Water is commonly used as a fire suppression agent for Class A fires. The effectiveness of water as a fire extinguisher can be improved by adding additives, such as emulsifiers, thickeners, and surfactants. However, most firefighting gels have poor wettability on combustibles due to high viscosity. Thermosensitive Hydrogels, which exhibit excellent fluidity and wettability at room temperature and turn into gels at a lower critical solution temperature (LCST), have recently gained attention for their unique characteristics.
Natural hydrogels, including cellulose and chitosan (CS), are widely available and thermosensitive. Hydroxypropyl methylcellulose (HPMC) is a non-ionic cellulose ether with great thermosensitivity, water retention, and adhesion thickening. CS is a biodegradable amino polysaccharide with a similar structure to HPMC. HPMC/CS thermosensitive hydrogels can be formed by intermolecular hydrogen bonding between the hydrophilic moieties of HPMC, CS, and water. Previous studies have synthesized HPMC/CS hydrogels with good thermosensitivity and minimal cytotoxicity. However, these hydrogels have limitations in phase-transition response time and the stability of the gel structure after dehydration.
To address these limitations, poly(ethylene glycol) (PEG) can be added to HPMC/CS mixtures to improve hydrophilicity and rheological properties through physical cross-linking. The wettability of thermosensitive hydrogels is crucial for their fire extinguishing performance, and gels with a porous structure can enhance swelling capacity, water-retaining capacity, and mechanical strength.
This study focuses on the development of Thermosensitive Porous Hydrogels based on a mixture of HPMC/PEG/CS. The spreadability, wettability, and adhesivity of the hydrogels during phase transition were investigated. The results can contribute to the development of a new type of water fire-extinguishing agent.
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