Surface Wettability of Cellulose Sponges on Effective Oil Uptake.

Designing absorbents having specific wettability toward both oil and water is the key for selective and effective oil absorption and removal. For this purpose, establishing explicit correlations between surface tension of oils and surface wettability of absorbent is crucial. In this study, we modified common low-cost cellulose sponges with various organosilanes to achieve a range of hydrophobicity/oleophilicity and then assessed their oil uptake selectivity and capability. Oil uptake was followed as mass uptake versus time and analyzed based on the spreading coefficient (S) of a liquid over a solid surface. The results showed that sponges needed to be hydrophobic, not necessarily superhydrophobic, to selectively absorb oil from an oil/water mixture. To achieve a fast uptake and a high uptake capacity, an S ≥ 0 was necessary, that is, when the sponges were completely wet by the oil. Increasing the porosity of cellulose sponge led to a slight increase in oil uptake capacity, and a greater increase resulted when bacterial cellulose sponges that consisted of smaller and more uniform voids/pores were used. S ≥ 0 could be used as a criterion for evaluating effective and rapid oil uptake for porous absorbents, especially for those containing heterogeneous pore structures, such as common cellulose sponges.

Natural Rubber Latex Foam Reinforced with Micro- and Nanofibrillated Cellulose via Dunlop Method.

Natural rubber latex foam (NRLF) was reinforced with micro- and nanofibrillated cellulose at a loading content of 5-20 parts per hundred of rubber (phr) via the Dunlop process. Cellulose powder from eucalyptus pulp and bacterial cellulose (BC) was used as a microcellulose (MC) and nanocellulose (NC) reinforcing agent, respectively. NRLF, NRLF-MC, and NRLF-NC exhibited interconnected macroporous structures with a high porosity and a low-density. The composite foams contained pores with sizes in a range of 10-500 µm. As compared to MC, NC had a better dispersion inside the NRLF matrix and showed a higher adhesion to the NRLF matrix, resulting in a greater reinforcement. The most increased tensile strengths for MC and NC incorporated NRLF were found to be 0.43 MPa (1.4-fold increase) and 0.73 MPa (2.4-fold increase), respectively, by reinforcing NRLF with 5 phr MC and 15 phr NC, whereas the elongation at break was slightly reduced. Compression testing showed that the recovery percentage was improved to 34.9% (1.3-fold increase) by reinforcement with 15 phr NC, whereas no significant improvement in the recovery percentage was observed with MC. Both NRLF-MC and NRLF-NC presented hydrophobic surfaces and good thermal stability up to 300 °C. Due to their highly porous structure, after a prolong immersion in water, NRLF composites had high water uptake abilities. According to their properties, the composite foams could be further modified for use as green absorption or supporting materials.