Flame Retardant Additives Research Articles

Effects of flame retardants on extinction limits, spread rate, and smoke release in opposed-flow flame spread over thin cylindrical polyethylene samples in microgravity

Though flame retardants are considered for use in spacecraft, their performances in microgravity are still poorly understood. To assess their effects on flame extinction, opposed flame spread rate, and smoke emission in the absence of buoyant flows, thin cylindrical samples of Low Density Polyethylene (LDPE) loaded with intumescent flame retardants are ignited in parabolic flights. Two types of flame retardants characterized by different mechanisms of intumescence are considered, namely Expandable Graphite, (EG), and Ammonium polyphosphate / Pentaerythritol, (AP), for which thermal stress and chemical recombination drive physical expansion, respectively. Observations are then reported and contrasted with results obtained at normal gravity for different flame retardant loads, under varying oxygen content at given ambient pressure and flow velocity. Focusing on the flame leading edge, results related to flame spread and flame extinction are analyzed first. At normal gravity, increasing the flame retardant load improves fire safety through an increase in the flame extinction limit on the one hand, and a reduction in the average flame spread rate for all oxygen contents studied on the other hand. In contrast, results in microgravity show no modification in the extinction limit over the range of flame retardant loads studied, and the benefits in average flame spread rate reduction are less pronounced. Investigating then radiative quenching at the flame trailing edge, smoke emission is never evidenced at normal gravity. However, in microgravity, the addition of flame retardants increases the range of conditions leading to smoke emission, which is detrimental to fire safety. These observations are valid for both flame retardants, yet more pronounced for EG-loaded samples than AP-loaded samples. These ambivalent effects on fire safety of AP and EG addition in microgravity, which are not evidenced at normal gravity, call for a cautious integration of flame retardants in the scope of space exploration.

Performance evaluation of melamine derivatives as flame retardant additive in chicken feather containing thermoplastic polyurethane biocomposites

The objective of this research is to examine the potential use of melamine derivatives namely melamine cyanurate (MC), melamine phosphate (MP), and melamine polyphosphate (MPP) as flame retardant additives in chicken feather (CF) containing thermoplastic polyurethane (TPU). The performances of the composites are evaluated using limiting oxygen index (LOI), vertical UL-94 (UL-94 V), and mass loss calorimeter (MLC) tests. The V0 rating is achieved with the addition of 10 wt% MC, 20 wt% MP, and MPP. The performances of the additives are ranked in the ascending order of MC, MP, and MPP in LOI test. MP and MPP show distinct better performance than MC in the condensed phase. However, the gas phase action of MC is much better. than MP, and MPP. The lowest pHRR (103 Kw/m2), THE (39 MJ/m2), and THE/TML ratio (1.4 MJ/m2g) are observed with the use of 20 wt% MPP, MP, and MC, respectively.

An Efficient Cross-Linked Phosphorus-Free Flame Retardant for Epoxy Resins.

Epoxy resins (EPs) have been widely used due to their great physical and chemical properties, but their poor flame retardancy limits their further application. In this work, we synthesized a flame retardant containing nitrile groups and a double bond to improve the flame retardancy of EPs. In this way, multiple cross-linking reactions can occur in the EPs to confer better flame retardancy by a simple heat treatment. The UL-94 vertical combustion test, CCT, and limiting oxygen index (LOI) test were used to characterize the flame retardant properties of the cross-linked flame retardant; the results show that with the 10 wt % addition of cross-linked flame retardant, the thermosets can pass the UL-94 V-0 rating. Meanwhile, the contents reached 20 wt %, and the peak heat release rate decreased 40% compared with neat EP.

