Dipropylene Glycol (DPG): Uses, Properties, and Safety Precautions Explained

For formulators, choosing a solvent usually comes down to three things: how fast it evaporates, what it will dissolve, and whether it causes trouble downstream. Dipropylene glycol (DPG) sits at a useful point on all three. It is a high-boiling, low-volatility glycol that mixes with water and with most organic solvents, which makes it a dependable carrier and coupling agent in products from paint and ink to perfume and polyester resin.

The questions buyers actually ask about DPG tend to be practical ones. Will it evaporate too fast in my coating and leave brush marks? Does it stay stable in a fragrance concentrate? How is it different from plain propylene glycol, or from diethylene glycol, which I would rather avoid for toxicity reasons? This article answers those questions with the numbers that matter.

Below we cover what dipropylene glycol is, the properties that show up in real formulations, the main industries that buy it, how it compares with propylene glycol and diethylene glycol, and the safety points worth knowing before it goes into your warehouse.

What Is Dipropylene Glycol?

Dipropylene glycol is a clear, colorless, slightly viscous liquid with the formula C6H14O3 and a molecular weight of 134.17. The CAS number is 110-98-5 and the EC number is 203-821-4. Commercial DPG is not a single molecule but a mixture of three isomers, all of them ether-linked dimers of propylene glycol. It is sold as a regular grade (around 99% purity) and in cosmetic and fragrance grades with a stricter specification on color and odor. Because it is hygroscopic and fully miscible with water, it pulls moisture slowly from humid air, which matters for how the product is stored and packaged.

Key Properties of Dipropylene Glycol

For industrial buyers, the properties that matter are the ones that show up on the production line, not just on the datasheet. Regular-grade DPG is typically 99% min purity, with a specific gravity of about 1.023 at 25 °C, a boiling point around 230 °C, and a flash point of roughly 138 °C (closed cup). The three points below are what usually decide whether DPG fits a formulation.

Low Volatility and High Boiling Point

DPG boils around 230 °C at atmospheric pressure, which is roughly 40 °C higher than propylene glycol. That slow evaporation is exactly what some products need: coatings that have to level out after application, inks that must not dry on the press, and fragrance oils that should release scent gradually instead of vanishing with the solvent.

In practical terms, the low vapor pressure also means less solvent loss during storage and blending, and fewer VOC concerns in solvent-heavy operations.

The higher boiling point also makes DPG a useful coalescing solvent in some waterborne systems: it keeps the film open long enough for the polymer particles to fuse before the water leaves, which is the difference between a smooth finish and a chalky one.

Solvency and Coupling Performance

DPG dissolves a wide range of materials, including water-soluble resins, oils, and many hydrocarbons. That makes it a coupling agent in the technical sense: it bridges water and oil phases in a formulation so they stay mixed instead of separating. In cosmetics, this is what keeps a perfume concentrate uniform. In coatings, it helps a waterborne system wet the substrate evenly.

Hygroscopicity and Formulation Stability

DPG attracts moisture from the air, which formulators use deliberately: it works as a humectant in personal care products and helps keep some products from drying out. The same property means containers should stay sealed in storage. DPG is also chemically stable under normal processing conditions and does not readily yellow or develop off-odors, which is why fragrance houses accept it as a long-term carrier.

It blends cleanly with water, alcohols, and most glycols, so it drops into existing formulations without phase separation or viscosity surprises.

Main Applications of Dipropylene Glycol

DPG shows up across industries that need a slow-evaporating, water-miscible carrier or intermediate. Its combination of solvency, low volatility, and low toxicity makes it a common choice, and in several cases it is the component that keeps a product stable on the shelf and in use.

The table below shows the main industries that use dipropylene glycol and what it does in each one.

Coatings and Printing Inks

In solvent-borne and waterborne coatings, DPG slows the drying curve, which gives the film time to level out and release air before it sets. Ink makers use it to keep press-side viscosity stable, because a solvent that evaporates too fast changes how the ink behaves over the course of a run. The same open-time benefit carries into adhesives and industrial cleaners.

Cosmetics and Fragrance

Fragrance houses use DPG as the workhorse carrier for perfume oil: it dissolves fragrance concentrates, has a very low odor of its own, and is generally recognized as low in toxicity for personal care use. It is also a humectant in skin and hair products, where it helps hold moisture without the sticky feel that some other glycols leave behind.

The grade matters here. Fragrance-grade DPG is held to a tighter color and odor specification than the regular industrial grade, and most fragrance houses qualify a specific supplier's grade before it goes into a concentrate. If you buy DPG for personal care, ask for the cosmetic-grade specification and a fresh certificate of analysis.

Resins and Plasticizer Intermediates

DPG is a reactant in unsaturated polyester resin production. Built into the polymer backbone, it adds flexibility and hydrolytic stability to the finished resin, which is why it shows up in gel coats and glass-reinforced parts. It is also esterified with benzoic acid to make DPG dibenzoate, a plasticizer used in flexible PVC and adhesives.

Functional Fluids and Other Industrial Uses

Brake fluid formulations combine glycols with corrosion inhibitors, and DPG contributes a high boiling point and low water pickup in service. It also appears in metalworking fluids and heat-transfer fluids, and it is the starting material for DPG diacrylate, a building block used in radiation-cured coatings.

Dipropylene Glycol in Glycol and Glycol Ether Systems

If you are comparing DPG with other polyols, the two most common reference points are propylene glycol (PG) and diethylene glycol (DEG). All three are water-miscible liquids with similar handling, but they differ in volatility, toxicity profile, and price, and those differences usually decide which one fits.

The table below compares dipropylene glycol, propylene glycol, and diethylene glycol on the points that usually decide a purchasing decision.

