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Dipropylene glycol (DPG) is a colorless, nearly odorless, and hygroscopic liquid commonly used as a solvent, plasticizer, and humectant.
It is a diol with two propylene glycol units linked together, and it has low volatility and low toxicity, making it suitable for use in cosmetics, fragrances, and industrial applications.
CAS Number:
25265-71-8
Synonyms:
1,2-Propylene glycol dipropyl ether,4-(2-Hydroxypropoxy)-2-propanol,DPG, Dipropylene glycol isomers mixture,Propylene glycol dipropyl ether
Dipropylene glycol (DPG) is a versatile compound with widespread industrial and commercial applications.
Its unique physicochemical properties make it valuable in personal care products, pharmaceuticals, and industrial processes.
This review provides an in-depth examination of the chemical properties, synthesis methods, analytical characterization, toxicological profile, environmental impact, and emerging applications of dipropylene glycol.
Emphasis is placed on recent advances in green chemistry, safety considerations, and future directions for research and development.
Introduction
Dipropylene glycol (DPG) is a member of the glycol family, a class of compounds characterized by the presence of two hydroxyl groups.
Glycols are widely used as solvents, humectants, and intermediates in chemical synthesis.
DPG, in particular, is a clear, odorless, and slightly viscous liquid that is produced as a by-product of the propylene oxide hydration process.
Its compatibility with a wide range of materials and low toxicity profile make it an attractive ingredient across multiple sectors.
The objective of this review is to provide a comprehensive overview of dipropylene glycol, encompassing its chemical nature, industrial production, analytical techniques, toxicological evaluation, and environmental implications.
Through this synthesis of current knowledge, we aim to highlight the importance of DPG in modern science and technology, identify knowledge gaps, and suggest potential directions for future research.
Chemical Properties and Structure
Dipropylene glycol consists of a mixture of isomers, mainly the primary and secondary alcohol forms. Its molecular formula is C6H14O3, and it has a molecular weight of approximately 134.17 g/mol.
The compound is produced during the reaction of propylene oxide with water, leading to a mixture of mono-, di-, and tripropylene glycols.
Key physical properties of DPG include a boiling point of around 230°C, a melting point of -80°C, and a viscosity of about 100 cP at 25°C.
It is miscible with water and most organic solvents, which contributes to its versatility in formulation science.
Chemically, DPG is stable under normal conditions but can undergo oxidation when exposed to strong oxidizing agents.
It participates in typical alcohol reactions, such as esterification and etherification, and serves as a reactive intermediate in the production of polyurethanes and plasticizers.
Analytical Techniques for Characterization
Several analytical methods are employed to identify and quantify dipropylene glycol and its isomers. These include:
Gas Chromatography (GC): Useful for separating and quantifying DPG isomers, especially when coupled with flame ionization detection (FID).
Mass Spectrometry (MS): Often combined with GC for molecular identification based on mass-to-charge ratios.
Fourier Transform Infrared Spectroscopy (FTIR): Provides information on functional groups, particularly hydroxyl groups.
Nuclear Magnetic Resonance (NMR) Spectroscopy: Enables structural elucidation of different isomers through hydrogen and carbon spectra.
High-Performance Liquid Chromatography (HPLC): Suitable for non-volatile samples and can be used with refractive index or UV detection.
These methods collectively ensure accurate identification, purity assessment, and quality control in both research and industrial settings.
Industrial Production and Synthesis
Dipropylene glycol is synthesized as a secondary product during the non-catalytic hydration of propylene oxide. The process involves the following steps:
Raw Material: Propylene oxide reacts with water under controlled temperature and pressure.
Reaction Mechanism: The reaction proceeds via nucleophilic attack of water on the epoxide ring, forming mono-, di-, and tripropylene glycols.
Separation and Purification: The product mixture is distilled to separate DPG from other glycols and water.
The yield and composition of the glycol mixture depend on the molar ratio of water to propylene oxide, reaction time, and temperature.
Advances in catalyst design and process optimization have improved the selectivity and efficiency of DPG production.
