Structure – The salient consideration in determining a molecule’s properties
The HLB model developed, in 1949 by Griffin1, remains one of the most significant contributions to the field of emulsions. We use the HLB system as a pragmatic method to aide in making emulsions. While having shortcomings it provides a systematic approach to selecting emulsifiers. Despite the fact the HLB system was developed over 70 years ago, little additional data has been developed since then to advance understanding of the physical chemistry related to oil and water interactions.
In 1996, we developed a concept called 3D HLB2,3 that expanded the HLB concept to include silicone hydrophobes. Now 70 years after the Griffin system and 23 years since 3D HLB, we are again finding reason to relook at these systems and apply them to more than just emulsions.
The underlying concept is that the structure of a surface active material in fact determines the functional properties of that molecule (surface tension, wetting, emulsification and much more). Simply put, the balance between the weight percent of water soluble group and the oil soluble group will geode the formulator in selection of the emulsifier in a particular emulsion. The functionality of the polymer in formulation depends upon the specific family of surfactant chosen.
This paper will in fact show that the HLB system allows for the prediction of a lot more than just emulsification, it provides insights that will allow for the predictions of surface tension, wetting, spreadability, cushion and playtime. Additionally, it applies equally to alkyl and silicone hydrophobes.
The data presented in this article was taken from a keynote presentation made by Tony O’Lenick on June 5, 2019 at the joint conference of IPCE and ASCS in Hong Kong.
The cosmetic chemist works with two critical elements in their formulations, oil and water, which make up the majority of the weight of their formulations. The interaction between these two elements with each other and with hair or skin is fundamental to formulation of our products.
Water is a compound. It has a specific molecular formula. It also has a CAS number. It also has rather well understood properties. One of the most important properties of water is it has a very high surface tension. The high surface tension of water and how it interacts with oils is vital to life as we know it. Table 1 shows some of the properties of water.