Halogen-free flame retardants: The path to an environmentally friendly and safe future

Introduction

In modern industrial production and daily life, materials such as plastics, rubber and textiles are widely used in fields like construction, electronics and transportation. However, most of these materials are flammable. Once exposed to a fire source, they can easily cause a fire, resulting in serious losses of life and property. To enhance the safety of materials, flame retardants have become indispensable additives. However, although traditional halogen-based flame retardants have remarkable flame-retardant effects, they are highly controversial due to their potential hazards to the environment and health. Against this backdrop, Halogen-Free Flame Retardants (Retardants, HFFRs) emerged as a new solution that combines environmental protection and safety.

The environmental protection issues of traditional halogen-based flame retardants

Halogen-based flame retardants (such as brominated and chlorinated flame retardants) have been widely used in the past few decades due to their high efficiency and low cost. However, scientific research shows that such flame retardants release toxic gases (such as dioxins, furans, etc.) when burning, which not only cause harm to the human respiratory system but also pollute the atmosphere and soil. In addition, halogen-based flame retardants have bioaccumulative properties and can enter the human body through the food chain, affecting the endocrine system and even potentially causing cancer.

The RoHS Directive (Restriction of the Use of Certain Hazardous Components in Electrical and Electronic Equipment) and the REACH regulation (Registration, Evaluation, Authorization and Restriction of Chemicals) of the European Union have imposed strict restrictions on some halogen-based flame retardants. Therefore, the development of efficient and environmentally friendly halogen-free flame retardants has become an inevitable trend in the industry's development.

The advantages of halogen-free flame retardants

Halogen-free flame retardants do not contain halogen elements such as bromine and chlorine. They mainly rely on environmentally friendly elements such as phosphorus, nitrogen, silicon, aluminum and magnesium to achieve flame retardant effects. Compared with traditional halogen-based flame retardants, halogen-free flame retardants have the following advantages:

1. Environmentally friendly
It does not release toxic gases when burning, reducing pollution to the air and soil, which is in line with the global development trend of green chemistry.

2. Low smoke and low toxicity
When a fire breaks out, halogen-free flame-retardant materials produce less smoke, which can increase the chances of escape and reduce the harm of toxic gases to the human body.

3. Recyclable
Some halogen-free flame retardant materials can be degraded or recycled after being discarded, which is in line with the concept of circular economy.

4. Comply with international regulations
Halogen-free flame retardants comply with environmental protection regulations in the European Union, the United States, China and other regions, which is conducive to the export of products and the expansion of international markets.

Types and applications of halogen-free flame retardants

At present, the common halogen-free flame retardants on the market mainly include the following types:

1.Phosphorus-based flame retardants
Phosphorus-based flame retardants achieve flame-retardant effects by decomposing at high temperatures to form phosphoric acid or polyphosphoric acid, creating a carbon layer that isolates oxygen. Representative products include: red phosphorus (used in rubber and plastics), phosphate esters (used in polyurethane foam and electronic device casings), and ammonium polyphosphate (APP) (widely used in building insulation materials).

2. Nitrogen-based flame retardants
Nitrogen-based flame retardants release inert gases (such as nitrogen and ammonia) when heated, diluting the concentration of flammable gases and promoting carbonization at the same time. Typical applications include: melamine and its derivatives (used in textiles and coatings), cyanuric acid melamine (MCA) (used in nylon and polypropylene).

3. Inorganic flame retardants
Inorganic flame retardants mainly function by absorbing heat and decomposing or forming an insulating layer. Common ones include: aluminum hydroxide (ATH) (used in wires and cables, building materials), magnesium hydroxide (MDH) (used in automotive parts, electronic devices), and zinc borate (used in plastics, rubber).

4. Silicon-based flame retardants
Silicon-based flame retardants enhance the high-temperature resistance of materials by forming a silicon-carbon layer. They are suitable for: silicone rubber (used in wires and cables, electronic packaging), and silicone-modified polymers (used in high-end electronic devices).

The market prospects of halogen-free flame retardants

With increasingly strict global environmental protection regulations, the market for halogen-free flame retardants is showing a rapid growth trend. According to data from market research institutions, the global halogen-free flame retardant market size exceeded 2 billion US dollars in 2023 and is expected to continue to expand at an average annual growth rate of 6% to 8% in the coming years. The main driving factors include: the growth in demand in the electronic and electrical industry (such as 5G equipment and new energy vehicle batteries), the promotion of green building policies (such as the green building standards of the European Union), and the improvement of consumers' environmental awareness (more inclined to purchase environmentally certified products).

In China, the proposal of the "dual carbon" goals (carbon peaking and carbon neutrality) has further promoted the development of halogen-free flame retardants. The government encourages enterprises to adopt green materials and reduce carbon emissions, which provides policy support for the innovation of halogen-free flame retardant technology.

Challenges and Future Development Directions

Although halogen-free flame retardants have many advantages, they still face some challenges:
1. High cost: The production cost of some halogen-free flame retardants (such as organophosphorus-based and nano-flame retardants) is still higher than that of traditional halogen-based products.

2. Flame retardant efficiency needs to be improved: Some halogen-free flame retardants require a higher addition amount to achieve the desired effect, which may affect the mechanical properties of the material.

3. Composite technology to be broken through: The future trend is to develop multi-functional composite flame retardant systems, such as "phosphorus-nitrogen synergistic flame retardant" and "nano-composite flame retardant", to enhance flame retardant efficiency and reduce costs.

In the future, with the research and development of bio-based flame retardants (such as chitosan and lignin derivatives) and intelligent flame retardant materials (such as self-healing flame retardant coatings), halogen-free flame retardant technology will become more environmentally friendly and efficient.

Conclusion

Halogen-free flame retardants represent the future direction of the flame retardant industry. They not only enhance the safety of materials but also reduce environmental pollution. Against the backdrop of the global green transformation, governments, enterprises and research institutions should enhance cooperation to promote the innovation and application of halogen-free flame retardant technologies and jointly build a safer and more sustainable future.

Choosing halogen-free flame retardants is not only a technological advancement but also a responsibility to the Earth.