Monograph of Inhibited Glycol

General Information:

Inhibited glycol or propylene glycol is an organic double alcohol with a chemical formula of C3H8O2 and a CAS number of 57-55-6. Its official IUPAC name is propane-1,2-diol. It is a thick, clear, and nearly odorless substance with a faintly sweet taste. Propylene glycol shares similarities with glycerin - hygroscopic, soluble with water, acetone, and chloroform.

Physical Properties:

Molecular mass:                            76.10 g/mol
Melting point:                                -59° C
Boiling point:                                187.6° C
Vapor pressure:                             0.2 (23° C)
Vapor density:                               2.62 (air=1)
Viscosity:                                    91.41 cp (10.45° C)
Surface tension:                           40.1 g/s2 (25° C)
Refractive index:                            1.4324 (20° C)
Heat of vaporization:                    66.27 kJ/mol
Heat of combustion:                     -1828 kJ/mol

Production:

Propylene glycol is usually sourced from either propylene oxide through hydrolysis, or glycerol. Production is more or less similar with glycerin, using either catalytic (150°-180°C) or non-catalytic high-temperature process (200°-220°C). Propylene glycol is manufactured using ion exchange resin or a
small amount of sulfuric acid or alkali. Final products include 20% propylene glycol, 1.5% dipropylene glycol, and other polypropylene glycols. Then, resulting glycols are further distilled to be purified prior to storage and distribution. To assure high quality and compliance with hygienic standards, production is monitored and controlled through a track-and-trace system from the start of process up to delivery point.

References:

Wikipedia - http://en.wikipedia.org/wiki/Propylene_glycol

University of Akron Chemical Database - http://ull.chemistry.uakron.edu/erd/Chemicals/8000/
7709.html

Cefic - http://www.propylene-glycol.com/production.html