Functional Solvent Overview

• 🔎 Chemical Name: 1,2-Propanediol

• 🧪 Synonyms: PG, Propane-1,2-diol

• 🧬 Chemical Formula: C₃H₈O₂

• 📂 CAS N°: 57-55-6

• 📘 FEMA: 2940

• ⚖️ MW: 76.09 g/mol

• 📝 Odor Type: Odorless

• 📈 Odor Strength: None

• 👃🏼 Odor Profile: Neutral, inert

• ⚗️ Uses: Solvent, Carrier, Humectant

• 🧴 Appearance: Colorless, viscous liquid

What is Propylene Glycol?

Propylene glycol is a synthetic, bifunctional alcohol classified as a vicinal diol. It contains two hydroxyl groups (-OH) that confer hygroscopic and hydrophilic properties. It is industrially synthesized from propylene oxide through a non-catalytic hydrolysis process. This results in a chemically stable, water-soluble molecule with low volatility and high compatibility with both hydrophilic and lipophilic ingredients. A renewable, bio-based route via glycerol is under active development to improve sustainability.

Historical Background

Propylene glycol was first described in the 19th century, but commercial synthesis did not begin until the 1930s, when petrochemical advances enabled large-scale production of propylene oxide. Initially used in industrial and pharmaceutical contexts due to its low toxicity and stability, it rapidly became an essential carrier in food, medicine, and cosmetics. Its use in perfumery emerged later with the development of water-based and alcohol-free fragrances, where solvent performance and safety are critical.

Olfactory Profile & Perfumery Applications

Although olfactorily inert, propylene glycol is a key functional ingredient in fragrance formulations. Its primary roles include:

• Solvent for polar aromatic compounds

• Diluent for essential oils and synthetic materials

• Carrier in water-based or alcohol-free fragrances

• Humectant in skin-contact and ambient spray formats

• Stabilizer in hydroalcoholic systems, enhancing miscibility

Due to its excellent sprayability and low evaporation rate, Solvet is widely used in body mists, roll-ons, air fresheners, and cosmetic formulations where alcohol use is restricted.

Industrial & Technical Uses

Outside of perfumery, propylene glycol is used across multiple regulated sectors:

• Pharmaceuticals: Excipient and solubilizer in injectable, oral, and topical products

• Food and Beverage: Carrier for flavors, humectant for baked goods (GRAS certified)

• Personal Care: Moisturizing agent in shampoos, lotions, and conditioners

• Technical: Component in antifreeze, de-icing fluids, plasticizers, and hydraulic systems

Its function as a safe, water-compatible solvent underpins widespread adoption in both consumer and industrial products.

Regulatory & Safety Overview

• IFRA: Not restricted (confirmed under IFRA 51st Amendment)

• EU Allergen List: Not listed among the 26 fragrance allergens

• FEMA GRAS: No. 2940 (approved for food use)

• REACH: Fully registered in the EU

• ECHA: Classified as non-toxic, non-sensitizing, not a CMR or endocrine disruptor

• Toxicology: Low acute toxicity; not sensitizing under standard dermal/inhalation use

• Irritation: Minimal risk; high concentrations may cause transient skin or eye irritation

Environmental Impact

• Biodegradability: Readily biodegradable in soil and aquatic environments

• Aquatic Toxicity: Low; large spills may cause temporary oxygen depletion

• Bioaccumulation: Not expected

• Sustainability Note: Bio-based PG derived from glycerol is commercially available and gaining adoption as a renewable alternative

Additional Information

• Boiling Point: 188.2 °C

• Flash Point: 103 °C (closed cup)

• Density @ 20 °C: 1.036 g/cm³

• Refractive Index: 1.432–1.435

• Solubility: Miscible with water, ethanol, acetone, chloroform

• Structure: Simple aliphatic diol with two hydroxyl groups in a vicinal (1,2-) configuration

• Code Name (Internal): Solvet

• Perfumery Format Compatibility: Excellent in emulsions, sprays, wipes, and roll-ons

• Incompatibility: Not compatible with highly lipophilic-only systems without co-solvent adjustment

Sources

• User-provided source

• Handbook of Pharmaceutical Excipients (Rowe et al., 2009)

• The Chemistry of Fragrances (Sell, 2019)

• OECD SIDS: Propylene Glycol (2001)

• FEMA GRAS Database

• ECHA Substance Information

• PubChem CID 1030

• FDA Food Additive Status List