Composites on fire at reduced scale: evaluation, characterization and modeling

Composite materials are increasingly being used in the design of aircraft, train, ship and buildings. They are very often structural parts and they must meet the difficult challenge of having adequate structural fire protection. In fire scenarios of particular relevance according to the targeted applications, suitable strategies to control fire hazards are needed for composite structures. There are three main methods available to design composite structures with improved fire resistance behavior: (i) use “normal” structural materials and add surface protection, (ii) use fire retarded versions of “normal” structural materials, and (iii) use structural materials with inherently good fire retardant properties. The first approach is of interest since it does not modify the intrinsic properties of the structural composites and does not lead to processing problems (e.g. incorporation of fillers in the material). It can be achieved with intumescent coatings: when heating beyond a critical temperature, the intumescent material begins to swell and then to expand forming an insulative coating limiting heat and mass transfers. Intumescence will be used in this work On the other hand, the evaluation of fire resistance of intumescent coatings protecting structural composite requires large scale equipment. Due to the complexity of fire phenomenon, full-scale tests are still the main and the most credible tool for investigating fire-related issues but they are however very costly, and generally, the cost significantly increases with scale. For those reasons we have developed reliable, repeatable and fast small scale tests including: (i) a furnace delivering temperature/time curves such as ISO 834, UL-1709 and other curves depending on specific fire conditions (curves ‘on demand’), (ii) a jet fuel fire test (according to ISO 2685 or NextGen) devoted to evaluate the fire resistance of components, equipment and structure located in ‘fire zones’ in aircraft (e.g. compartments containing main engines and auxiliary power units) and (iii) a mini Steiner tunnel (according to ASTM E84). It then permits the ‘high throughput’ development of intumescent coatings protecting composites. Examples using the mini Steiner tunnel and the reduced jet fuel fire test will be presented in the talk. The first example deals with the fire protection carbon fiber reinforced polymer (CFRP) in aircraft structure. Intumescent silicone based-coatings (low and high intumescing coatings) are evaluated on CFRP using a bench mimicking a jet fuel fire occurring at high heat flux (200 kW/m²) (Figure 1). It is shown the development of large intumescence (high intumescing coating) associated with appropriate thermal properties of the coating (heat conductivity measured as low as 0.3 W/m.K) provides efficient protection for the CFRP at the jet fire test. On the other hand, the formation of cohesive ceramic (low intumescing coating) with low heat conductivity (constant heat conductivity as a function of temperature of 0.35 W/m.K) also provides protection but its efficiency is lower than that of intumescent char. It is evidenced that intumescent silicone-based coatings are materials of choice for protecting CFRP in the case of jet fuel fire. Figure 1 – Jet fuel fire at reduced scale on CFRP protected by an intumescent coating In the second example, different intumescent coatings protecting polyethylene terephthalate (PET) rigid foams used in roofing structure are evaluated using the mini Steiner tunnel. Results show good correlation between the two scales and the approach developed at the small scale permits the fast screening of intumescent paints to predict their fire behavior at the large scale. Finally, mechanistic aspects of intumescence based on our small scale tests will be investigated including the chemistry, the physic, the rheology and the modeling of the intumescenc

Addressing the problem of plastic waste: Development of an enzymatic process for PET recycling

Every day, media and NGOs describe the society\u27s disaffection for plastics accused of polluting the planet. All major brand-owners made commitments to solve this problem (e.g. Coca-Cola, Nestlé, Danone, PepsiCo, Suntory, Unilever, L’Oréal, Nike) and announced a future with less plastic waste by 2025. Nevertheless, only 6 years before the announced term, no effective solution is yet available to meet these goals. Indeed, existing technologies like thermo-mechanical recycling leads to loss in mechanical properties of the polymer and even if several chemical recycling processes are under development, they suffer from the disadvantages of using organic solvents, high reaction temperatures and the need of an intensive waste sorting. Consequently, enzymatic recycling appears as a pertinent solution notably because the enzyme selectivity avoids a drastic sorting of waste and enables the recycling of complex plastics (multi-layers construction in some bottles of sparkling water for instance), it is an eco-friendly reaction in water and because of savings in energy consumption due to a low temperature of reaction. Using a computer-aided engineering strategy, we drastically improved the depolymerizing performance of the best identified enzyme candidate. Utilizing site-directed mutagenesis targeted at the active site, combined with three-dimensional fold stabilization, we engineered an enzyme variant, demonstrating an astounding increase in thermostability combined with a high activity. This enzyme is able to depolymerize 90% of PET waste (200g/kg) into monomers, terephthalic acid and ethylene glycol, in less than 10 hours. The downstream processing was developed and optimized leading to the demonstration that this enzymatic technology could enable the use of an industrial plastic waste to produce again PET monomers and ultimately a bottle from this recycled PET. We hope to demonstrate the strong potential of the enzymatic technology jointly developed by CARBIOS and LISBP to provide a breakthrough solution to help solve society’s growing plastic waste problem

