Intumescent Flame Retardant Research Articles

The Recyclability of Fire-Retarded Biobased Polyamide 11 (PA11) Composites Reinforced with Basalt Fibers (BFs): The Influence of Reprocessing on Structure, Properties, and Fire Behavior.

The growing requirements regarding the safety of using polymers and their composites are related to the emergence of more effective, sustainable, and hazardous-limited fire retardants (FRs). Significant amounts of FRs are usually required to effectively affect a polymer's burning behavior, while the knowledge of their recycling potential is still insufficient. At the same time, concerns are related not only to the reduced effectiveness of flame retardancy but also, above all, to the potential deterioration of mechanical properties caused by the degradation of temperature-affected additives under processing conditions. This study describes the impact of the four-time reprocessing of bio-based polyamide 11 (PA11) modified with an intumescent flame-retardant (IFR) system composed of ammonium polyphosphate (APP), melamine cyanurate (MC), and pentaerythritol (PER) and its composites containing additional short basalt fibers (BFs). Composites manufactured via twin-screw extrusion were subjected to four reprocessing cycles using injection molding. A comprehensive analysis of their structural, mechanical, and fire behavior changes in each cycle was conducted. The obtained results confirmed the safety of using the proposed fire-retarded polyamide and its composites while reprocessing under the recommended process parameters without the risk of significant changes in the structure. The partial increase in flammability of reprocessed PA-based materials caused mainly by polymer degradation has been described.

Preparation of bio-based trinity lignin intumescent flame retardant and its effect on burning behavior and heat transfer process of epoxy resin composites

The thermal insulation performance of intumescent coating coated on the surface of steel structure is of great significance to prevent the underlying steel structure from collapse in fire. Bio-based intumescent flame retardants gradually attract many attentions due to its environmental friendliness and rich natural sources. In this study, a new bio-based intumescent flame retardant trinity lignin intumescent flame retardant (TLI) is synthesized, which is added to epoxy resin (EP) to prepare EP/TLI epoxy intumescent coatings. The burning behavior of EP/TLI epoxy intumescent coatings is investigated by thermogravimetric (TG) analysis, limit oxygen index (LOI), vertical burning test and cone calorimeter test. Microscopic morphology of char layer is observed by scanning electron microscopy (SEM). The results show that when the TLI addition content is 20 wt% (EP/TLI-4), LOI reaches 26.5 %, UL-94 is V-0 rating. Compared to pure EP, the peak heat release rate (pHRR) and total heat release (THR) of EP/TLI-4 coating are reduced by 82.20 % and 78.27 %, respectively. The influence of chemical formulations, initial coating thickness and incident heat flux on heat transfer process of EP/TLI epoxy intumescent coatings is also investigated. At the same time, the thermal insulation mechanism of EP/TLI epoxy intumescent coating is presented.

ИОННОХРОМАТОГРАФИЧЕСКОЕ ИССЛЕДОВАНИЕ ОГНЕЗАЩИТНЫХ ВСПУЧИВАЮЩИХСЯ ПОКРЫТИЙ В ЭКСПЕРТИЗЕ ПОЖАРОВ

Fire protection of structures, as well as increasing the fire resistance of metal structures is an important task in reducing losses from fires. One common way to improve the fire resistance of a structure is to apply an intumescent flame retardant coating to the structure. Currently, expert practice has more often raised questions about establishing the presence or absence of fire protection on structures. The article considers the possibility of using the method of ion chromatography in order to determine the presence of fire-retardant components in the coating and determine the composition of the fire-retardant coating. The study was conducted on three flame retardant intumescent coatings with different binders. Two sample preparation methods were selected for the study: the study of directly aqueous solutions of intumescent coatings and the study of aqueous solutions of gases released during thermal destruction of coatings. Chromatograms of aqueous solutions of the tested coatings are given, indicating the presence of ions of fire-retardant components formed during hydrolysis. The results of the study showed that both methods have both advantages and disadvantages and can be used in preparation for analysis by ion chromatography to study flame retardant intumescent coatings.

Copper oxide decorated one-dimensional mineral nanorods: Construction of strengthened gas-phase and condensed-phase coupled intumescent flame retardant

Polycarbonate/acrylonitrile–butadiene–styrene (PC/ABS) features superior mechanical properties but suffers from high flammability, presenting a grand challenge in enhancing its flame retardancy with halogen-free additives. Herein, we developed an efficient flame-retardant system (BH/CuATP) by incorporating phosphazene additive (HP), copper oxide modified attapulgite (CuATP) and bisphenol A bis (diphenyl phosphate) (BDP). This system achieves a UL-94V-0 rating without melt-dripping and leads to reductions in the peak heat release rate (43.1 %), total heat release (29.8 %) and total smoke production (5.7 %). The strength effect of CuATP in both gas-phase and condensed-phase significantly contributes to its enhanced fire safety. Additionally, the mechanical properties of PC/ABS/B1H1/CuATP1 are improved due to the rod-like CuATP, showing enhanced comprehensive properties superior to other reported systems. This work presents valuable insights into the effectiveness of mineral-strength intumescent flame retardancy for PC/ABS, offering practical guidance for the development of high-performance PC/ABS composites.

