Franck Gyppaz, Nexans, underlined the importance of cables for fire safety and presented a new mineral PIN flame retardant solution. Quantities of cables are increasing everywhere, with demography and with increasing energy demand and new energy uses. One quarter of fires are of electrical origin. Although fires mostly start at the interfaces with components and connections, cables can be critical in fire propagation. Current non-halogenated FR solutions for cables imply high filler loadings which deteriorate cable mechanical properties. Nexans has developed a new PIN FR technology combining silicate, a base-releaser, a specific metakaolin with a reaction control additive and a carrier to ensure compatibility with cable materials. These react together in fire to form a concrete-like material which provides low-smoke fire resistance and maintains physical integrity. The FR solution can be delivered in a biopolymer-based tape rather than compounded into the cable polymers, enabling to achieve CPR B2ca-s1,d0 when protecting EPDM accessories (ethylene propylene diene monomer rubber). A tape based solution can replace cable bedding, giving higher cable flexibility, or could be applied to polymer plates and other materials.
Sebastian Hörold, Clariant (pinfa member) outlined developments in phosphinates as performance fire safety solutions for engineering plastics, in particular in response to demanding specifications for e-mobility. Non-halogenated FRs offer better electrical performance (CTI comparative tracking index) because antimony (ATO) is not used. Clariant has developed two new phosphinate PIN FR – synergist packages enabling improved glow wire ignition test performance (GWIT to 800°C @ 0.75 mm) and UL 94 V-0 @ 0.4 mm (for both, at 23% loading). Mechanical performance approaches that achieved with brominated FRs. REACH registration is completed. Depending on the FR-synergist package, high thermal stability (broad processing window), no blooming, water resistance and low density are possible. Phosphinates also combine fire safety, electrical and material performance for epoxies, PBT, TPU and polyurethanes for electric vehicle applications such as charging and high voltage connectors, battery structure and housing, adhesives, busbars.
Corina Neumeister, Nabaltec, presented a new mineral PIN FR system producing a structural ceramic protective layer in case of fire, corresponding to specifications for electric vehicles and other demanding applications, where rapid fire protection, maintaining of structure and prevention of fire heat transfer are all required. Mineral FRs alone result in fragile ash. The new FR solution, combining mineral PIN FRs with a ceramifier (glass agent), generates char which retains integrity at 600°C, resists temperatures up to 1000°C and limits heat transmission. It has been developed by Nabaltec with specific in-house testing, including ash bending and ash strength tests, 20 minute flame resistance and temperature at the back of a 3 mm sample. Issues with processability are currently being resolved and a compounding-ready mineral plus glass agent formulation will be commercialised in 2023 for use in polypropylene, polyamide, polyurethane resins and other engineering thermoplastics and thermosets, including glass fibre reinforced, for application in electric vehicle battery housings, electronics and industry.
Mike Bird, Imerys, outlined PIN FR synergist applications of the company’s engineered-morphology mineral specialities: talc, kaolins etc. Imerys is the world’s leading producer of white industrial minerals. Applications in polymers include for structural reinforcement, dimensional stability, conductivity, rheology and processing modifiers. Specific engineered minerals can provide enhanced fire resistance synergies and smoke density reduction, both by improving char structure and by catalytic functions of certain mineral components. Imerys’ current developments include applications for e-mobility based upon polyamide for electric vehicle battery casings, in synergy with phosphinate PIN FRs, improving fire performance (from UL 94 V-1 to V-0 @ 0.4 mm), reducing weight and improving mechanical properties (inc. impact resistance). Processing is also improved because the mineral removes possible acid release from compound decomposition during heating. Another development is use of engineered talc and kaolin in PE-EVA (ethylene-vinyl acetate) in synergy and partial replacement of ATH / MDH, achieving UL 94 V-0 @ 2 mm with reduced peak heat release rate and smoke density.
Michael Suchan, Evonik, presented developments to implement non-halogenated flame retardants in polyurethane foams. Companies worldwide are looking to move away from the halogenated FR TCPP (tris(1,3-dichloro-2-propyl)phosphate) to respond to demand for non-halogenated foams for green buildings and to reduce smoke toxicity. This is difficult as alternatives are today powders, and TCPP also has softener properties. Evonik provides additives, such as catalysts, as well as foam stabilisers and processing aids. Work is underway to address problems posed by suspensions of powder PIN FRs, such as shelf-life (deposition), viscosity, foaming nozzle blocking by particles and aggregation in the foam. Dispersion agents are challenging to develop as they must not deteriorate processing (many standard dispersion agents have defoaming properties) and must not increase viscosity. Solutions tend to be polyol and PIN FR specific, working in one foam formulation but not another. The dispersion agent must also function at low doses (< 5% w/w to FR particle) whilst also covering the whole particle surface.
David Stuart, NeoGraf, presented applications of expanded graphite (EXG) as a non-halogenated component of fire safety solution for polymers (see also pinfa Newsletter n°128). New formulations now offer onset temperatures up to 280°C, enabling use in a wide range of polymers including polyamides and ABS. Expanded graphite is used alone to achieve demanding fire performance and low smoke toxicity in train and aircraft seats (in polyurethane foams ???), but is most effective in synergy with PIN flame retardants, such as mineral hydroxides which render char glassy to reflecting heat, or phosphorus which can generate more durable char. Delivery in masterbatches (up to 50% EXG) or polymer-coated particles (0.1% w/w polymer/particle), with various polymers and resins, facilitates handling and processing, ensures polymer compatibility and avoids risks of corrosion, which can result from residual sulphuric acid in EXG (from production).
Darya Zeini, Bioenvision (previously Funzianano), presented R&D developments for silicon-containing POSS FR synergists (polyhedral oligomeric silsesquioxane), see pinfa Newsletters n°134 and 124. These are used as synergists (at < 1% loading) to improve char quality (silicon ceramification), accelerate char formation and increase ignition time. The organic group on POSS enables tailoring for specific polymer, either as reactive or additive. In addition to demonstrated use in polyurethane foams and thermoplastics (such as polypropylene), recent trials have shown effectiveness in acrylic adhesives. More tests are in progress together to investigate the effectiveness in epoxy resins.