DOPO-BASED FLAME RETARDANT: PREPARATION AND ITS APPLICATION IN SILICONE RUBBER BLENDS

ABSTRACT In this study, a phosphorus-containing flame retardant, polybis(4-hydroxypheyl)-2-(6-oxo-6-H-dibenzodibenzo [c,e][1,2] oxaphosphino-6-yl) methylene succinate (PHDO) was prepared by melt condensation between (6H-dibenz[c,e][1,2]oxaphosphorin-6-ylmethyl)-p-oxide-butanedioic acid (DDP) and 1,4-benzene dimethanol (PXG). Then, Fourier transform infrared spectroscopy (FTIR) and hydrogen nuclear magnetic resonance (1H NMR) were used to characterize the structure of this novel additive. It was added to silicone rubber (SR) in different proportions, and the flame retardant properties together with tensile behaviors of the SR blends were investigated. Results showed that the thermal stability was improved and the burning rate was slowed down after addition of this novel flame retardant. Vertical burning test, cone calorimetric evaluation, and limited oxygen index (LOI) measurement of the samples revealed that the SR with 15 phr of PHDO owned the best flame retardant properties and may pass UL-94 V-0 grade. This improved flame retardant performance may be ascribed to the formation of dense carbon layers, which effectively prevented the surface oxidation and inhibited combustion of the silicone matrix.

Cross-biome metagenomic analyses of the impact of pollutants on taxonomic and functional diversity of bacterial communities from different geographical regions

Due to anthropogenic activities, a large number of pollutants are disposed into the environment. The microbial communities in the environment are immensely diverse and critical mediators of various ecosystem processes. But it is not clearly known to what extent xenobiotics effect the composition and functionality of environmental microorganisms, across biomes in different geographic locations, with varying contaminating sources, categories of chemical pollutants, and their application types. Here, we investigated the impact of xenobiotics by metagenomic analysis of 16S rRNA from seawater, soil, sludge and sediment, for deciphering microbial diversity, community structure, functional enrichment and metabolic potentiality in relation to the application of pesticide (metaldehyde), herbicide (2,4-dichlorophenoxyacetic acid; DCPAA), insecticide (chlordecone) and flame retardant additives (organophosphate triesters; OPT and tris 2 chloroethyl phosphate; TCEP). Firmicutes was the most abundant phylum consisting of Clostridia, in association with DCPAA (Lutispora sp.), metaldehyde and TCEP treatments. The next two abundant phyla were Proteobacteria [class Deltaproteobacteria, Alphaproteobacteria (Pelagibacter ubique with OPT treatment) and Gammaproteobacteria], and Euryarchaeota consisting mostly of Methanobacteria with chlordecone and DCPAA. Both Desulfomicrobium and Sedimentibacter were predominant in the subtropical moist forest sediment, while Synechococcus and Pelagibacter dominated the temperate Mediterranean Sea. Ruminococcus and Lutispora were more abundant in rain forest compared to waste water solid, while Anaerovorax predominated subtropical moist forest. Sequences involved in house-keeping genes comprised the most abundant hits. The genes involved in environmental information processing such as ABC transporters catalyzing carbohydrate uptake, membrane transport and quorum sensing were over-represented with TCEP, DCPAA, OPT and metaldehyde. Exposure to different classes of xenobiotics revealed major differences in microbial structure and function abundances, mainly driven by environmental sources and biomes. Preponderance of core metabolic functional genes across all the metagenomes analysed is indicative of microbial community responding and adjusting itself to deal with these treatments and maintain its balance.

Effects of Phosphorus and Boron Compounds on Thermal Stability and Flame Retardancy Properties of Epoxy Composites.

While plastics are regarded as the most resourceful materials nowadays, ranging from countless utilities including protective or decorating coatings, to adhesives, packaging materials, electronic components, paintings, furniture, insulating composites, foams, building blocks and so on, their critical limitation is their advanced flammability, which in fire incidents can result in dramatic human fatalities and irreversible environmental damage. Herein, epoxy-based composites with improved flame-resistant characteristics have been prepared by incorporating two flame retardant additives into epoxy resin, namely 6-(hydroxy(phenyl)methyl)-6H-dibenzo[c,e][1,2]oxaphosphinine-6-oxide (PFR) and boric acid (H3BO3). The additional reaction of 9,10-dihydro-oxa-10-phosphophenanthrene-10-oxide (DOPO) to the carbonyl group of benzaldehyde yielded PFR, which was then used to prepare epoxy composites having a phosphorus content ranging from 1.5 to 4 wt%, while the boron content was 2 wt%. The structure, morphology, thermal stability and flammability of resulted epoxy composites were investigated by FTIR spectroscopy, scanning electron microscopy (SEM), thermogravimetric analysis, differential scanning calorimetry, and microscale combustion calorimetry (MCC). Thermogravimetric analysis indicated that the simultaneous incorporation of PFR and H3BO3 improved the thermal stability of the char residue at high temperatures. The surface morphology of the char residues, studied by SEM measurements, showed improved characteristics in the case of the samples containing both phosphorus and boron atoms. The MCC tests revealed a significant reduction in flammability as well as a significant decrease in heat release capacity for samples containing both PFR and H3BO3 compared to the neat epoxy thermoset.

