Polyethylene Glycol PEG-4000/6000 is a linear high-molecular polymer prepared by ring-opening polymerization of ethylene oxide with water or ethylene glycol as raw materials. Its general chemical formula is HO(CH₂CH₂O)nH, where the degree of polymerization n for PEG-4000 is approximately 70~90, and for PEG-6000, n is about 130~200. The molecular structure features active hydroxyl groups (-OH) at both ends and repeated ether bond (-C-O-C-) segments in the middle. This unique structure endows the product with excellent water solubility, lubricity, and moisture retention.
According to the product quality standard of Guoli Chemical, the active ingredient content (i.e., the polyethylene glycol polymer itself) of this product is not less than 99%, making it a high-purity chemical. Possible trace components include: free alcohol content ≤0.5% (unreacted polymerization initiator or low-molecular-weight alcohols), water content ≤1.0% (due to the product's certain hygroscopicity), and extremely trace amounts of catalyst residues. The product does not contain free phosphoric acid, monoesters, diesters, or other surfactant components.
The product has been tested with an iodine value of ≤1 gI₂/100g, indicating a highly saturated molecular structure with almost no unsaturated double bonds, thus chemically stable. Heavy metal content is controlled at ≤10 mg/kg, arsenic content ≤2 mg/kg, meeting the purity requirements for pharmaceutical and daily chemical industries. The main difference between PEG-4000 and PEG-6000 lies in their average molecular weight ranges: the former has a molecular weight of about 3400~4200, while the latter is about 5400~6600. Therefore, they differ in physical parameters such as melting point and viscosity.
| Parameter Name | PEG-4000 | PEG-6000 |
|---|---|---|
| CAS Number | 25322-68-3 | |
| Molecular Formula | HO(C₂H₄O)nH | |
| Average Molecular Weight | 3400~4200 | 5400~6600 |
| Degree of Polymerization n | Approx. 70~90 | Approx. 130~200 |
| Active Ingredient Content | ≥99% | |
| Water Content | ≤1.0% | |
| Free Alcohol | ≤0.5% | |
| Hydroxyl Value | 8~16 mgKOH/g | |
| Iodine Value | ≤1 gI₂/100g | |
| Acid Value | ≤0.1 mgKOH/g | |
| Heavy Metals | ≤10 mg/kg | |
| Arsenic | ≤2 mg/kg | |
| Melting Point Range | 50~63°C | |
| Appearance | White waxy solid or granules | |
| Ion Type | Nonionic | |
| Solubility | Easily soluble in water | |
Since the main component of both PEG-4000 and PEG-6000 is high-purity ethylene oxide polymer, they can be substituted for each other in most application fields. However, the appropriate molecular weight grade should be selected based on specific process requirements. Generally, PEG-4000 has a slightly lower melting point and lower melt viscosity, making it more suitable for formulations requiring higher fluidity (e.g., drop pill carriers, water-based paint lubricants). PEG-6000 has a higher molecular weight and greater hardness, making it more suitable for scenarios requiring a higher melting point and solid shaping strength (e.g., suppository bases, solid dispersion carriers).
When used in the pharmaceutical field, due to the active ingredient purity of over 99% and extremely low heavy metal content, it can be directly used as a pharmaceutical excipient. In daily chemical formulations, it can serve as an economical substitute for glycerin. In industrial applications (textiles, papermaking, metalworking), it is recommended to perform gradient experiments within the addition range of 1%~5% to determine the optimal dosage based on formulation compatibility and process temperature.