What is propylene glycol used for?
Propylene glycol (CAS 57-55-6) is used as a humectant, solvent, and carrier in food, pharmaceuticals, and cosmetics, and as a low-toxicity antifreeze and heat-transfer fluid in HVAC, deicing, and industrial systems. Because it is FDA-recognized as GRAS (generally recognized as safe) and available in USP, food, and technical grades, it appears in everything from processed foods to injectable medicines to engine coolants.
That versatility comes from a rare combination of traits: it dissolves both water- and oil-based ingredients, holds moisture, resists freezing, and has low toxicity. Below is a breakdown of where propylene glycol (PG) actually gets used, by industry, and how the grade you choose depends on the application.
What are the main uses of propylene glycol by industry?
Propylene glycol’s roles fall into two broad buckets: it either carries and preserves other ingredients (as a solvent and humectant) or manages heat and freezing (as a glycol coolant). The table maps the most common applications to the grade typically specified.
| Industry | What propylene glycol does | Typical grade |
|---|---|---|
| Food & beverage | Humectant, flavor/color carrier, moisture retention | USP / food grade |
| Pharmaceutical | Solvent and excipient in oral, topical, and injectable products | USP grade |
| Cosmetics & personal care | Humectant and carrier in lotions, deodorants, makeup | USP / food grade |
| E-liquid / vapor | Aerosol base fluid | USP grade |
| HVAC & process cooling | Non-toxic antifreeze and heat-transfer fluid | Industrial / inhibited |
| Aircraft & pavement deicing | Freeze-point depressant in deicing fluids | Industrial grade |
| Plastics & resins | Reactant in unsaturated polyester resins | Technical grade |
| Antifreeze (food-safe systems) | Coolant where toxicity matters (e.g., near food) | Industrial grade |
Grade guidance is general; confirm the specification required by your process and regulator.
Why is propylene glycol used in food?
Propylene glycol is an FDA-approved food additive used as a humectant, solvent, and preservative — it keeps baked goods and processed foods moist, dissolves flavors and colors so they distribute evenly, and helps extend shelf life. It is recognized as GRAS for many food uses. Food and beverage applications require USP or food-grade PG, not technical grade.
Why is propylene glycol used in pharmaceuticals and cosmetics?
In pharmaceuticals, propylene glycol is a workhorse solvent and excipient that dissolves active ingredients and stabilizes oral, topical, injectable, and ophthalmic products — it is a common carrier in lubricating eye drops — supporting consistent dosing. In cosmetics and personal care, propylene glycol is one of the most widely used humectants: it draws and holds moisture in lotions, creams, deodorants, makeup, and hair-care products, while its solvency carries fragrances and actives. Both uses call for USP-grade material.
Why is propylene glycol used as a humectant in skin and hair care?
A humectant attracts water and holds it in place, and propylene glycol does this while also thinning formulas and dissolving other ingredients. In skin care it keeps lotions and creams from drying out and improves spreadability; in hair care it helps conditioners and styling products retain moisture and stay stable. Its low toxicity and skin compatibility are why it appears so widely on personal-care ingredient lists.
Is propylene glycol a good antifreeze?
Yes — propylene glycol is the low-toxicity alternative to ethylene glycol antifreeze, which makes it the standard choice for HVAC loops, food-processing cooling, breweries, solar thermal systems, and aircraft/pavement deicing, where a leak or overspray could contact people, food, or the environment. It depresses the freezing point and transfers heat effectively, usually as an inhibited industrial-grade blend for corrosion protection.
Propylene glycol vs. ethylene glycol: what’s the difference?
Both are glycols used as antifreeze, but ethylene glycol is toxic if ingested, while propylene glycol has low toxicity and is food-safe in appropriate grades. Ethylene glycol offers slightly better heat transfer at lower cost; propylene glycol is chosen wherever toxicity, food contact, or environmental exposure is a concern.
What are the key properties of propylene glycol?
| Property | Value |
|---|---|
| CAS number | 57-55-6 |
| Chemical formula | C₃H₈O₂ |
| Molecular weight | 76.09 g/mol |
| Boiling point | 188°C (370°F) |
| Density | 1.036 g/cm³ |
| Flash point | 99°C (210°F) |
| Viscosity | ~48–59 cP (mPa·s) at 25°C — noticeably syrupy |
| Appearance | Clear, colorless, nearly odorless liquid |
| Solubility | Fully miscible with water |
Verify against the current SDS and PubChem entry for propylene glycol (CID 1030).
What grades and sizes of propylene glycol does RightPath stock?
RightPath Industries supplies propylene glycol (CAS 57-55-6) in USP, food, and technical grades, so you can match the exact specification your application and regulator require. We fill from small packaging through rail car, with lot control available for tightly controlled processes.
| Packaging | Typical use |
|---|---|
| Small pack | Lab / low volume |
| 55-gallon drums | Standard supply |
| 275-gallon totes (IBC) | Higher-throughput use |
| Tank truck | Bulk manufacturing |
| Rail car | Large-scale continuous supply |
See the full propylene glycol product page and browse related glycols in our catalog.
How do you order propylene glycol from RightPath?
Request a quote through the RightPath pricing form, call 888-255-2401, or email sales@rightpathind.com. Specify the grade (USP, food, or technical), packaging, and quantity, and we will cross-reference your current material, confirm availability, and can sequester and lot-control stock at one of our three U.S. warehouses for just-in-time delivery.
Request bulk pricing: Get a propylene glycol quote →
Frequently asked questions
Is propylene glycol safe?
Propylene glycol has low toxicity and is FDA-recognized as GRAS for many food uses, which is why it appears in food, pharmaceuticals, and cosmetics. Safety depends on using the correct grade (USP or food grade) for consumable applications and following the SDS for handling.
What is the difference between USP and technical grade propylene glycol?
USP grade meets United States Pharmacopeia purity specifications for food, pharmaceutical, and cosmetic use. Technical (industrial) grade is intended for non-consumable applications such as antifreeze, deicing, and resins, and should not be used where food or pharmaceutical purity is required.
Is propylene glycol the same as ethylene glycol?
No. They are different glycols. Propylene glycol has low toxicity and is used where food safety matters, while ethylene glycol is toxic if ingested and used mainly in automotive antifreeze.
What is propylene glycol used for in e-liquids?
Propylene glycol serves as an aerosol base fluid in e-liquids, carrying flavor and producing vapor. USP-grade PG is used for this application.
Does propylene glycol freeze?
Pure propylene glycol has a low freezing point and, when blended with water, sharply depresses the freezing point of the mixture, which is why it is used as antifreeze and in deicing and cooling systems.
What is the difference between propylene glycol and glycerin?
Both are humectants used in food, pharma, and cosmetics, but they are different molecules. Glycerin (glycerol) is thicker and sweeter and is often preferred in food and some skin care; propylene glycol is thinner, a stronger solvent, and better at carrying flavors and actives. Formulators often choose based on viscosity, solvency, and mouthfeel.
Where can I find the propylene glycol SDS?
RightPath provides a Safety Data Sheet with every propylene glycol order, covering handling, storage, and disposal for the specific grade you buy. Request it with your quote, and always follow the SDS rather than generic figures.
Sources & links: Propylene glycol product page · Glycols category · External authority: PubChem — Propylene glycol (CID 1030)