Propylene glycol-DONGYING EASTCHEM CO.,LTD

What Is Propylene Glycol?

Propylene glycol (propane-1,2-diol; CAS 57-55-6) is an organic compound with the formula C3H8O2, miscible with water, ethanol and a wide range of organic solvents. Under normal conditions it is a colorless, viscous liquid, nearly odorless, with a faintly sweet taste. Compared with its cousin ethylene glycol, PG is markedly lower in toxicity — the reason it is the only glycol accepted in food, pharmaceutical and personal-care applications. It is produced industrially by hydration of propylene oxide.

Physical and Chemical Properties

• Density 1.036 kg/L at 20 ℃; boiling point 188.2 ℃; freezing point −59 ℃ (supercools readily).
• Fully water-miscible, strongly hygroscopic, low volatility, low vapor pressure.
• Chemically a diol: reacts with unsaturated diacids to polyesters, with fatty acids to esters, and with PO to polyether polyols.
• Low oral toxicity (GRAS-listed for food use in many jurisdictions), non-carcinogenic, readily biodegradable.

Industrial Grades vs USP Grade

Industrial-grade PG (99.5–99.9%) serves resins, antifreeze and fluids. USP/EP grade — controlled for identity, purity, diethylene glycol traces and heavy metals — is required for food, pharmaceutical and cosmetic applications. Buyers should specify the pharmacopoeia grade explicitly when the end product touches people; EastChem supplies both, each with its own documentation package (COA for industrial; COA plus USP/EP certificates where applicable).

Main Applications

Unsaturated Polyester Resins

PG is a primary glycol for unsaturated polyester (UP) resins used in fiberglass-reinforced plastics, gel coats, buttons and coatings. It gives resins good water resistance and flexibility at a competitive cost, often blended with DEG or neopentyl glycol to tune properties.

Cosmetics and Personal Care

As a humectant, solvent and viscosity modifier, PG appears in creams, lotions, deodorants and toothpaste, frequently in combination with glycerol or sorbitol. It also acts as a moisture-adjusting and hair-uniforming agent in hair dyes. USP grade is standard for this sector.

Food and Pharmaceutical

In food, PG is an authorized carrier solvent for flavors and colors and an anti-dusting aid. In pharmaceuticals it solubilizes actives in oral and topical formulations. Its low toxicity is what makes these uses possible — the decisive difference from ethylene glycol.

Antifreeze and Heat-Transfer Fluids for Food Contact

Food and beverage plants, breweries and dairies use PG-based coolants in secondary loops and chiller jackets precisely because a leak cannot poison the product. It also serves as winter de-icing fluid for aircraft and runways where toxicity rules out EG.

Plasticizers, Cellophane and Tobacco

PG plasticizes cellophane film, conditions tobacco against drying, and esterifies to plasticizers and surfactant feedstocks. In agriculture it is a carrier for pesticide formulations.

Handling and Storage

PG is low-toxicity and non-regulated for transport. It is however hygroscopic: store sealed in a dry place, and for USP applications keep containers dedicated and closed to protect water specification. Shelf life typically exceeds 24 months. Packaging: 215 kg galvanized drums, 1000 kg IBC totes, or 20-ton flexitanks.

PG in Polyether Polyols and Resin Chemistry

Beyond its direct uses, propylene glycol is a initiator molecule for polyether polyols: reacting PG with propylene oxide builds di-functional polyols that become the soft segments of flexible polyurethane foams, CASE elastomers and coatings. PG-initiated polyols (molecular weights 400, 1000, 2000 and up) are the volume backbone of the foam industry — connecting PG supply directly to furniture, automotive and insulation markets. In unsaturated polyester, PG supplies the flexible diol segment; blends with DEG or neopentyl glycol tune water resistance, weatherability and crack resistance.

Humectant Comparison: PG vs Glycerol vs Sorbitol

In cosmetics formulation, PG is usually paired with or compared against glycerol and sorbitol solutions. Glycerol binds the most water but feels tacky at high doses; PG absorbs quickly, feels lighter and also improves preservative penetration; sorbitol adds humectancy with a fresh feel. Practical lotion formulas often combine 2–8% PG with 2–5% glycerol to balance efficacy and skin feel — a formulation pattern where PG’s low toxicity and clean odor are prerequisites.

