Document Type : Research Paper
Author
Forestry-Faculty of Natural Resources , University of Guilan, Iran
Abstract
Background and Objective: Particleboard is a Wood Composite materials that can be used with various lignocellulosic materials. Therefore, lignocellulosic wastes play an important role in this regard. One of the agricultural wastes that exists 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 depends 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 during 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 required in this study were prepared from rice husk particles that had been in the laboratory for eighteen years since their manufacture. These chips were made from natural rice husk particles with an slenderness ratio of 60, an flatness ratio of 10, and an aspect ratio of 6 as the raw material, along with 10 percent of urea-formaldehyde resin replaced with isocyanate resin at three levels of 0, 1, and 2 percent as a binder, and at temperatures of 170 and 180 degrees Celsius with a pressing time 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. Isocyanate resin increases the Modulus of Rupture and internal bonding and reduces the amount of water absorption and thickness swelling.Also, Isocyanate resin increases the percentage of the mechanical properties retention and prevent increasing the water absorption and thickness swelling after 18 years from the time of manufacture of the boards.
Conclusion: In general, from this study, the best result can be observed in 2% replacement of urea formaldehyde with isocyanate resin. The use of 2% isocyanate resin has caused a 100% increase in mechanical properties and a 50% decrease in physical properties. 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. While during this period, the amount of water absorption and swelling of the thickness of the boards has remained almost unchanged.
Conclusion: In general, from this study, the best result can be observed in 2% replacement of urea formaldehyde with isocyanate resin. The use of 2% isocyanate resin has caused a 100% increase in mechanical properties and a 50% decrease in physical properties. 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. While during this period, the amount of water absorption and swelling of the thickness of the boards has remained almost unchanged.
Conclusion: In general, from this study, the best result can be observed in 2% replacement of urea formaldehyde with isocyanate resin. The use of 2% isocyanate resin has caused a 100% increase in mechanical properties and a 50% decrease in physical properties. 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. While during this period, the amount of water absorption and swelling of the thickness of the boards has remained almost unchanged.
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