ADIPIC ACID
HAZARDOUS MATERIALS
CHEMICAL DATA NOTEBOOK SERIES #52
Adipic acid is a mildly corrosive, irritating, moderately toxic, white crystalline solid with no detectable odor. It is used in the manufacture of certain plastics (particularly nylon) and other synthetic resins, additives for food, adhesives, baking powders, foams, and lubricants. Although considered stable, it is incompatible with many chemicals.
PROPERTIES
Although adipic acid is a solid, it melts at the relatively low temperature of 303°F. The melt has a measured flash point of 376°F (one reference lists an open cup flash point of 300°F, which means it is producing sufficient vapors to form an ignitable mixture at its melting point). It is unusual that a solid material has a flash point, so pay attention to this material in any situation where it may be exposed to high heat. It has an ignition temperature of 788°F—again, a rather low value. There is no established flammable range for adipic acid, but a mixture of 10 to 15 mg (milligrams) of dust per liter of air will cause an explosion, which makes this mixture of dust in air its lower explosive limit.
The listing of an ignition temperature of 788°F in some references is questionable, since the material itself decomposes at 626°F. Decomposition of organic materials usually produces hydrocarbon gases, which are very flammable. So instead of vapors of adipic acid forming an ignitable mixture, a mixture of other hydrocarbon gases may explode when ignited. Emergency responders should be aware of this possibility.
Adipic acid solid has a specific gravity of 1.36, and the liquid (melted adipic acid) has a specific gravity of 1.07. Many of the decomposition products may have vapor densities greater than 1.0. The molecular weight of adipic acid is 146, and any vapors will have a density of 5.04. Adipic acid is slightly soluble in water. The molecular formula of adipic acid is COOH(CH2)4COOH.
HAZARDS
Adipic acid is an organic rather than an inorganic acid. Inorganic acids are known as “strong” acids, defined by the degree of ionization in water. Since organic acids produce almost no ions in water, they are classified as “weak” acids. However, do not be misled into believing that weak acids are not corrosive. Many organic acids, such as acetic acid, chloroacctic acid, and formic acid, are very corrosive in concentrated form. Adipic acid, however, is only mildly corrosive but may still cause skin burns and damage some metals.
Skin contact with adipic acid may cause some irritation. Contact with the eyes may be more serious, since adipic acid is a severe eye irritant. Single-dose ingestions usually are not toxic. Avoid breathing the dust of adipic acid.
Adipic acid, like all other organic compounds, will burn. Emergency responders may be surprised to see the material burn, thinking that corrosivity is the acid’s main hazard. Thus it is important to know the difference between organic and inorganic material and how each behaves in release situations.
Although adipic acid is considered a stable chemical, it reacts with many other chemicals. It does not react with water, but it does react with the following classes of chemical substances: amines, azo compounds, aldehydes, alcohols, caustics, cyanides, diazo compounds, dithiocarbamates, epoxides, inorganic fluorides, glycols, explosives, isocyanates, hydrazines, nitrides, nitriles, and sulfides. It also will react with certain metals, all polymerizable materials, strong oxidizing agents, and strong reducing agents. The reactions between adipic acid and such materials may be violent or exothermic or liberate toxic decomposition products, depending on what material it contacts. Some reactions may be worse than others. Exercise care whenever a mixture of chemicals may occur.
IDENTIFICATION NUMBERS AND RATINGS
CAS
(Chemical Abstract Services)
124-04-9
STCC
(Standard Transportation Commodity Code)
AU8400000
UN/NA
(United Nations/North America)
NA 9077
CHRIS
(Chemical Hazard Response Information System) ADA
DOT
(U.S. Department of Transportation)
ORM-E
NFPA 704 Rating
1-1-0
NONFIRE RELEASE
As with the accidental release of any hazardous material, notify the proper local, state, and federal environmental authorities immediately when a release might harm the environment. They will determine whether responder actions or acts of nature (wind, rain, flooding) have resulted in damage to the environment.
In the event of a spill on land, adipic acid can be collected and placed into secure containers (the solid form is easier to collect than the liquid). Small amounts may be shoveled into secure containers as long as those who do so are protected from contacting the product. Take care to use equipment that is compatible with adipic acid.
On larger spills, larger equipment such as front-end loaders and backhoes may be used. However, the larger equipment may produce dust, which may form an explosive mixture with the air. If it does produce dust, take care to avoid all ignition sources in the vicinity and downwind. Since the equipment can be an ignition source, equipment operators must be protected from the dust, and the equipment must be compatible with the adipic acid, or corrosion might cause serious damage. If excessive dust is produced by this mitigation technique, discontinue it.
Wind conditions at the time of the spill may cause large amounts of dust to be produced. If this occurs, eliminate all ignition sources downwind and consider evacuation in the same direction. To combat these winds, the spilled material may be covered with a compatible material, which itself may become contaminated.
In any event, if the material can be salvaged (by professionals), the environmental authorities will then examine the area contaminated by the product and direct a cleanup crew (of professionals) to remove and dispose of soil and other contaminated materials according to local, state, and federal regulations.