A Note on Stereochemistry

Industrial PG is racemic (equal R and S enantiomers), which is fully acceptable for food, cosmetic and industrial uses. Pharmaceutical buyers requiring the single-enantiomer form must specify it explicitly — it is a specialty product distinct from standard monopropylene glycol.

Food and Pharma Regulatory Context

PG carries the food additive number E1520 in the EU and GRAS-recognized status in the United States for specified uses; pharmacopoeia grades (USP, EP) define identity, purity, limits for diethylene glycol contamination and heavy metals. These frameworks are the reason PG — not EG — appears in flavor carriers, oral and topical drug vehicles, pet foods and theatrical fog fluids. Buyers for these sectors should request pharmacopoeia certificates with each lot; EastChem supplies USP/EP-grade material with the corresponding documentation.

De-icing and Aircraft Fluids

Type I and Type IV aircraft de-icing/anti-icing fluids are PG-based: thickened PG solutions hold on wings and absorb ice through freezing-point depression while remaining sufficiently low in toxicity for routine airport use. Runway and equipment de-icing likewise favors PG where environmental discharge rules restrict EG and urea. Performance depends on glycol purity and water content — another reason COA discipline matters in this sector.

Storage, Water Specification and Practical QA

PG’s hygroscopicity is the most common quality failure mode: drums left open in humid warehouses drift past the 0.2% water limit for USP material. Practical QA: keep containers sealed, use dedicated pumps, and schedule water testing (Karl Fischer) for material stored beyond six months. Stored dry and sealed, PG keeps specification for 24 months and more.

PG in Animal Nutrition

Propylene glycol is a recognized energy ingredient in ruminant feed — most importantly as a ketosis-support drench and feed component for dairy cows in early lactation, where its gluconeogenic effect helps counter negative energy balance. Typical drench doses run 250–500 g per head per day under nutritional guidance. The same low-toxicity profile that qualifies PG for food use underpins this application; feed buyers should specify feed-grade documentation. This is a further example of how PG and EG markets diverge: two molecules with similar physical jobs, separated completely by toxicology.

PG in Paints, Inks and Agrochemicals

As a coalescent-adjacent solvent and humectant, PG extends open time in water-based paints, keeps inks from skinning on rollers, and acts as an anti-freeze additive that protects latex paint through freeze-thaw cycles in storage. In agrochemistry it is a standard carrier solvent for emulsifiable concentrates and suspension concentrates, chosen for solvency, water miscibility and low phytotoxicity. These mid-volume uses round out the demand picture and explain why PG stock depth matters to distributors serving mixed customer bases.

A Practical Purchasing Checklist for Propylene Glycol

Before confirming a PG order, run this five-point check. One: grade match — industrial or USP/EP, stated on the contract, with pharmacopoeia certificates if human-contact material. Two: water specification guaranteed on the COA and retest date defined. Three: packaging integrity — new drums or certified IBC totes, sealed at filling. Four: documentation set — COA, MSDS, origin and, for food-channel customers, the food-contact declarations your market expects. Five: logistics capability — can the supplier consolidate your other glycols and oxygenated solvents to fill the container? A supplier answering all five affirmatively, with stock on hand, removes most of the friction that glycol buyers actually experience.

Consolidated Glycol Supply in Practice

Most glycol buyers need more than one molecule over a quarter: propylene glycol for the food-contact and cosmetics lines, ethylene glycol for coolant blending, diethylene glycol for resin and gas-drying duty. Ordering each from a different source triples the document work, the quality systems to audit and the containers to fill. Consolidated sourcing fixes all three: one COA format, one bank wire, one customs entry, and one container packed to the brim. That is the operating logic behind EastChem’s glycol family program — and the reason our customers’ purchasing teams treat glycols as a single managed category rather than three scattered line items on three different supplier files.

Why Source Propylene Glycol from Dongying EastChem

We are a 19-year chemical manufacturer with three subsidiaries holding a large stock of fresh PG. Good product quality is the foundation; what decides long-term reliability is service — complete documentation, on-time containers, and technical answers that arrive the same day. We help customers analyze their supply situation and consolidate procurement: PG ships together with ethylene glycol, DEG, and the feedstock propylene oxide. MOQ one 20′ container, samples in about 2 days, T/T or L/C.

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Dongying EastChem Co., Ltd
Email: info@dyeastchem.com · WhatsApp: +86 188 5467 0769
Dongying, Shandong, China