Rheological design of thickened alcohol-based hand rubs.

Area of Science:

• Rheology
• Consumer Product Design
• Material Science

Background:

• Consumer acceptance of hand sanitizers hinges on handleability and sensory perception.
• Poor rheological properties can lead to under-dosing (spillage) and under-utilization (undesirable hand feel).

Purpose of the Study:

• To establish design principles for the rheology of thickened alcohol-based hand rubs.
• To evaluate microgel and linear polymer formulations against these principles for optimal handleability and sensory properties.

Main Methods:

• Proposed four key rheological design principles: low runoff, spreadability, smoothness, and non-stickiness.
• Evaluated commercial and simplified hand gel formulations thickened with microgels (Carbopol 974P, Carbopol Ultrez 20, Sepimax Zen) and linear polymers (Jaguar HP 120 COS).
• Assessed formulations using shear thinning behavior, yield stress, low-shear viscosity, and filament breakage time.

Main Results:

• All tested additives achieved acceptable spreadability through shear thinning.
• Microgels provided yield stress and linear polymers increased low-shear viscosity, both contributing to low runoff.
• Linear polymer formulations exhibited filament breakage, potentially causing stickiness and a suboptimal hand feel.

Conclusions:

• Microgels offer a promising route to achieving desirable rheological properties for hand sanitizers, balancing low runoff and spreadability.
• Linear polymers may lead to undesirable sensory attributes like stickiness due to their rheological behavior.
• Further optimization of thickening agents is needed to enhance consumer experience and ensure effective hand hygiene outcomes.