Phosphogypsum utilization - Part III: as adhesive filler and composite materials

The aim of this work is to make use of phosphogypsum (PG) waste material, w hich is produced in phosphoric acid and phosphate fertilizer manufactures. A number of wood adhesive formulations based on polyvinyl acetate (PVAc) po lymer and phosphogypsum as a filler have been prepared, using different per centages of phosphogypsum, ranging between 5 similar to 20 wt pet. The prep ared formulations were tested for adhesion strength and compared with both natural and pure gypsum fillers. The results indicate that PG improves the adhesion strength when 5 wt pet added, and that may be due to filling the p orous surface of wood with the fine particles of PG, as well as coating the particles of the filler (PG) with PVAc units. Also, a number of formulatio ns based on urea-formaldehyde polymer have been prepared using phosphogypsu m as an active filler in the ratio of 40 similar to 75 wt pct to prepare co mposite materials used for some decoration purposes and construction. Mecha nical, physical, and thermal properties of these formulations were studied. Also, the activation energy was calculated. The results indicate that PG w ithout acid hardener can be used for preparation of composite materials bas ed on urea-formaldehyde between 40 similar to 63.64 wt pct for construction purposes in the humid atmosphere, while between 63.64 similar to 75 wt pct for decoration purposes. The improvement of the physical, mechanical and t hermal properties of the composite material may be attributed to the simult aneous hydration hardening action of phosphogypsum and the presence of 0.8% P2O5. These effects act as an active hardener for urea-formaldehyde resin and accelerate the cross-linking and network formation reinforced by the fi ne dusty inorganic particles of PG. The advantage of this method is to prep are composite material gypsum-urea-formaldehyde, which achieves the utiliza tion of large amount of PG, reducing the price of the main product phosphat e, minimizing the pollution and producing new materials which possess high thermal resistance, good mechanical properties and water resistance that ar e suitable for construction panels.