Regioselective oxidation of recycled cellulosic fibres for enhancement in the mechanical strength of resulting papers

Abstract

The worldwide recycling rate for paper is about 60% and there are ongoing efforts to enhance the recycling rates to 80%. The low strength of recycled paper primarily due to the contaminants in it fetches lower value to the recycled paper in the market and also limits its recyclability. The ways to circumvent the problem of contamination of paper have been addressed by adding additives. However, the use of additives increases the cost of the final recycled paper. Oxidation has been explored as an alternative to enhance the tensile strength of paper in this work as it can be used in existing paper recycling facilities without any modifications. Pulp fibres were collected from an active paper recycling mill and subjected to oxidation at various oxidation levels from 0.25 up to 1.5 mmol/g. It was found that the tensile strength of the paper increased by up to 89% with an increase in oxidation level up to 1 mmol/g and later decreased with a further increase in the oxidation level up to 1.5 mmol/g. The brightness of the paper increased by up to 3% with an increase in oxidation level up to 0.85 mmol/g and then a decrease with further enhancement in the oxidation level. The oxidized samples were also studied with infrared spectroscopy, x‐ray diffraction, electron microscopy, and optical properties to study the behaviour of the resulting material. A ring crush test and corrugating medium test were also performed on the oxidized pulp samples to establish the feasibility of the material for packaging applications.