Propylene Glycol

CAS No. 57-55-6

Propylene glycol is a colorless, almost odorless, clear and viscous hygroscopic liquid. As a highly commercially valuable diol, propylene glycol has excellent solubility, low toxicity, moisture absorption, and anti freezing and anti freezing properties. In industry, it is mainly divided into pharmaceutical/food grade (USP/EP/FCC Grade) and industrial grade (Industrial Grade), which are widely used in unsaturated polyester resins (UPR), food additives, pharmaceutical solvents, cosmetic water retaining agents, e-liquid, antifreeze and heat carrier media.

Technical Parameter	USP / EP Grade Standard	Industrial Grade Standard	Test Method
Assay (Purity)	≥ 99.8%	≥ 99.50%	GC
Appearance	Clear, colorless viscous liquid	Clear, colorless liquid	Visual
Water Content	≦ 0.20%	≦ 0.20%	ASTM E203 (Karl Fischer)
Color (Pt-Co / APHA)	≦ 10	≦ 10	ASTM D1209
Specific Gravity (@ 20/20°C)	1.035 - 1.037	1.035 - 1.037	ASTM D4052
Refractive Index (@ 20°C)	1.431- 1.433	1.431- 1.433	ASTM D1218
Heavy Metals (as Pb)	≦ 5 ppm	——	USP
Diethylene Glycol (DEG)	≦ 0.08%	——	GC
Residue on Ignition	≦ 0.007%	≦ 0.01%	USP

The Uses of Propylene Glycol in the Industry

Industry and Chemical Engineerin

Propylene glycol is the main raw material for making unsaturated polyester resins and is widely used to produce fiberglass products like bathtubs and boat hulls. It's also a key ingredient in low-toxicity antifreeze, airplane de-icing fluids, coolants, and industrial cleaners.

Food industry

As a legal food additive, propylene glycol is mainly used as a stabilizer, emulsifier, moisture-retainer, and thickener. It's often added to fresh dough products (like dumpling wrappers) and pastries to prevent cracking and improve texture.

Pharmaceutical industry

As a safe pharmaceutical excipient, propylene glycol is commonly used as a solvent and moisturizer in oral formulations, topical ointments, and injections, and it can also serve as a filler for soft capsules and a plasticizer for film coating materials.

Daily chemicals and personal care industry

Thanks to its excellent moisturizing and penetration properties, propylene glycol is widely added to skincare products, cosmetics, toothpaste, and shampoo, helping to keep things hydrated, prevent freezing, and aid the absorption of active ingredients.

Other apps

Propylene glycol is also used as a solvent in e-cigarette liquids and flavor bases, and it's also used in making synthetic resins, surfactants, and hydraulic brake fluids.