Mechanical reinforcement of methylcellulose hydrogels by rigid particle additives

Methylcellulose hydrogels are attracting considerable interest due to their unique thermo-reversible gelation. The present work focuses on the attempt to tune, control and improve the mechanical response of these hydrogels by using silica (SiO ₂ ), alumina (Al ₂ O ₃ ) and boron carbide (B ₄ C) particles, while preserving their ability to thermo-gelate. A systematic experimental study reveals the dependence of the flow stress of the hydrogel-composite on the type and size of particle additive. Methylcellulose composite hydrogels also show increased flow-stress dependence on temperature, compared to the parent hydrogel. Similarly, some of these novel composite exhibit very high strain-rate sensitivity, with up to 90 times increase of strength in the dynamic regime. Thus, the present study offers simple tools to fine-tune the mechanical properties of these highly applicable methylcellulose hydrogels, by using small amounts of additives. Of the studied composites, the best results for dynamic flow-stress increase were achieved with nanometric boron carbide particles. This could be due to the large surface area for interaction with the methylcellulose and with the particles serving as heterogenic focal points for phase-transition.