The physical and chemical properties
Depending on the size of the relative molecular weight, the physical form of PEG can range from white mucus Mw200 ~ 700 to waxy semi-solid (Mw 1000 ~ 2000) to hard waxy solid (Mw3000 ~ 20000). Polyethylene glycol is soluble in water and some common organic solvents. Liquid POLYETHYLENE glycol can be miscible with water in any proportion, while solid polyethylene glycol has only a limited solubility, but even polyethylene glycol with a relatively large molecular weight fraction is still more than 50% soluble in water. When the temperature rises, the solubility of polyethylene glycol increases rapidly. If the temperature is high enough (e.g., PEG-6000, 60℃), solid polyethylene glycol of all grades can be dissolved in any proportion with water. But as the temperature continues to rise close to the boiling point of water, polyethylene glycol (PEG) precipitates, even in a dilute solution, at a temperature that depends on the polymer's relative molecular weight and concentration. When polyethylene glycol is mixed with water, it exhibits slight volume shrinkage and is significantly exothermic.
Peg is stable under normal conditions, but it interacts with oxygen in the air at 120℃ or higher. In an inert atmosphere (such as nitrogen and carbon dioxide), it does not change even when heated to 200 ~ 240℃, and pyrolysis occurs when the temperature rises to 300℃. Adding antioxidants, such as phenothiazine with a mass fraction of 0.25 to 0.5, improves its chemical stability. Any of its decomposition products are volatile and do not produce hard crust or mucilaginous sediments.
Polyethylene glycol is a non-toxic and non-irritating high molecular polymer formed by condensation of ethylene oxide and water. Its molecular formula is H(OCH2)NOH. It is widely used in various pharmaceutical preparations. A range of products are available, depending on the degree of polymerization. Polyethylene glycol (PEG) is liquid when its molecular weight is less than 1000. If it's greater than 1000, it's solid. Polyethylene glycol 6000 and POLYETHYLENE glycol 4000 are the most commonly used substrates for drop pills.
Polyethylene glycol 6000 and POLYETHYLENE glycol 4000 are easily soluble in water, ethanol, acetone, chloroform, etc., and insoluble in petroleum ether, ether, ethylene glycol, dimethyl silicone oil, liquid paraffin, vegetable oil, etc. Polyethylene glycol 6000 and POLYETHYLENE glycol 4000 are white waxy solids, tasteless, with melting points of 55 ~ 60℃ and 48 ~ 53℃, respectively. At 100℃, the relative density is 1.072 ~ 1.075, the pH value of solution is 4.0 ~ 7.0, and the dielectric constant is 3.6. Pegylated 6000 and PEgylated 4000 have no physiological effect, good chemical stability, no hydrolysis, heat resistance, no corrosion, can absorb part of the liquid, help to dissolve the medicine, slightly wetting, after contact with water, first expanded into gel and then dissolved.
Polyethylene glycol (PEG) is soluble in other melted pill substrates, such as polyoxyethylene monostearate (S-40), polyvinylpyrrolidone (PVP), poloxamer, stearic acid, monostearic glyceride, etc. Therefore, it can be made into a composite matrix, and disintegrating agents, solubilizers, etc. Can be added to improve its properties. The hardness and heat resistance of polyethylene glycol 6000 are better than that of POLYETHYLENE glycol 4000. Generally, traditional Chinese medicine dropping pills contain extract, volatile oil, etc., which can reduce the hardness of dropping pills. Therefore, traditional Chinese medicine dropping pills are mainly used as matrix.
Some dropping pills also often use different proportions of polyethylene glycol 6000 and POLYETHYLENE glycol 4000 mixed matrix, such as using polyethylene glycol 4000 as the matrix, adding part of polyethylene glycol 6000 can improve the hardness, liquidity, heat resistance of dropping pills; When using POLYETHYLENE glycol 6000 as the matrix, adding part of POLYETHYLENE glycol 4000 can reduce the viscosity of the liquid and the dripping temperature, avoid the rounding difference of dropping pills and the phenomenon of towed needle tail. However, it has been found through experiments that when the ratio of POLYETHYLENE glycol 6000 to POLYETHYLENE glycol 4000 is 1:1 as a mixed matrix, its heat resistance is the worst, which is not conducive to drug transportation and storage.
Polyethylene glycol is soluble in most highly polar organic solvents, such as alcohols, alcohol-silicon mixtures, diols, esters, ketones, aromatic hydrocarbons, nitroalkanes, etc. It is insoluble in aliphatic hydrocarbons, cycloalkanes and other organic solvents of low polarity. The solubility of polyethylene glycol is related to its molecular weight fraction and temperature. Polyethylene glycol is also soluble in lower aldehydes, amines, organic acids, anhydrides, and monomers of polymers. But it does not dissolve in rapeseed oil, mineral oil and other compounds containing long hydrocarbon chains.
Liquid PEG (e.g. Peg-400) has a very good solubility in many pharmaceutical raw materials, which is a very useful property for applications.
Polyethylene glycol and polyethylene glycol fatty acid esters are widely used in the cosmetic and pharmaceutical industries. Polyethylene glycol (PEG) has many excellent properties, such as water solubility, non-volatility, physiological inertia, mildness, lubricity and moistening, softness and pleasant after use. The viscosity, hygroscopicity and microstructure of the product can be changed by using polyethylene glycol with different molecular weight grades. Polyethylene glycol (Mr<2000) with low molecular weight is suitable for use as a wetting agent and consistency modifier, for creams, lotions, toothpastes, shaving creams, etc., and also for uncleaned hair care products to give hair a silky sheen. Polyethylene glycol (Mr >2000) with high molecular weight is suitable for lipstick, deodorant bar, soap, shaving soap, foundation and cosmetic products. In detergents, PEG is also used as a suspension and thickener. Used in the pharmaceutical industry as a substrate for ointments, emulsions, ointments, lotions, and suppositories. Compulsory Polyethylene Glycol (such as Compulsory medicine NF, Dow Chemical Co.) is more suitable for cosmetics. The use of methoxy polyethylene glycol and polypropylene glycol is similar to that of polyethylene glycol.
The food Additives Supplement regulation of the Federal Food, Drug, and Cosmetic Regulations of the United States has approved the use of the food chemical pharmacopeia grade POLYETHYLENE glycol as a food additive, either directly or indirectly. The ADI value was set by FAO/ WHOin 1985 as 0 ~ 10mg/kg body weight. GRAS(FDA, § 172.820, 1985). Acute transoral toxicity (MICE)LD5033 ~ 35g/kg, intraperitoneal toxicity LD5010 ~ 13g/kg. Does not irritate the eyes, will not cause skin irritation and allergies.