Applications
DPG is utilized in a broad array of applications due to its solvency, low volatility, and hygroscopic nature:
Personal Care Products: Functions as a solvent, carrier, and humectant in lotions, deodorants, perfumes, and hair products.
Pharmaceuticals: Used as a solvent for oral, topical, and injectable formulations. Enhances drug solubility and bioavailability.
Industrial Solvents: Acts as a carrier in printing inks, paints, and coatings due to its high boiling point and solvency.
Deicing Fluids: A component in aircraft and runway deicing formulations.
Plasticizer Production: Serves as an intermediate in the manufacture of plasticizers and polyurethanes.
SAFETY INFORMATION ABOUT DIPROPYLENE GLYCOL
First aid measures:
Description of first aid measures:
General advice:
Consult a physician.
Show this safety data sheet to the doctor in attendance.
Move out of dangerous area:
If inhaled:
If breathed in, move person into fresh air.
If not breathing, give artificial respiration.
Consult a physician.
In case of skin contact:
Take off contaminated clothing and shoes immediately.
Wash off with soap and plenty of water.
Consult a physician.
In case of eye contact:
Rinse thoroughly with plenty of water for at least 15 minutes and consult a physician.
Continue rinsing eyes during transport to hospital.
If swallowed:
Do NOT induce vomiting.
Never give anything by mouth to an unconscious person.
Rinse mouth with water.
Consult a physician.
Firefighting measures:
Extinguishing media:
Suitable extinguishing media:
Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.
Special hazards arising from the substance or mixture
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas
Advice for firefighters:
Wear self-contained breathing apparatus for firefighting if necessary.
Accidental release measures:
Personal precautions, protective equipment and emergency procedures
Use personal protective equipment.
Avoid breathing vapours, mist or gas.
Evacuate personnel to safe areas.
Environmental precautions:
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Methods and materials for containment and cleaning up:
Soak up with inert absorbent material and dispose of as hazardous waste.
Keep in suitable, closed containers for disposal.
Handling and storage:
Precautions for safe handling:
Avoid inhalation of vapour or mist.
Conditions for safe storage, including any incompatibilities:
Keep container tightly closed in a dry and well-ventilated place.
Containers which are opened must be carefully resealed and kept upright to prevent leakage.
Storage class (TRGS 510): 8A: Combustible, corrosive hazardous materials
Exposure controls/personal protection:
Control parameters:
Components with workplace control parameters
Contains no substances with occupational exposure limit values.
Exposure controls:
Appropriate engineering controls:
Handle in accordance with good industrial hygiene and safety practice.
Wash hands before breaks and at the end of workday.
Personal protective equipment:
Eye/face protection:
Tightly fitting safety goggles.
Faceshield (8-inch minimum).
Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).
Skin protection:
Handle with gloves.
Gloves must be inspected prior to use.
Use proper glove
removal technique (without touching glove's outer surface) to avoid skin contact with this product.
Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices.
Wash and dry hands.
Full contact:
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
Splash contact
Material: Nitrile rubber
Minimum layer thickness: 0.11 mm
Break through time: 480 min
Material tested:Dermatril (KCL 740 / Aldrich Z677272, Size M)
It should not be construed as offering an approval for any specific use scenario.
Body Protection:
Complete suit protecting against chemicals, The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.
Respiratory protection:
Where risk assessment shows air-purifying respirators are appropriate use a fullface respirator with multi-purpose combination (US) or type ABEK (EN 14387) respirator cartridges as a backup to engineering controls.
If the respirator is the sole means of protection, use a full-face supplied air respirator.
Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).
Control of environmental exposure
Prevent further leakage or spillage if safe to do so.
Do not let product enter drains.
Discharge into the environment must be avoided.
Stability and reactivity:
Chemical stability:
Stable under recommended storage conditions.
Incompatible materials:
Strong oxidizing agents:
Hazardous decomposition products:
Hazardous decomposition products formed under fire conditions.
Carbon oxides, Nitrogen oxides (NOx), Hydrogen chloride gas.
Disposal considerations:
Waste treatment methods:
Product:
Offer surplus and non-recyclable solutions to a licensed disposal company.
Contact a licensed professional waste disposal service to dispose of this material.
Contaminated packaging:
Dispose of as unused product