Propylene glycol is the lighter molecule and the more common default. It evaporates faster, flows easier, and costs less per kilo, which is why it dominates food, pharma, and antifreeze uses. The trade-off is that its lower boiling point means faster solvent loss in coatings and less staying power in a fragrance. When a formulation needs a slower-evaporating glycol with the same clean toxicity profile, DPG is the usual step up.

Diethylene glycol is a different case. It is an excellent industrial solvent and a low-cost intermediate, and industry still uses large volumes of it in gas dehydration and polyester production. But its toxicity profile has pushed regulators and brand owners away from it in consumer products, and many markets now restrict DEG in cosmetics and food contact. DPG was widely adopted in personal care specifically as the lower-risk alternative.

So the practical choice is usually between PG and DPG, with DEG reserved for industrial applications where its hazards are managed. If your product needs slow evaporation, low odor, and a clean regulatory story, DPG is the middle ground that most formulators settle on.

Safety Considerations of Dipropylene Glycol

DPG is one of the lower-hazard industrial glycols. Most suppliers describe it as not classified as dangerous goods for transport, and it is generally recognized as low in acute toxicity. The day-to-day concerns are eye irritation, skin contact with concentrated material, and the fact that it is combustible rather than flammable.

The points below cover the precautions that matter in everyday handling.

• Proper Ventilation

DPG has very low vapor pressure, so airborne exposure is not the main concern in normal handling. What you do want to avoid is breathing the mists that can form during hot mixing or spray application, and keeping the area ventilated is the simple fix. In enclosed rooms where DPG is heated or agitated, general ventilation keeps mist and vapor levels comfortably low.

• Personal Protective Equipment (PPE)

Concentrated DPG can irritate the eyes and, with repeated contact, dry the skin. Gloves and safety glasses are the sensible minimum during transfer and blending. Where the product is handled in large volumes or at elevated temperature, a chemical-resistant apron adds a layer that costs little and prevents most splash problems.

If skin contact happens, wash with soap and water. For eyes, rinse with plenty of clean water for several minutes and seek medical attention if irritation persists. Keep the supplier's SDS accessible where the product is stored.

• Storage

Store DPG in tightly closed original containers in a cool, dry, well-ventilated area, away from direct sunlight, heat sources, and oxidizing agents. The hygroscopic nature of the product means an open or leaking drum will slowly pick up water, and moisture is the main thing that can degrade quality. Under proper storage, most suppliers give DPG a shelf life of about 24 months.

• Transportation

DPG is supplied in 200 L drums, 1000 L IBCs, and ISO tanks, with smaller packs for sampling and lab use. It is not classified as dangerous goods for transport in most markets, which simplifies road and sea logistics. Keep containers sealed during transit to prevent moisture pickup and contamination, and label them with the product name and CAS number.

Image Name: industrial-drums-for-dipropylene-glycol

Image Alt: Industrial Drums for Dipropylene Glycol

Choosing a Reliable Dipropylene Glycol Manufacturer

A solvent is only as consistent as the plant that makes it. Batch-to-batch variation in purity, moisture, or color shows up directly in your formulation, in the smell of a fragrance, the gloss of a coating, or the stability of a resin. A reliable manufacturer should be able to provide certificates of analysis, stable production capacity, and technical support when your formulation changes.

As a one-stop chemical supplier with 30 years of experience, Richnow Chem focuses on delivering high-quality industrial chemicals for applications including coatings, personal care, polyester resins, and specialty fluids.

What Richnow Chem Can Offer:

• Product quality verified through gas chromatography (GC) and full-component analysis

• Integrated management systems covering quality (ISO9001), environmental management (ISO14001), and occupational health and safety (OHSAS18001)

• Stable and reliable supply of industrial chemicals for global customers

• Diverse product packaging and shipping options, from drums to IBC tanks

• Technical support for formulation and application questions

Conclusion

Dipropylene glycol has earned its place in industrial formulations because it solves a recurring problem: how to keep a product stable, slow-evaporating, and easy to handle without dragging in toxicity concerns. Its high boiling point, clean solvency, and low odor make it the practical choice in coatings, cosmetics, and resins alike.

For buyers, the practical question is not whether DPG works. It is whether the supplier can deliver consistent purity and moisture batch after batch. Application requirements, grade selection, packaging, safety management, and supplier reliability all come into that decision, and all of them are worth verifying before you commit to a long-term supply.

FAQs About Dipropylene Glycol

What Is Dipropylene Glycol Used For?

Dipropylene glycol is used as a solvent, coupling agent, and humectant in coatings and printing inks, cosmetics and fragrances, unsaturated polyester resins, plasticizers, and functional fluids such as brake fluids. Its low volatility and water miscibility are the properties most products rely on.

Is Dipropylene Glycol Soluble In Water?

Yes. Dipropylene glycol is fully miscible with water at all proportions, and it also dissolves in most common organic solvents. That combination is what makes it a practical coupling agent between water and oil phases.

What Is The Difference Between Dipropylene Glycol And Propylene Glycol?

Propylene glycol is the single glycol monomer; dipropylene glycol is its dimer. DPG has a higher boiling point (around 230 °C versus about 188 °C), a lower vapor pressure, and a slightly higher viscosity, so it evaporates more slowly in coatings and holds fragrance longer. Both are low in toxicity, and DPG is usually the choice when slower evaporation matters.

Is Dipropylene Glycol Safe?

Dipropylene glycol is generally recognized as low in acute toxicity and is widely used in cosmetics and personal care. The main precautions are eye irritation on contact, skin dryness with repeated exposure, and standard combustible-liquid handling: keep it away from open flames and store containers sealed, since the product is hygroscopic.