FORMULATING


67


The role of plasticizers in enhancing stability and texture


Istvan Lippai, Steve Puleo, Joelle Lamontagne, Kamela Benga, Jessica Dynda - Koster Keunen


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 moulding. Hyatt’s breakthrough, patented in 1869–1870, was the addition of camphor as a plasticizer.1


The


resulting material, trademarked Celluloid, could be softened with heat and solvent, moulded 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 skin care 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


www.personalcaremagazine.com


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 skin care, 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.2 ■ Occlusives: materials that form a continuous hydrophobic film on the skin surface, dramatically reducing trans epidermal water loss (TEWL), basically a physical barrier.3 ■ 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.4 For true emollient performance, the material


must exhibit sufficiently low viscosity and favourable 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, and bulk viscosity, parameters that are strongly temperature-dependent. Many oils, waxes, or high molecular weight


(wax) esters are either too viscous at room temperature or crystallize upon cooling, severely limiting their ability to penetrate and ‘repair’ the skin surface effectively. The classical solution to this dilemma has long


been the careful selection and incorporation of a plasticizer. By selecting an appropriate plasticizer system, the scientist can also achieve additional functional benefits, which will be discussed later in this paper.


Defining plasticizers in a cosmetic context Etymologically, the term ‘plasticizer’ derives from the Greek πλαστικóς (plastikos), meaning ‘capable of being moulded’. In polymer science, a plasticizer is formally defined as ‘a substance incorporated into a polymer system to increase its workability, flexibility, or distensibility by lowering the glass-transition temperature and elastic modulus of the material’.5 In personal care formulations, plasticizers


perform multiple critical functions. They suppress April 2026 PERSONAL CARE MAGAZINE


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152