Aluminum Diethylphosphinate Research Articles

Flame retardancy, thermal, and mechanical properties of flame retardant PA6/SGF and PPS/PA6/SGF composites

AbstractFlame retardant polyamide 6/short glass fiber (FR PA6/SGF) and polyphenylene sulfide/PA6/SGF (FR PPS/PA6/SGF) composites were prepared by melt extrusion blending using aluminum diethylphosphinate (ADPP) as flame retardant. The thermogravimetric analysis (TGA) indicated that the flame retardant composites showed good thermal degradation with increasing ADPP loading. Flame retardancy mechanisms were studied by analyzing the residue chars. ADPP provided better flame inhibition, promoted formation of carbonaceous char, and improved thermal stability of PA6/SGF. Meanwhile, due to the self‐extinguishing performance of PPS, the flame retardancy of PPS/PA6/SGF was greatly affected by only 3.0 wt% of ADPP. With increasing ADPP content, both storage and loss moduli of FR PA6/SGF and FR PPS/PA6/SGF were increased accompanied with a slight increase of tan δ peak as compared to PA6/SGF and PPS/PA6/SGF, respectively. Besides, notched impact strengths of FR PA6/SGF‐10.0 and FR PPS/PA6/SGF‐10.0 increased by 69% and 5%, while tensile strengths decreased by approximately 5% and 32%, as compared to PA6/SGF and PPS/PA6/SGF, respectively. It demonstrates that ADPP and PPS components are efficient inorganic–organic hybrid flame retardant system. This provides a novel and innovative method for preparing halogen‐free flame retardant reinforced polyamide composites.

Enhancing flame retardancy and mechanical strength of glass fiber-reinforced biomass polyamide composites with surface-functionalized black phosphorus

Fiber-reinforced polyamide exhibits exceptional mechanical properties and durability; however, its widespread application is impeded by potential fire hazards. In this study, a hybrid material consisting of black phosphorus (BP) and polyhedral oligomeric silsesquioxane (POSS) was synthesized, denoted as BP-CO-POSS. The fire safety of fiber-reinforced polyamide demonstrated significant enhancement upon the incorporation of aluminum diethyl phosphinate (Alpi) and BP-CO-POSS. This enhancement was evident in various aspects, including the suppression of heat release behaviors, reduction in the emission of toxic gases, and an increase in the UL-94 rating. Notably, with the additional inclusion of 0.5 wt% BP-CO-POSS, a substantial decrease in both heat release rate (31.15 %) and total heat release (37.59 %) was observed when compared to the application of Alpi and BP alone, thus affirming the existence of a synergistic effect. This observation was substantiated through a comprehensive analysis of results obtained from both gas and condensed phases. This study offers a practical methodology for the widespread utilization of phosphorus-rich advanced materials, thereby further enhancing the fire safety of fiber-reinforced polymers.

Green synthesis of a P/N/B-containing aggregate for boosting fire-retardancy of PA6/aluminum diethylphosphinate composites

The intrinsic flammability of polyamide 6 (PA6) has significantly impeded its broad application regardless of its balanced physical properties. Aluminum diethylphosphinate (ADP), as a P-containing fire retardant, has been demonstrated to be effective in reducing flammability of PA6 because of its dual-phase modes of action by creating an intact protective char layer and inhibiting the burning process. However, the efficiency of ADP needs to be further improved for creating cost-effective fire-retardant PA6, in addition to its relatively high cost. To boost its efficiency, we, here, report a P/N/B-containing aggregate (MBA) as an effective synergist via green self-assembly of melamine (MA), boric acid (BA) and amino trimethylene phosphonic acid (ATMP) in an aqueous medium. The results show that the inclusion of 5 wt% MBA and 10 wt% ADP leads to a significantly reduced peak heat release rate (PHRR) by 52.5% compared to neat PA6, in addition to a desired UL-94 V-0 rating. A synergistic effect of 55.4 % is observed between MBA and ADP in terms of the PHRR value. This work provides a facile green strategy for developing eco-friendly multiple elements-containing fire retardants, which can be used as fire retardants alone or high-efficiency synergists for other fire retardants.

