Porous material preparation via hydrogel slurry templating technique

Rutkevicius, Marius

Abstract

A novel route for porous and composite material fabrication by templating materials over hydrogel slurries has been developed. The introduction of porosity was achieved by evaporating the water from the incorporated hydrogel particles and thus creating voids within the composite structure. The size of the hydrogel beads was tuned selectively making the technique particularly attractive due to the possibility to fabricate materials of different pore sizes. In addition to this, the technique is environmentally friendly as it does not require to use organic porogens or synthetic particles, but is based on naturally available gelling agents.

The technique was applied to produce porous building materials: cement, gypsum, clay-cement and PDMS. It was possible to introduce up to 75 vol% porosity within these materials using hydrogel slurry templating. The density reduction of these materials would allow easier transportation of building materials and the high porosity showed improved performance in acoustic absorbance of the materials and could lead to an efficient thermal insulation. Scanning Electron Microscopy analysis of porous cement composites showed formation of fibrous domains within the voids of the structure, which are believed to assist the classic sound absorption mechanisms by an additional dissipation of the sound energy. The sound absorption was particularly increased with smaller pore size and a higher degree of porosity within the composites. The reduced mechanical strength of these porous composites makes them suitable for fabrication of non-strength bearing soundproofing panels.

The technique was also applied to the production of porous food formulations: porous bouillon cubes and hollow-shell salt marbles. The porous bouillon cube composites dissolved faster compared to the non-porous samples, moreover, the reduction in the mechanical strength of the porous composites showed that they would be easier to crumble by the consumer, which makes them very attractive for industrial applications. Hollow-shell salt marbles were prepared by spray-gelling a hot hydrogel solution onto a bed of finely milled salt crystals. After coating the surface of the hydrogel with salt, the water from the core of the marble was evaporated producing hollow-shell salt particles. Upon dissolution in water, these marbles changed the solution conductivity faster than table salt, showing that such marbles would give saltier taste to the consumer with less amount of salt used. The produced particles could find an application in seasoning of dry foods such as crisps and could also be used in baking.

Finally, the hydrogel slurry templating technique was applied to produce composite soap-hydrogel bars. The increase in the hydrogel content within the composites slightly reduced the release of surface active ingredients upon dissolution in water, but due to the change in the texture of the composites the release could also be increased if stress was applied to the composite. The application of hydrogel slurry templating in soaps could reduce the environmental impact of detergents released from the disposed unused soap bars in the hotels.

Citation

Rutkevicius, M. Porous material preparation via hydrogel slurry templating technique. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4221434

• Thesis Type: Thesis
• Deposit Date: Apr 10, 2019
• Publicly Available Date: Feb 23, 2023
• Keywords: Chemistry
• Public URL: https://hull-repository.worktribe.com/output/4221434
• Additional Information: Department of Chemistry, The University of Hull
• Award Date: Mar 1, 2014