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Because of the unique properties of volatile siloxane fluids, they have numerous uses in a variety of industries. Their low heat of vaporization and smooth, silky feel make them especially attractive for use in personal care products.
In the past, one of the limitations of lower-molecular-weight materials has been their low inherent viscosity. Depending on the product form, they might not be a viable option. Over the past few years, however, Dow Corning has developed a number of rheology modifiers for low-viscosity siloxanes with extensive commercial applications.
Adding Higher-Viscosity Molecules
The most obvious way to impact lower-viscosity materials is to simply add higher-viscosity molecules to achieve an intermediate viscosity blend. The resulting material is likely to have properties of both materials – rather than intermediate properties.
For example, Dow Corning has gum-in-cyclics and gum-in-fluid blends that have higher viscosities than the cyclics/fluid without added gum and that also possess the characteristics of the individual components. Products that use these materials benefit from the smooth, silky feeling imparted by the volatile fluids, while deriving a desirable “after-feel” from the gum in the mixtures.
Using Rubber To Thicken
Silicone rubber chemistry gives rise to Dow Corning’s “higher tech” solutions for thickening low-molecular-weight siloxane fluids. There are a number of commercial products – and more on the way – that possess either:
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Small, pre-cured spherical rubber particles, or
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Irregular elastomeric particles that are swollen with silicone fluid as they are cured
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Premium E-Powders – Specially manufactured silicone rubber particles are typically called “E-Powders” and result from the curing of the particles in an emulsion matrix. Available as a dry powder or a suspension in water, these particles derive their unique sensory properties from:
• The rubber’s cross-link density
• The small, perfectly spherical shape of the particles
It is the combination of these two factors that give products containing E-Powders such a different feel – one can actually feel the sensation of the small “ball bearings” rolling on the skin. This premium “feel” characteristic commands high value in the skin-care marketplace.
A secondary benefit of E-Powders is their ability to absorb low-molecular-weight siloxanes and select organics. They swell with these fluids, thus providing a thickened matrix.
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Rubber particles, or "E-Powders," provide premium "feel" in skin care products; can be used as thickeners; and are used in fire extinguishers to combat electrical fires. |
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Matrix-cured elastomers – The desire for a thickened matrix from a more cost-effective product than the premium E-Powders yielded Dow Corning’s “matrix-cured” silicone elastomer product line.
These materials provide a very silky feel that lasts long after application. Because they employ relatively simpler process technology, their cost structure allows them to be formulated into more cost-sensitive products, such as antiperspirants. Additionally, the chemistry of these systems is robust, allowing Dow Corning to impart a difference in properties by altering our process slightly or by adding functionality to the elastomers.
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Dow Corning scientists work with gelant technology for improved personal care applications. |
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Controlling solubility has been one strategy to produce new products that are more compatible with organic materials or water. This has led to a unique "emulsifying elastomer" that allows customers to prepare high internal phase water-in-silicone emulsions without the use of high-shear equipment. This technology advance has opened up this product option to our customers who could not previously afford to prepare these “high tech” emulsion products. The matrix-cured elastomers have been extremely successful to date, and more product versions are planned that target your specific unmet needs.
New Silicone Poly(amide)
With the previous materials in our arsenal, you might wonder why Dow Corning needed yet another “thickener” when we started developing a new silicone poly(amide). The reason is not difficult to understand when you realize that all of the prior commercialized options thickened efficiently but were poor to moderate structurants. By “structurants,” we mean that most gelled or highly viscous product forms continued to rely on organic components for their mechanical integrity.
Using silicon chemistry in a way that had not been previously explored, we have produced a high-molecular-weight, thermoplastic silicone poly(amide) copolymer that has value in a variety of products, such as:
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Antiperspirant and deodorant sticks, gels, and roll-on products
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Skin care lotions and creams
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Lip products
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Hair care products
This copolymer has a unique feel, which is “harder” than most of our other product solutions and yields products with enhanced “glide.” It also has the capability to form solid products with significant strength when compared with other siloxanes – and even with many organic structurants!
It has also been found that this material’s structuring properties add sensory benefits to existing formulations when used at the additive level. We continue to explore this chemistry set to better understand what features and benefits can be derived from silicone poly(amides).
Beyond Personal Care
Many of our entrepreneurial customers outside of the personal care areas have found unique ways to use our rheology modifiers to thicken products and utilize the unique sensory benefits. There are specific uses in:
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Textile treatments
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Coatings
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Leather/synthetic leather treatment
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Polishes
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Plastics modification
We anticipate even more applications as our product offerings expand.
Dow Corning is not “resting on our laurels.” Further work is uncovering new possibilities for next-generation products. We are developing materials that deposit better, are more substantive to surfaces, and can be delivered from a variety of matrices.
Learn more about the many industries that Dow Corning has helped.
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