Effect of flame retardants on side-wall quenching of partially premixed laminar flames

A combined experimental and numerical investigation of partially premixed laminar methane-air flames undergoing side-wall quenching (SWQ) is performed. A well-established SWQ burner is adapted to allow the seeding of the main flow with additional gaseous products issued from a (secondary) wall inlet close to the flame’s quenching point. First, the characteristics of the partially premixed flame that quenches at the wall are assessed using planar laser-induced fluorescence measurements of the OH radical, and a corresponding numerical simulation with fully-resolved transport and chemistry is conducted. A boundary layer of enriched mixture is formed at the wall, leading to a reaction zone parallel to the wall for high injection rates from the wall inlet. Subsequently, in a numerical study, the wall inflow is mixed with dimethylmethylphosphonat (DMMP), a phosphor-based flame retardant. The DMMP addition allows the assessment of the combined effects of heat loss and flame retardants on the flame structure during flame-wall interaction. With an increasing amount of DMMP in the injected mixture, the flame stabilizes further away from the wall and shows a decrease in the local heat-release rate. Thereby, the maximum wall heat flux is significantly reduced. That results in a lower thermal load on the quenching wall. The flame structure analysis shows an accumulation of the intermediate species HOPO at the wall similar to the CO accumulation during the quenching of premixed flames without flame retardant addition. The study shows how the structure of a partially premixed flame is influenced by a wall that releases either additional fuel or a mixture of fuel and flame retardant. The insights gained from the canonical configuration can lead to a better understanding of the combined effects of flame retardants and heat losses in near-wall flames.

Analysis of the Influence of Organophosphorus Compounds and of Aluminium and Magnesium Hydroxides on Combustion Properties of Epoxy Materials

This paper presents the influence of selected flame retardant additives on heat release rate and thermokinetics properties of epoxy materials made of epoxy resin—Epidian 5. The epoxy resin underwent flame retardant modification with the use of organophosphorus compounds (Roflam F5, Roflam B7) and Al(OH)3, Mg(OH)2. The fire characteristics of the analysed epoxy resin were determined using the cone calorimeter method, and thermal analysis of epoxy resin and the surface morphology of the analysed epoxy materials was with the use of an SEM microscope with an EDS attachment. The lowest value of the heat release rate was recorded for hardened epoxy resin containing one component additive 5% by weight of Mg(OH)2, as well as two component additive 10% by weight of Roflam F5 and 5% by weight of Al(OH)3. Moreover, the initial temperature of thermal decomposition of phase I of the modified epoxy resin samples with Mg(OH)2 (sample 5M) or organophosphorus compounds and Mg(OH)2 (samples 5B + 10M and 5F + 10M) were higher compared to the unmodified epoxy resin for these samples. Considering the surface morphology of the samples with Mg(OH)2, it can be concluded that the additives cause a homogeneous charred layer.

Investigation of flame retardancy properties of polypropylene-colemanite and intumescent flame retardant additive blends

Polypropylene (PP) represents a considerable proportion of polyolefins (PO) used in different industrial applications such as automobile components, textiles, packaging, insulation, medical devices, various housewares and household appliances due to its efficient cost, desirable mechanical, thermal and electrical properties, easy processability and recyclability. Because of its carbonaceous structure, PP is a highly flammable material with a LOI value of 18 that presents serious fire hazard. In this research, Intumescent flame retardant (IFR) and colemanite were added to polypropylene to compose 30% of the total mass of the polymeric compounds and the synergistic effect of colemanite with intumescent flame retardant (IFR) additive in PP was investigated by limiting oxygen index (LOI), glow wire test (GWT), UL-94 test and mechanical properties measurements. The LOI, UL 94 and glow wire test results showed that colemanite had a significant effect on flame retardancy and LOI value which can reach to 37.6 % with loading level of 2 wt.% colemanite at the total amount of flame retardant additives kept constant at 30 wt.%. Additionally, the PP/IFR compounds passed UL 94 V0 rating and both 750 °C and 850 °C glow wire tests and with 2-8 wt.% colemanite loading. According to TGA analyses, the results indicated that colemanite improved the thermal stability of PP/IFR compounds and also promoted the formation of char layer. When colemanite mineral added to polypropylene without IFR system, it has no effect on flame retardancy properties of polypropylene. When all properties have been taken into consideration, colemanite can be used up to 6 wt% in IFR.

