Propylene glycol and its uses

In chemical terms, propylene glycol 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 Monopropylene Glycol (also called MPG). It is a key product in engine coolants, heat transfer fluids, and automotive transmission fluids thanks to its thermal properties.

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

Propylene glycol, in its various forms, is widely used across numerous 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 cosmetics, pharmaceutical, food, and automotive industries, as well as in the synthesis of many chemical compounds.

Propylene glycol is non-toxic to humans and the environment. Unlike other glycols, monopropylene glycol is recognized as low-toxicity and non-hazardous to the environment. It is recognized as safe by the European Chemicals Agency (ECHA) and the U.S. Food and Drug Administration (GRAS, Generally Recognized As Safe).

Food-Grade Glycols:

For use as emulsifiers or texturizing agents in flavorings: 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 specifically 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.

Diluted MPG Antifreeze is a ready-to-use antifreeze heat transfer fluid specifically formulated for cooling systems, whether industrial, solar, or air-conditioning-related. It comes pre-diluted in water and is available in three variants, each with a specific freezing point.

Propylene glycol as a base for industrial manufacturing

Several propylene glycols are used as industrial solvents and base materials for manufacturing paints, cosmetics, textiles, and parapharmaceutical products. Here are some of the propylenes used as industrial raw materials: Polypropylene Glycol (PPG), Dipropylene Glycol (DPG), Dipropylene Glycol Monomethyl Ether (DPM), and Propylene Carbonate (PC). This list is non-exhaustive. 

Characteristics of propylene glycol

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 specified, propylene glycol is commercialized as a racemic mixture. (A substance form composed of an equal molecular mixture of both optical enantiomers.)

Propylene glycol is a clear, colorless liquid exhibiting physical properties such as:

Solubility: Propylene glycols are highly water-soluble, 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 exhibits a degree of flow resistance.

Thermal Conductivity: Propylene glycol has excellent thermal conductivity, meaning it is an effective heat conductor.

It also possesses important chemical characteristics: 

Reactivity: Propylene glycol is a stable, low-reactivity compound at room temperature. It does not react easily with other chemical substances, making it versatile across numerous applications.

Polarity: Propylene glycol is a polar compound due to the presence of hydroxyl groups (OH). Its polarity allows it to interact with other polar substances, such as water, and influences its solubility in various solvents.

Boiling and Melting Points: 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 a Heat Transfer Fluid and Antifreeze

Propylene glycol is a chemical compound commonly used as a heat transfer fluid and antifreeze across numerous applications. Due to its low toxicity, it is used in industrial heating and cooling systems, solar panel manufacturing, as well as in HVAC and refrigeration systems.

Monopropylene glycol antifreeze exhibits outstanding properties as a heat transfer fluid, offering a relatively low freezing point that allows it to remain liquid at sub-zero temperatures, while providing excellent thermal stability and high thermal conductivity. Furthermore, its moderate viscosity ensures efficient heat transfer, minimizing energy loss. Its ability to prevent scale formation and corrosion also makes it a popular choice in numerous industrial and automotive applications. In summary, propylene glycol is a versatile, dependable heat transfer fluid delivering exceptional thermal performance and freeze protection across a wide range of applications.

Food-Grade Glycols:

For use as emulsifiers or texturizing agents in flavorings: 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 specifically 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.

Diluted MPG Antifreeze is a ready-to-use antifreeze heat transfer fluid specifically formulated for cooling systems, whether industrial, solar, or air-conditioning-related. It comes pre-diluted in water and is available in three variants, each with a specific freezing point.

Propylene glycol as a base for industrial manufacturing

Several propylene glycols are used as industrial solvents and base materials for manufacturing paints, cosmetics, textiles, and parapharmaceutical products. Here are some of the propylenes used as industrial raw materials: Polypropylene Glycol (PPG), Dipropylene Glycol (DPG), Dipropylene Glycol Monomethyl Ether (DPM), and Propylene Carbonate (PC). This list is non-exhaustive. 

Use in the Manufacture of Industrial Chemicals

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

As a solvent, propylene glycol can effectively dissolve and disperse many compounds, making it a valuable ingredient in the production of paints, printing inks, varnishes, and coatings. 

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

Uses in the Food Industry

Propylene glycol also finds numerous applications 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 carrier, and humectant in food products such as beverages, desserts, sauces, and baked goods.

It helps maintain the texture, moisture, and freshness of food products while enhancing flavor and aroma retention. It also acts as a stabilizer in food products, preventing undesirable crystallization and improving emulsion stability. Propylene glycol is also used in vape nicotine products, which are increasingly popular. However, it is important to note that propylene glycol used in the food industry is food-grade and complies with 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 humectant 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 into formulations, facilitating the creation of homogeneous products. As an emollient, it helps soften and smooth skin and hair, providing a soft, supple feel.

It has the ability to hydrate the skin by attracting and retaining moisture, helping maintain optimal hydration. Propylene glycol is also used to stabilize emulsions, allowing oil and water phases to remain homogeneously mixed.

Frequently asked questions

What is propylene glycol?

Propylene glycol is an organic chemical compound. It is widely used across 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 exhibits low toxicity compared to similar substances. However, excessive exposure can cause skin or eye irritation. It is important to follow appropriate safety and handling recommendations.

What is the difference between propylene glycol and ethylene glycol?

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

When should you use a propylene glycol-based antifreeze?

Propylene glycol-based antifreeze is typically used when freeze protection is required for heating, cooling, or air conditioning systems. It is commonly used in engine cooling systems, solar heating systems, HVAC systems, and industrial facilities where preventing freeze damage is essential.

What is the price of propylene glycol?

The price of propylene glycol can vary depending on various factors such as quality, quantity, and supplier. We recommend checking with local suppliers and distributors for precise pricing information.

What are the other names for propylene glycol?

Propylene glycol is also known by the names propane-1,2-diol or PG (commonly used abbreviation).