Propylene glycol

Infobox on Propylene glycol
Example of Propylene glycol
Facts
Origin	-
Stowage factor (in m3/t)	-
Humidity / moisture	-
Ventilation	-
Risk factors	See text

Propylene glycol

Description

What is propylene glycol?
Propylene glycol is a synthetic liquid substance that absorbs water. Propylene glycol is also used to make polyester compounds, and as a base for de-icing solutions. Propylene glycol is used by the chemical, food, and pharmaceutical industries as an antifreeze when leakage might lead to contact with food. The Food and Drug Administration (FDA) has classified propylene glycol as an additive that is "generally recognized as safe" for use in food. It is used to absorb extra water and maintain moisture in certain medicines, cosmetics, or food products. It is a solvent for food colours and flavours, and in the paint and plastics industries. Propylene glycol is also used to create artificial smoke or fog used in fire-fighting training and in theatrical productions. Other names for propylene glycol are 1,2-dihydroxypropane, 1,2-propanediol, methyl glycol, and trimethyl glycol. Propylene glycol is clear, colourless, slightly syrupy liquid at room temperature. It may exist in air in the vapour form, although propylene glycol must be heated or briskly shaken to produce a vapor. Propylene glycol is practically odourless and tasteless.
The freezing point of water is depressed when mixed with propylene glycol owing to the effects of dissolution of a solute in a solvent (freezing-point depression); in general, glycols are non-corrosive, have very low volatility and very low toxicity (however, ethylene glycol is toxic to humans and many animals).

What happens to propylene glycol when it enters the environment?
Waste streams from the manufacture of propylene glycol are primarily responsible for the releases into the air, water, and soil. Propylene glycol can enter the environment when it is used as a runway and aircraft de-icing agent. Propylene glycol can also enter the environment through the disposal of products that contains it. It is not likely to exist in large amounts in the air. There is little information about what happens to propylene glycol in the air. The small amounts that may enter the air are likely to break down quickly. If it escapes into the air, it will take between 24 and 50 hours for half the amount released to break down. Propylene glycol can mix completely with water and can soak into soil. It can break down relatively quickly (within several days to a week) in surface water and in soil. Propylene glycol can also travel from certain types of food packages into the food in the package.

How might I be exposed to propylene glycol?
Propylene glycol has been approved for use at certain levels in food, cosmetics, and pharmaceutical products. If you eat food products, use cosmetics, or take medicines that contain it, you will be exposed to propylene glycol, but these amounts are not generally considered harmful. People who work in industries that use propylene glycol may be exposed by touching these products or inhaling mists from spraying them. These exposures tend to be at low levels, however. Propylene glycol is used to make artificial smoke and mists for fire safety training, theatrical performances, and rock concerts. These artificial smoke products may also be used by private citizens. These products are frequently used in enclosed spaces, where exposure may be more intense.

How can propylene glycol ether enter and leave my body?
Propylene glycol can enter your bloodstream if you breathe air containing mists or vapours from this compound. It can also enter your bloodstream through your skin if you come in direct contact with it and do not wash it off. If you eat products that contain propylene glycol, it may enter your bloodstream. Exposure of the general population to propylene glycol is likely since many foods, drugs, and cosmetics contain it. Propylene glycol breaks down in the body in about 48 hours. However, studies of people and animals show that if you have repeated eye, skin, nasal, or oral exposures to propylene glycol for a short time, you may develop some irritation.

How can propylene glycol affect my health?
Propylene glycol breaks down at the same rate as ethylene glycol, although it does not form harmful crystals when it breaks down. Frequent skin exposure to propylene glycol can sometimes irritate the skin.

Is there a medical test to determine whether I have been exposed to propylene glycol?
Propylene glycol is generally considered to be a safe chemical, and is not routinely tested for, unless specific exposure, such as to a medicine or cosmetic, can be linked with the observed bad symptoms. Since propylene glycol breaks down very quickly in the body, it is very difficult to detect.

What recommendations has the federal government made to protect human health?
The government has developed regulations and guidelines for propylene glycol. These are designed to protect the public from potential adverse health effects.The Food and Drug Administration (FDA) has classified propylene glycol as "generally recognized as safe," which means that it is acceptable for use in flavourings, drugs, and cosmetics, and as a direct food additive. According to the World Health Organization, the acceptable dietary intake of propylene glycol is 25 mg of propylene glycol for every kilogram (kg) of body weight.

Application

Propylene Oxide based glycols are used in a multitude of different areas for example as solvents, extraction liquids and humectants. They are used as antifreeze agent for refrigerators and sprinkler systems, as solvents and humectants for printing colours and ink-pads as well as plasticers for cellophane. Furthermore Propylene Glycol is used as a component for the production of fire-resistant brake and hydraulic fluids, as a starter molecule for raw materials of colors and paints, as a raw material for de-icing of planes as well as in heating fluids for high-temperature work.

1,2-Propylene Glycol (MPG) is a colorless, liquid, nearly odorless by-product of Propylene Oxide and is generated by adding water.

Dipropylene Glycol (DPG) is a by-product from monopropylene glycol production. DPG is a colorless, liquefied, nearly odorless liquid. Dipropylene Glycols are used as components for fragrances, as solvents for the production of semi-conductors and ink-pads, as additives for the leather industry, as a component for hydraulic fluids and as additives for color emulsions.

Tripropylene glycol stabilized (TPG) is a condensation product of 1,2-propylene glycol. TPG is presented as a mixture of isomers which are formed by the reaction of propylene oxide and water. TPG is a clear, colorless, hygroscopic, water soluble fluid with medium viscosity, low vapour pressure and a faint glycol-specific odor. Tripropylene glycol is used in textile soaps, lubricants and cutting oil concentrates, in body care applications like stick deodorants and as a solvent to dissolve inks (ink removal creams).

Shipment / Storage

Propylene glycol, Industrial grade properties:

• Boiling Point: 186 – 189°C.
• Melting Point: -59°C.
• Flash Point: 99°C
  
  

Miscibility, fully in water, acetone, ethanol, chloroform, diethyl ether.

Shipped containerised in drums or in bulk on board tanker vessels.

Cargo Handling Requirements on board tanker vessels

• Prepurging of Vessel’s Tanks: No
• Pre-purge Oxygen Content: N/A
• Pre-purge Dew Point: N/A
• Blanket Required: Yes
• Percent Oxygen in Nitrogen Blanket: 5%
• Vapor Space Purge: No
• Loading Temperature Range: 10 – 35°C.
• Transit Temperature Range: 10 – 35°C.
• Discharge Temperature Range: 10 – 35°C.
• Maximum Heating Coil Temperature: Not required unless temp falls below 0°C.
• Adjacent Maximum Cargo Temperature: 35°C.
  
  

For overseas carriage aspects of Chemicals, the readers are recommended to acquire or have access to a good chemical dictionary, and a copy of the International Maritime Dangerous Goods (IMDG) Code, issued by the International Maritime Organisation. Also consult the applicable MSDS sheet.

Risk factors

May cause irritation to skin and eyes.