Why do emulsifiers with the same HLB value perform differently?
Shopping around the list of raw materials and doing proofing of recipes, I have to deal with HLB values almost every day.Whether it is the deployment of daily water lotion, moisturizing cream, or the development of sunscreen, makeup, and care products, everyone will look at the hydrophilic and oleophilic balance value of the Emulsifier for the first time.Over time, many people have formed a fixed thinking: as long as the HLB values of the two emulsifiers are matched, the effect of use will not be much worse.
After getting started and practicing, many people will encounter a situation: two emulsifiers with exactly the same HLB value are packed into the same formula, and the state of the finished product is very different.Some samples are still evenly textured after a month, and some are layered and bleached in just a few days; some are moisturized and refreshing, and some are watered with a touch of water, and some are sticky and heavy when applied, and the feeling of stuffy skin is obvious. Even the color and fineness seen by the naked eye are clearly distinguished.
Many novice formulators are confused about this. Obviously, the reference standards are the same. Why is the landing effect different?In fact, the answer is very simple: HLB is just a reference number, it is not the only yardstick for judging the strength of emulsifiers.In the field of daily chemical product research and development, relying on a single value to select raw materials is itself a misunderstanding that is easy to step on.
Numbers are only appearances, and molecular structure is the inner background.
The calculation logic of the HLB value is to count the ratio of the hydrophilic group to the oleophilic group of the emulsifier, which is equivalent to making a simple label for the raw material, which cannot show the complex molecular morphology.This also means that the same value does not mean that the molecular structure is similar.
There are a wide range of emulsifiers on the market, including polyoxyethylene structure, polyglycerol structure, long fat chain, branched chain molecules..., so that even if you have the same HLB raw materials, the behavior patterns in the oil-water system are very different.When the grease is dispersed into the water, the emulsifier will actively gather on the surface of the oil droplets to form a protective film. The density, toughness, and arrangement of this film determine the stability of the entire system.
Some emulsifiers have compact molecular arrangements, and the protective film they build is solid and dense, which can steadily lock in oil droplets and withstand external influences such as temperature changes and transportation bumps. There are also some emulsifiers of the same value. The molecules are arranged loose, and the film formed is thin and fragile. After a little alternation of hot and cold, the entire emulsion structure will be destroyed.In actual production, in order to strengthen the bearing capacity of the system, many formulas will work synergistically with SODIUM ACRYLOYLDIMETHYL TAURATE COPOLYMER, and use the Thickening suspension system to fill in the shortcomings and further maintain product stability.
Aside from the film-forming ability, the length and branching morphology of the molecular chain will also change the basic properties of the emulsifier from the root cause.The same HLB value, the adsorption speed and space occupation of straight-chain molecules and branched-chain molecules at the interface are not the same. These subtle differences that cannot be seen by the naked eye will eventually be magnified into a huge gap in the performance of the finished product.
Oil-phase adaptability has more right to speak than digital matching
Making recipes is like building blocks. Emulsifiers are connectors, and all kinds of oils and fats are the core modules.No matter how beautiful the parameters of the connector are, they do not match the module, and the entire structure still cannot be used normally. This is also the biggest shortcoming of the HLB value-it cannot reflect the adaptation relationship between the emulsifier and the grease.
There are many types of oils and fats used in daily chemical formulas, and the polarity and molecular characteristics of different oils and fats are different.The commonly used C12 15 alkyl benzoate, vegetable oils, synthetic esters, isoalkanes, etc. have obvious differences in characteristics between each other.Two emulsifiers with the same HLB may have full affinity for a certain type of grease, and when they are placed in another grease system, they will have problems of insufficient binding and insufficient dispersion.
To give a very intuitive example, for polar non-polar oils and fats, highly adaptable emulsifiers can be quickly integrated into the system to achieve the best oil-water balance, while another emulsifier of the same value, even if the theoretical parameters are up to standard, will slowly separate oil and water due to insufficient compatibility with grease.Compared with the value, the fit between grease and emulsifier is the key to determining the success or failure of emulsification.
