Hydrogenated styrene/isoprene copolymer is a chemical compound, a styrene by-product. This copolymer is used in cosmetics and skincare products for its film-forming properties and water resistance.

The name describes the structure of the molecule:

• Hydrogenated indicates that the compound has been treated with hydrogen to saturate double bonds, making it more stable. 
• Styrene and Isoprene are the monomers that form the copolymer, where styrene provides rigidity and isoprene elasticity. 

Significant substances used in the production method:

Benzene, ethenyl-, 2-methyl-1,3-butadiene.

The main raw materials for its production are:

• Styrene. An aromatic monomer that provides rigidity and strength to the polymer.
• Isoprene. A diene monomer that imparts elasticity and flexibility to the polymer.
• Hydrogen. Used in the hydrogenation process to saturate the double bonds in the copolymer, improving thermal and chemical stability.

Industrial Chemical Synthesis

• Preparation: The mixture is prepared by combining styrene and isoprene in a polymerization reactor.
• Polymerization: The styrene and isoprene monomers are polymerized together, often in the presence of a catalyst, to form the styrene/isoprene copolymer.
• Hydrogenation: The styrene/isoprene copolymer is exposed to hydrogen in the presence of a catalyst. This process hydrogenates the double bonds in the polymer, making it more stable.
• Cooling and Recovery: After hydrogenation, the polymer is cooled and recovered from the reactor.
• Purification and Modification: The polymer can be further purified and modified to achieve desired properties, such as viscosity or flexibility.

Form and Color.

 Typically appears as a clear to slightly opaque solid or viscous liquid, depending on its concentration and the formulation in which it is used.

What it is used for and where

Cosmetics

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.

Properties. Offers excellent flexibility, adhesion, and water resistance to cosmetic formulations, making it ideal for long-wear and waterproof makeup.

CAS: 68648-89-5

Commercial applications

Use in Cosmetics: This copolymer is widely used in the cosmetics industry, particularly in makeup products like lipsticks, lip glosses, and eye shadows. It acts as a film former and stabilizer, enhancing the texture and longevity of products.

Skin Care Products: Sometimes used in skin care products for its ability to form a breathable, non-occlusive film, thus helping to lock in moisture.

Safety

Styrene is a fat-soluble organic molecule obtained from the Friedel-Crafts reaction between benzene and ethylene. It is a residual monomer that can be absorbed through the skin. It can cause neurotoxic effects.

Bibliografia_____________________________________________________________________

Kraeling, M. E., & Bronaugh, R. L. (2005). In vitro percutaneous absorption of acrylamide and styrene from cosmetic vehicles through fuzzy rat and human skin. Cutaneous and Ocular Toxicology, 24(1), 65-79

Abstract.. Acrylamide (ACR) and styrene (STY) are residual monomers that remain as impurities in polymers used in hair, nail, and skin care products. These residual monomers may be substantially absorbed through skin. Acrylamide is known to be a neurotoxin in humans and a carcinogen in animals, while styrene has been reported to cause neurotoxic effects in humans and animals and carcinogenic effects in rodents. Therefore, studies were conducted to measure the extent of ACR and STY absorption in fuzzy rat and human skin relevant to exposures from personal care products using in vitro diffusion cell techniques. [14C]-ACR was applied to skin in flow through diffusion cells for 24 h using an oil-in-water (O/W) emulsion at doses of 2.2 and 13.3 μg/cm2 (fuzzy rat skin) and 0.2, 2.2, and 13.3 μg/cm2 (human skin). [14C]-ACR was also applied to human skin using a 2% polyacrylamide gel cream at a dose of 0.3 μg/cm2. [14C]-STY was applied to fuzzy rat and human skin using the O/W emulsion at a dose of 4.1 μg/cm2. The total amount of ACR or STY that penetrated into skin layers and receptor fluid at the end of the 24 h experiment was measured and expressed as the percent of applied dose penetrated. Absorption was defined as the amount of ACR or STY absorbed into the receptor fluid. At the both the 2.2 and 13.3 μg/cm2 dose levels using the O/W emulsion, ACR was rapidly absorbed through both fuzzy rat and human skin, with peak absorption occurring at 6 h. For fuzzy rat skin, total ACR penetrated was 52.9±1.3% at the lower dose level and 49.7±2.4% at the higher dose level. For human skin, total ACR penetrated was very similar with and 48.9±1.4% (0.2 μg/cm2 dose level), 49.5±4.4% (2.2 μg/cm2 dose level), and 60.6±12.1% (13.3 μg/cm2 dose level). The total ACR penetrated was reduced to 38.7±11.9% when ACR was applied using the 2% polyacrylamide gel cream (0.3 μg/cm2 dose level). The amounts of total STY that penetrated into fuzzy rat and human skin using the O/W emulsion vehicle were identical at 1.3% (4.1 μg/cm2 dose level). Although absorption of STY was relatively low, it was nevertheless rapid with peak absorption occurring at 6 h. Approximately 84–92% of the total ACR or STY penetrated was absorbed into the receptor fluid while only 8–16% of the total ACR or STY penetrated remained in the skin at 24 h. For these monomers, rodent skin satisfactorily simulated the barrier properties of human skin; there was no significant difference in ACR and STY absorption between fuzzy rat and human skin.