Propylene glycol and its uses

Propylene glycol, in the chemical sense, is an organic solvent. It is commonly referred to as monopropylene glycol or MPG, which represents its simplest form.

Its most widely used form is Mono Propylene Glycol (also known as MPG). It is a key product in coolants, heat transfer fluids, and automotive transmission fluids due to its thermal properties.

Food-grade monopropylene glycol is a raw material grade of standard MPG, used primarily as a solvent, emulsifier, and texturizing agent in food products such as sauces, beverages, and ice creams, as well as in the composition of e-liquids.

Propylene glycol, in its various forms, is widely used across many industries. It should be noted that the term "propylene glycol" can also refer to other forms of propylene glycols, such as dipropylene glycol and tripropylene glycol, which have different properties. Propylene glycol is found as a component or additive in the cosmetic, pharmaceutical, food, and automotive industries, as well as in the synthesis of many chemical compounds.

Propylene glycol is not toxic to humans or the environment. Unlike other glycols, monopropylene glycol is considered to have low toxicity and to be non-hazardous to the environment. It is recognized as safe by the European Chemicals Agency (ECHA) as well as the U.S. Food and Drug Administration (GRAS, Generally Recognized As Safe).

Food-grade glycols:

For use as emulsifiers or texturing agents for flavors: food-grade MPG is the appropriate glycol. It is also used in e-cigarette liquids.

Heat transfer fluids

Concentrated technical MPG is a highly concentrated antifreeze heat transfer fluid, specially designed for use in industrial refrigeration, solar panels, central heating, and tank cooling. It is non-toxic to health and the environment. To use it, simply add water (preferably demineralized) yourself as needed.

As for diluted MPG antifreeze, it is a ready-to-use antifreeze heat transfer fluid, specially formulated for cooling circuits, whether industrial, solar, or air conditioning-related. It is pre-diluted in water and is available in three derivatives, each with a specific freezing point.

Propylene glycol as bases for industrial manufacturing

There are several propylene glycols used as solvents and industrial bases for the manufacture of paints, cosmetic products, textiles and parapharmacy products. Here are some of the propylenes used as raw materials in industry: Polypropylene glycol (PPG), Dipropylene glycol (DPG), Dipropylene glycol MonoMethyl Ether (DPM) and Propylene Carbonate (PC). This list is non-exhaustive. 

Propylene glycol characteristics

Propylene glycol exists in two isomeric forms: R-(-)-propane-1,2-diol (CAS 4254-14-2) and (S)-(+)-propane-1,2-diol (CAS: 4254-15-3). Unless otherwise indicated, propylene glycol is sold in racemic form. (A form of a substance composed of an equal molecular mixture of the two optical inverses.)

Propylene glycol is a clear, colorless liquid with the following physical properties:

Solubility: propylene glycols are highly soluble in water, meaning they mix easily with water in all proportions. This makes them useful as solvents and blending agents.

Miscibility: propylene glycols are miscible with many organic solvents, meaning they can mix with other organic substances.

Viscosity: it has a relatively high viscosity, meaning it is thick and has some resistance to flow.

Thermal conductivity: propylene glycol has excellent thermal conductivity, meaning it is a good conductor of heat.

It also has important chemical characteristics: 

Reactivity: propylene glycol is a stable compound with low reactivity at room temperature. It does not easily react with other chemical substances, which makes it versatile in many applications.

Polarity: propylene glycol is a polar compound due to the presence of hydroxyl groups (OH). Its polarity gives it properties for interacting with other polar substances, such as water, and can influence its solubility in various solvents.

Boiling and melting point: propylene glycol has a boiling point of approximately 188 degrees Celsius and a melting point of approximately -59 degrees. These points define the temperatures at which propylene glycol transitions from liquid to gas, and from solid to liquid (melting).

Uses of propylene glycol

Use as heat transfer fluid and antifreeze

Propylene glycol is a chemical compound commonly used as a heat transfer fluid and antifreeze in many applications. Due to its low toxicity, it is used in industrial heating and cooling systems, the manufacture of solar panels, as well as in air conditioning and refrigeration systems.

Monopropylene glycol antifreeze has remarkable properties as a heat transfer fluid, as it has a relatively low freezing point, allowing it to remain liquid at sub-zero temperatures, while offering good thermal stability and high thermal conductivity. Furthermore, its moderate viscosity enables efficient heat transfer, thereby reducing energy losses. Its ability to prevent the formation of deposits and corrosion also makes it a popular choice in many industrial and automotive applications. In summary, propylene glycol is a versatile and reliable heat transfer fluid, offering exceptional thermal performance and freeze protection in a variety of applications.

