Valencia, Spain, 19th April: eight pinfa members presented PIN fire safety solutions and regulatory developments: Adeka, Avient, Budenheim, Clariant, ICL, Imerys, Nabaltec, William Blythe. Workshop participants included compounders from across Europe and the workshop provided an expert training in formulation and compounding of fire performance polymers, as well as visits to Aimplas research lab and testing pilots.
Tobias Moss, Budenheim, reminded attendees why society needs flame retardants. Around 130 000 people die in fires worldwide each year, and fires cost around 1% of GDP. Flame retardants represent around one third of polymer additives with an annual world market of around 10 billion € growing at c. +6% per year, with PIN flame retardants showing the fastest growth.
Corina Neumeister, Nabaltec, summarised different fire performance tests and what information they bring, and outlined the mechanisms of PIN flame retardants, including char formation, intumescence, heat absorption, release of inert gases and gas phase flame inhibition. PIN FRs have the advantage of not releasing acid during processing, nor during use life, so protecting equipment or electronic circuits. Their mode of action results in low smoke toxicity and low smoke release, and this can be accentuated by synergies with PIN smoke suppressants.
Pascal Amiguoet, Avient, explained that flame retardants play several roles in fire protection, depending on their selection and combination in different polymers: prevent or delay the start of fire, reduce heat release rate, and maintain structure (for example by protecting steel or concrete from heat and so from collapse in case of fire, or by maintaining structure of cables so ensuring that power or data continue to be transmitted). Flame retardants always have impacts on polymer properties and cost, as do other additives, so a challenge is to identify what is really needed by the customer for the final product and to propose a formulation offering the best cost – performance balance whilst ensuring the required level of fire safety.
Begoña Galindo, Aimplas, presented the Aimplas Flame Retardant R&D group, created 2008, developing biobased flame-retardant additives, intrinsically flame-retardant polymers, recycling and fire testing. Processing is very important to ensure effectiveness of flame retardant additives. Twin screw extruders with distributive screw configuration and low specific mechanical energy avoid high temperature peaks along the process, so ensuring optimal mixing of the additive without degradation.
Ana Mangas Roca, Aimplas, presented reactive extrusion (REX) technology. This enables a high level of mixing and reaction control, but is complex to manage because many parameters must be closely controlled in one single installation. REX units can also operate mechanochemistry, that is reaction of solid components. Aimplas operates a full-scale pilot unit for testing and trials. Results are promising. To date there is little industrial application but applications are being sought.
Laurent Ratte, SCC Consultants, presented compounding simulation software. From inputs data (material and additives characteristics, screw design and operating conditions), simulation gives insights about material behaviour evolution and process efficiency. Software simulation enables to identify likely formulation ranges and so target testing. Test results are then used to improve the simulation and so material properties and process quality.
Laurent Ferry, IMT Mines Alès, outlined research into bio-based flame retardants. Many research papers have been published over recent decades, looking at flame retardant properties of natural phenolic carbon molecules (e.g. lignin, tannin), which can stabilise charring by cross-linking, natural molecules containing nitrogen and/or phosphorus (e.g. chitin, casein, phytic acid, DNA from fish waste), as well as bio-based carbon molecules doped with synthetically sourced phosphorus. Alginate can be used to produce fire resistant insulation foams. Phytic acid offers the advantages of being naturally widely available (in seeds), high phosphorus content, possibility to react with different metals for synergetic effects. To date there is no significant industrial uptake of these bio-based PIN FRs. Some are widely and reliably available, but all pose challenges of water uptake, purity and cost. See pinfa Newsletter n°139, summary of ECOFRAM 2022 conference.
Mireia Fernández, Aimplas, outlined different processes for recycling of plastics, including chemical recycling, and how to apply them to FRs recovery.
- Solvent recycling: Dissolution and precipitation techniques are used to separate polymers from additives allowing the recovery of both fractions. Research is looking for alternatives to chemical solvents, such as biobased solvents or supercritical CO2.
- Solvolysis: specific solvents are used to depolymerise given polymers and obtain the starting monomers. Separation and purification of the dissolved additives and monomers is a challenge.
- Polymers are broken down to gas and liquid fractions, which can be used as fuel or to replace crude oil in refining. Some additives can be separated and recovered.
Adrian Beard, pinfa Chairman (Clariant), discussed what is a “sustainable flame retardant”, based on the EU Green Deal objective of Safe and Sustainable-by-Design Chemicals (SSbD). This requires looking at many factors, as a priority no or minimal health and environmental hazards and compatibility with safe end-of-life recycling or disposal, and climate impacts, but also life cycle analysis including Critical Raw Materials, smoke toxicity, social benefits and impacts. Clariant is making this analysis for a phosphinate PIN FR used in a USB-C socket. The full analysis implies collection of very much data, including specific studies on possible impacts during processing, collection of exposure data (the PIN FR is not classified hazardous, so no CSR exists to date) and an environmental footprint study. This exercise shows the complexity of the SSbD concept and that it cannot generate a yes/no quantified result, but will enable identification of sustainability “hotspot” challenges.