A universal strategy toward flame retardant epoxy resin with ultra-tough and transparent properties

Flame-retardant epoxy composites have important application value in flexible optoelectronic devices, artificial intelligence and 5G fields. The flame retardancy of these composites, however, are often promoted at the expense of mechanical properties and transparency, particularly the toughness. In this work, we propose a simple strategy of introducing proper rigid-flexible groups into phosphorus-based flame retardant which realizes a dual performance improvement simultaneously in epoxy resin. The modified flame retardant epoxy resin has a limiting oxygen index (LOI) value of 32.3%, a high transmittance of approximately 92%, an excellent smoke and heat suppression properties. Remarkably, the addition of phosphorus-based flame retardant containing rigid-flexible groups (TOD) significantly enhances the mechanical properties of epoxy resin, especially the toughness. The impact strength is obviously increased from 6.8 kJ/m2 to 25.2 kJ/m2, with an increase of 271%, which mainly due to the flexible Si-O segment in TOD. This work provides a universal strategy for the design of flame retardant, ultra-tough and transparent epoxy resin, implying its enormous potential to promote the commercial application of epoxy resin.

Tolsa highlights latest ADINS additive products at K 2022

Tolsa S.A., a supplier of flame-retardant synergists and specialized additives for a range of markets, is showcasing its ADINS® range of flame-retardant additives for PP, PVC, rubber polymer systems, and silicones, along with its ADINS® Protection range for biocide applications. Tolsa will highlight the latest developments for both material families at the K 2022 exhibition (Hall 8B/D46) which runs Oct. 19-26 in Düsseldorf, Germany.

New line of non-halogen flame retardants from FRX

FRX Innovations, a developer and manufacturer of flame-retardant additives, has announced a new line of non-halogen additives which is reported to increase the potential of its Nofia copolymer flame retardants.

Preparation and Performances of Polyether Polytriazole Elastomers Based on Click Chemistry

Since the polyurethane elastomer synthesis process is susceptible to moisture, polytriazole polyethylene oxide-tetrahydrofuran (PTPET) elastomer was used as a replacement owing to its mild production environment. In contrast to the conventional flask-synthesis method, the twin-screw reactor instrument could provide more meaningful data in the synthesis. In this study, PTPET elastomer was prepared by the MiniLab twin-screw reactor method for the first time, and the activation energy of the PTPET elastomer was calculated using the torque variation obtained from the MiniLab twin-screw reactor during the synthesis process at two different temperatures. The addition of flame retardants could endow the composites with more useful properties. The PTPET composites poly (phenylsilsesquioxane) (PTPET-PPSQ), octaphenyl polyhedral oligomeric silsesquioxane (PTPET-OPS) and PTPET-PhVPOSS (phenyl/vinyl polysilsesquioxane) were synthesized by using the MiniLab twin-screw reactor. The prepared PTPET elastomer and composites were fully characterized by FT-IR, TG, DSC, swelling test, mechanical test, SEM and combustion test. The characterization results show that the addition of the flame retardants has little influence on the original structure and properties of PTPET elastomer. The flame retardancy was characterized by the combustion test showing that all PTPET composites form a certain thickness of char layer during the burning process. These results indicate that the addition of flame retardants maintains the outstanding properties of PTPET elastomer and also endows the materials with a certain extent of flame retardancy; thus, it is believed to be a good engineering material that could be applied in many realms.

