Dynamic Rheology of Agar Gel Based Aqueous Binders

Dynamic rheology was used to study the gelation behavior of agar gel based aqueous binders (1–3 wt%) for powder injection molding. Typical gelation temperatures, Tgel, and liquefaction temperatures, Tliq, were 36° and 78°C, respectively. The thermal history of the gels was found to influence Tgel and the asymptotic storage modulus, G′. A higher degree of undercooling (ΔT=Tgel−Thold) enhanced the driving force for gelation. G′ master curves were created and revealed a relatively weak frequency dependence. G′ increased significantly with agar content. The shape of the gel's relaxation spectrum was found to be independent of agar content, indicating that the nature of the relaxation processes does not change significantly.