The CIRCOPLAST project aims to tackle a major dual challenge: improving the recyclability of plastics containing brominated flame retardants while developing more sustainable, bio-based fire retardant solutions that are compatible with the circular economy. In this context, CREPIM (Center for Research and Studies on Material Fire Retardant Processes) plays an important role thanks to its recognized expertise in the field of polymer fire behavior. Fire safety is a key parameter in accessing certain regulated markets (electrical and electronic equipment, construction, rail, maritime, aeronautics), and CREPIM evaluates the fire reaction properties that give access to these types of markets on a daily basis.
CREPIM is involved in this project on several levels: fire characterization of recycled plastics, formulation and implementation of flame-retardant polymers and model mixtures, evaluation of fire and smoke performance according to international standards, and support for the development of bio-based flame retardants, particularly those based on lignin. The aim is to enable the reuse of recycled plastics in higher value-added applications (electrical equipment, construction, transport), while complying with regulatory requirements for fire safety.
During the first few semesters, CREPIM, in collaboration with CENTEXBEL, focused on establishing essential reference materials for evaluating decontamination processes. Two experimental ABS (acrylonitrile butadiene styrene) mixtures, containing either decabromodiphenyl ether or decabromodiphenyl ethane, were developed by CREPIM using a twin-screw extruder. These formulations, whose composition is known, serve as starting points for studying the effectiveness of brominated flame retardant extraction techniques and have been shared with CIRCOPLAST partners for further analysis.
Pictures: Left image – twin-screw co-rotating extruder capable of producing mixtures on a kilogram scale. Right image – micro-extruder capable of producing mixtures on a gram scale.
The role of CREPIM is also to define a standardized fire testing strategy that reflects industrial and regulatory requirements. To this end, four methods have been selected for the CIRCOPLAST project:
- Limiting Oxygen Index (ISO 4589-2), to assess the flammability of materials,
- Vertical UL94 test, to characterize flame propagation,
- Cone calorimeter (ISO 5660-1), to measure heat output, combustion kinetics, and smoke release.
- Tubular furnace test (NF X 70-100), to measure the toxicity of gaseous effluents produced during the combustion of plastics.
These fire reaction tests will initially be carried out on virgin plastics and will establish a baseline before studying recycled polymers and modified formulations. The objective is to integrate lignin derivatives into polymer matrices as soon as possible and to evaluate their flame-retardant potential.
The ISO 4589-2 test is a method used to evaluate the maximum oxygen concentration at which a material cannot sustain combustion for more than 3 minutes and over which a flame does not propagate over a distance of more than 50 mm. The main criterion monitored is the self-extinguishing of the material under given combustion conditions. This test is notably used to assess the flammability of certain electrotechnical equipment in the railway sector (EN 45545-2 standard).
Picture: ISO 4589-2 test apparatus in place at CREPIM
The UL94 vertical test is a widely used method for providing a preliminary indication of the flammability of plastics intended for electrical and electrotechnical applications. Three classification levels are possible, from highest to lowest performance: V-0, V-1, and V-2. This classification is not intended to reflect the material's behavior in a real fire situation, but it has the advantage of being simple to implement and internationally recognized.
The ISO 5660-1 cone calorimeter method was developed by NIST in the United States and is used to determine a material's contribution to a fire. Its principle is based on measuring oxygen consumption, which is directly related to the heat output. It allows for the determination of many key combustion parameters: ignition time and duration, heat output, quantity of smoke released, mass loss, and combustion kinetics. It is a reference method for evaluating the reaction to fire of materials.
Picture: detail of a sample undergoing ISO 5660-1 testing at CREPIM
Finally, the NF X 70-100 tubular furnace test is based on the analysis of the mass of toxic gases emitted during combustion or pyrolisis. It allows measurement of the concentration of several gases, such as carbon monoxide (CO), carbon dioxide (CO₂), hydrobromic acid (HBr), hydrochloric acid (HCl), hydrogen cyanide (HCN), hydrofluoric acid (HF), sulfur dioxide (SO₂), and nitrogen oxides (NOx). The test is carried out in a tubular furnace typically heated to approximately 600 °C (with possible temperatures between 400 and 800 °C). The sample is exposed to this temperature for 20 minutes, and the gases produced by pyrolysis or combustion are collected, analyzed, and quantified. The emission of toxic fumes is expressed in milligrams per gram of material, assuming a sample mass of 1 gram.
Photo: Layout of the NF X 70-100 testing equipment at CREPIM
The initial work carried out illustrates CREPIM's role in the CIRCOPLAST project: defining relevant testing protocols and preparing for the integration of innovative and environmentally friendly flame-retardant solutions. The next steps will allow for a direct comparison of the fire performance of virgin, recycled, and bio-based plastics, paving the way for new, safe, and circular applications for recycled plastics.
