Flammability, combustibility and flame retardant

Flammability

Flammability is the ease with which a combustible substance can be ignited, which can cause a fire or combustion or even an explosion. The degree of difficulty required to ignite a substance is measured by a fire test. Internationally, a variety of test protocols exist to measure combustion. Achieved ratings are used to store and manage highly combustible materials inside and outside the structure and in surface and air transport, along with building codes, insurance requirements, fire codes and other regulations governing the use of building materials. For example, in order to change the occupancy by changing the combustion of the content, the owner of a building must apply for a building permit so that the basis for the overall fire protection design of the facility can be considered.

Some flammable substances are below-

i. Gasoline - Petrol / a complicated mixture of hydrocarbons that includes isomers of octane, C₈H₁₈

ii. Ethanol / CH₃CH₂OH

iii. Rubber

iv. Isopropyl alcohol / CH₃CH (OH) CH₃

v. Methanol / CH₃OH

vi. Wood

vii. Acetone / CH₃COCH₃

viii. Paper

ix. Nitromethane / CH₃NO₂

Rating         Degree of flammability                                                             Examples

0                  Materials that do not burn                                                               water

1                  Materials that must be preheated before they ignite        lubricating oils, cooking oils

2                  Materials that must be moderately heated or exposed to relatively high ambient temperatures before they ignite                                                                                                    diesel fuel

3                  Liquids and solids that can ignite under almost all temperature conditions                                                                                                                                                                          gasoline, acetone

4                 Materials that rapidly vaporize at atmospheric pressure and normal temperatures, or readily disperse in air and burn readily                                                                                natural gas, propane, butane

Combustibility

Combustibility is a measure of how easily a substance explodes in flames through fire or combustion. This is an important property to consider when using or storing a substance. It is also important in processes that produce flammable substances as a by-product. Easily combustible substances usually require special care. These measures may include the installation of a fire sprinkler or storage remote from a potential source of ignition. Low-combustion materials may be selected for construction where fire risk must be minimized, such as in apartment buildings, homes, or offices. The use of combustible resources increases the risk of fire accidents and deaths. Fire-resistant materials are preferred for building materials and upholstery.

Flame retardant

The word flame retardant includes a variety of chemicals that are added to materials such as plastics and textiles and finishing and coating surfaces. Flame retardants are activated by the presence of an ignition source and are intended to prevent or slow the further development of ignition by a variety of different physical and chemical methods. These can be added as a copolymer during the polymerization process, or later added to the polymer in a molding or extrusion process, or (especially for textiles) as a topical finish. Mineral flame retardants are usually binders while organohalogen and organophosphorus compounds may be reactive or binding.

Flame retardant chemicals

i. Brominated flame retardants

It contains bromine and is the most abundantly used flame retardant. It is used in many consumer goods, including electronics, furniture, building materials, etc., and have been linked to endocrine disruption among other effects.

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ii. Polybrominated diphenyl ethers (PBDEs)

Its do not chemically bind with the products to which they are added (furniture, electronics, etc.) so they easily release from these products and enter air and dust. Its can lower birth weight/length of children, and impair neurological development.

iii. Tetrabromobisphenol A (TBBPA)

It is widely used to make computer circuit boards and electronics, and also used in some textiles and paper, or as an additive in other flame retardants.

iv. Hexabromocyclododecane (HBCD)

It is an additive that is primarily used in polystyrene foam building materials. The primary risk for humans is to get out of the products and get into the dust inside the house. Low levels of HBCD have also been found in some foods.

v. Organophosphate flame retardants (OPFRs)

As PBDEs are phased out, some OPFRs have been identified as replacements.

Flame retardant environmental impact

The environmental behavior of flame retardants has been studied since 1990. Primarily brominated flame retardants have been found in many ecological parts and organisms, including humans, and toxic properties of some individual substances. Therefore, the authorities, NGOs, and equipment manufacturers have demanded alternative measures. The EU-funded collaborative research project ENFIRO began with the notion that there was insufficient environmental and health information for established brominated flame retardant alternatives. To make the evaluation completely comprehensive, it was decided to try to evaluate the life-cycle of a reference product containing halogen-free vs. brominated flame retardants as well as compare components and fire performance. About a dozen halogen-free flame retardants were studied, from engineering plastics, printed circuit boards, encapsulants to textiles and intuitive coatings. A good environmental and health profile of a large group of flame retardants studied was found: ammonium polyphosphate (APP), aluminum diethyl phosphonate (Alpi), aluminum hydroxide (ATH), magnesium hydroxide (MDH), melamine polyphosphate (MPP), dihydrooxaphosphaphenanthrene (DOPO), zinc stannate (ZS) and zinc hydroxstannate (ZHS). Overall, the tendency to organic deposits in their fatty tissues was found to be much lower than in the brominated flame retardants studied. Fire behavior tests of various flame retardants have shown that halogen-free flame retardants produce less smoke and toxic fire emissions, excluding aryl phosphates RDP and BDP in styreneic polymers. Leaching experiments have shown that the nature of the polymer is an influential factor and comparable to the leaching behavior of halogen-free and brominated flame retardants.

Many halogenated flame retardants, including aromatic rings, most of which are brominated flame retardants, possibly thyroid hormone disruptors. The thyroid hormones triiodothyronine (T3) and thyroxine (T4) carry iodine atoms, another halogen, and structurally like many aromatic halogenated flame retardants, including PCBs, TBBPA, and PBDEs. Many flame retardant compounds are also toxic, and in some cases, decay products may be the primary toxic agent:

i. Halogenated compounds, including aromatic rings, can become compounds such as dioxin and dioxin, especially when heated, such as during production, fire, recycling, or exposure to the sun. Chlorinated dioxins are one of the highly toxic compounds listed by the Stockholm Convention on Persistent Organic Pollutants.

ii. Polybrominated diphenyl ether with a large number of bromine atoms, such as decaBDE, is less toxic than PBDEs with a low number of bromine atoms such as pentaBDE. However, because high-order PBDEs are organic or inorganically degraded, bromine atoms are removed, resulting in more toxic PBDE congeners.

iii. When some halogenated flame retardants such as PBDEs are metabolized, they produce hydroxylated metabolites that may be more toxic than the original compound. These hydroxylated metabolites, for example, may compete more strongly with binding to transthyretin or other components of the thyroid system may have stronger estrogen simulations than parent compounds, and may stimulate neurotransmitter receptor activity.