Influence of phosphomolybdate modified with quaternary ammonium salts on enhancing the flame retardancy and antibacterial characteristics of epoxy resin/aluminum diethylphosphinate composites

In this work, we synthesized a series of compounds, denoted as xCTAB@AMP, by incorporating varying different molar fractions of cetyltrimethylammonium bromide (CTAB) into ammonium phosphomolybdate (AMP). The effects of CTAB modification on the surface characteristics, morphology and hygroscopicity of AMP were studied. Moreover, we explored the combined flame-retardant impact between xCTAB@AMP and aluminum diethylphosphinate (ADP) when incorporated into epoxy resin (EP), as well as the resulting composite's mechanical properties, thermal stability and antibacterial properties. The EP composite containing 50 molar percent CTAB-modified AMP (EP/50CTAB@AMP/ADP) demonstrated remarkable flame retardancy, achieving a UL-94 V-0 rating and increasing limiting oxygen index (LOI) to 30.0%. This formulation significantly lowered the peak heat release rate (PHRR) to 452 kW/m2, a 65% reduction to that of EP, and the total heat release (THR) to 68 MJ/m2, a 24% decrease to that of EP. Additionally, compared to EP, the peak smoke production rate (PSPR) of this composite was decreased by 30% (0.28 m2/s), the total smoke production (TSP) was reduced by 25% (30.2 m2), and peak carbon monoxide release rate (PCOP) was diminished by 34% (0.038 g/s). The combination of 50CTAB@AMP and ADP in the EP matrix exhibited an exceptional synergistic flame-retardant effect. Concurrently, the CTAB modification bolstered the interfacial interactions between AMP and the EP matrix, which enhanced the mechanical properties of EP/AMP/ADP composites. As a result, the tensile strength and elongation at break of the EP/50CTAB@AMP/ADP composite increased by 13% and 15%, respectively, compared to the EP/AMP/ADP. Moreover, the 50CTAB@AMP maintained its inherent antibacterial activity, which endowed the EP/50CTAB@AMP/ADP composite with a potent inhibitory effect against Staphylococcus aureus, a common pathogenic bacterium.

Upcycling of SARS-CoV-2 Rapid Antigen Test Cassettes into Flame Retardant Plastics.

The COVID-19 pandemic resulted in the generation of large quantities of medical waste and highlighted the importance of efficient waste management systems. One good example of this is rapid antigen tests, which contain valuable resources, and which are usually incinerated after their use. The present study aimed to evaluate the potential of waste rapid antigen test cassettes (RATCs) as a resource for the preparation of sustainable flame-retardant plastics. Milled RATCs were compounded with different concentrations (10-30 wt.%) of aluminium diethylphosphinate (ADP) and injection moulded into test specimens. Prepared samples were exposed to ultraviolet (UV) ageing for varying durations and characterised by Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), tensile tests, Charpy impact tests, and vertical burning tests. FT-IR analysis revealed that RATCs are composed mainly of high-impact polystyrene (HIPS), which was further confirmed by suitable glass transition temperatures (Tg) determined by DSC and DMA. The addition of ADP resulted in progressive embrittlement of HIPS with increasing concentration, while flammability decreased significantly and reached V-1 classification at loading of 30 wt.%. UV ageing caused photo-oxidative degradation of HIPS, which resulted in decreased strain-at-break, while flammability was not affected.

A Dangerous Couple: Sequential Effect of Phosphorus Flame-Retardant and Polyurethane Decrease Locomotor Activity in Planarian Girardia tigrina.

