Document Type : Research Paper
Author
Associate Professor, Faculty of Natural Resources, University of Guilan, Iran
Abstract
Background and Objective: Particleboard is a wood composite material that can be produced using various lignocellulosic materials. Therefore, lignocellulosic wastes play an important role in this regard. One of the agricultural wastes that is available in large quantities in the north of Iran is rice husk. It can be used in the production of particleboard. The lifespan and durability of particleboard depend on the quality of raw materials, binders, manufacturing conditions, and how it is used. As a result, achieving the durability of mechanical properties and dimensional stability of these boards is importance in the applications of indoor and outdoor exposure. Therefore, the aim of this study is to investigate the effect of isocyanate resin on the physical and mechanical properties retention of the rice husk particleboard.
Materials and Methods: The samples in this study were prepared from rice husk particles which has been stored in the laboratory for eighteen years after manufacture. These boards were made from natural rice husk particles with a slenderness ratio of 60, a flatness ratio of 10, and an aspect ratio of 6 as the raw material, and 10 percent of urea-formaldehyde resin which was partially replaced with isocyanate resin at three levels of 0, 1, and 2 percent as a binder. Three pressing temperatures of 170 and 180 degrees Celsius and three pressing times of 5 and 6 minutes. A total of 36 experimental boards were made with three replicates for each treatment. Test samples were prepared from each board according to EN326-1 guidelines. The measured properties included water absorption and thickness swelling at 2 and 24 hours, Modulus of Rupture, Internal Bonding, and their percentage of retention. For statistical analysis of the data, a completely randomized block design at a confidence level of 95% was used, and for comparison of means, the Tukey test was used in SPSS software.
Findings: The results of this study showed that isocyanate resin affected all physical and mechanical properties of the boards. The use of 2% isocyanate resin has caused a 100% increase in mechanical properties and a 50% decrease in physical properties. Retention percentages for water absorption and thickness swelling in the 2% isocyanate treatment were obtained 92% and 98%, respectively. In other words, the water absorption and thickness swelling of the boards increased 8 and 2% respectively between 2008 and 2025.The percentage of the modulus of rupture and internal bonding retention of boards made with 2% replacement of urea formaldehyde with isocyanate after 18 years has been 35 and 25%, respectively.
Conclusion: In general, the best result can be observed in samples produced with 10% resin (2% isocyanate plus 8% urea-formaldehyde) at a pressing temperature of 180°C and a pressing time of 6 minutes. In these samples, the highest retention percentages were for water absorption and thickness swelling.
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