Food-grade glycols:

For use as emulsifiers or texturing agents for flavors: food-grade MPG is the appropriate glycol. It is also used in e-cigarette liquids.

Heat transfer fluids

Concentrated technical MPG is a highly concentrated antifreeze heat transfer fluid, specially designed for use in industrial refrigeration, solar panels, central heating, and tank cooling. It is non-toxic to health and the environment. To use it, simply add water (preferably demineralized) yourself as needed.

As for diluted MPG antifreeze, it is a ready-to-use antifreeze heat transfer fluid, specially formulated for cooling circuits, whether industrial, solar, or air conditioning-related. It is pre-diluted in water and is available in three derivatives, each with a specific freezing point.

Propylene glycol as bases for industrial manufacturing

There are several propylene glycols used as solvents and industrial bases for the manufacture of paints, cosmetic products, textiles and parapharmacy products. Here are some of the propylenes used as raw materials in industry: Polypropylene glycol (PPG), Dipropylene glycol (DPG), Dipropylene glycol MonoMethyl Ether (DPM) and Propylene Carbonate (PC). This list is non-exhaustive. 

Use in industrial chemical manufacturing

Propylene glycol is widely used in the chemical industry for the manufacture of various products. Due to its unique physical and chemical properties, it is used as a solvent, suspending agent, and stabilizer in many manufacturing processes. 

As a solvent, propylene glycol is capable of effectively dissolving and dispersing many compounds, making it a valuable ingredient in the production of paints, printing inks, varnishes, and coatings. 

Furthermore, propylene glycol acts as a stabilizer by preventing chemical degradation and oxidation of oxygen-sensitive substances. Its ability to improve the stability and shelf life of chemical products makes it an essential ingredient in many industrial applications. In summary, propylene glycol plays an essential role in the manufacture of industrial chemicals as a solvent, suspending agent, and stabilizer, offering reliable performance and versatility in many production processes.

Uses in the food industry

Propylene glycol also finds many uses in the food industry due to its specific properties. It is often used as a safe food additive approved by regulatory authorities. Propylene glycol is commonly used as a solvent, flavoring agent, and humectant in food products such as beverages, desserts, sauces, and baked goods.

It helps maintain the texture, moisture, and freshness of foods while improving flavor and taste retention. It also acts as a stabilizer in food products, preventing unwanted crystallization and improving emulsion stability. Propylene glycol is also used in nicotine vaping products, which are increasingly popular. However, it is important to note that propylene glycol used in the food industry is of food grade and meets strict safety standards. 

Uses in the cosmetics industry

Propylene glycol is widely used in the cosmetics industry due to its beneficial properties for beauty product formulations.

It acts as a versatile solvent, emollient, and moisturizer in many cosmetic products such as creams, lotions, hair care products, and makeup. As a solvent, it helps dissolve and blend active ingredients and colorants in formulations, facilitating the creation of homogeneous products. As an emollient, it helps soften and smooth skin and hair, providing a feeling of softness and suppleness.

It has the ability to moisturize the skin by attracting and retaining moisture, which helps maintain optimal hydration. Propylene glycol is also used to stabilize emulsions, allowing the oily and aqueous phases to remain evenly mixed.

Frequently asked questions

What is propylene glycol?

Propylene glycol is an organic chemical compound. It is widely used in various industries due to its properties as a solvent, humectant, emollient and stabilizer.

What is propylene glycol used for?

Propylene glycol has many uses. It is used as a solvent, suspending agent, food additive, cosmetic ingredient, and pharmaceutical excipient. It is found in products such as paints, food products, beauty products, medications, and coolants.

Is propylene glycol toxic?

Propylene glycol is considered relatively safe and has low toxicity compared to other similar substances. However, excessive exposure can cause skin or eye irritation. It is important to follow appropriate safety and usage recommendations.

What is the difference between propylene glycol and ethylene glycol?

The main difference between propylene glycol and ethylene glycol lies in their toxic properties. Propylene glycol is considered safe and is often used in food and cosmetic applications. In contrast, ethylene glycol is toxic and is primarily used as an antifreeze for vehicle cooling systems.

When should a propylene glycol-based antifreeze be used?

A propylene glycol-based antifreeze is generally used when freeze protection is needed for heating, cooling, or air conditioning systems. It is commonly used in engine cooling systems, solar heating systems, air conditioning systems, and industrial installations where it is essential to prevent freeze damage.

What is the price of propylene glycol?

The price of propylene glycol can vary depending on various factors such as quality, quantity, and supplier. It is recommended to check with local suppliers and distributors for accurate pricing information.

What are the other names for propylene glycol?

Propylene glycol is also known as propane-1,2-diol or PG (a commonly used abbreviation).