3 Methods for Flame Retardant Systems

3 Options for Cost-Effective Flame-Retardant Additives

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Unexpected events can cause spikes in prices and demand for additives, impacting supplies and production costs. For instance, the price of antimony trioxide (ATO) recently increased. This additive is used to boost the effectiveness of halogenated flame retardants in molding compounds.

This blog explores several options for flame-retardant additives, providing insights for formulators to adapt their purchasing decisions in light of fluctuating prices.

Continuous need for flame-retardant additives

Since the 1970s, flame retardants have been integral in enhancing the safety of both consumer and industrial products by reducing flammability or impeding the spread of fire.

These chemical compounds are formulated into or applied to various goods including textiles, coatings, electronics, wire, cable and insulation to bolster their fire-resistant properties.

A multitude of flame-retardant additives with diverse chemical compositions are available on the market. Selection criteria is based on the polymer used, compounding process, specific application needs and the desired characteristics of the final product. Cost considerations also play a significant role in the decision-making process.

World events affect costs

The bridge collapse at the Port of Baltimore serves as a recent example of how world events can impact manufacturer’s production costs. China, the largest producer of ATO, ships much of its supply through the Port of Baltimore. The halt of operations at this crucial port bridge for an unknown time period could prompt panic buying and a price surge.

While ATO remains an important flame retardant that cannot be eliminated, diversifying with other materials can help mitigate its reliance and overall costs. For instance, incorporating amorphous silicon dioxide can reduce the need for ATO and subsequently cut expenses (more details on this later).

Let’s explore three flame retardant methods:

  1. Vapor phase inhibition
  2. Solid phase char formation
  3. Quench and cool systems

1) Vapor phase

Vapor phase inhibition occurs when flame retardant additives react with the burning polymer in the radical gas phase. These additives disrupt the production of free radicals, cooling the system and reducing or suppressing the supply of flammable gases.

Brominated flame retardants (BFRs) are used for their effectiveness in vapor phase inhibition. Bromine, specifically, is utilized because it releases active bromine atoms into the gas phase even before the material reaches its ignition temperature. These atoms suppress the chemical reaction within the flame, thereby extinguishing or slowing the spread of the fire.

Albermarle brominated flame retardants reduce flammability by providing resistance to ignition and aiding in extinguishing fires by interfering with the reaction. They can improve the performance of products while reducing the deterioration of their physical properties. The company’s Saytex® line of brominated flame retardants are ideal for applications when overheating is a concern such as wire and cable, electronics, and circuit boards.

Synergists optimize formulas

Antimony trioxide serves as a synergist commonly integrated into brominated flame-retardant formulations. When combined with halogens like bromine, this blend yields an exceptionally efficient flame-retardant system for plastics, rubber, paper, textiles and electronics. Notably, the absence of ATO necessitates approximately double the amount of halogenated compound to achieve equivalent levels of fire retardancy.

For example, when BrightSun Antimony Oxide manufactured by Minmetals Inc. is mixed with halogenated flame retardants during the vapor phase, it forms a compound that serves as a “free radical trap” in capturing any free radicals that can increase the spread of flames. BrightSun also aids in the formation of “char” on the substrate to prevent the release of volatile gas.

SIDISTAR® Silicon Dioxide Lowers ATO Loading

In situations where ATO supply is limited or costs are high, Elkem SIDISTAR® silicon dioxide can replace ATO loading up to 50% in any flame retardant compound while maintaining the integrity of flame retardant properties.

By substituting ATO with lest costly SIDISTAR® additives, you can lower costs without loss of flame retardancy. Optimized formulations also decrease compound density, which reduces costs and the weight of finished products.

Watch this video that shows a vertical burn test using ATO with SIDISTAR to increase the efficiency of fire retardants and improve char formation.

2. Solid phase char formation 

Solid-phase flame retardants promote char formation during a fire. These additives react with the burning polymer, forming a carbonaceous layer on the surface of the material. This layer serves as a protective barrier, inhibiting the release of combustible gases and safeguarding the underlying material from the heat of the flame.

Melamine-based flame retardants are known for their ability to promote solid phase char formation. During the condensed phase, the development of cross-linked structures such as melem and melon enhances the stability of the char. When combined with phosphorus synergists, melamine can further reinforce char stability by forming nitrogen-phosphorus compounds.

Elkem SIDISTAR® silicon additives improve char formation by making it stronger and tighter.  Different than precipitated silica or fumed silica, SIDISTAR is an amorphous silicon dioxide. When combined with other flame retardants, it serves as a performance additive and processing aid to strengthen the char and increase additive efficiency. SIDISTAR additives also reduce the development of smoke and burning droplets.

3. Quench and cool systems

Quench and cool systems use hydrated materials to improve flame resistance. When exposed to fire, these hydrated minerals release water molecules to cool the substrate and disrupt the combustion process.

Flame retardant compounds such as aluminum and magnesium hydroxides (MDH) are used for quench and cool systems. Both compounds break down endothermically when subjected to high temperatures, releasing inter-gases like water vapor. This action dilutes the combustible gases and reducing the likelihood of ignition.

Elkem SIDISTAR® polymer additives have a synergistic effect with MDH in halogen-free retardant (HFFR)compounds. A 2% replacement of MDH outperforms a compound with increased MDH levels. SIDISTAR also improves polyolefin-based HFFR cable compounds while offering a savings in pound or per cubic foot.

Choosing the right blend of flame-retardant additives and synergists for formulation depends on costs, blendability, availability, specifications and thermal stability. As many flame retardants are on the market, each product requires careful consideration before choosing one for your application.

If ATO prices rise, you may want to consider an alternate technology such as SIDISTAR or some combination. HM Royal is a reliable source of both ATO and SIDISTAR. We also provide expert guidance in choosing the right flame-retardant system for an application. Contact us to discuss your unique needs.

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