The usage effect of nano-alumina on the mechanical and surface properties of HDF made of oxidized fibers

Current research was conducted to investigate the effect of nano Alumina modification on the mechanical and Surface properties of High-Density Fiberboard (HDF) made from oxidized fibers. Surface activation of fiber was done with 40% nitric acid. After fibers gluing with urea-formaldehyde (7% and 9% based on the dry weight of fibers), the boards were made by hot pressing. For veneering, two types of paper with grammage of 70 and 80 g/m2 impregnated with melamine-formaldehyde and nano-alumina 0, 1.5 and 3% were applied. According to the results, the highest bending strength, modulus of elasticity and hardness were measured in nitric acid-modified fibers/ 9% glue/ grammage of 80 g/m2/3% nano-alumina samples that was significant increase compared to the control boards a significant increase. The samples weight loss due to abrasion was decreased with increasing the veneers grammage and nano-alumina, which confirmed the positive effect of nano-alumina. Veneer grammage did not show significant effect on the resistance to cigarette burn, but the highest concentration of nano-alumina resulted to improve this surface resistance via increase of thermal conductivity

Investigation on the physical properties and internal bonding of HDF made of oxidized fiber

Current research was conducted to investigate the physical properties and internal bonding of High-Density Fiberboard (HDF) made from oxidized fibers and different amount of glue. In order to surface modification, fiber was treated with 40% nitric acid. After fibers gluing with urea-formaldehyde (7% and 9% based on the dry weight of fibers), the boards with a density of 0.9 g/cm3 were made by hot pressing at 175°C and 4 minutes. The results of spectroscopy were confirmed the reduction of hydroxyl functional groups and the increase of the carboxylic group due to oxidation. The results of short term immersion test in water showed that in boards containing oxide-modified fibers and 9% urea-formaldehyde glue were measured the minimum water absorption and thickness swelling with mean of 78.5 and 28.65%, respectively.Spring back of modified boards containing less glue was affected by the stresses release and debonding of the wood elements that resulted in internal bonding loss