The effect of fiber characteristics from old corrugated container (OCC) paper on the strength properties of OCC/polypropylene composites was evaluated. Fibers with different contents of lignin (2.8%, 3.8%, 5.3%, and 7%) were produced using soda pulping. Wettability, tear, and tensile strength of the fibers were measured as the indication factors to assess the strength of reinforcing component in the composites. The weight portions of the OCC fibers, polypropylene, and maleic anhydride-grafted polypropylene (MAPP) were selected at 20%, 77%, and 3% of the total weight of the composite, respectively. The composite compounds were formed using a counter-rotating twin screw extruder, and the specimens were made in an injection molding machine. The interaction of fiber characteristics and fiber lignin content on the mechanical properties of composite was investigated. The results revealed that with lower fiber lignin content, both flexural and tensile properties were increased. Consequently, by forming better fiber dispersion and by reducing stress regions in the composite, impact strength was also improved. Lower lignin content resulted in better mechanical properties than fiber characteristics.
There are several methods to measure the contact angle between the solid surface and liquid phase. One of the most applicable ones is known as the sessile drop method, on which a liquid droplet is deposited on a solid surface to measure the contact angle by a high-resolution camera. In this paper, molten thermoplastic droplets are placed directly on the surface of modified wood in order to assess the compatibility between hydrophobic thermoplastics and hydrophilic wood surfaces. For this purpose, two groups of spruce veneers are treated with acetic acid anhydride (AA) or maleic acid anhydrides (MA), respectively. Droplets from high density polyethylene (HDPE) are deposited on the wood surfaces at isothermal conditions. The results show that thermoplastic droplets exhibited higher contact angles at AA treated surfaces than at MA treated ones. This suggests that MA reduces the polarity of the wood surface compared to AA, which has an increased compatibility with wood surface.
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