Propylene glycol is a substance you often see in the ingredients list of cosmetics for everyday use. Some are labeled as 1,2-propanediol and others as 1,3-propanediol, so what is the difference?1,2-Propylene glycol, CAS No. 57-55-6, molecular formula C3H8O2, is a chemical reagent, miscible with water, ethanol and many organic solvents. It is a colorless viscous liquid in normal state, nearly odorless and slightly sweet on fine smell.It can be used as wetting agent in cosmetics, toothpaste and soap together with glycerin or sorbitol. It is used as a wetting and leveling agent in hair dyes and as antifreeze agent.1,3-Propylene glycol, CAS No. 504-63-2, molecular formula is C3H8O2, is a colorless, odorless, salty, hygroscopic viscous liquid, can be oxidized, esterified, miscible with water, miscible in ethanol, ether.
It can be used in the synthesis of many kinds of drugs, new polyester PTT, pharmaceutical intermediates and new antioxidants. It is the raw material for the production of unsaturated polyester, plasticizer, surfactant, emulsifier and emulsion breaker.Both have the same molecular formula and are isomers.1,2-Propylene glycol is used as an antibacterial agent or a penetration promoter in cosmetics at high concentrations.At lower concentrations, it is generally used as a moisturizer or cleansing aid.At lower concentrations, it can be used as a pro-solvent for active ingredients.The skin irritation and safety at different concentrations are completely different.1,3-Propylene glycol is mainly used as a solvent in cosmetics. It is an organic polyol moisturizing solvent that helps cosmetic ingredients penetrate into the skin.It has higher moisturizing power than glycerin, 1,2-propanediol and 1,3-butanediol. It has no stickiness, no burning sensation, and no irritation problems.
The main production methods of 1,2-propanediol are:1. Propylene oxide hydration method;2. Propylene direct catalytic oxidation method;3. Ester exchange method; 4.glycerol hydrolysis synthesis method.1,3-Propylene glycol is mainly produced by:1. Acrolein aqueous method;2. Ethylene oxide method;3. Glycerol hydrolysis synthesis method;4. Microbiological method.1,3-Propylene glycol is more expensive than 1,2-Propylene glycol. 1,3-Propylene glycol is a little more complicated to produce and has a lower yield, so its price is still high.However, some information shows that 1,3-propanediol is less irritating and less uncomfortable to the skin than 1,2-propanediol, even reaching the level of no uncomfortable reaction.Therefore, in recent years, some manufacturers have replaced 1,2-propanediol with 1,3-propanediol in cosmetic ingredients to reduce the discomfort that may occur to the skin.Skin discomfort caused by cosmetics may not be caused by 1,2-propanediol or 1,3-propanediol alone, but may also be caused by a variety of factors. As people’s concept of cosmetic health and safety deepens, the strong market demand will further prompt many manufacturers to develop better products to meet the needs of the majority of beauty lovers!
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