Monopropylene Glycol (MPG) is a derivative of Propylene Oxide (PO) and is produced in a two-step process. The first step is the reaction of PO with water into a mixture of MPG and Dipropylene Glycol (DPG) and the second step is the distillation and purification of the mixture into its two separate components (MPG and DPG) with MPG being the main component. Shell Chemical companies supply MPG in two different qualities: the industrial grade and the Unites States Pharmacopoeia (USP) grade, which is produced applying Good Manufacturing Practices (GMP) as described for pharmaceutical excipients.
MPG is a colourless, viscous and odourless liquid. It is highly hygroscopic and miscible in all ratios with water, alcohols, esters, ketones and amines. It has limited miscibility with halogenated hydrocarbons and is not miscible with aliphatic hydrocarbons.