Recognizing and Understanding Reactive Chemicals Part 3

FUNDAMENTALS OF REACTIVE CHEMICAL CHEMISTRY

Peroxide formers–chemicals with the ability to form explosive peroxides such as ethyl ether or tetrahydrofuran

Reoxidation:  peroxides fored by the reaction of a peroxidizable compound with molecular oxygen through a process called auto-oxidation or peroxidation

Exposure to air: allows O2 into the chemical chain and may deplete the inhibitor allowing o2 to bond to the chemical chain

Exposure to light and or heat: allows energy source into the chemical that can increase peroxide formation and also deplete the inhibitor

Storage conditions: fluctuations of temp cause containers to breathe, bringing o2 into the container and evaporating the chemical.  Peroxides thus become concentrated in solution and on the threads.

Loss of inhibitor: inhibitor often called stabilizers, are used to prevent the formation of peroxides by reacting with atmospheric o2 instead of the o2 reacting with the chemical and bonding to the chain.  When the inhibitor is spent or used up, then o2 is able to react with the chemical and peroxides begin to form.

Hazards
peroxides are very unstable due to the O – O bond. they are insensitive to heat, friction, impact, and light. They can explode, thus igniting the solvent they are in, causing a fireball. peroxides are less volatile than the solvent or chemical they are formed in and tend to concentrate in solution or on container threads. peroxides are most dangerous when dry, but available literature indicates that a percentage of 0.008 (80ppm) are dangerous. this is why containers that have been previously opened and contain a small amount of the original solvent tend to the cause the most problems. peroxide test strips indicate the level of hydrogen peroxide which reflects directly on the level of other types of peroxides present. Hydroperoxides are believed to be the most dangerous, and the overall hazard associated with a given peroxide forming chemical structure generally decreases for its higher molecular weight derivatives.

Warning signs
some of the warning signs for possible peroxide formation are:

age – shelf life is very important when assessing peroxide forming chemicals. opened containers of these chemicals are recommended to be disposed of within one month after first opening the cap, and unopened containers are recommended to be disposed of within one year from when purchased. the inhibitor or stabilizer can be lost over time, thus allowing peroxides to form.

storage conditions – be aware of container condition, any visible contamination, the types of container, and temperature fluctuations during storage. Bulged, damaged, rusty, containers must be approached with extreme care.

visible formation – peroxides may be visible when concentrated and can be in the form of clouds, needles, a large mass suspended in the liquid, or powdery residue or crystals around the cap.

Stabilization – stabilization of peroxides is achieved through special procedures developed by ONYX. they usually involve a remote opening and a chemical reduction or dilution with a suitable solvent.

LIST A- RED LABEL

(THREE MONTHS)

PEROXIDE HAZARD ON

STORAGE

 Isoprophyl Ether

Divinyl Acetylene

Vinylidene Chloride

Potassium Metal

Sodium Amide

LIST B-YELLOW LABEL (TWELVE MONTHS)

PEROXIDE

HAZARD ON CONCENTRATION

Ethyl Ether

Tetrahydrofuran

Dioxane

Acetal

Methyl I-Butyl Ketone

Ethylene Glycol Dimethyl-Ether

Vinyl Ethers

Dicyclopentadiene

Diacetylene

Methyl Acetylene

Cumene

Tetrahydronaphthalene

Cyclohexene

LIST C-YELLOW LABEL (TWELVE MONTHS)

HAZARD DUE TO PEROXIDE INITIATION OF POLYMERIZATION 

Styrene

Butadiene

Tetrafluoroethylene

Chlorotrifluoroethylene

Vinyl Acetylene

Vinyl Acetate

Vinyl Pyridine

Chlorobutadiene

MONOMERS
a monomer is a molecule or compound, usually containing carbon, and of relatively low molecular weight, which is capable of conversion to a polymer by combination with itself at, or other similar molecules or compounds. This chemical reaction can be started through the addition of stimuli into the chemical chain. stimuli can be heat, light, pressure, or Organic Peroxides.

Inhibitors
an inhibitor is a compound that retards the chemical reaction taking place. the inhibitor may react with the initiator stimuli so that the chemical chain reaction cannot start. one class of inhibitors are the antioxidants. they retard the oxidation process. examples of inhibitors are: Hydroquinone, Tert-Butyl Catechol, Phenolthiazine, Butylated Hydroxy Toluene.