Innovative polyelectrolyte treatment to flame-retard wood

Fire protection has been a major challenge in wood construction for many years, mainly due to the high flame spread risk associated with wood flooring. Wood fire-retardancy is framed by two main axes: coating and bulk impregnation. There is a growing need for economically and environmentally friendly alternatives. The study of polyelectrolyte complexes (PECs) for wood substrates is in its infancy, but PECs’ versatility and eco-friendly character are already recognized for fabric fire-retardancy fabrics. In this study, a new approach to PEC characterization is proposed. First, PECs, which consist of polyethyleneimine and sodium phytate, were chemically and thermally characterized to select the most promising systems. Then, yellow birch (Betula alleghaniensis Britt.) was surface-impregnated under reduced pressure with the two PECs identified as the best options. Overall, wood fire-retardancy was improved with a low weight gain of 2 wt.% without increasing water uptake

Quantification of thermal barrier efficiency of intumescent coatings on glass fibre-reinforced epoxy composites

In this work, the thermal barrier efficiency of three commercial intumescent coatings of varying thicknesses on glass fibre-reinforced epoxy (GRE) composites has been studied using cone calorimetric parameters and temperature profiles through the thicknesses, obtained by inserting thermocouples in the sample during the experiment. The methodologies developed to measure char expansion of the three coatings during the cone experiment as well under slow heating conditions using an advanced rheometric expansion system have been discussed. While the expansion ratios in the two experiments were different, the trends were similar. Thermal conductivities of the chars as a function of time were measured, which could be related to the intumescence steps of respective coatings. The accurate measurements of these parameters are important in predicting the surface requirements of an ideal coating that can enable a given composite structure to survive a defined thermal threat for a specified period of time

Bench-scale fire stability testing – Assessment of protective systems on carbon fibre reinforced polymer composites

Abstract Fire resistance testing of components made of carbon fibre reinforced polymers (CFRP) usually demands intermediate-scale or full-scale testing. A bench-scale test is presented as a practicable and efficient method to assess how different fire protective systems improve the structural integrity of CFRPs during fire. The direct flame of a fully developed fire was applied to one side of the CFRP specimen, which was simultaneously loaded with compressive force. Three different approaches (film, non-woven, and coatings) were applied: paper with a thickness in the range of μm consisting of cellulose nanofibre (CNF)/clay nanocomposite, nonwoven mats with thickness in the range of cm and intumescent coatings with a thickness in the range of mm. The uncoated specimen failed after just 17 s. Protection by these systems provides fire stability, as they multiply the time to failure by as much as up to 43 times. The reduced heating rates of the protected specimens demonstrate the reduced heat penetration, indicating the coatings' excellent heat shielding properties. Bench-scale fire stability testing is shown to be suitable tool to identify, compare and assess different approaches to fire protection

GRASS : flame retardant artificial turf : safe and sustainable

Artificial grass is mainly composed of organic polymers with a consequent potential fire hazard. However, the behaviour of artificial grass in case of fire has been poorly studied and is thus misunderstood. The GRASS project has two objectives: informing the public that natural turf has a different fire behaviour than artificial turf and improving fire behaviour of artificial turf by developing innovative, eco-friendly and industrially applicable processes. In the project, constant consultations take place with a resonance group of stake holders represented by producers, installers, sports organisations, governments and end users. The involvement of the resonance group is sufficient guarantee that the new processes emanating from this project will be acceptable for all actors involved in the artificial turf sector (from production and end usage to recycling) and that they will be put into practice

Contribution of infill materials to the fire behavior of artificial grass

Artificial grass is mainly composed of organic polymers with a consequent potential fire hazard. However, the behavior of artificial grass in case of fire has been poorly studied and is thus misunderstood. The purpose of this study is thus to have a better understanding of the contribution of the different components of the artificial turf in the fire performances. In this work, the influence of the nature of the infill is more specifically investigated

Relevance of cyclin D1b expression and CCND1 polymorphism in the pathogenesis of multiple myeloma and mantle cell lymphoma

BACKGROUND: The CCND1 gene generates two mRNAs (cyclin D1a and D1b) through an alternative splicing at the site of a common A/G polymorphism. Cyclin D1a and b proteins differ in their C-terminus, a region involved in protein degradation and sub-cellular localization. Recent data have suggested that cyclin D1b could be a nuclear oncogene. The presence of cyclin D1b mRNA and protein has been studied in two hemopathies in which cyclin D1 could be present: multiple myeloma (MM) and mantle cell lymphoma (MCL). The A/G polymorphism of CCND1 has also been verified in a series of patients. METHODS: The expression of cyclin D1 mRNA isoforms has been studied by real-time quantitative PCR; protein isoforms expression, localization and degradation by western blotting. The CCND1 polymorphism was analyzed after sequencing genomic DNA. RESULTS: Cyclin D1 mRNA isoforms a and b were expressed in mantle cell lymphoma (MCL) and multiple myeloma (MM). Cyclin D1b proteins were present in MCL, rarely in MM. Importantly, both protein isoforms localized the nuclear and cytoplasmic compartments. They displayed the same short half-life. Thus, the two properties of cyclin D1b recognized as necessary for its transforming activity are missing in MCL. Moreover, CCND1 polymorphism at the exon/intron boundary had no influence on splicing regulation in MCL cells. CONCLUSION: Our results support the notion that cyclin D1b is not crucial for the pathogenesis of MCL and MM