Experimental and Numerical Simulation Analyses of Flame Spread Behaviour over Wood Treated with Flame Retardant in Ancient Buildings of Fuling Mausoleum, China

AbstractTo protect ancient buildings from fire, prevent the occurrences of fire, and minimise the losses caused by fire to the maximum extent possible, this study combined experimental measurements and numerical simulations to analyse the flame spread behaviour over wood treated with flame retardants. First, some wood blocks were treated with a nitrogen and phosphorus (water-based) flame retardant, and then a smoke combustion experiment was performed to test the smoke density. Scanning electron microscopy was also employed to observe the flame retardant effect. Next, a fire dynamic simulation software was used to simulate and analyse the results of the flame spread behaviour over the yellow pine collected from the Long’en Hall of Fuling Mausoleum, that was treated with flame retardants. The results showed the variation trend of the fire site’s heat release rate (HRR) over time to be consistent with the movement of fire spread after its occurrence. Compared with pristine wood, the flame retardant-treated wood exhibited a HRR reduction of 53.1%. The addition of flame retardants also reduced the concentration of the released smoke and CO2 gas, decreased the temperature of the fire site, and enhanced visibility.

Non-flammable sandwich-structured TPU gel polymer electrolyte without flame retardant addition for high performance lithium ion batteries

The energy density and cycle stability of lithium-ion batteries (LIBs) are improving, but LIBs are likely to burn or even explode in case of accidents. Therefore, the safety of LIBs has attracted tremendous attention. It is a significant problem to increase battery safety while maintaining cycle stability and energy density of LIBs. We show that thermoplastic polyurethane gel polymer electrolytes (TPU GPE) with no flame retardant have noncombustible characteristics. It is found that LiPF6 can be used as a flame retardant of TPU polymer. When TPU GPE is decomposed by heating, LiPF6 is decomposed into LiF and PF5. When PF5 interacts with H2O, it produces H4P2O7 and H3PO4. TPU nanofiber's protective layer of H4P2O7 and H3PO4 may efficiently isolate oxygen and heat. It was discovered through a pouch cell thermal runaway test that an NCM811 pouch cell with GPE will not burn. The pyrolysis process of LiPF6 in the presence of H2O and O2 was simulated by Amsterdam Modeling Suite. The results reveal that an effective method to solve the fire danger of LIBs successfully is to replace the commercial separator with a TPU membrane. This discovery can effectively promote the commercialization of GPE.

The Influence of Flame Retardants on Combustion of Glass Fiber-Reinforced Epoxy Resin.

For the first time, next to the flammability tests (LOI, UL-94 HB, VBB, TGA), experimental tests and computer simulation have been conducted on the flame spread and combustion of glass fiber-reinforced epoxy resins (GFRER) with 6% graphene and 6% DDM-DOPO flame-retardant additives. The downward rates of flame spread (ROS) in opposed flow with oxidizer and the upward ROS along GFRER composites have been first measured as well as the distribution of temperature over the combustion surface of the composites with flame-retardant additives and without them. The LOI and UL-94 HB tests showed a reduction in the flammability of GFRER when flame retardants were added and predicted a higher effectiveness of DDM-DOPO compared to graphene. Adding DDM-DOPO resulted in increasing the rate of formation of the volatile pyrolysis products and their yield, indicating, together with the other data obtained, the gas phase mechanism of the flame retardant’s action. Adding graphene resulted in an increase in the soot release on the burning surface and an increase in the amount of non-volatile pyrolysis products on the burning surface, reducing the amount of fuel that participated in the oxidation reactions in the gas phase. The developed numerical combustion model for GFRER with a DDM-DOPO additive, based on the action of DDM-DOPO as a flame retardant acting in the gas phase, satisfactorily predicts the effect of this flame retardant on the reduction in downward ROS over GFRER for 45–50% oxygen concentrations. The developed model for GFRER with graphene additive, based on a reduction in the amount of fuel and increase in the amount of incombustible volatile pyrolysis products when graphene is added, predicts with good accuracy downward ROS over GFRER depending on oxygen concentration.

The Impact of β-Radiation Crosslinking on Flammability Properties of PA6 Modified by Commercially Available Flame-Retardant Additives.