Initiators

Initiators are an energy source that are required in order for the polymerization process to start. initiators can be light, oxygen, heat, shock, or a chemical compound. organic peroxides and similar compounds are examples of a chemical initiator. they readily form free radicals that combine with the monomer until the supply of the monomer is exhausted.

Hazards

Monomers are generally flammable or combustible. polymerization may cause the release of high temperature and pressures. some substances pose a hazard in that they spontaneously polymerize under unique conditions. if the material is confined in a bottle, drum, or other container an extremely hazardous situation can occur. when polymerization has started, the process is very difficult to control or stop.

Stabilization

uninhibited containers must be remotely opened and an appropriate inhibitor adds in a sufficient amount to assure stability for transportation and disposal.

TEMPERATURE SENSITIVE MATERIALS

a material, usually an organic peroxide or Azo compound that will decompose or exhibit a vigorous auto-accelerated reaction when exposed to elevated to elevated temperatures. temperature sensitive materials are separated into two classes: organic peroxides or self-reactive materials.

Organic peroxides – any organic compound containing oxygen (O) in the bivalent structure (-O-O-). organic peroxides may be considered derivatives of hydrogen peroxide, where one or more of the hydrogen atoms have been replaced by organic radicals. organic peroxides are organic oxidizers.

Self-Reactive Material – Materials such as Azo compounds (structure N=N) that can exothermically decompose at transportation temperatures (0 to 115 deg F). contamination may also initiate exothermic decomposition. self-reactive materials are flammable solids.

TEMPERATURE LEVELS

SADT – Self Accelerating Decomposition Temperature – the lowest temperature at which a temperature sensitive material will undergo self-accelerating decomposition. if a materials decomposition reaction is vigorous enough to cause container bulging or bursting, the material must be kept below its’ SADT during packaging, shipment, and facility storage.

RST – Recommended Storage Temperature – the recommended temperature (manufacturer reported) at which it is safe to store an organic peroxide or self-reactive material. this temperature is based on quality considerations. a violent reaction will not take place until the SADT is reached. between the RST and SADT decomposition will generally be slow and only detected by analysis.

DOT Terms:

emergency temperature is similar to the SADT.

control temperature is similar to the RST.

HAZARDS

the decomposition of organic peroxides causes the release of heat, oxygen, and flammable; all the basic requirements for a fire. the production of heat will cause more decomposition, producing more heat, and so on, until the SADT is reached. if the heat produced reached the autoignition point of the flammable gas, the result will be a fire or explosion if confined.

CHEMICAL SENSITIVITY SUBCLASSES

(per ONYX protocol)

TH Materials – Highly Temperature Sensitive – temperature sensitive materials with SADTs of 79 ° F or less. If an SADT value is unavailable, a RST of 40° F is substituted for materials classification. these materials must be refrigerated at 0° F or less for shipment.

TM Materials – Moderately Temperature Sensitive – temperature sensitive materials with SADTs of greater than 79° F, and less than or equal to 140° F is used for classification. These materials must be refrigerated at 40° F for shipment.

TL Material – Low-Temperature Sensitive – temperature sensitive materials that have SADTs or RSTs of greater than 140° F . these material do not require refrigeration.

EXPLOSIVE AND SHOCK SENSITIVE MATERIALS

EXPLOSIONS

An explosion may be broadly defined as the sudden and rapid escape of gases from a confined space accompanied by high temperatures, violent shock, and loud noise. The generation and violent escape of gases is the primary criteria of an explosion and is present in each of the three basic types of explosions known to man.

Mechanical Explosion – the mechanical explosion is illustrated by the gradual buildup of pressure in a steam boiler or pressure cooker. As heat is applied to the water inside the boiler, steam, a form of gas, is generated. If the boiler or pressure cooker is not equipped with som type of safety valve, the mounting steam pressure will eventually reach a point when it will overcome the structural material resistance of its container and explosion will occur. Such a mechanical explosion would be accompanied by high temperature, a rapid escape of gases or steam and a loud noise.

