The Role of Plasticizers in Enhancing Stability and Texture
INTRODUCTION
Historical Context and the Birth of Modern Plasticization
Plasticizers in Personal Care Products: From 19th-Century Billiard Balls to Enhanced Tactile Performance and Skin Penetration
The concept of plasticization traces its origins to the 1860s, during a period of acute global ivory shortage caused by the booming popularity of billiards in Europe and North America. Traditional billiard balls were carved from elephant ivory, and besides its obvious and unnecessary brutality, supply could no longer meet demand. In 1863, the American inventor John Wesley Hyatt began experimenting with nitrocellulose, a rigid and brittle polymer. Pure nitrocellulose, however, was far too stiff and explosive for practical molding.
Hyatt’s breakthrough, patented in 1869–1870, was the addition of camphor as a plasticizer.[4] The resulting material, trademarked Celluloid, could be softened with heat and solvent, molded under pressure into perfect spheres, and cooled, and hardened into a tough, glossy product. Celluloid became the first commercially successful thermoplastic and ushered in the plastics/plasticizer era.
The principle discovered by Hyatt, that certain additives can dramatically enhance polymer chain mobility without chemically altering the base polymer, rapidly found applications far beyond billiards. By the early 20th century, a number of chemistries emerged for different matrices and applications, the most demonstrative among them being PVC where a rigid construction material (e.g. window frames) can be made into a soft and stretchy film (e.g. pool liners). Eventually, these plasticizers made their way into personal care products.
Today: Basic Necessities in Skincare
Modern personal care products are expected to deliver exceptionally high sensory and performance standards: uniform texture, lasting physical stability, a non-tacky finish, and a luxurious, smooth, creamy skin feel that consumers immediately associate with premium quality. Achieving these characteristics is far from trivial when one considers the complex, multicomponent nature of typical formulations. These systems routinely combine high-molecular-weight waxes (film-formers, thickeners), inorganic pigments and fillers, volatile and non-volatile oils, surfactants, fragrances, preservatives, active ingredients, and water, each contributing with different and sometimes conflicting physical properties.
Without careful rheological and interfacial control, the final product can become (excessively) brittle, prone to phase separation, or exhibit cracking upon drying. Films may lack flexibility, resulting in flaking, or become uneven, emulsions may feel greasy or sticky. All or any of these defects can directly translate into reduced consumer acceptance.
In the specific realm of skincare, particularly moisturizing products, efficacy historically revolves around three well-established categories:
- Emollients: lipophilic substances that “repair” the skin surface by filling intercellular spaces and micro fissures in the stratum corneum, restoring smoothness and flexibility.[1]
- Occlusives: materials that form a continuous hydrophobic film on the skin surface, dramatically reducing trans epidermal water loss (TEWL), basically a physical barrier.[2]
- Humectants: molecules with some hygroscopicity, capable of binding water from the environment (or deeper skin layers, i.e. Epidermis/Dermis) and delivering it to the Stratum Corneum.[3]
For true emollient performance, the material must exhibit sufficiently low viscosity and favorable wetting properties to flow rapidly into microscopic skin crevices via capillary action. This process is governed by Young–Laplace capillary pressure, surface tension (interfacial) tension, contact angle, […]
