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The plastics and rubber industries rely heavily on organic peroxides for use in accelerators, activators, catalysts, cross-linking agents, curing agents, hardeners, initiators and promoters. Because of the unstable (O-O) bond, organic peroxides are known to be severe fire and explosion hazards. Therefore, these substances must be treated with great care during handling, storage and transportation.
Below is a list of safety measures to take into consideration when storing and handling organic peroxides. This list is not exhaustive and you should always consult the accompanying safety data sheet (SDS) for specific requirements for your specific product.
Types of Hazards
All organic peroxides should be considered highly combustible. Once ignited, most organic peroxides burn vigorously. Some peroxides react so violently that they are considered explosively combustible. To ensure worker safety, manufacturers must follow local fire codes and ordinances for the handling and use of organic peroxides.
The flammability of organic peroxides is affected by their decomposition products. When heated to the decomposition point, organic peroxides will generate vapors and heat. Many of these vapors are extremely flammable and may cause an explosion. If the auto-ignition temperature is reached, an explosion may occur even without the presence of fire.
Thermal (Heat) Sensitivity
All organic peroxides are sensitive to heat. As a general rule, the more reactive the peroxide, the more heat-sensitive it is. Many initiators require a controlled temperature storage environment. For example, high-activity initiators must be stored at refrigerated temperatures, while other initiators may require storage at temperatures below 0 °F (-18 °C).
When peroxide is heated to its decomposition point, the peroxide bond breaks, releasing heat. The released heat accelerates the decomposition of the remaining product. This may continue until the acceleration is out of control and the product catches fire or explodes. If a decomposition has occurred after the air has cleared, there may not be any evidence of fire. Extreme care should be taken so that the vapors released during decomposition are not exposed to additional ignition sources, such as lit cigarettes, matches, lighters, sparks or flames.
The best safeguard against decomposition due to heat is to carefully follow the recommended storage instructions for each product noted on the storage container and SDS. If the product requires refrigeration, temperature alarm systems are recommended to alarm in the event that refrigeration fails.
The decomposition of organic peroxides can be accelerated by chemical contamination, in addition to heat. Certain chemicals like accelerators, acids and bases will cause rapid decomposition to occur at ambient temperatures. Many heavy metals such as copper, iron and brass will have a similar effect over a longer period of time.
Cobalt or amine accelerators, often used in reinforced plastics, are especially dangerous if they come in contact with organic peroxides. These chemicals are often used in the same processes as organic peroxides to promote the cure of unsaturated polyester resins. Special care must be taken to ensure that accelerators never come into direct contact with organic peroxides. In the event of chemical contamination, the same hazards exist as with thermally induced decomposition.
Safe Storage of Organic Peroxides
Storage temperature is one of the most important considerations to take into account when storing organic peroxides. It is essential that you follow storage temperature recommendations. Most organic peroxides can be stored at ambient temperatures (less than 90 °F [30 °C]). However, for a shelf life of more than a month, peroxides should be stored at a maximum of 77 °F (25 °C).
Peroxides should always be stored out of direct sunlight and away from any heat sources, such as steam pipes, heaters and hot materials. Some organic peroxides may require refrigeration. Any refrigerators containing organic peroxides should be equipped with a remote monitoring system to alert in the event of a refrigeration failure.
When receiving any organic peroxide shipments, immediately inspect all containers to ensure that they have arrived undamaged and are properly labeled. Be sure to reject any damaged containers. Suppliers will ship organic peroxide in their recommended storage containers. Whenever possible, organic peroxide should be stored in this packaging. Repackaging organic peroxides is not advised and can be dangerous if the new packaging is not clean or contains an incompatible material. After use, it is not recommended to return any unused materials to their original storage container, and they should be discarded as indicated on the SDS.
When not in use, containers should always be tightly closed. Storing open or partially open organic peroxides or diluted peroxides can lead to evaporation which can result in exposure to the more hazardous dry peroxide.
If the material is shipped with a venting cap, it is essential that a direct like-for-like venting cap be used if a replacement is needed. Venting caps should be checked regularly to ensure that they are working properly and not allowing hazardous gases to build up inside the container. Vented containers should never be stacked on top of one another.
Large quantities of organic peroxides should be stored in a specifically designed, isolated storage building. The building should be constructed with fire and explosion safety in mind and in compliance with NFPA-applicable codes.
Safe Handling of Organic Peroxides
Organic peroxides have strict handling requirements that should be followed closely. Due to their unstable nature, it is critical that organic peroxides are stored and handled in well-vented areas away from heat or flame sources.
When handling a container of organic peroxide, you should observe the following safety measures:
- Wear clean gloves and handle the material like a corrosive.
- Wear protective, sensible clothing.
- Wear safety goggles or eye protection.
- Avoid skin contact.
- Avoid breathing in peroxide fumes, vapors or particles.
The material should only be handled away from other chemicals or near known compatible chemicals. Make sure that all weighing and handling materials are clean and do not contain any traces of incompatible chemicals. If the container must be moved, ensure that it is handled gently to avoid friction or impact. When transferring peroxides to metering or dosing vessels, or when adding peroxides to resin batches, add the material slowly. Avoid splashing or spilling the product. Never mix peroxides with accelerators.
In case of a fire, use water spray, dry chemical or carbon dioxide to extinguish it. Water will help control the spread and promote cooling. However, water alone will not extinguish an organic peroxide fire, so an additional extinguishing agent is necessary. Organic peroxide fires are intense and explosive, so they should be contained swiftly and carefully.
In the event of human exposure to organic peroxides, seek medical attention and always consult the SDS. Exposure may cause eye, skin and/or respiratory irritation, nausea, drowsiness or dizziness.