Is fire retardant biodegradable? (5 classes of fire retardants)

This article shall look into the biodegradability of fire retardants.

It shall also cover other areas such as:

  • Classes and types of fire retardants.
  • Properties of fire retardants.
  • The mechanisms of fire retardation.
  • The effects of fire retardants on the environment.

Is fire retardant biodegradable?

No, fire retardants are not biodegradable because they are chemical compounds that are synthesized from non-organic chemical substances which are not susceptible to microbial degradation.

Biodegradation is the process by which naturally occurring organic materials are broken down by microorganisms such as bacteria and fungi into small particles which are not harmful to the environment.

Biodegradation is carried out by different agents such as UV radiation, light, wind, and water but the most effective agents of biodegradation are bacteria and fungi.

Biodegradation occurs in three distinct stages: biodeterioration, bio-fragmentation, and assimilation.

The biodeterioration process loosens up the structure of the organic substance. For instance, the cell wall of plants is weakened by light, wind, water, and UV radiation.

Bio-fragmentation involves the breakdown of organic matter into smaller, nontoxic particles by bacteria and fungi, releasing water and carbon dioxide in the process.

Assimilation is the last stage of biodegradation and it involves the microorganisms taking up the products of bio-fragmentation into their biological machinery to be used to make energy.

Biodegradation can either involve the microorganisms using oxygen, aerobic biodegradation or it can involve the microorganisms which do not use oxygen, anaerobic biodegradation.

What is a fire retardant?

These are chemicals that are added to manufactured materials such as plastics and textiles to prevent the fast spread of fire in case of a fire outbreak.

They are mostly additives to these materials.

They prevent the spread of fire ignition through chemical and physical processes. Some fire retardants are added to polymers as copolymers or applied as a topical finish.

Some retardants are just additives and do not react while others become reactive during an ignition.

Classes of fire retardants.

Fire retardants can be divided into the following classes:

Mineral retardants: these include fire retardants such as aluminum hydroxide, huntite, hydromagnesite, hydrates, borates, red phosphorus, and magnesium hydroxide.

Organohalogen retardants: this class includes organochlorine compounds such as chlorendic acid derivatives, chlorinated kinds of paraffin, and organobromine compounds such as decabromodiphenyl ether, decabromodiphenyl ethane, polymeric brominated compounds such as brominated polystyrenes, brominated carbonate oligomers, brominated epoxy oligomers, tetrabromobisphenol A and hexabromocyclododecane.

Organophosphorus compounds: include organophosphates such as triphenyl phosphate, diphenyl phosphate, tricresyl phosphate, phosphonates such as dimethyl methyl phosphonates, and phosphonates such as aluminum diethyl phosphonates.

Phosphorus and halogen: Tris( 2,3-dibromopropyl) phosphate, chlorinated organophosphates such as tried( 1,3-dichloro-2-propyl)phosphate.

Organic compounds such as carboxylic and dicarboxylic acids.

What are the mechanisms of retardation?

Retardants can either function as gases or as solids. 

Endothermic degradation.

When some retardants are exposed to high temperatures, they break down in an endothermic reaction. 

An endothermic reaction is a chemical reaction where the reagents or the products absorb the surrounding heat energy.

Huntitey, carbonates, and hydrates together with magnesium and aluminum hydroxides react in this form.

When the retardants absorb heat from the substances that contain them, they cool the substances down, therefore reducing the spread of fire. 

Thermal shielding.

These types of fire retardants work by forming a barrier between the burning materials and those which are not burning.

Intumescent materials such as soft char and hard char are used. Intumescent materials are those materials that expand upon heating, increasing in volume and therefore making a rift between burning materials and those that are not.

The retardants that employ this method include the non-halogenated organic and inorganic phosphate compounds which upon heating from the phosphoric acid char layer.

Dilution of the gas phase.

Inert gases such as water vapor and carbon dioxide are produced by some retardants that break down when exposed to heat.

These gases dilute the burning/combustible gases, lowering their partial pressure and partial pressure of oxygen gas, slowing the combustion rate and therefore reducing burning.

Gas-phase radical quenching.

Some retardants such as chlorinated and brominated materials undergo breakdown when exposed to heat to produce hydrogen chloride(HCl) and hydrogen bromide (HBr).

As the flames are burning, it produces hydrogen (H) and hydroxyl (OH) radicals.  

The HCl and HBr radicals from the retardants react with hydrogen and hydroxyl radicals to form inactive chloride(Cl) or bromine(Br) radicals.

Chloride and bromide radicals are less reactive as compared to hydrogen and hydroxyl radicals and therefore reduce the rate of combustion, preventing the spread of fire.

What are the environmental issues of fire retardants?

Fire retardants are made from very sensitive chemical compounds. The reactions and interaction of the compounds with other substances have been studied over time.

