What are Fire Retardants?

Fire retardants are chemicals that are used to stop or slow down the action of fire. These compounds/substances are used in numerous materials such as textiles, plastics, and coatings to prevent the spread of fire.

What are Fire Retardants Applied to?

The retardants can be applied to the following:

  • Electronics and electrical devices
  • Building and construction materials, including electrical wires, cables, and insulation materials
  • Fireproof clothing
  • Automobile industry, etc.

How do Fire-Retardants Work?

Flame retardants used in plastic materials are divided into two categories, namely additive and reactive.

  • Additive flame retardants are incorporated and dispersed into the plastic during polymerization. If they are chemically compatible with the plastic, they act as plasticizers or they are considered as fillers. Typical non-reactive flame retardants include chlorinated paraffins, brominated organics, phosphate ester, aluminum trihydrate, magnesium hydroxide, borates, and antimony trioxide
  • Reactive flame retardants are chemically bound to the polymer molecule by incorporating them into the polymer backbone. As reactive flame retardants are chemically bound to the host polymer, they are prevented from bleeding out; and generally, show greater flame retardancy than additive compounds due to their greater availability throughout the life cycle of the polymer into which they are incorporated. But it can also change the mechanical properties of the adhesive. These include tetra-bromo-biphenyl A, di-bormo-neophenyl glycol, brominated styrene, etc.

Different types of flame retardants?

Halogenated flame retardants are the largest flame retardants. In halogens, fluorine and iodine are not used as flame retardants since neither effectively interfere with the combustion process. Chlorine-containing flame retardants release HCl (hydrogen chloride) over a wide temperature range so the flame retardant concentration is reduced and thus less effective. Bromine is the most effective halogen flame retardant since its bonding to carbon enables it to interfere at a more favorable point in the combustion process.

Why Non — Halogenated Flame Retardants?

Many halogenated flame retardants are with aromatic rings, including most brominated flame retardants. Halogenated compounds with aromatic rings can degrade into dioxins and dioxin-like compounds (resistant to environmental degradation through chemical, biological, and photolytic processes, and adversely affect human health and the environment around the world), particularly when heated, such as during production, a fire, recycling, or exposure to the sun

Non –halogenated flame retardant:

Non-halogenated flame retardants promote environmental sustainability as it has exceptional smoke suppressant properties and are affordable. Aluminum trihydrate, phosphorus, melamine based, are some of the commonly used halogen-free flame retardants. Phosphorous containing compounds are the most popular and are most widely used. The compound is reacted as an additive flame retardant. The flame retardant mechanism is that the phosphorus-containing compound is converted by thermal decomposition to phosphoric acid. The phosphoric acid then dehydrates the oxygen-containing polymer and causes charring.

How are Flame Retardants selected for Adhesives?

The major problem with incorporating flame retardants in adhesives is that very often a significant amount is required, and they interfere with the other properties of the adhesive and contribute to the cost.
The key criteria used to select a particular flame retardant are:

  • Fire retardancy
  • Efficiency & cost
  • Smoke & combustion products
  • Ease of compounding
  • Compatibility
  • Effect on physical, chemical, electrical and other properties
  • Environmental regulations

What are Flame Resistant Plastics?

Some high-performance plastics can be classified as flame-retardant plastic, non — flammable plastic, or inherently self-extinguishing, making them suitable for use where fire protection is an issue. There are various standards that classify the flammability of plastics. Normally, the internationally accepted flammability test for plastics described in UL94 is performed.

UL 94

UL 94 (Underwriters Laboratories test standard UL 94) is one of the most widely used flammability tests for determining relative flammability for plastic materials. It measures the ability of the plastic parts to extinguish the flame after ignition, and its dripping behavior in response to a small open flame or radiant heat source under controlled laboratory conditions.

What are Flame Resistant Plastics According to UL94?

Classification of flame-resistant plastics according to UL94 follows these criteria:

  1. UL94-HB plastic (horizontal burning): Material burns and drips.
  2. UL94-V0 plastic (vertical burning): Burning period 10 seconds. After repeated flaming: 50 seconds, flaming drips are not admissible.
  3. UL94-V2 plastic (vertical burning): Burning period 30 seconds. After repeated flaming: Burning period 250 seconds, flaming drips are admissible.
  4. UL94-V1 plastic (vertical burning): Burning period 30 seconds. After repeated flaming: 250 seconds, flaming drips are not admissible.