Superabsorbent polymers (SAP), which are widely used in the food, agricultural and personal care industries, can absorb water at hundreds of time their own weight. The most common superabsorbent, sodium polyacrylate is non-renewable. Here, nanocellulose-based superabsorbent are produced from hardwood kraft pulp as a renewable and sustainable absorbent material. TEMPO-oxidised cellulose nanofibre (TOCN) foams of varying concentrations and surface charges were frozen and lyophilised. The resulting aerogel absorbency was tested in water and saline. Aerogel of 0.5 wt% fibre consistency frozen at -86oC showed the best performance (125 g H2O/ g fibre). Mapping the porous structure showed a wide size distribution ranging from nano to micron sizes. Increasing fibre surface charge increased absorption capacity due to large amount of participating carboxylic groups. To improve the wet strength of the aerogel, polyelectrolytes of different molecular weights and charge densities were mixed with TEMPO-oxidised nanocellulose fibre at high COO- content under strong shear. The addition of amine groups improved the mechanical strength of the composite by crosslinking nanocellulose with polyelectrolyte. The free swell capacity of the polyelectrolyte-TOCN composite (75g/g) also increased in saline compared to nanocellulose foam (60g/g) due to introducing positive amine group in the structure. These superabsorbent composites can be engineered by controlling polyelectrolyte addition, charge density, and fibre concentration to govern the structure-property relationships. Nanocellulose based superabsorbents represent an attractive biodegradable renewable alternative for various superabsorbent applications.

Nanocellulose-polylelectrolyte superabsorbent composites

2019 Spring National Meeting

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