Reinforced absorbent material: a cellulosic composite of TEMPO-oxidized MFC and CTMP fibres

This research aims to develop new materials based on renewable resources that can fulfill the functions necessary in the absorption core of a disposable diaper. Absorbent foam was recently produced from softwood kraft pulp by TEMPO oxidation, disintegration and freeze drying. In this study, the TEMPO-oxidized MFC was mixed with pulp fibres, thus forming a cellulosic composite, in an attempt to improve the mechanical stability of the freeze-dried absorbent material. The fibres were added in different amounts and the freeze-dried materials were evaluated for their absorption and retention properties. The results of this study suggest that the composite material has a better mechanical stability than the absorbent foam without fibres. It was shown that using spruce CTMP fibres in the composite resulted in better absorption and retention capacities than in a composite with softwood kraft pulp fibres. The higher stiffness of the CTMP fibres is a probable explanation for this difference. For the composite material with CTMP fibres, liquid porosimetry showed that pore size distribution was more or less retained when put under load. Furthermore, it was seen that the retention properties reached a maximum around 85 % CTMP fibres and 15 % TEMPO-oxidized MFC. In the centrifuge retention test, the retention of the TEMPO-oxidized MFC in the composite material reached about the same capacity as conventional superabsorbent polymers.