C24-28 Alkyl Methicone is a high molecular weight silicone compound, where the alkyl group ranges from C24 to C28. It is primarily used in cosmetics for its emollient properties and ability to provide a smooth, non-greasy feel. The longer alkyl chains contribute to its performance in creating a protective barrier on the skin and hair, enhancing softness and shine.
Chemical Composition and Structure
Chemical Composition: C24-28 Alkyl Methicone consists of methicone, a type of silicone oil, modified with long-chain alkyl groups ranging from C24 to C28. The methicone backbone provides the silicone's characteristic properties, while the long alkyl chains improve its spreadability and conditioning effects.
Structure: The molecule is structured with a silicone backbone (dimethylsiloxane) and long-chain alkyl groups attached. This structure gives the compound its emollient and conditioning properties, creating a film-forming effect that enhances the texture and appearance of formulations.
Physical Properties
- Appearance: Typically a clear, viscous liquid or solid, depending on the specific formulation and temperature.
- Solubility: Generally insoluble in water but soluble in organic solvents. It disperses well in various cosmetic formulations.
- pH: Stable across a wide pH range, making it suitable for diverse cosmetic products.
Production Process
- Silicone Polymerization: Dimethylsiloxane is polymerized to form the base methicone structure.
- Alkylation: The base methicone is then reacted with long-chain alkyl groups (C24-C28) to modify its properties and improve its performance as an emollient.
- Purification: The resulting product is purified to remove any residual byproducts and ensure safety and efficacy.
- Formulation: Incorporated into various cosmetic formulations to enhance texture and provide conditioning benefits.
Applications
- Medical: Not commonly used in medical applications.
- Cosmetics: Used in hair care products (conditioners, styling products) and skin care products (moisturizers, sunscreens) to improve texture, provide a smooth feel, and enhance shine. It helps to reduce frizz and provide a non-greasy finish.
INCI Functions:
Skin conditioning agent. It is the mainstay of topical skin treatment by restoring, increasing or improving skin tolerance to external factors, including melanocyte tolerance. The most important function of the conditioning agent is to prevent skin dehydration, but the subject is rather complex and involves emollients and humectants.
Surfactant - Suspending agent. Cosmetic or pharmaceutical suspensions are known to be thermodynamically unstable and it is therefore essential to include in the formulation a suspending agent capable of dispersing any sedimented particulates and reducing the rate of sedimentation. The presence of this agent increases the consistency of the suspension medium and exerts a protective colloidal action with a surfactant action.
CAS 158061-44-0
- Food: Not used in food products.
Environmental and Safety Considerations
Generally regarded as safe for topical application (1). However, like all silicones, it should be used according to established guidelines to avoid potential allergic reactions or skin irritations. Individuals with sensitive skin or allergies should exercise caution. It is important to ensure that the ingredient is responsibly sourced and free from harmful chemicals.
References__________________________________________________________________________
(1) Nair B; Cosmetic Ingredients Review Expert Panel. Final report on the safety assessment of stearoxy dimethicone, dimethicone, methicone, amino bispropyl dimethicone, aminopropyl dimethicone, amodimethicone, amodimethicone hydroxystearate, behenoxy dimethicone, C24-28 alkyl methicone, C30-45 alkyl methicone, C30-45 alkyl dimethicone, cetearyl methicone, cetyl dimethicone, dimethoxysilyl ethylenediaminopropyl dimethicone, hexyl methicone, hydroxypropyldimethicone, stearamidopropyl dimethicone, stearyl dimethicone, stearyl methicone, and vinyldimethicone. Int J Toxicol. 2003;22 Suppl 2:11-35. PMID: 14555417.
Abstract. Dimethicone is a fluid mixture of fully methylated linear siloxane polymers end-blocked with trimethylsiloxy units. Methicone is a linear monomethyl polysiloxane. The other dimethicones and methicones covered in this review are siloxane polymers of Dimethicone and Methicone. Most of these ingredients function as conditioning agents in cosmetic formulations at current concentrations of use of < or =15%. Clinical and animal absorption studies reported that Dimethicone was not absorbed following oral or dermal exposure. Dimethicone, Methicone, and Vinyldimethicone were not acutely toxic following oral exposure. No adverse reactions were found in rabbits following short-term dermal dosing with 6% to 79% Dimethicone, yet adverse effects were noted with a hand cream formulation containing 1% Dimethicone, suggesting something else in the preparation was toxic. Mice and rats were dosed for 90 days with up to 10% Dimethicone without adverse effect. Dimethicone did not produce adverse effects in acute and short-term inhalation-route studies, Methicone and Vinyldimethicone were negative in acute exposure studies using rats, but Hexyl Methicone was toxic to rats at 5 mg/L delivered in small particle (mean diameter of 0.29 micro) aerosols. Most dermal irritation studies using rabbits classified Dimethicone as a minimal irritant. Dimethicone (tested undiluted and at 79%) was not a sensitizer in four assays using mice and guinea pigs. It was not a sensitizer at 5.0% in a clinical repeated insult patch test using 83 panelists. Most ocular irritation studies using rabbits classified Dimethicone as a mild to minimal irritant. Dimethicone was tested in numerous oral-dose (using rats) and dermal-dose (using rats, rabbits, and monkeys) reproductive and developmental toxicity studies. In a few studies, treated males had significantly decreased body weight and/or decreased testes or seminal vesicles weights. No treatment-related adverse findings were noted in dosed pregnant females or fetuses. Dimethicone was negative in all genotoxicity assays. It was negative in both an oral (tested at 91%) and dermal (tested at an unknown concentration) dose carcinogenicity assay using mice. The Cosmetic Ingredient Review (CIR) Expert Panel considered it unlikely that any of these polymers would be significantly absorbed into the skin due to their large molecular weight. Although adverse effects were noted in one inhalation study with small aerosol particles, the expected particle sizes for cosmetic products would primarily be in the range of 60 to 80 micro, and less than 1% would be under 10 micro, which is an upper limit for respirable particles. Overall, the safety test data support the safety of these ingredients at the concentrations they are known to be used in cosmetic formulations. Accordingly, the CIR Expert Panel was of the opinion that Stearoxy Dimethicone, Dimethicone, Methicone, Amino Bispropyl Dimethicone, Aminopropyl Dimethicone, Amodimethicone, Amodimethicone Hydroxystearate, Behenoxy Dimethicone, C24-28 Alkyl Methicone, C30-45 Alkyl Methicone, C30-45 Alkyl Dimethicone, Cetearyl Methicone, Cetyl Dimethicone, Dimethoxysilyl Ethylenediaminopropyl Dimethicone, Hexyl Methicone, Hydroxypropyldimethicone, Stearamidopropyl Dimethicone, Stearyl Dimethicone, Stearyl Methicone, and Vinyldimethicone are safe as used in cosmetic formulations.
