Performance and textural properties of personal care products

GELS

Hydrogels are becoming a major influence in personal care products today.

There is a need for hydrophilic, skin adhesive, biocompatible hydrogels that can be used in a variety of applications such as shampoo, hair setting gels, face masks, skin fresheners and scented gels (air fresheners). Currently there are numerous hydrogels on the market, ranging from viscous solutions to elastic solids. The reason for this recent interest is that hydrogels can act as moisturising agents and they can deliver numerous therapeutic ingredients in a controlled manner.

Hydrogels can be made from biomaterials such as carrageenan or agar, or they can be prepared from synthetic polymers. The gels are viscoelastic materials with varying gel strengths depending on the formulation. Higher solids gels yield a stiffer, more elastic gel. The current hydrogel technologies are ideal for various cosmetic and personal care applications. These gels are easy to manufacture, either as bulk solutions or preformed gels, and the gels have good mechanical strength and can be modified easily by changing certain parameters.

The physical properties of the hydrogels can be tailored to meet a variety of performance requirements. Gels can be made with varying levels of tack, gel strength or mobility. Semi-fluid hydrogels can be formulated with active ingredients for cosmetics packaged in jars or tubes. Strong, immobile hydrogels can be formed on flexible film for facial masks, or between two layers of release films for cooling-gel products. The gels form a flexible film when dried, and they rapidly hydrate when in contact with fluids.

Measuring Gel Strength, Rupture Force & Elasticity

The measurement of gel strength is of widespread interest in the manufacture of personal care products. The strength of gels can also be utilised in products such as toothpaste, creams and pastilles to modify the consistency of the required end product. Other gel properties such as gel elasticity and rupture force are also important textural characteristics. 

The properties of a gel can be measured by the mechanical resistance to stress of an aqueous gel of the material, of particular concentration. 

Using a Cylinder Probe (typically 0.5” or 1" radiused), the probe is lowered into the gelled system at a fixed rate to a distance of (for example) 15mm, which does not lead to fracture of the gel surface. The strength of the gel is assessed as the peak force (i.e. the force to reach the chosen distance) or the force to penetrate to a smaller chosen depth.

Standard probes such as that required for gelatine testing (according to the ISO Standard), as shown in Figure 13, are also available for the assessment of Bloom strength or rupture characteristics of gels  by penetrating to a greater distance if necessary (typical graph as shown in Figure 14).   

For self-supporting gels and a more fundamental test approach, the elastic moduli can be determined by compressing cylindrical shape hydrogel samples (fixed on sandpaper to avoid slip as shown in Figure 15) with a larger surface area cylinder probe at a test speed of 0.1mm/sec. Elastic moduli are determined from the initial parts of the stress-strain curves.

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.

No-one understands texture analysis like we do!

To discuss your specific test requirements, click here...

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...