A guide to propylene glycol, USP versus industrial grade, its applications, and how it differs from ethylene glycol, from a US-based distributor.
Propylene glycol (PG, CAS 57-55-6) is a clear, water-miscible liquid used as a humectant, solvent, and carrier. USP grade serves food, beverage, personal care, and pharmaceutical uses; industrial grade serves antifreeze, heat-transfer, and resin applications. It is chosen over ethylene glycol wherever human or animal contact is possible. Stratus Chemical supplies both grades with COA and SDS.
Propylene glycol (PG, CAS 57-55-6) is a clear, colorless, nearly odorless viscous liquid that is fully miscible with water. It is hygroscopic, meaning it attracts and holds moisture, which is why it works so well as a humectant, and it has a low freezing point, which makes it useful in heat-transfer and de-icing fluids.
The grade you need is driven by your application and its regulatory requirements:
| Grade | Typical use | Notes |
|---|---|---|
| USP / EP | Food, beverage, personal care, pharmaceutical, flavor & fragrance | Meets pharmacopeia monographs; commonly available Kosher certified |
| Industrial / technical | Antifreeze and coolants, heat-transfer fluids, unsaturated polyester resins, de-icing | Lower cost where pharmacopeia compliance is not required |
If your product is ingested, inhaled, or applied to skin, specify USP. For industrial systems, technical grade controls cost.
They are different chemicals with very different toxicity profiles. Ethylene glycol is significantly more toxic if ingested, which is why propylene glycol is chosen wherever incidental human or animal contact is possible, food-plant heat transfer, RV and marine antifreeze, and any food, pharmaceutical, or personal-care use. Ethylene glycol remains common in automotive engine coolant. The two are not interchangeable, always specify which one your system requires.
Propylene glycol is commonly supplied in drums, totes, and bulk. Stratus provides a Certificate of Analysis and SDS with shipments, and can provide Letters of Conformance and Kosher certificates for USP-grade material where the manufacturer holds current certification.
Propylene glycol is used as a humectant, solvent, and carrier in food, beverage, personal care, and pharmaceutical products, and as the lower-toxicity antifreeze and heat-transfer fluid in food plants, HVAC, and RV and marine systems. It is also used in unsaturated polyester resins and de-icing fluids.
They are different chemicals. Ethylene glycol is significantly more toxic if ingested, so propylene glycol is used wherever incidental human or animal contact is possible, including food, pharmaceutical, personal care, and food-plant or RV antifreeze applications. They are not interchangeable.
USP grade propylene glycol meets the United States Pharmacopeia monograph and is the grade specified for food, beverage, personal care, and pharmaceutical applications. Industrial or technical grade is used where pharmacopeia compliance is not required.
USP-grade propylene glycol is commonly manufactured under Kosher certification. Stratus can provide the current Kosher certificate and a Letter of Conformance where the manufacturer holds valid certification, ask when requesting a quote.
The CAS number for propylene glycol is 57-55-6.
Propylene glycol is commonly supplied in drums, totes, and bulk, with a Certificate of Analysis and SDS provided. Share your grade and volume for current options.
Tell us the grade, form, and volume. We'll respond with pricing and availability within one business day.
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