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The possibility of making glues of natural origin (pure lignin and ligningluoxal(instead of chemical resins for making plywood from poplar layer was investigated. For this purpose, lignin was reacted with glyoxal and the lignin-glyoxal glue was produced. To make the desired plywood, pure lignin (L.100%), lignin-glyoxal 15% (L.85%, G.15%), and lignin-glyoxal 30% (L.70%, G.30%) were used as the adhesive at three different levels. Ammonium chloride (1%) as the hardener and wheat flour (30%) as the filler based on the dry weight of the adhesive were also used. Plates made with urea formaldehyde resin at 160 g/m2 were considered as control samples. After the laboratory boards were produced, the physical and mechanical properties of samples, such as thickness swelling after 2 and 24 h of immersion in water, shear strength, modulus of rupture and modulus of elasticity, were measured. In addition, the groups and bonds in the pure lignin and lignin-gloxal adhesives were identified by Fourier transform infrared (FTIR) spectroscopy. In most tests and compared to the boards made of the adhesives and control boards, the lignin-glyoxal 30% (L.70%, G.30%) glue came closest to the performance of the control glue. [ABSTRACT FROM AUTHOR]

Effects of wollastonite substitution were investigated relative to the mechanical, physical, and microstructural properties of a wood fibercement composite. Wollastonite content of 0%, 3%, 6%, and 9% and lignocellulosic material (kraft fibers) content of 10%, 20%, and 30% were used based on the dry weight of cement. Then the lignocellulosic material and the resulting board samples were compared to a control (without wollastonite). Modulus of rupture (MOR), modulus of elasticity (MOE), water absorption, and fire resistance tests were conducted to examine the characteristics of the board composite. The results showed that the mechanical properties of wood fiber-cement composite were improved by the 9% wollastonite substitution. The fire-resistance of the composite board was improved when the wollastonite content was increased. Furthermore, cement boards with 9% wollastonite exhibited lower water absorption in comparison to the other specimens. Scanning electron microscopy (SEM) results showed that the calcium hydroxide formed hydrated calcium silicate gel (C-S-H gel) after the addition of wollastonite. The SEM images showed that the micro-structure of the boards were improved by increasing the nano-wollastonite content. [ABSTRACT FROM AUTHOR]

Hybrid composites of polyethylene/wood flour/nanoclay with different concentrations of nanoclay were fabricated using melt compounding followed by injection molding. Composites were weathered in a xenon- arc type accelerated weathering apparatus for 2000 h. Physical properties of the composites were evaluated by colorimetery and water absorption before and after weathering. Changes in surface chemistry were monitored using spectroscopic techniques. The results indicated that water absorption of the composites increased after weathering, but nanoclay can reduce the intensity of weathering to some extent by decreasing water absorption. Weathering increased the degree of color change and lightness of the samples; however, the lightness of the samples containing nanoclay was less than that of neat wood-plastic composites. Fourier transform infrared spectroscopy revealed a lower carbonyl index of composites containing nanoclay. X-ray diffraction patterns revealed that the nanocomposites formed were intercalated. The order of intercalation for samples containing 2 wt% nanoclay was higher than that of 4 wt% at the same maleic anhydride grafted polyethylene content, due to some agglomeration of the nanoclay. [ABSTRACT FROM AUTHOR]