Understanding the interplay among organophosphorus flame retardants (OPFRs), microplastics, and freshwater organisms is crucial for unravelling the dynamics within freshwater environments and foreseeing the potential impacts of organic pollutants and plastic contamination. For that purpose, the present research assessed the exposure impact of 10 mg L-1 flame-retardant aluminium diethylphosphinate (ALPI), 10 μg mg-1liver microplastics polyurethane (PU), and the combination of ALPI and PU on the freshwater planarian Girardia tigrina. The exposure to both ALPI and PU revealed a sequential effect, i.e., a decrease in locomotor activity, while oxidative stress biomarkers (total glutathione, catalase, glutathione S-transferase, lipid peroxidation) and metabolic responses (cholinesterase activity, electron transport system, and lactate dehydrogenase) remained unaffected. Despite this fact, it was possible to observe that the range of physiological responses in exposed organisms varied, in particular in the cases of the electron transport system, cholinesterase activity, glutathione S-transferase, catalase, and levels of total glutathione and proteins, showing that the energetic costs for detoxification and antioxidant capacity might be causing a lesser amount of energy allocated for the planarian activity. By examining the physiological, behavioural, and ecological responses of planarians to these pollutants, insights can be gained into broader ecosystem-level effects and inform strategies for mitigating environmental risks associated with OPFRs and microplastic pollution in freshwater environments.

Synergistic flame retardancy of aluminum diethylphosphinate and piperazine pyrophosphate/β‐cyclodextrin in polylactic acid

AbstractPolylactic acid has good biodegradability and processability, but its flammability and serious droplet characteristics limit its development and application. Therefore, developing safer flame‐retardant PLA materials is crucial. This research develops a novel flame‐retardant polylactic acid (PLA) material blend, utilizing aluminum diethylphosphinate (AlPi), piperazine pyrophosphate (PAPP), and β‐cyclodextrin. Optimal synergy occurs at a 5:1 PAPP/β‐CD mass ratio with 4 wt.% AlPi. This combination significantly reduces the heat release peak from 294.89 to 144.21 kW·m−2 and generates non‐combustible residues. The sample forms a stable, uniform carbon layer during combustion due to hydrogen bond crosslinking and Lewis acid–base reactions. The activation energy (Eα) is raised from 264.99 to 281.08 kJ·mol−1 between 312 and 402°C. Thus, an AlPi‐PAPP‐β‐CD based P‐C‐N composite flame retardant is investigated, offering a promising research direction for developing fire‐safe polylactic acid materials. This research may yield valuable insights for diverse applications.

Research on the synergistic flame retardation of epoxy resin through surface-modified aluminum diethylphosphinate in conjunction with DOPO and CFA

Surface modification of aluminum diethylphosphinate (ADP) was successfully achieved through the utilization of silane coupling agent KH-560. Simultaneously, the modified aluminum diethylphosphinate (K-ADP) served as the primary flame retardant, with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as the phosphorus-based flame retardant and charring‐forming agent (CFA) as the nitrogen-based synergistic flame retardant. This approach was employed to investigate the flame-retardant modification of epoxy resin. The optimal dosage of the surface modifier was investigated through moisture absorption test and viscosity measurements. Synergistic flame-retardant interactions among K-ADP, DOPO, and CFA were examined using techniques such as cone calorimetry test, thermogravimetric analysis, and residual char infrared analysis. The results indicated that the optimal dosage of KH-560 is 5%, resulting in a significant reduction in moisture absorption to 0.195%. At 80 °C, the addition of K-ADP leaded to only a 22.7% increase in system viscosity, demonstrating a notable viscosity reduction effect. When the addition of K-ADP is 14%, the Limiting Oxygen Index (LOI) value reached 30.5%, achieving a V-0 rating. Moreover, by maintaining the total addition at 14% and introducing DOPO and CFA, it is evident that most of samples meet UL-94 V-0 rating, with the LOI elevated to 32.2%. CCT results indicated a significant decrease in both average heat release rate and total smoke production, reduced by 24.1% and 7.0%, respectively. This notably enhanced the flame-retardant and smoke-suppressant properties of the EP composite material. The addition of K-ADP, DOPO, and CFA improved the mechanical performance of the EP composite material, surpassing the effectiveness of adding ADP individually.

