The behavior of chemical products is a function of their physical properties. And, the values of physical properties is a function of their molecular structure and composition. Thus, understanding how to manipulate physical properties is key to designing chemical products.

This poster demonstrates how physical properties affect the performance of a wide range of common chemical products:

Post Foaming Shaving Gel: the mixture of isopentane + isobutane used in many post foaming shaving gels have bubble points above room temperature and dew points below skin temperature. Thus, the propellant is a liquid when first dispensed and becomes a vapor when heated after applied to the skin.

Battery Tester: this device uses a mixture of a dye and an acid. The dye is clear at low pH (acidic) and dark at high pH (basic). The acid is insoluble in the mixture at low temperatures and very soluble at high temperatures. The mixture is used to cover a yellow line on the test strip. A weak battery heats up only a portion of the test strip, thus dissolving the acid, lowering the pH, making the dye clear, and showing only a portion of the yellow line. A strong battery heats up the entire test strip, thus dissolving the acid, lowering the pH, making the dye clear, and showing the entire yellow line.

Incandescent Light Bulb: originally, light bulbs contained a tungsten filament inside an evacuated glass bulb. However, over time, the inside of the glass would darken and the filament would break. What was happening was that the tungsten was evaporating from the high temperature filament and condensing on the lower temperature glass. To reduce this process, an inert gas was placed inside the bulb. This inert gas, if it had the right properties, would reduce the rate of diffusion of the tungsten and thus extend the product life of the light bulb.

Flatting Additive: one method for designing a coating with a flat finish versus a gloss finish is to incorporate many small particles into the formulation. Once the coating dries, these small particles will cause a microscopically rough surface which reflects incoming light in many different directions. One problem with these small particles is that they are typically of a higher density than the surrounding formulation causing them to settle to the bottom of the container. Coating each particle with a low density wax can make the particle neutrally buoyant and thus eliminate settling.

Hand Cleaners: to remove greases and oils, a hand cleaner must be lipophilic. To be able to be removed by water, a hand cleaner must be hydrophobic. To accomplish these two opposing goals, hand cleaners are formulated as an oil in water emulsion. The surfactants used should have an HLB value (a hydrophilic-lipophilic balance) in the range of 8 to 16.

Aircraft Anti-icing Fluid: to prevent the accumulation of ice and snow on the wings of an aircraft, they are typically coated with a mixture that contains a freezing point depressant and a thickener. The freezing point depressant melts incoming ice and snow and the thickener keeps the mixture from dripping off of the wing. However, this mixture must be completely removed from the wing before take-off to ensure good aerodynamic performance. This can be done by selecting a thickener that imparts a non-Newtonian, shear-thinning behavior. When the aircraft is at rest, this fluid is thick and thus remains on the wing. When the aircraft moving rapidly down the runway, this high shear causes the fluid to thin and thus shed off of the wing.

For more information on using physical properties to guide the design of chemical products, please visit our consulting webpage.