Burning Questions: Search for environment-compatible flame retardants
To inhibit or resist the spread of fire flame retardants are applied in a wide range of commercial products like computers, cars, furniture, paints and foams. Some of the brominated flame retardants are under discussion or are banned by the EU as they are considered harmful due to their persistent nature and toxicity. ENFIRO (Life Cycle Assessment of Environment-Compatible Flame Retardants: Prototypical Case Study) is a European research project coordinated by IVM and is recently finalized. The main aim of the project was to study the substitution options for some harmful flame retardants resulting in a comprehensive dataset on the viability of production and application, environmental safety, and a life cycle assessment.
In total 14 halogen-free flame retardants (HFFRs) as alternatives for decaBDE, TBBP-A, and brominated polystyrenes were selected. These flame retardants were studied in five applications - printed circuit boards (PCBs), electronic components, injection moulded products, textile coatings and intumescent paint.
ENFIRO showed that all of the selected alternative flame retardants do fulfill the regulatory fire test. A method was developed using intrinsic flammability properties as well as a simple method for characterizing the fire performance and fire toxicity of polymers using three parameters (fire spread, smoke/ carbon monoxide, inefficiency of combustion). With this model a comparative fire performance assessment of HFFRs vs BFRs could be made. An important finding was that halogen free systems have clear benefits as demonstrated, e.g. less visible smoke, in some cases lower peak heat release rate with halogen free products, and less toxic components in smoke. Both polymers with brominated and halogen-free FR showed similar loss in mechanical properties compared to the polymer alone. All formulations (HFFR and BFR) showed equal or better performance regarding processability for injection moulding. For all polymer systems investigated a HFFR option was found. The results for the PCBs showed that the HFFRs where as good as or better compared to the reference PCBs produced using BFRs. A novel intumescent coating system was developed for pure HIPS, showing good fire performance results and excellent results were obtained for the industry fire standards relevant to the electronics industry as well.
From the initial selection of 14 alternative flame retardants seven were found to be less toxic and also accumulated less in the food chain than the BFRs. Environmental fate models predicted that the organic HFFRs would be found primarily in soils, sediments and dust and to a lesser extent in water and air. Controlled air emission experiments showed that all organic HFFRs emitted from polymers at elevated temperature but not at lower temperatures. Leaching experiments showed that both HFFRs and BFRs can leach to water. For some polymers no differences in leaching behaviour were found between BFRs and HFFRs, but some HFFR systems had higher leaching properties than BFRs (e.g. polymeric based BFRs). The type of polymer is the main parameter determining the leaching behaviour. Analysis of organic HFFRs in dust from microenvironments and environmental samples showed highest concentrations on and around electronic equipment, in sediment and sewage sludge.
The environmental and human risk assessments showed that the predicted environmental and human exposure concentrations were below the toxicity thresholds for the selected HFFRs. However, the lower risk of selected HFFRs compared to selected BFRs is mainly due to the lower hazards of the HFFRs, and not due to a lower exposure. Reducing the leaching of HFFRs is a next challenge for the development of new FRs. The comparative life cycle assessment (LCA) of BFR vs HFFRs, using a laptop as case study showed that the waste phase was the most relevant. Especially, the formation of brominated dioxins out of BFRs during improper electronics waste treatment had a strong negative impact on the LCA-scores. Overall the LCA performance of the HFFR scenario was better than for the BFR scenario. The same life cycles were also evaluated on social criteria using a Social Life Cycle Assessment. Several hotspots are found in the raw material mining phase.
In conclusion, ENFIRO showed that viable alternative flame retardants are available. Some HFFRs showed less risk for the environment and human health, and show similar fire performance and technical application capabilities as BFRs.
ENFIRO coordinated by IVM researcher Dr. Pim Leonards, started in September 2009 and ended November 2012. The ENFIRO consortium is a unique collaboration between industries, SME's and universities with a wide variety of scientific disciplines. The ENFIRO project team includes VU University Amsterdam (IVM), University of Ulster, Clariant Produkte (D) GmbH, IRIS Vernici s.r.l., Procoat, IVAM, Stockholm University, Utrecht University (IRAS), Swerea IVF AB, University of Amsterdam, Callisto Productions Ltd, and ITRI Ltd. The project is carried out with financial support from the European Community's Seventh Framework Programme (no 226563).
Contact information: Dr. Pim Leonards
More information: website ENFIRO (www.enfiro.eu)