Posted on 22/05/2018 in News 32 2018
Green chemistry and chemical substitution

Jonathan Crozier, pinfa Sector Group manager, Cefic, and Chris Thornton, consultant, explained that PIN flame retardant fire safety solutions are essential to support EU objectives of bio-economy, sustainability (especially sustainable construction materials), circular economy and social inclusion. PIN FRs can be sourced from natural materials, from bio-sourced or from recycled materials. Selection of PIN FRs with optimal health and environmental profiles can limit obstacles to future plastics recycling currently posed by “legacy” halogenated FRs.
Manfred Döring, Fraunhofer LBF, outlined how “green chemistry” principles can be applied to bio-based flame retardants. Base natural materials should preferably by hydrophobic, thermally stable and enable bonding of functionalities. Bio-molecules such as tartaric acid, phytic acid, glycerine and pentaerythriol have such characteristics. Bio-polymers can offer stable, non-migrating solutions which are compatible with material polymers. He presented tests using DOPO (phosphorus PIN FR) reacted onto bio-based acytylate polymers in polyamide.

Ine De Vilder, Centexbel, presented the LIFE-FLAREX project (see pinfa Newsletter n°90) which is assessing alternative flame retardants for textiles, compared to brominated FRs, with and without ATO (antimony trioxide). The project has selected, amongst others, a number of phosphorus-based PIN FRs and will assess the technical performance (application to textile, impacts on textile properties) and toxicity (skin absorption), enabling comparative risk assessment. Furthermore, a LCA study will be performed on all FR treated textiles.

Hakan Kanli, Etimine SA, Turkey, outlined challenges for the future of borates as flame retardants. Borates are natural, mined minerals: sodium borate (tincal), colemanite (calcium borate) and sodium-calcium borate (ulexite). Boron is on the EU list of Critical Raw Materials (CRMs) because it is essential for certain industries (i.e. 73% of boron use is in glass and ceramics, 15% in fertiliser) and Europe is dependent on imports. Around ¾ of global boron reserves are in Turkey. Most of the borate chemicals used in flame retardants – except zinc borate, which is not today classified – are included in the list of SVHC (Substance of Very High Concern), due to their harmonised classification as Cat. 1B for reproductive toxicity. Industry however considers boron compounds should be classified only as Cat. 2 for reproductive toxicity. There is no restriction for borates for industrial and/or professional uses and there is also possibilities for consumer uses through the specific concentration limits assigned to borates individually. Borates have been “postponed” from the REACH Annex XIV Priority List because of the complexity of dispersive uses and consequent difficulties to define Authorisation procedures.

Rodolphe Sonnier, IMT Mines d’Alès, France, presented studies of smoke emission for different polymer / flame retardant combinations, plotting the smoke production rate versus the heat release rate. He shows that smoke emission is related to the aromaticity and to the carbon fraction in the polymer. In EVA, the inorganic PIN FRs ATH and MDH show lower smoke production per kg polymer consumed compared to neat EVA. In polyethylene, smoke production per kg consumed is higher with DOPO (phosphorus-based) and TBBA (brominated) FRs.

Carine Chivas-Joly, LNE (French National Laboratory of Metrology and Testing), presented tests of incineration of EVA cables containing mineral nanoparticles: aluminium oxide hydroxide (boehmite) and alumina. The tests show that nanoparticles are present after incineration in both soot and ash, but that the form is modified: particle size increases in soot and decreases in ash. Also, boehmite, which is non cyto-toxic as used initially, develops low levels of cytotoxicity after incineration, and cycto-toxicity of alumina also increases in fire.

Toussaint Barboni, University of Corsica Pascale Paoli, summarized studies of smoke toxicity from forest fire smoke. Among the compounds emitted during a forest fire, there are gases, VOCs and aerosols. The major compounds emitted are CO2, H2O, CO, NOx and aerosols. The main tars component is levoglucosan, from cellulose degradation. Soots are small particles smaller than 1 μm and penetrate deep into the bronchi. Toxicants compounds include: benzene, polyaromatic hydrocarbons (PAH), phenol, alkanes, aldehydes (formaldehyde and acrolein), ketones and alcohols, as well as gaseous toxicants including nitrogen oxides and carbon monoxide.

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