What Is Tripropylene Glycol?
Tripropylene glycol is a type of glycol that has two hydroxyl groups (-OH) in its molecule.
It does not exist in nature and is synthesized artificially. Substances similar to the molecular structure of tripropylene glycol include propylene glycol and dipropylene glycol. Tripropylene glycol has a molecular structure similar to dipropylene glycol, with an additional propylene bond.
Tripropylene glycol is liquid and colorless at room temperature. It is a flammable liquid and should be kept away from fire.
Uses of Tripropylene Glycol
Uses for tripropylene glycol include intermediate raw materials for various polyurethanes and various acrylic esters, solvents for paints and inks, antifreeze solutions, and intermediate raw materials for polyester resins. Tripropylene glycol is also used as a raw material for synthesizing other compounds. Compounds synthesized with tripropylene glycol as a starting material include tripropylene glycol diacrylate.
Tripropylene glycol is also used as a cosmetic ingredient, as is propylene glycol or dipropylene glycol. Unlike propylene glycol, which is often used for moisturizing and antiseptic purposes, tripropylene glycol is used to provide water retention or emulsion stability effects.
Tripropylene glycol is a relatively safe and low-toxicity substance, but it should be used with caution because it can cause skin problems in rare cases, such as in people with alcohol hypersensitivity.
Characteristics of Tripropylene Glycol
Tripropylene glycol is characterized by its relatively high hydrophilicity due to the presence of both hydroxyl (-OH) and ether (-O-) groups in its molecule. In other words, tripropylene glycol is a highly polar organic compound. As such, it has properties that are somewhere between those of oil and water.
Tripropylene glycol is completely miscible and soluble with water. It is also easily soluble in polar organic solvents such as alcohols. Due to its high polarity, it has a high boiling point of about 270°C. Since its melting point is below -30°C, it does not become solid and remains liquid even below the freezing point.
Structure of Tripropylene Glycol
Tripropylene glycol has a structure similar to three propylene glycols joined in series via an ether bond. Specifically, the molecular structure is such that the -OH groups at both ends of the middle propylene glycol are joined to each of the remaining two propylene glycols as an ether bond. Since there is one -OH group at each end of the molecular chain, it is a type of diol.
The molecular formula is simply HO (C3H6O) 3H, but the part in parentheses is generally branched rather than linear. In more detail, it is CH3CHOHCH2OCH (CH3) CH2OCH (CH3) CH2OH. The molecular structure consists of a -OH at each end of the molecular chain with two ether bonds between the two ends flanked by hydrocarbons.
Other Information on Tripropylene Glycol
How Tripropylene Glycol Is Made
Tripropylene glycol, like propylene glycol or dipropylene glycol, is generally produced from propylene oxide. In detail, it is obtained by ring opening of propylene oxide in the presence of water. In this process, propylene glycol is obtained as the main product, while tripropylene glycol is obtained as a by-product.
Therefore, tripropylene glycol is not necessarily produced in large quantities. Tripropylene glycol can be efficiently produced if the reaction occurs to combine only three propylene oxides, but it is difficult to control the reaction completely.
For example, dipropylene glycol with two propylene oxides attached would also be produced. A method to produce only tripropylene glycol specifically has been investigated, but it has not yet become a mainstream production method.