Improving fire safety of thermoplastic poly(ether ester) elastomer by black phosphorus nanosheets and aluminum diethylphosphinate system

AbstractThermoplastic poly(ether ester) elastomer (TPEE) is a highly flammable material with severe melt‐dropping, which greatly limits its range of applications. Here, black phosphorus nanosheets (BPs) and aluminum diethylphosphinate (ADP) were used to improve the fire safety of TPEE for the first time. Results demonstrated that ADP/BPs as a synergistic combination exhibits good dispersity and excellent flame retardancy, also has minimal negative effects on the mechanical performances of the TPEE composites. By comparing TPEE/ADP‐22 and TPEE/ADP‐10/BPs‐4, the introduction of BPs significantly reduced the addition of ADP while keeping the material at the higher vertical burning grade, ~54.5% reduction in ADP usage. Compared with neat TPEE, TPEE/ADP‐10/BPs‐4 fulfilled V‐0 level, avoided dripping, and the limiting oxygen index value increased to 34.0%. Moreover, TPEE/ADP‐10/BPs‐4 performed the best in cone calorimetry test, both the peak heat release rate and total heat release reduced the largest, by 44.2% and 25.3%, respectively. The detailed studies of the flame‐retardant mechanism found that ADP/BPs showed the fire‐retardant impact of the condensed phase and gaseous phase. This work expands BPs in the flame‐retardant application and could facilitate to prepare the anti‐dripping flame‐resistant TPEE.Highlights BPs as an efficient flame retardant were added into TPEE for the first time. ADP/BPs as a synergistic combination has an excellent fire‐retardant effect. The introduction of BPs significantly reduced the addition of ADP. TPEE/ADP‐10/BPs‐4 showed the highest FPI and the lowest FGI. ADP/BPs has lowest negative effects on the mechanical performances of matrix.

Lightweight Biobased Polyurethane Composites Derived from Liquefied Polyol Reinforced by Biomass Sources with High Mechanical Property and Enhanced Fire-Resistance Performance.

Lightweight biobased insulation polyurethane (BPU) composite foams with high fire-resistance efficiency are interested in building effective energy and low environmental impact today. This study focuses on manufacturing lightweight BPU from liquefied bamboo polyols and biomass resources, including rice husk and wood flour. Then, they are combined with three flame retardant (FR) additives, such as aluminum diethyl phosphinate, aluminum trihydroxide, and diammonium phosphate, to improve their fire resistance performance. The physicochemical properties, microstructure, thermal stability, mechanical properties, and flame-retardant properties of the BPU composites are characterized to optimize their compromise properties. The results showed that composites with optimized FRs achieved UL94 V-0 and those with nonoptimized FRs reached UL94 HB. The limiting oxygen index exhibited that the fire resistance of BPU composites could increase up to 21-37% within FR additives. In addition, the thermal stability of BPU composites was significantly improved in a temperature range of 300-700 °C and the compressive strength of the BPU composites was also enhanced with the presence of FRs. The scanning electron microscopy observation showed an influence of FRs on the morphology and cell size of the BPU composites. The bio-PU-derived samples in this study showed significantly low thermal conductivity values, demonstrating their remarkable thermal insulation effectiveness.

