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Short overview is given of BAM's research within the topic "Flame Retardancy of Polymeric Materials". Fire science is identified as a crucial compentenc of BAM following our mission "Safety in Technology and Chemistry". In the area of polymers we work interdisciplinary, in the dimensions from nm to 2m, and we love to combine experiment and simulation. Multimethodical examples are given to describe the burning phenomena and flame-retardant modes of action. Further some examples are presented for tailored bench-scale fire testing and assessing concepts. Our goal is to provide the fundaments for a evidenced-based development of future materials.
Due to the high flammability and smoke toxicity of polyurethane foams (PUFs) during burning, distinct efficient combinations of flame retardants are demanded to improve the fire safety of PUFs in practical applications. This feature article focuses on one of the most impressive halogen-free combinations in PUFs: expandable graphite (EG) and phosphorus-based flame retardants (P-FRs). The synergistic effect of EG and P-FRs mainly superimposes the two modes of action, charring and maintaining a thermally insulating residue morphology, to bring effective flame retardancy to PUFs. Specific interactions between EG and P-FRs, including the agglutination of the fire residue consisting of expanded-graphite worms, yields an outstanding synergistic effect, making this approach the latest champion to fulfill the demanding requirements for flame-retarded PUFs. Current and future topics such as the increasing use of renewable feedstock are also discussed in this article.
Valorizing “non-vegan” bio-fillers: Synergists for phosphorus flame retardants in epoxy resins
(2022)
Sustainable, biogenic flame retardant adjuvants for epoxy resins are receiving increased focus. Zoological products like insects, bone meal, and eggshells are available in large quantities, but remain uninvestigated as functional fillers to epoxy resins, although they are potential synergists to flame retardants. The efficacy and flame retardancy of “non-vegan” additives in combination with flame retardants is investigated and the fire behavior and thermal decomposition of bio-sourced epoxy resin composites is characterized. By comparing the fire performance of composites containing flame retardants or fillers at varying loadings (5, 10, and 20%), their role as synergists that enhance the function of organophosphorus flame retardants in bio-epoxy composites is identified and quantified. Peak heat release rates were 44% lower in composites containing both filler and flame retardant versus those containing only flame retardants, and fire loads were reduced by 44% versus the pure resin, highlighting the ability of “non-vegan” fillers to function as synergists.
The important take home message of this chapter: When multicomponent flame retardant systems are applied to polymeric materials, it becomes possible to address multiple fire properties, increase efficiency, and minimize flame retardant use to maximize polymer property balance. Flame retardants are combined or used together with adjuvants or synergists; fibers and fillers make a crucial contribution to their fire properties. Multicomponent systems are discussed in their capacity as an overall powerful strategy for achieving and optimizing non-halogenated flame-retardant polymeric materials.
The incorporation of nanoparticles like multilayer graphene (MLG) into elastomeric composites boosts their technical performance, such as their mechanical behavior and electrical conductivity. Common filler types (carbon black (CB) and aluminum trihydroxide (ATH)) generally fulfill single, specific purposes and are often used in high loadings. CB typically reinforces rubber mechanically, while ATH increases flame retardancy. Small amounts of MLG reduce these high filler contents and maintain the multifunctional characteristics of rubber composites. In chlorosulfonated polyethylene (CSM) + ATH, an intrinsically flame-retardant rubber was designed to achieve the highest standards such as maximum average of heat emission (MARHE) <90 kW m−2, 3 phrMLG was substituted for 15 phr CB and/or 3 phr ATH via an industrially applicable processing approach. Replacing either CB or ATH resulted in a property profile that was multifunctionally improved in terms of features such as mechanical performance, reduced sorption, and flame retardance. MLG nanocomposites are reported to show promise as an industrially utilizable route to obtain multifunctional high-performance rubbers.
Efficient flame retardancy is often achieved only when applying multicomponent systems. Flame retardants are combined or used together with adjuvants or synergists; fibres and fillers contribute to fire properties crucially. Multicomponent systems are discussed in their capacity as general and powerful strategy for achieving and optimizing flame retardant polymeric materials.
Antimicrobials can exert specific physiological effects when used in combination that are different from those when applied alone. While combination effects have been extensively mapped for antibiotic-antibiotic combinations, the combination effects of antibiotics with antimicrobials used as biocides or antiseptics have not been systematically investigated. Here, we investigated the effects of combinations of antibiotics (meropenem, gentamicin, and ciprofloxacin) and substances used as biocides or antiseptics [octenidine, benzalkonium chloride, cetrimonium bromide, chlorhexidine, Povidone-iodine, silver nitrate (AgNO3), and Ag-nanoparticles] on the planktonic growth rate of Pseudomonas aeruginosa. Combination effects were investigated in growth experiments in microtiter plates at different concentrations and the Bliss interaction scores were calculated. Among the 21 screened combinations, we find prevalent combination effects with synergy occurring six times and antagonism occurring 10 times. The effects are specific to the antibiotic-biocide combination with meropenem showing a tendency for antagonism with biocides (6 of 7), while gentamicin has a tendency for synergy (5 of 7). In conclusion, antibiotics and biocides or antiseptics exert physiological combination effects on the pathogen P. aeruginosa. These effects have consequences for the efficacy of both types of substances and potentially for the selection of antimicrobial resistant strains in clinical applications with combined exposure (e.g., wound care and coated biomaterials).
The multicomponent flame retardant system of melamine polyphosphate (MPP), melamine cyanurate (MC) and aluminum diethylphosphinate (AlPi) is proposed and investigated for thermoplastic polyurethane (TPU). The synergy between those additives and the resulting superior fire performance are discussed. Systematically varied sets of flame retarded TPU with various MPP/MC/AlPi ratios were investigated in terms of fire behavior, pyrolysis products and mechanical properties. The total amount of the additives was always 30 wt.-%. Further, the influence of various AlPi concentrations was investigated. The optimal MPP:MC ratio was determined while keeping the amount of AlPi constant. The combination of 8 wt.-% MPP, 12 wt.-% MC and 10 wt.-% is proposed as the most promising halogen free flame retardant formulation for TPU, because it yielded a reduction in PHRR from 2660 kW/m2 (TPU) to 452 kW/m2 and enabled V-0 classification in the UL 94 test. Combinations of MPP and MC as well a high concentration of AlPi are beneficial for the mechanical properties e.g. tensile strength and elongation at break of the formulations and could be a strong competitor to commercial flame retarded TPUs.
A siloxane compound (MVC) and a bi-group phosphaphenanthrene/triazine compound (TGD) were employed in epoxy thermosets to explore high-efficiency flame retardant systems. With only 1wt% MVC and 3wt% TGD, an epoxy thermoset passed UL 94 V-0 rating test and achieved a limiting oxygen index value of 34.0%, exhibiting an excellent flame retardant effect. The MVC/TGD system not only decreased the peak value of heat release rate and effective heat of combustion but also imparted an improved charring ability to thermosets, thereby outstandingly reducing the flammability of 1%MVC/3%TGD/EP. Compared with the fire performance of 4%TGD/EP and 4%MVC/EP, the MVC/TGD system showed an obvious flame retardant synergistic effect, mainly depending on the general improvement of flame inhibition, charring and barrier effects of the thermoset during combustion. Evolved gas analysis combinedwith condensed-phase pyrolysis product Analysis jointly revealed the details of the changed pyrolysis mode.