Flowability of Gel-Matrix and Magnetorheological Response for Carrageenan Magnetic Hydrogels.

The relationship between rheological features in the absence of a magnetic field and magnetic response was investigated for κ-carrageenan magnetic hydrogels containing carbonyl iron particles. The concentration of carrageenan was varied from 1.0 to 5.0 wt%, while the concentration of carbonyl iron was kept at 70 wt%. The magnetic response revealed that the change in storage modulus Δ decreased inversely proportional to the carrageenan concentration. A characteristic strain γ where ' equals to ″ was seen in a strain range of 10. It was found that Δ' was inversely proportional to the characteristic stress at γ. Another characteristic strain γ where the loss tangent significantly increased was also analyzed. Similar to the behavior of γ, Δ' was inversely proportional to γ. The characteristic stresses at γ and γ were distributed at 80-720 Pa and 40-310 Pa, respectively. It was revealed that a giant magnetorheology higher than 1 MPa can be observed when the characteristic stresses at γ and γ are below approximately 240 Pa and 110 Pa, respectively.