A comparative study was conducted investigating the influence of β-radiation crosslinking (β-RC) on the fire behavior of flame retardant-modified polyamide 6 (PA6). In order to provide a comprehensive overview, a variety of commercially available flame-retardant additives were investigated, exhibiting different flame retarding actions such as delusion, char formation, intumescence and flame poisoning. This study focused on the identification of differences in the influence of β-RC on fire behavior. Coupled thermal gravimetrical analysis (TGA) and Fourier transformation infrared spectroscopy (FTIR) were used to conduct changes within the decomposition processes. Dynamic thermal analysis (DTA) was used to identify structural stability limits and fire testing was conducted using the limiting oxygen index (LOI), vertical UL-94 and cone calorimeter testing. Crosslinking was found to substantially change the fire behavior observed, whereas the observed phenomena were exclusively physical for the given formulations studied: warpage, char residue destruction and anti-dripping. Despite these phenomena being observed for all β-RC formulations, the impact on fire resistivity properties were found to be very different. However, the overall fire protection properties measured in UL-94 fire tests were found to deteriorate for β-RC formulations. Only β-RC formulations based on PA6/EG were found to achieve a UL-94 V0 classification.

Microstructure design of polyester industrial yarns with excellent flame retardancy and high strength

In order to solve the problem that it is difficult to balance the high strength and flame retardancy of polyester industrial yarn, the possibility of controlling the uniform dispersion of flame retardant without affecting the crystallization of polyester was discussed in this paper. The long-chain branched flame retardant with good thermal stability in the range of processing temperature was chosen to blend with high viscosity polyester. The addition of flame retardant reduced the melt viscosity and the crystallization ability of polyester, so the melt spinning and drawing process of the flame retardant polyester industrial yarn were optimized for the sufficient crystallization of polyester based on the rheological and crystallization properties of flame retardant polyester. Due to the steric effect of flame retardant, it was eliminated from the crystal region and only existed in the amorphous region of polyester. As a result, the microstructure with high crystallinity and orientation and the morphology with a uniform dispersion of flame retardant were obtained. The flame retardant high strength polyester industrial yarn was successfully prepared with a limiting oxygen index of 32.0% and a breaking strength of 8.0 cN/dtex, which meets the UL-94 V-0 standard and shows good durability of flame retardant after washing and rubbing treatment, achieving the goal of flame retardancy and high strength for the polyester industrial yarn.

Environmental, Health, and Legislation Considerations for Rational Design of Nonreactive Flame-Retardant Additives for Polymeric Materials: Future Perspectives.

Increasing polymer usage has demanded functional additives that decrease fire hazards for end users. While traditional flame-retardant (FR) additives, such as halogenated, phosphorus, and metal hydroxides, greatly reduce flammability and associated fire hazards, research has continually exposed a litany of health and environmental safety concerns. This perspective aims to identify the key components of a successful FR additive and address material, environmental, and health concerns of existing additives. Legislation surrounding FRs and persistent organic pollutants is also discussed to highlight political perception that has resulted in the increased chemical regulations and subsequent banning of FR additives. Finally, future directions of this field regarding nonreactive additives, focusing on the use of bioinspired materials and transition metal chemistries to produce alternatives for polymers with efficacies surpassing traditional additives are presented.

Flame Retardancy Performance of Continuous Glass-Fiber-Reinforced Polypropylene Halogen-Free Flame-Retardant Prepreg

Thermoplastic resin matrix has a high melt viscosity, which is difficult to impregnate with fibers. The addition of flame retardant will further increase the viscosity of the melt and increase the difficulty of impregnation. It is possible to reduce the effect of flame retardant on melt viscosity by adding high-flow polypropylene. In this study, the effect of adding flame retardant on the impregnation quality of prepreg tape was investigated. By adding high-flow polypropylene to improve the melt viscosity of flame-retardant-modified polypropylene, continuous glass-fiber-reinforced polypropylene flame-retardant prepreg tape was successfully prepared. Intumescent flame retardant (IFR) was added at 20 wt%, 25 wt%, 30 wt% of the polypropylene matrixes, which were prepared by melt impregnation. The composites were analyzed with thermogravimetric analysis, limiting oxygen index testing, UL-94 flame retardancy testing, cone calorimeter testing (CCT) and scanning electron microscopy. Tests involving the flame retardant showed that when the added amount of flame retardant reached 25%, the UL-94 flame retardancy grade reached V0. Compared with the CCT sample heating data, taking economic considerations into account, 25 wt% IFR addition was the most suitable.