Polyethylene glycol is the high-molecular polymer mixture obtained from the intra-molecular dehydration and condensation of the glycol. Depending on the different sizes of the molecular weight, the physical form of polyethylene glycol can vary from white mucus (Mw: 200 ~ 700) to a waxy semi-solid (Mw 1000 ~ 2000), until a hard, waxy solid (Mw3000 ~ 20000). Polyethylene glycol is soluble in most organic solvents of high polarity, such as alcohols, alcohol-silicon mixture, glycols, esters, ketones, aromatic hydrocarbons and nitro alkanes. It is insoluble in aliphatic hydrocarbons, naphthenic and other low polarity organic solvent. The solubility of polyethylene glycol is related to the fraction of its molecular weight and temperature. Liquid polyethylene glycols can be miscible with water in any ratio while solid polyethylene glycols only have limited solubility. But even for the polyethylene glycol of the greatest relative molecular mass fraction, it still has water solubility being greater than 50%. Upon increased temperature, the water solubility of the solid polyethylene glycols sharply increases. If the temperature is high enough (e.g. PEG-6000, 60 ℃), all fractions of solid polyethylene glycol can be miscible with water in any proportion. But when the temperature continues to rise to close to the boiling point of water, even for more dilute solution, polyethylene glycol will be precipitated out with its precipitation temperature depending on the polymer molecular weight and concentration. When the polyethylene glycol is mixed with water, there is slight volume shrinkage and it is significantly exothermic. Furthermore, polyethylene glycol can also soluble in the monomer of the low-grade aldehydes, amines, organic acids, acid anhydrides, and polymers. But it is insoluble in compound such as rapeseed oil, mineral oil that containing long hydrocarbon chains.
Polyethylene glycol and polyethylene glycol fatty acid ester has a very wide application in the cosmetic industry and the pharmaceutical industry. Since polyethylene glycol also has many excellent properties such as being water-soluble, non-volatile, physiologically inert, mildness, lubricity, and can make the skin be moist, soft with pleasant post-usage feeling. You can select polyethylene glycol of different molecular weight fractions to change the viscosity, hygroscopicity and organic structure. Polyethylene glycol of low molecular weight (Mr <2000) is suitable for being used as wetting agent and consistency regulator that can be used in creams, lotions, toothpaste and shaving cream, etc., it can also be applied to non-washing hair care products that can given filamentous gloss to the hair. High-molecular weight polyethylene glycol (Mr> 2000) is suitable for being applied to lipstick, deodorant sticks, soap, shaving soap, foundation and cosmetics and so on. In cleaning solvents, polyethylene glycol is also used as suspending agents and thickening agents. In the pharmaceutical industry, it can be used as the matrix of ointments, creams, ointments, lotions and suppositories. The commercialized polyethylene glycol (such as Polyethylene Glycol NF, Dow chemical Co.) for food and drug is actually more suitable for being applied to cosmetic. The application of methoxy polyethylene glycol and polypropylene glycol is similar with that of polyethylene glycol.
In the supplement rules regarding to food additives documented in the US Federal Food, Drug and Cosmetic Act regulations, it has allowed for either directly or indirectly applying food chemicals pharmacopoeia grade polyethylene glycol as a food additive. In1985, FAO / WHO provided that the ADI value is 0 ~ 10mg / kg of body weight. GRAS: (FDA, §172.820, 1985). The acute oral toxicity (mice) has a LD50 of 33 ~ 35g / kg while the intraperitoneally toxicity gives a LD50 of 10 ~ 13g / kg. It does not irritate the eyes and will not cause skin irritation and allergies as well.