Water-washed cottonseed meal (WCSM) has been shown the potential to be used as renewable and environmentfriendly adhesives in wood products industry. Recently, WCSM was produced from defatted meal in a pilot scale. In this study, we initially compare the adhesive strength of the pilot-produced WCSM with that of a synthetic glue Vinavil 2259 L. WCSM may be used as the conventional D1 wood adhesives for nonstructural interior application per European standard EN204/205. Non-structural D3 type adhesives is more widely used in protected outside. Under the testing conditions, WCSM possessed very high heat resistance according to European standard EN14257 (WATT 91)-adhesive strength after 1 hour at 80°C. However, the dry strength (EN204/205) and water resistance (specimen were put in water for 4 days and then pulled in the dynamometer) of WCSM were lower than those of the synthetic glue Vinavil 2259 L. Blending WCSM with Vinavil 2259 L improved the water resistance of WCSM, allowing the classification of the WCSM adhesive as D3. Further work will be focused on the increase of solid content of the final adhesive slurries and the improvement of their water resistance.
Water-based poly(vinyl acetate) dispersions are widely used as wood adhesives with dielectric heating systems. However, little is known about the effects of radio frequency (RF) exposure or heat on the adhesive characteristics and on the performances of bonded joints. In this study, the properties of bonded joints exposed to RF were compared with hot pressing and with standard drying, and the observed behavior was explained. Joint characteristics were evaluated by means of both conventional (e.g., shear strength in both dry and wet conditions, etc.) and unconventional (e.g., bondline temperature, moisture content at interface, etc.) procedures, and also selected properties of polymeric film were measured (e.g., water absorption, analysis of the fraction dissolved in water, glass transition temperature [T g ], etc.) to explicate the observed differences. Results evidenced that the effect of both RF and heating was to appreciably speed up the drying process. However, when high values of energetic impulse (owing to both hot pressing and RF) were given to the assemblies, permanent changes were induced into the polymeric glueline. This occurrence was a time-driven process and reflected mainly on the mechanical performance in wet conditions, which improved appreciably in comparison to the standard reference series. The reason of such behavior was connected to the poly(vinyl alcohol) phase present inside the polymer, and a role was also assigned to AlCl 3 , used as complexing agent of the polymeric protective colloid.
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