Posted on 15/10/2019 in Furniture & Textiles 2019
Challenges for FRs in applications and products

Shuyu Liang, Sika Technology
Flame retardants are of increasing interest to Industry, in response to a worldwide increase in fire safety and environment awareness. Sustainability is a key requirement in fire safety, meaning environmentally friendly products, based on green chemistry, green production, and compatible with recycling. Some sectors, such as shipping and marine, already have demanding fire safety specifications, requiring innovative products and solutions. Sika today drives the needs of using sustainable solutions in constructions in response to today’s new materials and new building designs. The commitment to achieving up-to-date fire norms should be expected in all fields. New processes such as 3D-printing will need new solutions for fire safety. Industry should provide a full package for fire safety, integrating design, materials, flame retardants and application services. This integrated approach can facilitate innovation and can reduce overall costs, which remain a key challenge for green fire safety approaches.
Sika Technology is a fast growing Swiss-based company, innovating for over 100 years in products and services in sealing, bonding, damping, reinforcing and protecting, in building and construction and today in industry and automotive. Sika has over 20 000 staff and 200 factories worldwide.

Serge Bourbigot, University of Lille, outlined the challenges for flame retardants in 3D-printing, noting that fire performance of 3D-printed materials depends on variables such as printing direction, printing parameters, infill pattern and geometry for ‘solid’ items and printer quality (which influence porosity of final article). This can make fire testing results variable and inconsistent. Innovative fire safety enabled by 3D-printing include integration of a fire resistant outside layer into the print, new design of biphasic materials, as well as use of novel PIN FR combinations and synergists, such as glass microbubbles and nanoclays.

Marcos Batistella, C2MA Alès, discussed 3D-printing using SLS (Selective Laser Sintering) technology with polyamide 12, as increasingly used industrially for production of parts for industries such as aerospace which require high levels of fire performance. Commercially available PIN FRs (APP, cyanurate melamine, phosphite …) were tested, looking both at the fire performance of the 3D-printed parts and at impacts on processing parameters (sintering temperature range, coalescence in printing). Conclusions were that some but not all of the PIN FR combinations could achieve both fire performance and 3D-printing quality in these PA12 tests.

Petri Moisio, Meyer Turku Shipyard, explained the importance of fire safety onboard during the cruise ship construction process. The shipyard, which the conference visited, is today constructing top-range cruise ships, currently a 1 800 m2 floor surface liner (the size of a modern hospital). Sections of the ship are built onshore, then transported (1 200 t crane) and welded onto the vessel under construction in dry dock. There is a major risk of fire being started onboard by “hot works” (welding, etc) taking place near flammable materials. Four minutes of fire are estimated to cost a million euros. The shipyard has some 150 hot works per day on a cruise ship under construction, and each one is specifically identified, authorised and monitored using a real-time online / mobile device system. Fire risk is further reduced by requiring flame retardant materials for packaging of construction materials and equipment to be installed, and flame retardant specifications for protective films and other materials. Flammable materials are as far as possible removed from the ship during construction but the metal structure of the ship is only around 10% of its value, with 90% being electrical and electronic equipment, furnishing and decoration. These must all respect maritime fire performance requirements.

Sebastian Eibl, German Army, underlined that the end-customer does not know which flame retardants are being used in products. The only solution for the end-customer is chemical analysis. He presented examples of deterioration with ageing of polyurethane camouflage nets. The army’s chemical analysis showed that the problem is related to appearance of phosphoric acid, with the low pH then breaking down the polyurethane polymer. Further analysis identified red phosphorus, RDP, a sulphur-phosphorus compound and melamine (which may or may not come from melamine polyphosphate). Analysis showed deterioration with age irrespective of different phosphorus-based FR chemicals identified and that deterioration was related to folding for storage, leading to humidity. Modelling suggested that in humid conditions, 50% of the phosphorus FRs in the plastic can be decomposed. Also, with PIN FR polyurethane, antimony was identified to be accessible (water soluble on the surface) posing potential health concerns.

Xuebao Lin, BAM Germany, presented tests of weathering resistance of PIN FR polymers for E&E applications. The fire protective barrier effect of mineral FRs (ATH or boehmite in EVA) showed in some cases to improve with ageing, possibly because of surface agglomeration of the minerals. In TPU (thermoplastic polyurethane) with melamine cyanurate, however, polymer degradation after ageing led to deteriorated melt-dripping and fire spread. A self-developed cable module test (to simulate at bench sale the full-scale vertical test) showed to provide good indications of fire spread behaviour.

Mauro Zammarano, NIST, described a reduced-scale test aiming to predict full-scale fire performance of upholstered furniture. Despite reductions in smoking, upholstered furniture remains the biggest cause of home fire deaths in the USA. At the same time, some States are limiting the use of some flame retardants (California, Maine). NIST has therefore carried out fire testing of fire barrier materials in full-scale chair mock-ups, and reduced-scale testing (10 cm cube of material + barriers). In full-scale tests, the best fire barrier materials can reduce the peak heat release rate (PHRR) by a factor of about three and increase time to PHRR from 3 to around 25 minutes. After this time, liquid pyrolysis products produced by the foam percolated through the barrier and caused a rapid increase in heat release rate. The reduced-scale test was able to predict the time to PHRR and the plateau heat release rate before PHRR observed in full-scale tests.

Gabrielle Peck, University of Central Lancashire, presented the results of four, reduced height (5 m) BS 8414 facade fire tests, in which both the heat release and smoke toxicity had been quantified. Three of the facades used non-combustible aluminium composite material ACM A2, while the fourth used a polyethylene (PE) cored ACM. These were used alongside three insulation products, mineral wool, PIR foam (for both ACM A2 and ACM PE) and phenolic foam. The 3 megawatt wood crib fire was sufficient to destroy the ACM panels above it, exposing the insulation, which burnt almost completely. Where the ACM had failed, the combustible insulation products also burnt away. As may be expected, most of the toxicity in the main exhaust resulted from the 3 MW wood crib, predominantly a mixture of CO2 and CO. The toxicity in the cavity between the ACM and the insulation was significantly greater, with hydrogen cyanide being the major toxicant from PIR, suggesting possible risks if the effluent were to blow in through a vent or broken window.

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