Rheology properties of Dodecyl-β-D-maltoside stabilised mineral oil-in-water emulsions

• Main Authors: Niraula, B., King, T.C., Misran, M.
• Format: Article
• Published: 2003
• Subjects: QD Chemistry
• Online Access: http://eprints.um.edu.my/6857/
• Institution: Universiti Malaya

Rheology properties of dodecyl-β-D-maltoside stabilized mineral oil-water (o-w) emulsions were studied. A strain controlled Rheometer was used for this purpose. Shear sweep was carried out to observe the η(γ) behavior, whereas oscillatory sweep was carried out to observe the G�(�) and G�(�) behaviors. All rheology properties examined in this work including η(γ), �(γ) G�(�) and G�(�) were found to be exhibiting typical non-linear power law dependence. η-γ profiles suggested that these sample do not exhibit zero shear rate limiting viscosity and terminal relaxation time, that η of these samples decays exponentially as a function of both the γ and surfactant concentration with a characteristic power law index, exponent of which decreases with surfactant concentration. Plot of �(γ) suggested that � was not a linear function of γ at low-shear rate domain, but an exponentially growing function with a certain power exponent. At zero shear rate the stress response was not zero, implying that samples under investigation were shear thinning non-ideal plastic-like materials, with characteristic �Y response. Much like η which increased with surfactant concentration at any given shear rate, both �Y and η0 increased with surfactant concentration. Analysis of � dependence of dynamic moduli suggested that at a very low � domain below 1Hz, the G� response of these samples was dominant over G� response, and that the G� response was a more or less a linear function of �, suggesting that these samples are solid-like materials. On the other hand, at higher � domain beyond 1Hz, the G� response of these samples was dominant over G� response, but neither G�(�) was found to be a linear function of � 2, nor G�(�) a linear function of �, implying that the samples under examination were neither liquid-like nor solid-like materials. These in turn suggested that these samples cannot be characterized by Maxwell model type fluid flow behavior. Both the dynamic moduli decreased with surfactant concentration. Cole-Cole plot representing G� response against G� strongly deviated from the usual semi-circle characteristic of Maxwell model type fluid flow behavior, further confirming that these samples do not exhibit Maxwell model type fluid flow behavior. While tanδ grew linearly as a function of �, it was comparably high in both the low and high � domain, implying that these o-w emulsion exhibited more liquid-like viscous behavior than solid-like elastic behavior. The tanδ was both � and surfactant concentration dependent. While it decreased with both the surfactant concentration and � at low-frequency domain, it was almost independent of both the surfactant concentration and �.