The NGOs and government authorities have questioned the use of brominated flame retardants(BFRs) due to their toxic properties.

In the studies, brominated retardants were found to accumulate in the fatty tissues of exposed people. The brominated flame retardants also produced more smoke and toxic gases in the environment.

A study on non-brominated retardants was done and they were found to have better health and environmental profile than the brominated flame retardants.

The studied retardants included: ammonium polyphosphate, aluminum diethyl phosphinate, aluminum hydroxide, magnesium hydroxide, melamine polyphosphate, zinc stannate, and zinc hydroxystannate.

The non-halogenated retardants were found to have a lower tendency to accumulate in the fatty tissues than the brominated flame retardants. They also produced less smoke and toxic emissions from burning.

Toxicity of fire retardants.

According to a study, fire retardants can cause different toxic effects on the body’s endocrine systems such as the thyroid system.

Initially, the fire retardants used were polychlorinated biphenyls(PCBs). These retardants release toxic chlorine compounds into the environment which causes health issues.

In 1977, the polychlorinated biphenyls were banned in the U.S. brominated flame retardants were introduced for industrial uses and have also raised major concerns about their suitability for the environment.

The European Union banned some brominated flame retardants such as polybrominated diphenyl ethers. 

Companies producing decabromodiphenyl ether(decaBDE) flame retardants, commonly used in electronics, wire, and cable insulation, textiles, automobiles, and airplanes were asked by the U.S government to phase out these products by 2012. 

The California state listed chlorinated Tris( 1,3-dichloro-2-propyl) phosphate as a cancer-causing chemical.

A study was done in 2014 by Araki, et al in, Japan, found that phosphorus flame retardants such as Tris (2-chloro-iso-propyl) phosphate and tributyl phosphate were associated with dermatitis, allergic rhinitis, and asthma.

What are the mechanisms of fire retardant toxicity?

There are various ways in which the toxicity of fire retardants can reach a person. They include the following:

Direct exposure.

Halogenated retardants such as brominated flame retardants contain aromatic rings resembling that of thyroxine(T4) and triiodothyronine(T3) thyroid hormones.

When a person is exposed to these flame retardants, the chemicals compete for active sites on the thyroid hormones since the hormones also contain iodine, a halogen similar to those in flame retardants.

As iodine competes for the active site, they interfere with the body functions controlled by the thyroid hormones. This eventually interferes with normal body functions.

Flame retardants also interfere with the reproductive hormones such as progesterone, estrogens, and androgens.

Degradation products.

When flames degrade, they produce toxic substances such as dioxins which affect the hormonal balance in the body.

Are flame retardants eco-friendly?

Yes, when flame retardants are degraded on exposure to heat, they break down into toxic products that pollute the environment.

Organophosphorus flame retardants have been detected in wastewater. Some of the products did not get away after water treatment.

During processing, the industries produce toxic emissions that are toxic to both plants and animals. 

Conclusion.

This article has answered the question of the biodegradation of fire retardants.

It has also covered other areas such as:

  • Types of fire retardants.
  • Mechanisms of fire retardants.
  • Environmental effects of the retardants.
  • Toxicity of fire retardants.
  • Eco-friendliness of fire retardants.

For any questions or comments please use the comment section below.

Frequently Asked Questions (FAQs): is fire retardant biodegradable?

Is fire retardant toxic to the environment?

Yes, brominated flame retardants are toxic to the environment because they produce emissions that pollute the air and also the products of their degradation pollute water.

Is flame retardant more natural?

No, most flame retardants are synthesized from chemicals such as organophosphates and brominated aromatic compounds.

Is fire retardant toxic to humans?

Yes, flame retardants such as brominated flame retardants have been found to cause damage to the thyroid system.

Organophosphate flames have been found to cause dermatitis and rhinitis diseases.

Flame retardants accumulate in the body systems to cause chronic illnesses.

Citations.

Muhammad Maqsood and Gunnar Seide. Biodegradable Flame Retardants for Biodegradable.

Retrieved from:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7407105/#:~:text=Most%20of%20the%20flame%20retardants,occur%20in%20specific%20environmental%20conditions.

Rhoda Afriyie Mensaha, Oisik Dasa ( April 2022) Polymer testing: A review of sustainable and environment-friendly flame retardants used in plastics

doi.org/10.1016/j.polymertesting.2022.107511

Retrieved from:

https://www.sciencedirect.com/science/article/pii/S0142941822000393#:~:text=One%20of%20such%20approaches%20is,of%20them%20are%20environmentally%20safe.

Ramadan Elgamsya, Ahmed Elsabbagh (November 2022). Developing fire retardant composites of biodegradable polyethylene reinforced with agricultural wastes.

doi.org/10.1016/j.asej.2022.101768

Retrieved from:

https://www.sciencedirect.com/science/article/pii/S209044792200079X

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