PNB - Propylene Glycol Monobutyl Ether

About This Product

Propylene glycol n-butyl ether, PnB, has the formula C7H16O2 and CAS number 5131-66-8. It is a clear colourless liquid with limited rather than complete water miscibility, reflecting the four-carbon butyl chain, and it has the highest boiling point and slowest evaporation of the mono-propylene glycol ethers. Slow evaporation is what it is chosen for. In a drying coating, solvents leave in sequence, and the last to go determines how well the film levels. A solvent that flashes off too early leaves the resin unable to flow, so brush marks and orange peel are locked in; a tail solvent that lingers keeps the film mobile long enough for surface tension to pull it flat. PnB performs that role, and its strong solvency for resins means it also keeps the binder in solution as the faster components leave, preventing the resin from precipitating and blushing. In cleaning formulations the butyl chain gives it the strongest grease-cutting power of the P-series, though with lower water tolerance than PnP. It is used as a coalescent and tail solvent in coatings, in industrial cleaners and degreasers, printing inks, and in coil and can coatings. Bio Green Chem supplies PnB to specification on assay, alpha isomer content, water, acidity, colour and residue.