Chemical treatment of recycled pulp fibers for property development: Part 2. Effects on old newspapers

The recycling of paper is an important issue and requires a systematic and investigative approach. However, it is necessary to scrutinize alternative methods on the strength of the development of recycled fibres to explore the impact of recycling on properties of recycled fibres. In this study, it was found that repeated treatments of recovered fibres with all three chemicals usually enhance their ability to re-swell and improve bonding potential in fibre networks. This is evidenced by higher water retention values (WRV) and improved strength properties. The highest WRV value of 2.65 g/g was observed with a 10.0% ethyl acetate treatment in the third recycling stage, which indicates approximately 660% higher WRV compared with control samples (0.34 g/g). Measurements also showed that the optical properties of lightness and the brightness properties of the sheets show variations. However, the highest brightness improvement of 3.8% was observed at 5.0% ethyl acetate treatment at the second recycling stage. This level of treatment has also given the highest lightness value of 73.97, which indicates only 0.54% improvement. The maximum tensile strength value of 23.89 N·m/g was observed at the third recycling stage with 10.0% formamide charge. However, this level of treatment also gave the highest burst at 1.50 kPa·m2/g and tear value of 2.88 N·m2/g, which indicates a 128.2% higher burst and 176.9% higher tear strengths, compared with control samples, respectively.