Halogenated vs. Non-Halogenated Flame Retardants: What’s the Difference and Why It Matters

As industries grapple with the growing pressure to meet environmental regulations and consumer demand for safer, more sustainable materials, the pivotal debate between halogenated and non-halogenated flame retardants (FRs) has come to the forefront. Understanding the differences between these two classes of flame retardants is crucial for manufacturers, designers, and sustainability professionals navigating today’s complex material landscape.

What Are Halogenated Flame Retardants?

Halogenated flame retardants, containing elements from the halogen group, primarily bromine and chlorine, are highly effective at suppressing flames by disrupting the combustion process in the vapor phase. These compounds often work in tandem with an antimony trioxide synergist, a key component that enhances their flame-retarding properties. During pyrolysis, they release hydrogen halides (e.g., HCl or HBr), which react with the antimony oxide to retard flame-propagating free radicals, demonstrating the comprehensive nature of flame retardants.

What Does It Mean If Something Is Halogenated?

A halogenated compound contains one or more halogen atoms—fluorine (F), chlorine (Cl), bromine (Br), or iodine (I)—bonded to carbon. These elements are highly reactive and effective at disrupting combustion, which is why halogenated compounds are widely used in flame retardants, solvents, and refrigerants.

Common Halogenated Compounds You Should Know

Carbon Tetrachloride (CCl₄) – Historically found in fire extinguishers
PBDEs (Polybrominated Diphenyl Ethers) – Flame retardants in electronics and textiles
Brominated epoxy polymers – flame retardants for molding and high temperature resins
PCBs (Polychlorinated Biphenyls) – Formerly used in electrical transformers, now banned due to toxicity
PTFE – used as an anti-drip in many resins

Why are they still in use?

Highly effective at lower loadings than non-halogen
Broadly compatible with many polymers
Often more cost-effective than alternatives
Weatherable grades available
Can have lower impact sealing or printability
Industry adoption

Drawbacks:

Environmental and health concerns due to toxic byproducts and potential for bioaccumulation, especially with fluorinated chemistries
Regulatory restrictions, especially in Canada, the EU, and parts of Asia
Require synergists like antimony trioxide, which is facing global shortages and price volatility
Can affect mechanical properties
Can be reactive with other chemistries included in the final if not appropriately designed or components are not disclosed
Can affect clarity and color
Can negatively affect printing or sealing properties
Generally worse for smoke development compared to non-halogen solutions

What Are Non-Halogenated Flame Retardants?

Non-halogenated FRs avoid halogen elements altogether, relying instead on phosphorus, nitrogen, or mineral-based chemistry. These compounds work by forming a protective char layer or releasing water vapor to cool the material during combustion.

Types and Mechanisms:

Intumescent (phosphorus/nitrogen): Form a solid char barrier
Metallic hydroxides (e.g., aluminum or magnesium hydroxide): Absorb heat and release water
Endothermic cooling agents: Reduce temperature and slow combustion
Many systems use a combination of chemistries for optimal FR performance

What Are Non-Halogenated FR Additives?

Non-halogenated flame-retardant additives include:

Phosphorus-based compounds (e.g., ammonium polyphosphate)
Nitrogen-based compounds (e.g., melamine cyanurate)
Mineral fillers (e.g., aluminum hydroxide, magnesium hydroxide)
Clay and other non-combustible fillers

These additives work by:

Promoting char formation
Diluting combustible gases
Absorbing heat through endothermic decomposition
Removing combustible material

They are increasingly used in applications requiring low smoke and toxicity, such as transportation, construction, and electronics.

Advantages:

Lower toxicity and black smoke emission
Increasingly favored in green certifications and eco-labels
Better UV stability in some formulations
Can be better for clarity and color compared to halogens
Lower concern with reactivity with other components in the final part
No presence of antimony trioxide in the FR package

Challenges:

Often require higher loading, which can affect mechanical properties
May need formulation adjustments to maintain performance
Some options are heat-sensitive or have odor issues at high temperatures
Generally higher cost
Can negatively affect mechanical properties
Can have printing or sealing issues
Many cannot be used in high temperature resins due to limited heat stability

Market Trends and Regulatory Drivers

The shift toward non-halogenated FRs is accelerating due to:

EU bans on halogenated FRs in electronics enclosures (effective March 2025)
Rising costs and limited availability of antimony trioxide
Growing demand for transparent, recyclable, and low-smoke materials in packaging, construction, and automotive sectors

Application Spotlight: Where These Technologies Show Up

At Techmer PM, we’ve seen a surge in demand for non-halogenated FRs across a wide range of applications:

Application	Halogenated FRs	Non-Halogenated FRs
Electrical Enclosures	Cost-effective and built into many prints and codes	Increasingly required by EU RoHS and OEMs
Automotive Interiors	Good performance and has been color matched for various applications	Preferred for low smoke and toxicity
Building Materials	Effective but under scrutiny	Favored for LEED, green building credits, ASTM E84 applications, and wire and cable

Why the Shift Toward Non-Halogenated FRs?

Several factors are driving the transition:

Health and environmental concerns over halogenated byproducts
Regulatory pressure, especially in the EU and Asia
Supply chain volatility, such as the rising cost and scarcity of antimony trioxide (a synergist in halogenated systems)
Customer demand for safer, greener materials
Need for high clarity films but with FR performance

Choosing the Right Solution

There’s no one-size-fits-all answer. The choice between halogenated and non-halogenated FRs depends on:

Application requirements (e.g., transparency, mechanical strength)
Regulatory landscape
Performance requirements
Resin system
Full chemical analysis for final part
Cost and supply chain considerations
Environmental and brand positioning goals

At Techmer PM, we offer both halogenated and non-halogenated flame-retardant solutions tailored to your specific needs. Whether you’re navigating UL testing, optimizing formulations, or preparing for upcoming regulatory changes, our team is here to help.