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

Sutcu A., Sahin H. T., Tutus A.

Drewno : prace naukowe, doniesienia, komunikaty

2018

vol. 61, nr 201

177--192

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.

Chemical treatment of recycled pulp fibres for property development: Part 1. Effects on bleached kraft pulps

Sutcu A., Sahin H. T.

Drewno : prace naukowe, doniesienia, komunikaty

2017

vol. 60, nr 200

95--109

It was observed that sodium hydroxide, formamide, and ethyl acetate treatments enhance fibre swelling (re-swelling) abilities, especially after the first recycling stage. The highest water retention values (WRV) of 2.76 g/g were found at the second recycling stage of 7.5% formamide treatment (7.5Fa2). However, the highest air permeability value of 8.83 m2/sec. was found at the third recycling stage of 5.0% in ethyl acetate treated samples (5Et3). The optical properties of the whiteness and brightness of the sheets presented a variation in the recycled sheets and with further recycling, usually resulted in marginal changes. The sodium hydroxide treatment usually resulted in a 1.2%–24.6% improvement of tensile strength. However, the highest burst strength improvement of 49.6% was achieved at a 7.5% NaOH charge at the first recycling stage (7.5Na1). The formamide treatments resulted in approx. 5.3% to 53.2% tensile strength improvement. The highest burst of 4.48 kPa m2/g was found at the first recycling stage of 7.5% (7.5Fa1) conditions with formmaide, which indicates 88.2% higher than control (C1). Moreover, the highest tensile (38.8%) and burst strength (87.8%) improvements were found in the ethyl acetate treatment at the first recycling stage of 7.5% chemical charge level, while the highest tear strength improvement (102.6%) was found at the second recycling stage of 7.5% treatment level. It was realised that increasing the ethyl acetate concentration is usually positively correlated with all three strength properties of the sheets.