Alloying synergistic flame retardant effect on PA6 by polyimide containing alkyl hypophosphate structure

A novel flame retardant − bismaleimide polyalkyl phosphinate aluminium (BPPA), containing both imide and phosphinate structures, was designed and synthesized to investigate the intramolecular synergistic flame retardant effect between imide and phosphinate structures and alloying effect of the imide structure with PA6. Based on the flame retardant and mechanical properties of BPPA/PA6 composites, the alloying flame retardant effect of BPPA on PA6 was systematically investigated. The PA6 material had almost no char after burning; however, BPPA can produce a large amount of residue and form a dense char layer during combustion of PA6 matrix, effectively reducing the heat release, while BPPA also improved the mechanical properties of PA6 composites through the alloying effect. The peak heat release rate (pk-HRR) decreased by 55.8 %, and the residue yield increased by 9.2 wt% for 20BPPA/PA6, compared with the PA6. After compounding aluminum diethylphosphinate (ADP) and BPPA, the flame retardancy of the composites can be further improved. The LOI value of the 8ADP/6BPPA/PA6 was increased to 29.8 % and passed the test of UL94 V-0 level. Its pk-HRR and residue yield were similar to that of the 14BPPA/PA6, which indicated that the compounding system of ADP and BPPA can provide excellent charring properties and gas-phase flame retardancy of PA6. Meanwhile, the alloying BPPA with PA6 not only reduced the effect on the tensile strength of ADP on PA6, but also improved the breaking elongation of the composite. In conclusion, it provides a new direction for developing high-performance halogen-free flame retardant polyamides.

PTFE-based flame retardant coatings optimized by melamine polyphosphate/aluminum diethyl hypophosphite/anhydrous transparent powder through orthogonal experiment

Hence, a novel hydrophobic intumescent flame-retardant coating is prepared using melamine polyphosphate (MPP), aluminum diethylphosphinate (ADP), and anhydrous transparent powder (ATP) as intumescent flame retardants (IFR), doped with polytetrafluoroethylene emulsion (PTFE) for flame-retarding plywood. The IFR/PTFE coatings are prepared using the sol-gel method. Firstly, the cone results demonstrate a significant enhancement in the flame retardancy of IFR/PTFE coatings. The Total Heat Release (THR) is reduced from 35.71 MJ·m−2 to 16.07 MJ·m2, while the Flame Retardancy Index (FRI) increases from 1 to 32.52. Moreover, according to the 3D Jander model (n = 3), the activation energy (Eα) for the coating rises from 209.52 to 253.50 kJ·mol−1 in the range of 327 °C to 430 °C. The coating achieves a maximum water contact angle of 113°. Notably, the optimal formulation of IFR is explored through orthogonal experiments, and the further optimized formulation (MPP: 21.16 wt%, ADP: 5.05 wt%, ATP: 10.17 wt%) is predicted using regression analysis model based on the Design of Experiments (DOE) method. Generally, it explores a strategy for preparing efficient IFR/PTFE hydrophobic coatings with promising prospects.

Phosphorus-Based Flame-Retardant Acrylonitrile Butadiene Styrene Copolymer with Enhanced Mechanical Properties by Combining Ultrahigh Molecular Weight Silicone Rubber and Ethylene Methyl Acrylate Copolymer.

