Thermal Stability of Creams, Ointments, and Other Cosmetics by Non-Contact Technology

oct 19 2018

Microstructural thermal stability determines the likelihood of a material to undergo phase transitions in response to thermal stress, which may occur due to the manufacturing process or storage conditions. It is a critical metric in the formulation of complex solutions containing lipids such as fatty molecules or oils.

Numerous care products such as creams, ointments, and cosmetics use lipids like wax as the structural carrier for coloring agents or emollient materials. These organic products are used to minimize the presence of chemicals for concern and ensure that care products are safe for application. The downside of this practice is the complex mechanical and thermal stability of constituent parts within the component. Wax blends are difficult to incorporate into a formulation and are generally prone to phase transitions when subjected to thermal stress. Lipids in creams and ointments may, therefore, be responsible for the development of undesirable heterogeneities in end-product cosmetics.

These heterogeneities can arise in cosmetics at almost any stage of the manufacturing and storage processes and may result in poor product quality in terms of both performance and aesthetics. Thermal instability is directly responsible for multiple common product failures. Lipsticks that crack and begin to exude fluid are likely to have undergone polymorphic phase transitions due to the unsuitable thermal stability of one or more of its constituent wax species.

Crystal formation within creams and ointments is also attributed to thermal stress. Ointment formulations contain waxes that are often co-crystalized (crystallization is favored by the wax and leads to a higher melting point). During thermal cycles, different lipid phases melt and separate to re-crystalize together, but separately from other phases.

Thermal Stability Analysis

Analyzing the thermal stability of creams, ointments, and cosmetics requires a non-contact assessment of the product’s microstructure in response to elevated temperatures. This is due to the stringent demands of cosmetic quality assurance. The benefit of non-contact tests is that the sample structure is not denaturated by the experimental conditions.

Common thermal stress tests are used to: ensure the highest quality of care products; and evaluate the behavior of the material under thermal stress that is characteristic of standard use conditions, and conditions throughout the product’s lifespan.

The Rheolaser CRYSTAL is an advanced thermal stability analyzer that was engineered for non-contact analysis on macroscopic sample materials. It measures the micro-dynamic evolution of a sample as a product of time and temperature, providing an accurate analysis of phase transitions in relation to simulated service conditions. This process of accelerated aging is monitored across multiple temperature cycles to give the most accurate picture of a product’s thermal stability across its full lifecycle. Phase transition temperature is directly monitored on the sample with an IR probe which guarantees an accurate and reliable temperature profile.

This technology provides a rapid assessment of the thermal stability of complex formulations with heterogeneous constituents. It operates across a dynamic temperature range of 4 – 90°C with a fast temperature ramp speed of 0.1 – 25°C/minute.

The Rheolaser CRYSTAL has proven successful in material characterization and quality assurance in the cosmetics industry, providing long-term thermal stability analysis of various products. This can be used to accurately characterize the potential for failure due to thermally-dependent phase evolutions.

Thermal Stability Analysis with Formulaction

Formulaction products represent some of the most advanced analyses for complex formulations currently available. We have developed a wide range of material analyzers suitable for characterizing formulations in an array of industrial and commercial sectors.

The Rheolaser CRYSTAL is uniquely suited for assessing the thermal stability of products as varied as food and beverages, pharmaceuticals, and cosmetics. If you need any more information, please do not hesitate to contact us.

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