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Screening a successful emulsifier combination for the system can be time consuming. The hydrophilic-lipophilic balance (HLB) system was created to aid in the selection of an effective non-ionic emulsifier combination to match the calculated required HLB (RHLB) value of the oil to be emulsified.
However, this tool can only be served as a simple formulating guideline since it was invented for ethoxylated or traditional non-ionic emulsifiers. It has gradually become insufficient for the modern essential oil-free emulsifiers and formulas of increased complexity. Many formulators now seek to achieve long term stability with the addition of polymeric emulsifiers.
Pemulen™ polymeric emulsifiers are high molecular weight crosslinked acrylic copolymers. Hydrophobically modified with C10-30 alkyl acrylate comonomer, they are best described as hairy microgels when neutralized by a base.
These microgels can anchor their lipophilic portion into the oil droplets while their hydrophilic groups create a compacted gel network; hence, providing emulsion stabilization through both associative stabilization and particle suspension. This comprehensive emulsion stabilizing mechanism allows these polymeric emulsifiers to form cost effective oil-in-water emulsions with any oil phase, regardless of their required HLB.
Due to the electrolyte sensitivity of these polymers, their microgels deswell quickly on contact with the electrolytes of the skin, providing immediate oil deposition and a refreshing sensory experience.
Pemulen™ polymeric emulsifiers can be used to support the growing prevalence of conventional emulsifier-free claims. Because of their emulsion stabilizing efficiency, Pemulen™ polymeric emulsifiers can be used as a sole emulsifier at low use levels (0.1-0.4%) to replace traditional emulsifiers.
The benefits of a conventional emulsifier-free formulation may include low irritation, light sensory, and water resistant properties as these polymers do not lead to re-emulsification upon rewetting.
Lubrizol currently offer three grades of acrylate-based polymeric emulsifiers.
- Pemulen™ TR-1 polymeric emulsifier generates a high viscosity emulsion, and can stabilize up to 30% of oil phase.
- Pemulen™ TR-2 polymeric emulsifier provides low viscosity emulsions, and can stabilize up to 60% of oil phase as it contains higher levels of hydrophobic groups than Pemulen™ TR-1 polymeric emulsifier. However, the downsides of the traditional Pemulen™ polymeric emulsifiers are the potential for long dispersion time, lack of efficiency at lower pH, and undesirable “cheese cake” texture which can occur through associative structuring with other co-ingredients such as fatty alcohol and fatty acids.
- To improve processing time and formulation flexibility, Pemulen™ EZ-4U polymeric emulsifier was recently developed to serve the market needs.
Extremely easy to use, Pemulen™ EZ-4U polymeric emulsifier can be used in either cold or hot processed formulations, and disperses directly into agitated water in as little as five to 10 minutes, while generating less foam than other traditional polymeric emulsifiers. This powdered polymeric emulsifier has also a high bulk density which makes it low dusting and easier to handle.
Compared to traditional polymeric emulsifier technologies, Pemulen™ EZ-4U polymeric emulsifier offers rheology modification over a wide pH range (4.0-9.0). A pH curve was generated for 0.2 weight percent polymer in water from dispersion pH up to a pH of 6. The figure below demonstrates that Pemulen™ EZ-4U polymeric emulsifier builds viscosity at a lower pH than the traditional polymeric emulsifiers, and then plateaus at a relatively low pH.
Pemulen™ EZ-4U polymeric emulsifier also provides significant emulsion stabilization improvement vs. other Pemulen™ polymeric emulsifiers by offering efficient yield value in use level as low as 0.05%.
One of the key advantages Pemulen™ EZ-4U polymeric emulsifier offers relative to other polymeric emulsifiers such as Pemulen™ TR-1 and TR-2 polymers is significantly improved formulation flexibility. It is well known that Pemulen™ TR-1 and TR-2 polymeric emulsifiers can demonstrate a strong interaction with other co-ingredients in a formulation (over time). This interaction leads to an undesirable change in texture of the formulation that under extreme conditions is very rigid and reminiscent of “cheesecake”. As this texture change is a result of associative structuring, co-ingredients used to structure, co-emulsify, or co-stabilize a formulation are often most problematic.
Pemulen™ EZ-4U polymeric emulsifier reduces associative structuring with other hydrophobic co-ingredients such as fatty alcohols or other co-emulsifiers in the formulation, resulting in a smoother glossy texture.
Figure 4: Reduction of the structuring effect in emulsions containing fatty alcohols, comparing 0.4% Pemulen™ EZ-4U polymeric emulsifier with traditional polymeric emulsifiers, at pH 5. Left, smooth emulsion made with Pemulen™ EZ-4U polymeric emulsifier. Right, emulsion made with traditional polymeric emulsifier with cheesecake effect
Pemulen™ EZ-4U polymeric emulsifier imparts a fresh initial feel upon application, leading to a soft, non-sticky afterfeel with a low amount of residue. When it comes to formulating mild, refreshingly smooth emulsions, Pemulen™ EZ-4U polymeric emulsifier from Lubrizol Skin Essentials provides both quality and ease of formulation.
Mild and smooth emulsions, made simple. Read how Pemulen™ EZ-4U can help with your personal care formulations.
As a leader in rheology modification technology, Lubrizol continues to invest and embody the skill as a cutting-edge solution provider. To keep up with the recent skin care technical inquiries of customers’, Lubrizol devotes to deliver solutions targeting effective thickening under challenging conditions, polymeric emulsification, and cascading sensory impact. Our mission is to become a partner to our customers and help boost their creativity with innovative concepts, strong technical and regulatory support, as well as flexibility in supply and delivery.
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