The present work proposes to investigate the effect of an ultrahigh molecular weight silicone rubber (UHMW-SR) and two ethylene methyl acrylate copolymers (EMA) with different methyl acrylate (MA) content on the mechanical and fire performance of a fireproof acrylonitrile butadiene styrene copolymer (ABS) composite, with an optimum amount of ammonium polyphosphate (APP) and aluminum diethyl phosphinate (AlPi). ABS formulations with a global flame retardant weight content of 20 wt.% (ABS P) were melt-compounded, with and without EMA and UHMW-SR, in a Brabender mixer. During this batch process, ABS P formulations with UHMW-SR and/or EMA registered lower torque values than those of ABS P. By means of scanning electron microscopy (SEM), it was possible to observe that all ABS composites exhibited a homogenous structure without phase separation or particle agglomeration. Slightly improved interfacial interaction between the well-dispersed flame-retardant particles in the presence of EMA and/or UHMW-SR was also noticed. Furthermore, synergies in mechanical properties by adding both EMA and UHMW-SR into ABS P were ascertained. An enhancement of molecular mobility that contributed to the softening of ABS P was observed under dynamic mechanical thermal analysis (DMTA). An improvement of its flexibility, ductility and toughness were also registered under three-point-bending trials, and even more remarkable synergies were noticed in Charpy notched impact strength. Particularly, a 212% increase was achieved when 5 wt.% of EMA with 29 wt.% of MA and 2 wt.% of UHMW-SR in ABS P (ABS E29 S P) were added. Thermogravimetric analysis (TGA) showed that the presence of EMA copolymers in ABS P formulations did not interfere with its thermal decomposition, whereas UHMW-SR presence decreased its thermal stability at the beginning of the decomposition. Although the addition of EMA or UHMW-SR, as well as the combination of both in ABS P increased the pHRR in cone calorimetry, UL 94 V-0 classification was maintained for all flame-retarded ABS composites. In addition, through SEM analysis of cone calorimetry sample residue, a more cohesive surface char layer, with Si-O-C network formation confirmed by Fourier transform infrared (FTIR), was shown in ABS P formulations with UHMW-SR.

A 2D biobased P/N-containing aggregate for boosting fire retardancy of PA6/aluminum diethylphosphinate via synergy

Engineering polyamide 6 (PA6) is preferred for its superior mechanical properties, yet the intrinsic flammability restricts its industrial applications. As one of the biomass phosphorus-containing chemicals, phytic acid (PA) is favorable for its high phosphorus content and aggregation ability, making it expected to enhance the fire retardancy of PA6. Herein, a melamine-phytate aggregate (MPA) is prepared by electrostatic interaction in aqueous solution, and applied as a synergist for aluminum diethylphosphinate (ADP) in PA6. The strong synergistic effect exists between ADP and MPA towards PA6, especially when their mass ratio is 3:1 and the total loading is 18 wt%. Compared to the neat PA6, this formula allows for remarkable decreases in peak heat release rate (PHRR), total heat release (THR), and maximum average heat release rate (MARHE) by ∼ 48 %, ∼ 27 %, and ∼ 30 %, respectively, as well as a high synergistic efficiency of ∼ 43 % in PHRR. This PA6 composite also presents a V-0 rating in the vertical burning (UL-94) test and a high limiting oxygen index (LOI) of 29.7 %. This work offers an eco-friendly strategy for developing bio-based P/N fire-retardant aggregates for fabricating PA6 materials with high fire safety.

Block it and rock it: Smoke suppressants that form a protective layer in PA 6.6

To ensure fire safety, polymers are filled with flame retardants and smoke suppressants. To meet the highest requirements, it is essential to understand the decomposition of those polymeric materials. This study reveals interactions between polymer, smoke suppressants, and flame retardants, and discusses their impact on the materials’ flame retardancy, smoke emission, smoke toxicity, and particle emission in conventional loadings to provide deeper general understanding. Low melting oxide glass, melem, spherical silica, sepiolite, melamine polyphosphate, and boehmite in an aluminum diethylphosphinate flame-retarded polyamide 6.6 were investigated. All smoke suppressants improve the protective layer and act as an adjuvant. Silica and melem performed best under forced flaming conditions. Spherical silica reduces the peak of heat release rate by 39% and the total heat evolved by 14%, whereas 10 wt% melem lowers the total smoke production by 41%. Melem alters the mode of action of aluminum diethylphosphinate from gas to more condensed phase activity. This change reduces flame inhibition and hence smoke toxicity, but further improves the protective layer due to charring reactions in the decomposition mechanism. In addition, the sizes of the smoke particles decrease because of the prolonged time in the pyrolytic zone. This study highlights that interactions between polymer, flame retardants, and smoke suppressants can significantly determine the smoking and burning behavior.

