Posted on 20/03/2024 in 2024
pinfa-NA SPE Flame Retardant Week 2024

pinfa-NA’s online event for plastics professionals, with the Society of Plastics Engineers, attracted over 100 participants, with eight strongly attended speaker sessions over four days, plus panel sessions. This National Week of Flame Retardants covered regulatory developments impacting flame retardants worldwide, how PIN FRs work in different plastics, fire performance testing and standards and a range of different innovative PIN FRs for different polymers and applications.

Each speaker presentation (20 minutes) was followed by online questions, with active exchanges both with speakers and between participants in the online Chat. A wide range of questions were raised and discussed, with technical questions on specific compounds and applications answered both online or after the event directly to participants.

Roger Avakian, polymer formulation expert, summarised different non-halogenated flame retardant and drip suppressant technologies. He noted that PIN FRs can act by different mechanisms: inhibition of combustion reactions in the gas phase, lease of inorganic gases (diluting oxygen available to fire), heat sink by release of steam or formation of a protective char or ceramic barrier layer (“condensed phase”). Specific  fire tests are designed to assess fire performance of plastics in conditions reflecting prevention of real fires.

Margaret Baumann, Performance Polymers, updated on regulatory developments impacting flame retardants and synergists worldwide. Investors and customers are also pushing industry to move away from chemicals identified as having environment or health hazards. Most regulations to date and expected target certain problematic halogenated FRs (polybrominated PBDEs, HBCD, TBBPA, TCPP and expected in the future TBNPA) or in some cases all halogenated FRs (e.g. for certain applications: State of New York, EU Ecolabel). However, several non-halogenated phosphorus esters (TPP) are also regulated. A significant question today is that of perfluorinated drip suppressants (e.g. PTFE polytetrafluoroethylene, KPFBS potassium perfluoro butanesulfonate). Apple has announced that it will phase out PTFE. The PIN FR industry today proposes non-halogenated solutions to avoid flaming dripping in PIN FR plastics (see pinfa Newsletters n°s 154, 156).

James Zhou, Avient, explained the distinctions between and roles in fire safety of codes, standards, regulations, specifications and guides. He presented ten aspects of polymer fire behaviour, and how PIN FRs can mitigate or improve these: thermal degradation, ignition, extinction, dripping and flaming droplets, flame spread, heat release rate, fire endurance, smoke evolution, toxic smoke gases, char formation. Non-toxic polymeric phosphorus PIN FRs are available which reduce smoke emission and smoke toxicity, and can achieve UL 94 V-0 (?3.2 mm) in several polymers with PIN flame retardants.

Xiudong Sun, FRX Polymers, presented application of the company’s polyphosphonate PIN FR in a range of polymers including: TPUs, polycarbonate (PC), PC/PBT, PC/ABS. The polymeric phosphorus-based PIN FR offers low toxicity, non-migrating and is transparent, with a range of melt-flow characteristics. It is suitable for thermoplastics (including spinning, film extrusion) and for thermoset oligomers and reactive. Examples include polyphosphonate homopolymers and carbonate copolymers used in PFAS free formulations. Phosphorus content rangers from 6.6 to 10.6 %. The product is Greenscreen® Benchmark 3, TCO and Oeko-Tex approved, and a ChemSec Marketplace named alternative to brominated FRs. FRX polymers presented data on PFAS and PTFE free formulations using polyphosphonates with and without synergists.

Maz Bolourchi, Imerys, presented performance benefits of the company’s specific mineral PIN FR synergists. The company offers nine different types of mineral as polymer additives, with tailored particle shapes, sizes and chemistries, including for fire performance of engineering plastics, polyolefins, rubbers etc. The mineral additives can improve compound properties, improve melt flow, reduce impact of glass fibres on processing (debundling) and reduce corrosion of processing equipment. Fire resistance is improved by enhancing char integrity. Applications include automobile, electronics, building and construction.

Brian Hanrahan, Lumina / Celestial Materials, presented the company’s anorthosite inorganic PIN FR, a natural high-purity, non-alkaline, Feldspar calcium – aluminium – silicate mineral, mined in Greenland. In fire, the mineral reacts in heat to generate a ceramic protective coating on the polymer surface. To date, UL 94 V2  is achieved in high density polyethylene at 30% loading. Work is underway to improve effectiveness by adding an activator and drip suppressants. The anorthosite can be combined with the widely-used inorganic PIN FRs ATH and MDH.

Amit Paul, Paxymer, presented the company’s carboxylic and acrylate copolymers (see pinfa Newsletter n° 88), which are a PIN FR synergist effective with phosphorus, inorganic and nitrogen flame retardants in a number of different polymers. Use of the synergists at 1 – 5 % loading increases the protective char layer in fire and makes the char layer less brittle, accentuates gas phase fire inhibition, reducing dripping, smoke emission and smoke toxicity. The synergist can also improve compound processing and mechanical performance for a given fire performance. Paxymer sees a trend towards acceptance of more complex compound formulations, necessary to achieve demanding fire standards and performance specifications with safe and sustainable additives.

Gary Wnek, Case Western Reserve University, discussed non-halogenated PIN intumescent coatings to reduce flammability and smoke emission of HDPE (high density  polyethylene) and other highly flammable thermoplastics. PIN components tested include poly acrylic acid, tannic acid (bio-based), ammonium polyphosphate, sodium silicate, with an epoxy binder to generate a coating. Resistance of up to one hour to a direct flame was achieved. In addition, intumescence was rapid enough to quickly cover a hole through the coating and HDPE (up to an 18 mm diameter), and so prevent burning.

A final discussion panel session brought together the above speakers with Qingliang He (Lanxess), Paul Hardy (Amfine), Emmanuel Laval (RioTinto), Tobias Moss (Budenheim), Subra Narayan (Clariant), Rainer Sauerwein (Nabaltec).

The discussion noted that the market for PIN flame retardants is growing faster than the overall flame retardant market (c. +8% versus +6% per year) – see also pinfa Newsletter n°156. Investments are being made by industry to ensure supply in response to this growing demand.

Formulation with PIN FRs to achieve demanding fire testing specifications can be discussed with suppliers and experts, because there is no one solution to work with all polymers, and combinations of PIN FRs and PIN synergists can be identified to provide solutions and to reduce FR loadings.

Questions raised included development of bio-based PIN FRs, data on life cycle analysis, compounding to achieve fire performance requirements with glass fibres and PIN FRs, questions about regulatory perspectives for melamine and boron compounds, PIN smoke suppressants and PIN solutions to replace antimony and perfluorinated anti-drip additives.

National Week of Flame Retardants 2024, SPE (Society of Plastics Engineers) and pinfa North America, online, 22-25 January 2024, register here to watch recordings of all sessions

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