Chemical Explosion – a chemical explosion is caused by the extremely rapid conversion of a solid or liquid explosive compound into gasses having a much greater volume than the substances from which they are generated. When a block of explosive detonates, the produced gases will expand 10,000 to 15,000 times greater than the original volume of the explosive, the expansion of these generated gases is quite rapid, reaching velocities of approximately 5 miles per second. Temperature generated by the conversion of a solid into a gas state may reach 3,000 o 4,000 ° C. the entire conversion process takes only fraction of a second and is accompanied by shock and loud noise. All explosives manufactured by man are chemical explosives with the single exception of atomic explosives.

Atomic Explosion – an atomic explosion may be induced either by fission, the splitting of the nucleus of atoms, or fusion, the joining together under great force of the nuclei of atoms. Nuclear fission or fusion occurs only in extremely dense and heavy elements which are atomically unstable or radioactive. When fission or fusion occurs a tremendous release of energy, heat, gas, and shock takes place. The atomic bombs dropped on Japan in World War II were rated as equivalent to 20,000 tons or 40 million pounds, of TNT in explosive power, yet the amount of fissionable material required to produce this energy weighed approximately 2.2 pounds.

TERMS – Deflagration vs. Detonation

Detonation – a detonation is the extremely rapid, self-propagating decomposition of an explosive, accompanied by a high pressure-temperature wave and is always supersonic.

Deflagration – a deflagration is a very rapid auto combustion of particles of an explosive, as a surface phenomenon, and is always subsonic.

EFFECTS

PRIMARY – the primary effects of an explosion include the blast pressure, shock front, and shock wave.

Blast Pressure – when an explosive charge is detonated, very hot, expanding gases are formed in a period of approximately 1/10,000th of a second. The gases exert pressures of about 700 tons per square inch on the atmosphere surrounding the point of detonation and rush away from the point of detonation at velocities of up to 7,000 miles per hour, compressing the surrounding air. The mass of expanding gas rolls outward in a circular pattern from the point of detonation like a giant wave, weighing tons, smashing and shattering any object in its path. Like an ocean wave rushing up on the beach, the further the pressure wave travels from the point of detonation, the less power it posses until, at a great distance from its creation, it dwindles to nothing. This wave pf pressure is usually called the blast pressure wave. The blast pressure wave has two distinct phases which will exert two different types of pressures on any object in its path. These phases are the positive pressure phase and the negative pressure phase.

Positive pressure – when the blast pressure wave is formed at the instant of detonation, the pressures actually compress the surrounding atmosphere. This compressed layer of air becomes visible in some cases as a white, rapidly expanding circle. Known as the Shock Front, this layer of compressed air is the leading edge of the positive pressure wave. The shock front is only a fraction of an inch thick and is that part of the atmosphere which is being compressed before it is set in motion to become part of the shock wave.

Negative pressure – at the instant of detonation when the positive pressure wave is formed, it begins to push the surrounding air away from the point of detonation. This outward compressing and pushing of air forms a partical vacuum at the point of detonations so that when the pressure wave finally dwindles to nothing, a broad partial vacuum exists in the area surrounding the point of detonation. This partial vacuum causes the compressed and displaced atmosphere to reverse its movement and rush inward to fill the void. The displaced air rushing back toward the point of detonation has mass and power, and although this air is not moving nearly as fast inward as the pressure wave moving outward, it still has great velocity. If the force of a positive pressure wave can be compared to a cyclone, the negative pressure wave is comparable to a strong gale. This inward rush of displaced air will strike and move objects in its path. The negative phase is less powerful, but lasts three times as long as the positive phase.

Secondary – the secondary effects of an explosion include structural fires and fragmentation. Fragments propelled by the shock front will travel in a straight line until they lose velocity, ricochet, or become imbedded.

COMPOSITION AND BEHAVIOR OF CHEMICAL EXPLOSIVES

An explosive is a chemically unstable material which produces an explosion or detonation by  means of a very rapid, self-propagating transformation of the material into more stable substances, always with the liberation of heat and with the formation of gasses. Shock and loud noise accompany this transformation. The primary requisite of a chemical explosive is that it contain enough oxygen to initiate and maintain extremely rapid combustion. Since an adequate supply cannot be drawn from the air, a source of oxygen must be incorporated into the combustible elements of the explosive or added by including other substance in the mixture.