If there is a chance that it will rain or that water will reach the spilled solid adipic acid, containment dikes may be built around the material to contain any water that has dissolved adipic acid. A dike also will prevent running water from entering the area where the spill has occurred. Any contaminated water may be suctioned from the diked area, and any remaining liquid may be absorbed by the addition of cement powder, clay, fly ash, sand, soil, or any similar material. All contaminated water and sorbent must be disposed of in the same manner as contaminated soil.
If any adipic acid enters a sewer, notify all downstream processors of the sewage (and sewage water) immediately. Sewage treatment plants can divert the flow to an area where the water may be treated and/or removed. Prevent entry of adipic acid into the sewer by diking or otherwise blocking catch basins and manhole covers.
Avert entry of adipic acid into streams and other waterways. Any that does enter a stream will sink to the bottom (if the flow of water is not fast) and slowly dissolve. The water’s volume and speed will determine the speed with which the adipic acid dissolves in it. If adipic acid does enter a waterway, notify all downstream users immediately.
If the stream is slow-moving, and the product has sunk to the stream bed, it will remain there and slowly dissolve. It may be vacuumed from the stream and stored in secure containers. Drop sand bags in front of the product to prevent it from moving downstream if the flow is light. In any case, diversion dams can contain the contaminated water and lead it into holding areas for removal or treatment.
Treatment of contaminated water includes the use of materials that will either neutralize the product or remove it. Contact the manufacturer of the product to find out the proper neutralization agents. At least one reference recommends solutions of sodium bicarbonate (baking soda) or sodium carbonate (baking power or soda ash). Activated charcoal may be added to the water and mixed. The charcoal then must be removed from the water after it has adsorbed the product. This may be done by suctioning the contaminated water through a filter onshore. All contaminated charcoal must then be disposed of in the same manner as the contaminated soil.
Consult environmental authorities before dredging or pumping stream or lake beds. Such actions might spread the contamination rather than eliminate it. These same authorities will decide when the water is no longer contaminated and thereby safe for downstream consumers to use.
A major concern in an accidental release of adipic acid is the possibility of it contacting any of the chemicals with which it is incompatible. I have given you a list of “families” of chemicals—each of which contains several dozen chemicals that might produce an unwanted reaction.
If the release occurs in a rail accident, it is imperative that emergency responders be aware of all other chemicals carried by the train, their locations, and their amounts. Because of the vast amounts of chemicals carried by rail that might produce violent reactions, it is important to develop a good communications system with the railroads and incorporate it into training. Many if not all railroads are more than anxious to provide training sessions for hazardous-materials response teams, and jurisdictions with these teams should encourage such training.
FIRE SCENARIO
Adipic acid, when exposed to heat radiated from a fire, will melt when raised to the relatively low temperature of 303°F. At 376°F, its flash point, it will produce vapors sufficient to form an ignitable mixture with the air near the surface of the melted material. This means that adipic acid, a solid, may really be a Class B material, and firefighting techniques for liquids will have to be used here. Use alcohol foam, carbon dioxide, dry foam, and water fog or spray as extinguishing agents, depending on the amount spilled, the location, and weather conditions.
Once the material has melted and begins to burn, its temperature (at least that of the material closest to the flames) will rise rapidly. Adipic acid will begin to decompose at 626°F, liberating many flammable gases that might also be corrosive and/or toxic. The combustion of these gases will accelerate the melting, vaporizing, and decomposing of the product.
Any container of adipic acid exposed to heat will be in danger of bursting. As the adipic acid melts and vaporizes, pressure inside the container will rise and, if not relieved, will cause the container to fail catastrophically. If the container is metal, pieces of shrapnel will accompany the pressure relief explosion. Keep all drums and tanks of adipic acid cool by applying water from as far away as possible.
FIRST AID
For inhalation, remove the victim to fresh air. If the victim has stopped breathing or breathing has become difficult, administer artificial respiration (mouth-to-mouth resuscitation may expose the provider of first aid to material in the victim’s mouth or vomit). Provide medical attention immediately.
SYNONYMS
acifloctin
acinetten
adilactetten
adipinic acid
1,4-butanedicarboxylic acid
hexanedoic acid
1,6-hexanedoic acid
molten adipic acid
For ingestion, seek immediate medical attention. Although the toxicity of adipic acid is not considered high, information on the effects of ingestion is not readily available.
For skin contact, remove all contaminated clothing and wash all affected body areas with large amounts of water. Medical attention is necessary if irritation of the skin persists after washing.
For eye contact, immediately flush the eyes with large amounts of water for 15 minutes, occasionally lifting the eyelids. Provide immediate medical attention.
PROTECTIVE CLOTHING AND EQUIPMENT
Select protective clothing and equipment that prevent contact of the material with the eyes, skin, and respiratory system. Rubber boots, gloves, and aprons will offer protection, and turnout gear should be similarly resistant to this corrosive. Dustproof safety goggles, splashproof goggles (for liquids and solutions), and face masks impervious to adipic acid will protect the face and eyes. Manufacturers of encapsulating suits claim that suits made from natural rubber, neoprene, nitrile rubber, and polyvinyl chloride (PVC) offer protection. Wear positive-pressure, self-contained breathing apparatus whenever dusts, mists, and vapors may be present.
