Performance and textural properties of personal care products

PEELABLE PERSONAL CARE PRODUCTS

Measuring Peeling Characteristics

There are many personal care products which rely upon a good peeling function as their primary physical characteristic. 

Medical bandages, sanitary towels, and nappies are just a few examples of products that at some point will require to be peeled from skin or another surface and therefore this adhesive strength will need to be measured in order to be monitored and/or controlled. Waxing strips are used as a method of hair removal at home and are typically treated with wax to remove hair. 

The benefit of waxing strips are that they do not require a heat source in order to grip the hair. Whether applying cloth strips to heated wax on unwanted hair in a salon or whether using formulated strips for home-use the success of this treatment is based on the adhesive interaction that occurs with the hair in order to remove it when the strips are peeled off.

Tackiness of the strip can be measured with the aid of temperature control by securing onto a Peltier Plate (Figure 16). The Peltier Plate provides a constant controlled testing platform to equilibrate the sample, thus providing a more accurate measurement. Temperature affects adhesion properties and so testing the adhesive strength of wax strip samples at a constant temperature (e.g. 35°C for skin) on a Peltier Plate may be the preferred method.

During an adhesive test, the probe (typically a domical probe or 1" diameter spherical probe) descends to begin the bonding process and maintains the pre-determined compression force for the dwell time. During this stage the viscosity of the wax, the duration of the dwell and the chemistry of the materials will affect the strength of the created bond. The probe then begins to withdraw and the adhesive wax elongates while stressing the just-created bonds. The sample is bonded adhesive side up to the test platform using double sided adhesive tape for successful measurement.

Alternatively, for improved sample mounting and the quick transition to the next test site (but without temperature control), the Multiple Holed Plate in conjunction with an Adhesive Indexing Rig (Figure 17) is suggested. This rig allows a strip to be held under a plate which accommodates 10 testing holes. A 7mm diameter domical probe is employed to centrally enter each one of these indexed holes. Information that can be obtained from the curves includes area under the curve, peak force and distance to separation.

If a measure of the adhesive strength between the wax strip and a skin sample is required, then a Flexible Substrate Clamp (also in Figure 17) is suggested, whereby the strip is gripped via a clamp, allowing the exposed wax surface to be presented above 10 indexed test slots. During the test the wax strip enters each slot and repeatably contacts and withdraws from the skin sample. 

However, the peel strength of wax strip formulations is likely to provide the most imitative objective test and can be investigated using neonate porcine skin secured to a sliding platform of a 90 Degree Peel Rig (Figure 18) using cyanoacrylate adhesive. A strip of defined width is attached to the skin and the end clamped with a tensile grip attached to the arm of the Texture Analyser. The clamp then moves upwards while simultaneously the sliding section is free to move horizontally, such that the angle formed at the interface between the film and skin is maintained at approximately 90 degrees. Peel strength is recorded as the maximal force per unit length of the separating interface.

Alternatively a 180 Degree Peel test can be carried out against a chosen rigid material (Figure 19); these have traditionally  been popular. For accurate peel strength measurement, a constant force application before removal is required and can be difficult to regulate. This can be facilitated by either a manual or automatic roller. 

There is a Texture Analysis test for virtually any physical property. Contact Stable Micro Systems today to learn more about our full range of solutions.

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For more information on how to measure texture, please visit the Texture Analysis Properties section on our website.

The TA.XTplus texture analyser is part of a family of texture analysis instruments and equipment from Stable Micro Systems. An extensive portfolio of specialist attachments is available to measure and analyse the textural properties of a huge range of food products. Our technical experts can also custom design instrument fixtures according to individual specifications.

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Watch the video below to see a summary of the types of testing possibilities that are available for the measurement of cosmetic and skincare products.



You can also visit our website's Cosmetics and Skincare Applications page...