Fire protection remains a key requirement in many industrial sectors, and adhesives play an important yet often underestimated role in this area. Adhesive formulations help reduce the risk of ignition, slow flame spread and lower heat release during a fire. For decades, the standard approach to flame retarding adhesives has been antimony trioxide in combination with halogenated flame retardants. Today, however, the market environment and regulations are driving a move away from such systems and towards more sustainable alternatives.
The adhesive segment is currently facing unprecedented challenges related to antimony trioxide. In recent years, the price of ATO has multiplied, with an increase estimated at 6–10 times[1]. At the same time, regulatory requirements for traditional flame retardant chemistries are tightening, and end users are increasingly requesting alternative solutions that enable raw material diversification. As a result, adhesive manufacturers are under pressure to implement new systems that maintain fire performance while meeting cost, regulatory and environmental criteria.
Market and sector impacts of ATO issues
The consequences of rising costs and regulatory pressure on antimony trioxide are felt across many sectors in which adhesives have a critical structural or functional role. This applies to construction, automotive and aerospace alike, where requirements on flame retardancy, smoke development and in-service stability are particularly stringent.
In construction, innovative materials used in building envelopes, flooring systems and interior finishes often rely on specialized adhesives for durable bonding, panel installation and floor laying. Fire-resistant adhesives in these applications must meet not only performance requirements but also increasingly strict building code provisions and environmental certification criteria. At the same time, the rising cost of traditional flame retardant additives complicates economic evaluations of projects.
In automotive applications, vehicle manufacturers seek to combine enhanced safety requirements with continued vehicle lightweighting. Adhesives used at different stages of vehicle assembly must provide suitable flame retardancy while avoiding substances that raise environmental concerns, such as traditional systems based on ATO combined with halogens. An additional issue is the sector’s cost sensitivity to large price fluctuations of antimony trioxide, which makes it difficult to maintain stable project profitability.
The aerospace industry places particularly high demands on adhesives, where flame retardant properties of materials are critical for approval and use. Adhesive systems employed in aircraft structures and interior fittings are subject to extensive certification procedures, and every component of the formulation, including the flame retardant, undergoes detailed evaluation.
Clariant phosphinates as an alternative to antimony trioxide
In response to the market challenges described above, Clariant has developed advanced phosphinate-based flame retardants as an alternative to antimony trioxide in adhesive formulations. These solutions are the result of many years of research and development work focused on creating more sustainable technologies without reducing the effectiveness of fire protection.
Unlike traditional flame retardant systems based on halogens and antimony trioxide, Clariant’s phosphinate technologies rely on different mechanisms under fire conditions. When exposed to heat, these formulations can form protective layers that limit flame spread and reduce heat release rates and additionally help to avoid or delay ignition by quenching flammable gases in the flame zone.
Key benefits of phosphinates in adhesives
Clariant’s phosphinate-based flame retardants are characterized by several important features from the perspective of adhesive manufacturers and end users.
- The formulations are halogen free, which supports the achievement of the United Nations Sustainable Development Goals, among others by promoting safer materials (SDG 3) and supporting circular economy and recycling (SDG 12). This alignment is also related to initiatives such as GlobalABC aimed at reducing the environmental impact of building materials.
- Broad compatibility with various polymer systems allows phosphinates to be used in many adhesive types, facilitating the implementation of a single additive family across multiple product lines.
- Comparable loading levels to ATO-based systems simplify reformulation and limit the need for far-reaching changes to existing recipes.
- A competitive cost position, especially in light of the sharp increase in antimony trioxide prices, helps to ease price pressure along the supply chain.
- Enhanced supply security thanks to Clariant’s extensive manufacturing network, which is relevant in the context of volatile raw material markets.
Performance characteristics and fire testing
The switch from antimony-based systems to phosphinate systems does not have to result in a deterioration of performance. Clariant’s solutions have shown at least comparable, and in many cases improved, results compared to traditional ATO systems in key fire tests.
This includes reducing flame spread rate, lowering peak and total heat release, decreasing the amount and density of smoke, and increasing the formation of a protective char layer. These characteristics allow adhesive manufacturers to comply with or exceed current fire safety standards while reducing the drawbacks associated with the use of traditional antimony trioxide systems.
Application areas in adhesives and beyond
Clariant’s phosphinate-based flame retardants show wide applicability in various adhesive applications. In construction they can be used in floor installation systems, panel bonding formulations and structural adhesives for engineered wood products. In automotive, they are used in adhesives for interior components, structural adhesives for joining dissimilar materials and adhesive systems for lightweight composites.
In aerospace, these solutions are applied in high-strength structural adhesives, interior panel installation systems and specialty formulations for bonding components that are critical to safety and functionality. The use of phosphinates is not limited to the adhesive segment itself. These flame retardants are also applied to protect engineering thermoplastics in electrical and electronic applications, in wire and cable systems, automotive components and fiber-reinforced composites.
Construction. Photo: Clariant
Development directions and a shift in the flame retardant paradigm
As regulatory frameworks tighten and sustainability criteria gain importance in material selection, the move away from antimony trioxide is becoming not only a necessity but also an opportunity to modernize adhesive formulations. Clariant’s phosphinate-based flame retardants offer an option that addresses current challenges while preparing manufacturers for future market and legislative requirements.
The combination of comparable performance, cost competitiveness and a more favorable environmental profile provides a basis for reformulating adhesive systems towards halogen-free solutions. In addition, supply security is becoming an important factor in an unstable supply chain environment, and Clariant’s manufacturing capabilities help to mitigate the risk of interruptions in the availability of flame retardant additives.
Outlook for flame retardant technologies in adhesives
The dynamic rise in antimony trioxide prices and increasing regulatory pressure on traditional ATO systems have created an inflection point for adhesive manufacturers. Clariant’s phosphinate-based flame retardants provide a timely response to these challenges while enabling a transition to halogen-free fire protection systems.
By providing halogen-free solutions that are competitive in both cost and performance, Clariant enables manufacturers in the construction, automotive and aerospace sectors to maintain required fire safety standards while supporting environmental objectives. The development path of flame retardant technologies in adhesives is shifting away from traditional materials such as antimony trioxide and towards innovative systems that balance fire performance requirements, the need for more sustainable solutions and economic viability.
Why antimony is no longer suitable for modern adhesives. Photo: AI-generated, Clariant
This article is based on company material. Author of the original article: Sebastian Moschel, Application Development Manager Passive Fire Protection at Clariant.