Study on the synergistic flame-retardancy of phenyl/vinyl siliconesquioxane and aluminum diethyl phosphinate on polyethylene terephthalate

Polyethylene terephthalate (PET), a widely used engineering thermoplastics, is inherently flammable, presenting significant fire risks. Aluminum diethyl phosphinate (ADP) is widely used in PET, while they tend to increase smoke hazards in its flames retardancy. A novel flame-retardant ladder phenyl/vinyl polysilsesquioxane (VPPSQ) acting as both a charring flame retardant and smoke suppressant was introduced into the PET/ADP composites. For PET/ADP6/VPPSQ4, the limiting oxygen index increased to 32.8 % from 23.3 %, and the amount of heat and smoke released was significantly reduced, compared with neat PET. Additionally, the hazard of dripping was eliminated and the UL 94 rating reaches to V-0 level. This work provides a new strategy for eliminating multiple fire hazards of smoke, heat and dripping of PET. The gas phase flame retardancy effect of ADP is primarily present during the initial stages of combustion, with the carbonization action of ADP becoming more crucial during the middle and later stages of burning. However, the char layer formed by PET/ADP is unstable and undergoes further degradation. When VPPSQ is introduced into PET/ADP, the pyrolysis products of VPPSQ, including silicon fragments, SiO2, and graphitized structures, significantly enhance the thermal stability and barrier effect of the char layer.

Morphology-manipulated aluminum diethylphosphinate and flame-retardant properties in thermoplastic polyurethane

Morphology-manipulated aluminum diethylphosphinate and flame-retardant properties in thermoplastic polyurethane

Flame-retardant epoxy resin: synergistic effect between aluminum diethylphosphinate and piperazine pyrophosphate

Flame-retardant epoxy resin: synergistic effect between aluminum diethylphosphinate and piperazine pyrophosphate

Strong synergistic effects between P/N-containing supramolecular microplates and aluminum diethylphosphinate for fire-retardant PA6

Mechanically strong polyamide 6 (PA6) is an important engineering plastic, but its inherent flammability usually causes fire hazards. Aluminum diethylphosphinate (ADP) can reduce the flammability of PA6 yet fails to effectively suppress the heat release. Herein, we report a phosphorus/nitrogen (P/N)-containing supramolecular microplate (MTP) synthesized by an aqueous reaction between melamine and amino trimethylene phosphonic acid (ATMP). Combining 5 wt% MTP and 15 wt% ADP, the resulting PA6 exhibits a 67 % reduction in peak heat release rate (PHRR) and a 29 s delay in ignition time compared with those of pure PA6, as well as a UL-94 V-0 rating and a high limiting oxygen index (LOI) of 28.3 %. The barrier effect of the char in the condensed phase is mainly responsible for such high fire safety. This work provides a green approach to synthesizing strong P/N-based synergists for ADP, allowing the creation of high-performance fire-retardant PA6.

A Multi-Material Flame-Retarding System Based on Expandable Graphite for Glass-Fiber-Reinforced PA6.

A synergistic multi-material flame retardant system based on expandable graphite (EG), aluminum diethylphosphinate (AlPi), melamine polyphosphate (MPP), and montmorillonite (MMT) has been studied in glass-fiber-reinforced polyamide 6 (PA6). Analytical evaluations and fire performances were evaluated using coupled thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) as well as cone calorimetry, UL-94 fire testing, and limiting oxygen index (LOI). A combination of EG/AlPi/MPP/MMT has been shown to provide superior flame-retarding properties when integrated at 20 wt.% into glass-fiber-reinforced PA6 (25 wt.%), achieving UL-94 V0 classification and an oxygen index of 32%. Strong residue formation resulted in low heat development overall, with a peak heat release rate (pHRR) of 103 kW/m2, a maximum of average heat release rate (MAHRE) of 33 kW/m2, and deficient total smoke production (TSP) of 3.8 m2. Particularly remarkable was the structural stability of the char residue. The char residue could easily withstand an areal weight of 35 g/cm2, showing no visible deformation.