The potential of deinked waste paper sludge in gypsum fiberboard production

Application of cellulosic fibers and minerals of deinked waste paper sludge has a great impression on utilization and characteristics of final product. This study was designed to produce use gypsum-fiber board from the DIP sludge. The gypsum: sludge ratio was considered as 100:0, 90:10, 80:20, 70:30 and 60:40. Two types of gypsum boards were prepared with fixed 12 mm thickness and cold pressing time of 10 and 20 minutes at 30 kg/cm2. The results revealed that, regarding the fact that the DIP sludge contains a variety of short fibers with excessive amount of minerals, increasing the sludge loading could affect the compatibility of gypsum and sludge. The effect of sludge on physical and mechanical properties of gypsum fiber boards was significant to probability of 99%, in a way that maximum water absorption, maximum thickness swelling and minimum density of the boards for the treatment of 40:60 percent of gypsum to sludge was gained as follows in respect: 29.7%, 2.15 % and 0.66 g/cm3. On the other hand, MOR and MOE for board with gypsum: sludge ratio of 70:30 were gained 1.765MPa and 1.598 GPa, respectively. The effect of pressing time on physical properties of gypsum fiberboard was not significant at the probability of 95%. According to the obtained results, it has been suggested that such boards could be used in covering and ceiling isolating applications.