-polar polymer matrices and leads to a decline in mechanical properties due to their polarity and hydroxyl groups, employing modification methods such as thermal treatment (steaming) can address these challenges. This study seeks to utilize steam treatment on poplar wood flour and recycled polypropylene, which is abundantly available in various sources. The primary objective of this research is to improve the physical and mechanical properties of wood-plastic composites, thereby producing a product of acceptable quality for industrial applications by reducing production costs and utilizing waste materials.
Methodology: To this end, Tabriz poplar wood flour was prepared and subjected to steam treatment at 180°C for one hour. For composite fabrication, virgin and recycled polypropylene were used alongside maleic anhydride as a coupling agent. Materials were mixed in an internal mixer based on specific weight ratios (40% wood flour and 60% polymer), and samples were prepared using injection molding. Prior to testing, samples were conditioned under standard environmental conditions (23°C temperature and 50% relative humidity). To determine physical and mechanical characteristics, tests for water absorption, thickness swelling, tensile strength, flexural strength, and impact strength were conducted. Additionally, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) were employed for structural analysis.
Results: Regarding physical properties, the lowest water absorption and thickness swelling were observed in samples containing steamed fibers and virgin polymer. These results indicate the removal of some hemicelluloses and a reduction in hydroxyl groups due to steaming, leading to increased hydrophobicity. In terms of mechanical properties, the highest tensile, flexural, and impact strengths were found in samples made from steamed poplar wood flour and virgin polypropylene. Scanning electron microscopy images demonstrated better distribution and superior adhesion between steamed fibers and the polymer matrix. FTIR results indicated a decrease in the intensity of peaks related to hydroxyl groups and the degradation of hemicelluloses. Although the use of recycled polymer caused a slight decrease in properties, this difference was not statistically significant.
Conclusion: The results showed that steaming reduced water absorption and thickness swelling while enhancing mechanical properties. The most significant finding was the improvement in adhesion between the fiber phase and the polymer due to the removal of hemicelluloses. In addition to improving physical properties, combining steamed wood flour with virgin polypropylene increased mechanical strengths. Furthermore, while the use of recycled polymer was accompanied by a slight decrease in properties, it is of industrial and economic importance due to its environmental benefits and cost reduction, and can serve as a suitable alternative when combined with virgin polymer.
Keywords
Steam treatment of fibers
recycled polypropylene
scanning electron microscopy (SEM)
X-ray diffraction (XRD)
Fourier-transform infrared spectroscopy (FTIR)

Subjects

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Iranian Journal of Wood and Paper Industries
Volume 16, Issue 4
Winter 2026
Pages 591-604