Skin feeling, appearance and structure
Emulsifiers with the same HLB value can create a product that has a skin feeling that can go in two different directions.Some emulsifiers have excellent liquid crystal structure formation ability. During the application process, the internal moisture will be slowly released, the touch is delicate and silky, and the moisturizing feeling is full. Whether it is daily skin care lotion or light sunscreen, it is very suitable. Other types of emulsifiers tend to form a closed oil film, which is full of moisturizing power, but the ductility deteriorates, and the heavy film will make oily skin and mixed oily skin feel stuffy.
The line of sight then falls on the appearance of the product, the particle size of the milk droplets directly determines the visual texture, and the particle size is also determined by the structure of the emulsifier.Emulsions with small and uniform particle sizes look transparent and delicate, and have a full sense of high-grade. Systems with large milk droplets will appear muddy and heavy as a whole.Especially in the makeup industry, such differences will be infinitely magnified.In pre-makeup, concealer, and soft-focus products, many formulas will add Dimethicone vinyl dimethicone crosspolymer to optimize the texture. With different emulsifiers, the final soft-focus effect and silky touch also have their own characteristics. These rich use performance cannot be predicted in advance by relying on HLB values.
The makeup category itself has more special requirements for raw materials, and it has also spawned an exclusive application system, the Emulsifier makeup special emulsion system, which has standards that are different from ordinary skin care formulas.The requirements of powder compatibility, film-forming speed, and makeup-holding ability are superimposed layer by layer. Even if the HLB value of many conventional emulsifiers is up to standard, it is difficult to meet the demanding needs of makeup. This is also an important reason why skin care emulsifiers and makeup emulsifiers cannot be mixed. The reason.
The formula is an overall project, and a single parameter cannot support a complete system.
Modern daily chemical formula, compound matching and multi-raw material synergy are the mainstream gameplay in the industry.A qualified finished product contains dozens of raw materials such as emulsifiers, thickeners, active ingredients, preservatives, and flavors. All ingredients affect and restrict each other to form a complete system.
The HLB value is set for a single emulsifier, and the reference value will decrease significantly in the face of intricate complex ligand systems.The electrolytes, active substances, and high-molecular polymers in the formula will all change the original interfacial behavior of the emulsifier.The original stable performance of the emulsifier, after being combined with a specific active ingredient, the state may go down sharply, while another emulsifier with the same HLB value can coexist harmoniously with various raw materials to maintain the stability of the system.
It is precisely because of this that professional formula research and development will not regard HLB as the final answer.When screening raw materials, everyone will first use HLB to delineate the approximate range, and then test them one by one based on oil characteristics, molecular structure, skin feeling requirements, and application scenarios.From standing at room temperature, circulating at high and low temperatures, to simulating transportation vibration, after rounds of testing, the true strength of the emulsifier of the same value will be completely revealed.
Look at the HLB value rationally: it is the starting point, not the end point
Objectively speaking, HLB, as a classic theory that has been used for many years, is an essential knowledge for getting started with formulas. It can help practitioners quickly distinguish between hydrophilic and oleophilic properties, complete the preliminary screening of raw materials, and find the general direction for formula construction.For the rapid elimination of obviously mismatched raw materials, HLB still has irreplaceable practical value.
However, industry technology is constantly upgrading, and product demand is becoming more refined. The idea of relying only on a single parameter for research and development will not keep up with the current market rhythm.From skin care, care to makeup, consumers have higher and higher requirements for product stability, skin feeling, appearance value, and experience. This requires formulators to think outside the digital realm and gain an in-depth understanding of the molecular properties, interface behavior, and compatibility of emulsifiers.
In today's field of daily chemical research and development, knowing how to distinguish the limitations of HLB and combining all system thinking to do formula design is the core ability to be based on the industry.A simple HLB value can open the door to the formula for you, but if you want to create a high-quality, stable, and outstanding product, you always rely on a comprehensive understanding of raw materials, systems, and application scenarios.
Stop being bound by a single number of ideas, and jump out of misunderstandings, so that you can go further on the road of formula research and development.
Hubei Mingya New Material Technology Co., Ltd.
