How to Measure the Physical Properties of Cosmetic Packaging

The development of cosmetics for release into a competitive market is a high-cost endeavor, so it would be inefficient for these high stakes products to be shipped in low-quality packaging, or for the container to degrade during its shelf life. The packaging is the first thing the customer sees in the shop so from this point of view the graphics and physical design are important to make it stand out amongst other similar products. However, the main purpose of packaging is to ensure the product arrives in a customer’s hands in perfect condition and to prevent any losses caused by shipping, handling, or storage.

The majority of obstacles faced by a product can be imitated using physical testing with a Texture Analyser. Any given company will have a standard set of tests for new products or for spot-checking the quality of products already on the market. Physical testing and Texture Analysis measure the strength of each component and joint, assessing whether or not the container will continue protecting its contents after shipping or long storage time.

Shipping can be imitated using force cycle tests to represent the repeated loading the product will face during its journey, whereas storage testing may involve a timed compression with a large platen to mimic the action of stacking many products on a shelf. Bottle tops are widely-used and the strength of the cap itself is an important measure, as this influences the transportation restrictions. Points for consideration include the worst-case scenario a package may face, and what the cumulative effects will be of days of shipping or months of storage amongst other packages, or even in a cosmetics drawer in the consumer’s home.

Packaging tests will cover either the whole assembly (a whole lipstick tube), one part of the packaging (the lid of a hairspray), or a sample of the material itself (a dogbone specimen of a plastic used for a talc bottle).

Typical Texture Analysis Tests for Cosmetics Products

How to Measure Packaging Strength and Seal Strength

The absolute material strength of a product is an important part of this testing process which can easily be measured by mounting a chosen width of material in Self-tightening Roller Grips on a Texture Analyser and performing a tensile test. Adhesives are widely used in cosmetics packaging, particularly in a seam at the edge of a sachet. These are assessed by performing a T-peel test on a small section of the sachet joint, using Tensile Grips, to hold the sample in order to stretch it to point of failure.

Tensile test measurements and typical graph

The customers’ safety must also be considered, and this is relevant when testing a property such as a puncture strength of an aerosol deodorant can, which would use a needle probe (or similar small diameter cylinder probe) to perform a penetration test to measure the force required to cause failure.

How to Measure Aerosol/Dispenser Actuation Force

The forces involved in using a product must be within a suitable range for any customer ability in the intended market. For any given action (such as pulling, snapping, or pressing) an acceptable range of forces can be determined by referring to tabulated results of the forces a child, healthy adult, the elderly or infirm customer is capable of. The product container can then be tested in a quantitative way (using, for example, a Hemispherical probe shaped like a finger) on a Texture Analyser, and the forces verified. For example, if the dispensing of body lotion requires a high force to remove, it may be too difficult for some customers to use that product without assistance, rendering it inconvenient and/or unacceptable.

Actuation Force measurement

How to Measure Sachet/Tube Content Removal

Another commonly-used packaging method is polymer-based sachet. In this case, the ease of opening is determined by the tearing force, the strength of seal (from the hot press process), and friction of the material surface. When a consumer is opening the package, if the friction does not match with the tearing strength, they cannot get enough grip on the package for a high tear force and it will slip in their hands.

A Sachet/Tube Extrusion rig can also be used to measure the force to extrude the contents of a sachet or tube style packaging to allow manufacturers to quantify the ease of removal and application of cosmetic products. The rig positions the product vertically between two rollers, clamping the closed end with a grip at the top. The grip then pulls the sachet/tube upwards through the rollers, forcing the contents out whilst measuring the force required.

Sachet/Tube Extrusion Rig and a typical graph

Weathering and aging tests are often used to speed up the degradation process, especially when the product may be stored in extreme temperature environments. Heated cabinets with temperature control are the standard piece of equipment used in this case. A container is filled with its formula and heated to a specific temperature for a given time period. Once this aging is over, the container is taken back to the Texture Analyser and its physical properties are tested once again, along with an assessment of decoloration, weight loss of the contents, and stress cracking.

Testing Solution Summary

Exponent software is extremely valuable to this type of testing as standard projects can be saved to enable each set of test settings to load at the press of a button, along with automatic data analysis and report generation. A wide variety of international standards can also be built into the software. With data appearing graphically on-screen in real-time, the suite of Texture Analysers along with their expert software is ideal for use in quality control.
 

For a full summary of typical texture analysis tests that can be performed on cosmetic products:

This information has been sourced, reviewed and adapted from materials provided by Stable Micro Systems Ltd.

For more information on this source, please visit Stable Micro Systems Ltd.