Explosive mixtures – in the case of exploding substances, as contrasted to detonating substances, the combustible and oxidizer are blended mechanically. When making black powder for example, the charcoal, sulfur, and potassium nitrate are first separately ground into fine powder and then mechanically mixed together. The result of this type of  this type of blending is known as an explosive mixture. Mechanical blending is generally used when manufacturing a class of explosives known as low explosives or propellants such as pistol and rifle powders. In some cases, a bonding agent such as water is added to the mixture to form a paste. When dry, the paste mixture is broken into pieces and ground to produce a finer mixture than would result from simply blending the separate ingredients.

Explosive compound – the first requirement of detonating substance is that the union between the combustible and the oxidizer must be as close enough relationship, detonating explosives must be chemically blended. For example, in creating the chemical compound nitroglycerin, glycerin is poured slowly into nitric acid forming a new compound whose elements are in the closest possible union. All high explosives, in contrast with low explosives, are composed of chemical compounds consisting of tightly bonded combustibles and oxidizers.

STABILIZATION – SHOCK SENSITIVE MATERIALS

(per ONYX Protocol by Reactive trained personnel)

Levels of Sensitivity

S1 – Low to Moderate Sensitivity When Dry- Nitrated flammable solids such as Trinitrophenol and Trinitrotoluene. Must be stablized to >90% wet with water.

S2 – Moderate To High Sensitivity When Dry- Materials such as Black powder and Nitrosoquanidine. Must be stabilized in solvent to 20% and slurry with clay.

S3 – Extremely Reactive And Forbidden Materials Highly Shock Sensitive – materials such a Dipicrylamine and Trinitromethane. Stabilization is a case by case procedure.

AIR MOISTURE AND WATER REACTIVES

AIR REACTIVE – materials that will liberate toxic or corrosive gases, or ignite upon contact with air such as diethyl zinc and boron dust. Air reactives must be packaged to prevent contact with air during transportation. For example, White Phosphorus fumes and ignites in air, is highly toxic, and is usually stored under water for transportation.

Organometallic compounds – metal attached to an organic molecule, usually dissolved in a solvent. Solvents can be Hexane, Toluene, Tetrahydrofuran, Methylene Chloride. Examples are: Diethyl Zinc, Butyllithium, Aluminum Alkyls (Trimethyl Aluminum).

Diethyl Zinc burns spontaneously in air forming zinc oxide, carbon dioxide, and water.

WATER AND MOISTURE REACTIVE – materials which will react and decompose when exposed to water, decomposition may generate hazardous, flammable, toxic, or explosive gasses.

Alkali Metals – Lithium, Sodium, Potassium, Cesium, Rubidium, and Francium. They replace the hydrogen in water, creating a hydroxide and generating Hydrogen gas. Heat is evolved which can then ignite the hydrogen.

Metallic Hydrides – composed of an alkali metal, Aluminum or sometimes Boron. React with water to release hydrogen gas and caustic hydroxides. Examples are: Lithium Hydride, Sodium Borohydride, Lithium Aluminum Hydride, Boranes.

Lithium hydride reacts with water to produce lithium hydroxide and hydrogen gas.

Metal powder dusts – Magnesium, Zirconium, Titanium, Aluminum, and Zinc. When in the form of dusts or powders they may explode, especially when the absorb moisture. The particle size, distribution, moisture content, ignition temperature of the metal, and amount of absorbed gases such as Oxygen will affect the potential for explosion and fire risk.

Amides – Amides are the product of an alkali metal with Ammonia. These compounds degradate upon contact with air or moist air to form unstable nitrates and often explode when exposed to water. Sodium Amide will oxidize to form Sodium Hyponitrite, Sodium Trioxodinitrate, Sodium Tetraoxodinitrate, Sodium Pentaoxodinitrate, and Sodium Hexaoxodinitrate. Upon contact with water, Sodium Amide may explode violently.

REACTIVE KEY WORDS

Peroxide Formers:

-Ethers

-Furans

-Amides

Monomers:

-Styrenes

-Acrylates

-Vinyl

Temperature Sensitive Materials:

-Peroxide

-Azo

-Nitriles

Explosives and Shock Sensitive Materials:

-Tri and Tetranitro

-Picrates

-Fulminates

Air and Water Reactive Materials:

-Metals and Metal Dusts

-Organometallic Liquids

-Carbides

-Hydrides