Chemical Properties
clear viscous liquid
General Description
Thick odorless colorless liquid. Mixes with water.
Reactivity Profile
PROPYLENE GLYCOL(57-55-6) is hygroscopic. PROPYLENE GLYCOL(57-55-6) is sensitive to excessive heat (tends to oxidize at high temperatures). This compound can react with oxidizing materials. PROPYLENE GLYCOL(57-55-6) is incompatible with acid chlorides, acid anhydrides, chloroformates, and reducing agents. PROPYLENE GLYCOL(57-55-6) dissolves many essential oils. A mixture of this compound with hydrofluoric acid and silver nitrate was put in a glass bottle which burst 30 minutes later.
Air & Water Reactions
Water soluble.
Health Hazard
Liquid may irritate eyes.
Potential Exposure
Propylene glycol is used as a solvent;
emulsifying agent; food and feed additive; flavor, in manu-
facture of plastics; as a plasticizer, surface-active agent;
antifreeze, solvent, disinfectant, hydroscopic agent; coolant
in refrigeration systems; pharmaceutical, brake fluid; and
many others.
Fire Hazard
This chemical is combustible.
First aid
If this chemical gets into the eyes, remove any
contact lenses at once and irrigate immediately for at least
15 minutes, occasionally lifting upper and lower lids. Seek
medical attention immediately. If this chemical contacts the
skin, remove contaminated clothing and wash immediately
with soap and water. Seek medical attention immediately.
If this chemical has been inhaled, remove from exposure,
begin rescue breathing (using universal precautions, includ-
ing resuscitation mask) if breathing has stopped and CPR if
heart action has stopped. Transfer promptly to a medical
facility. When this chemical has been swallowed, get medi-
cal attention. Give large quantities of water and induce
vomiting. Do not make an unconscious person vomit.
Incompatibilities
Incompatible with oxidizers (chlorates,
nitrates, peroxides, permanganates, perchlorates, chlorine,
bromine, fluorine, etc.); contact may cause fires or explo-
sions. Keep away from alkaline materials, strong acids
(especially nitric acid), strong bases, permanganates,
dichromates; may cause a violent reaction.
Description
Propylene glycol is used as antifreeze in breweries and
diaries, in the manufacture of resins, as a solvent, and
as an emulsifier in food. It was present as an
occupational sensitizer in the color-film developer
Flexicolor.
Waste Disposal
Dissolve or mix the
material with a combustible solvent and burn in a chemical
incinerator equipped with an afterburner and scrubber.All federal, state, and local environmental regulations must
be observed.
Occurrence
Reported found in several varieties of mushrooms, roasted sesame seed, oat groats, parmesan cheese, cocoa,
pecans and truffle.
Definition
An alcohol in which the hydroxyl groups are attached to a carbon atom of a branched or straight-chain aliphatic hydrocarbon.
Indications
Propylene glycol solution (40% to 60%, v/vCH2CH[OH]CH2OH, propylene glycol)
applied to the skin under plastic occlusion hydrates the skin and causes desquamation
of scales. Propylene glycol, isotonic in 2% concentration, is a widely used vehicle
in dermatologic preparations. Hydroalcoholic gels containing propylene glycol or
other substances augment the keratolytic action of salicylic acid. Keralyt gel consists
of 6% salicylic acid, 19.4% alcohol, hydroxypropylcellulose, propylene glycol, and water and is an extremely effective keratolytic agent. Overnight occlusion is used
nightly until improvement is evident, at which time the frequency of therapy can
be decreased to every third night or once weekly. This therapy is well tolerated,
is usually nonirritating, and has been most successful in patients with X-linked
ichthyosis vulgaris. Burning and stinging may occur when applied to damaged skin.
Patients with other abnormalities of keratinization with hyperkeratosis, scaling, and
dryness may also benefit.
Preparation
Manufactured by treating propylene with chlorinated water to form the chlorohydrin, which is converted to the glycol by
treatment with sodium carbonate solution. It is also prepared by heating glycerol with sodium hydroxide.
Production Methods
Propylene glycol generally is synthesized commercially by
starting with propylene, converting to the chlorohydrin, and
hydrolyzing to propylene oxide, which is then hydrolyzed
to propylene glycol. It can also be prepared by other
methods.
Brand name
Sentry Propylene Glycol (Union Carbide); Sirlene (Dow Chemical).
Aroma threshold values
Detection: 340 ppm
Carcinogenicity
Dewhurst et al. and
Baldwin et al. in studies on the carcinogenicity of
other chemicals used propylene glycol as the solvent. As a
result they tested propylene glycol alone for carcinogenic
activity in rats and mice. Dewhurst et al. used a single
injection of 0.2 mL, whereas Baldwin et al. gave rats
and mice three to five subcutaneous injections, amount not
specified. In neither case were tumors observed during a
period of about a year or 2 years .
Wallenious and Lecholm applied propylene glycol
to the skin of rats three times a week for 14 months but found
no tumor formation. Stenback and Shubik confirmed
these findings when they applied propylene glycol at undiluted
strength and as a 50 and 10% solution in acetone to the
skin of mice during their lifetimes.
No tumors have been reported in the lifetime dietary
feeding studies . In fact, Gaunt et al.
specifically state that no tumors were found in the rats.
Environmental Fate
Propylene glycol can be released into the environment via
industrial releases or by disposal of consumer products.
Propylene glycol is readily soluble in water and has a low
sorption partition coefficient (KOC), so has the ability to move
through soil and to leach into ground water. Because of low
vapor pressure (0.1 mmHg at 25°C) and high water solubility,
there is minimal volatilization to the atmosphere from
surface water releases as well as substantial removal of its
vapors by wet deposition. Its low octanol/water partition
coefficient (KOW) indicates that bioconcentration and biomagnification
should not happen. Propylene glycol is readily
degraded in surface water and soil, by chemical oxidation and
microbial digestion, with a short half-life (1–5 days) in
aerobic or anaerobic conditions. It is also rapidly degraded in
the atmosphere by photochemical oxidation, with a half-life
about 1 day. Although environmental releases can and do
occur (airports must monitor storm water runoff of deicing
solutions), human health effects are likely to be minor, at
least in comparison to effects from potential exposures in
clinical scenarios.
Purification Methods
Dry the diol with Na2SO4, decant and distil it under reduced pressure. [Beilstein 1 IV 2468.]
Toxicity evaluation
Propylene glycol has a low degree of toxicity in animals as well
as humans, such that very high doses are needed to elicit effects
in acute toxicity studies. The toxic effects of propylene glycol
appear to be similar in animals and in humans. Central
nervous system (CNS) depression, hematologic toxicity,
hyperosmolarity, metabolic acidosis, cardiovascular effects,
and renal toxicity encompass the main acute and subacute
syndromes for propylene glycol. Most of the effects of
propylene glycol can be ascribed to high concentrations of the
parent molecule or to the accumulation of D,L-lactate in the
blood. Due to its alcohol moiety, propylene glycol at very high
concentrations is the most likely reason for the CNS depression.
Also, because high concentrations of propylene glycol will
increase the osmolarity of the blood, the hyperosmotic effects
are likely due to the parent molecule. The cardiovascular and
renal effects may be a result of the hyperosmolarity in combination
with the metabolic acidosis. The acidosis itself results
from the accumulation of lactate (both D- and L-forms), which
has been well documented in both animals and humans.