Development of a pyrolysis reaction model for epoxy based flame retardant composites: Relationship between pyrolysis behavior and material composition

This paper presents a methodology to develop a pyrolysis reaction model that captures the flammability behavior of epoxy-based intumescent flame retardant coatings (EP/IFR) as a function of material composition. This approach adopted Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Microscale Combustion Calorimetry (MCC) experiments as well as the inverse modeling of the experimental results using ThermaKin2Ds and COMSOL Multiphysics modeling framework. The interactive reactions between EP and IFR were identified and quantified in the resulting lumped model, which is based on fitting of experimental data. It was found that the developed model was able to reproduce the TGA/DSC/MCC data within the prescribed criteria for EP/IFR blends with different material compositions. The model’s extrapolating capability was further validated through accurately predicting the experimental TGA data under different thermal conditions and for blends with different IFR ratios which were not used for model development. Additional TG-FTIR and XPS experiments were conducted to quantify the effect of IFR additive on the evolution of gaseous products and char formation. With a higher ratio of IFR, the amount of fuel dilution gases (i.e., CO2, NH3) was increased and the amount of combustible organic gaseous products was reduced. This work provides the core subset parameters for comprehensive pyrolysis modeling and enables the intelligent design of EP/IFR coatings with enhanced flame resistance.

Construction of multifunctional coating for polyester/cotton fabrics using layer-by-layer assembly of biomaterials and spraying of fluorine-free polydimethylsiloxane

Polyester/cotton (T/C) fabric has the excellent properties of both cotton and polyester, and is widely used in the textile field. However, the fabric is highly flammable. Further, the facile growth of bacteria on the fabric surface may lead to contamination that precludes application in some areas. Multifunctional T/C fabrics with flame retardancy, superhydrophobicity and antibacterial property have been prepared by construction a surface coating of phytic acid, chitosan, ferric ion and polydimethylsiloxane via a finishing method. The coated T/C fabric exhibits excellent flame retardancy with a LOI value of 30.2 % and a char length of 10.0 cm for combustion. The coated T/C fabrics also display superhydrophobicity with a water contact angle (WCA) greater than 150°. The multifunctional coated T/C fabrics exhibit good antibacterial properties with inhibition of bacterial growth for E. coli and S. aureus of over 98 %. Thermogravimetry and scanning electron microscopy suggest that the multifunctional coating on T/C fabrics produces an intumescent flame retardant effect involving both the promotion of char formation in the condensed phase and the evolution inert species to the gas phase to dilute the fuel load in the combustion zone. A new strategy for the preparation of textile fabrics with good flame retardancy, superhydrophobicity and antimicrobial properties by application of a multifunctional surface coating has been developed.

Edible squid ink proteoglycans as a multifunctional sustainable additive for silk coatings: Fire protection, UV shielding and as a colorant

Today, marine biomolecules have attracted great interest in the field of flame-retardant (FR) science due to their sustainability and charring properties. Squid ink is mixed bio-colloid rich in proteoglycans, melanin, and metal ions. Here, squid ink was applied to endow silk with outstanding FR performance and ultraviolet protection through surface coating. After coating with 40 g/L squid ink, silk displayed excellent ultraviolet shielding performance with a high UV protection factor (UPF) of 71.5, attributing to powerful ultraviolet absorption ability of melanin. Besides, the coated silk also exhibited outstanding FR performance, characterized by a shorter char length (7.1 cm) and a higher FR-Index (2.5). The heat release performance of the treated silk dramatically decreased, and the peak heat release rate (pHRR) and heat release capability (HRC) both decreased by 49.1 %. Moreover, a significant reduction in total smoke production (TSP ∼ 60 %) was also observed in cone calorimetry test. A reduction in these fire parameters indicated a great improvement in the fire safety of silk. Interestingly, due to the natural adhesiveness of the proteoglycan mixed colloid, the coated silk could withstand 10 washing cycles while maintaining FR properties. Subsequently, further analyses of the cone residues confirmed the formation of a compact and stable char layer. The squid ink coating exerted an intumescent FR action on silk.

Mechanical, Dielectric and Flame-Retardant Properties of GF/PP Modified with Different Flame Retardants.

With the rapid development of electronic information technology, higher requirements have been put forward for the dielectric properties and load-bearing capacity of materials. In continuous glass fiber-reinforced thermoplastic composites, polypropylene matrix is a non-polar polymer with a very low dielectric constant and dielectric loss, but polypropylene is extremely flammable which greatly limits its application. Aiming at the better application of flame retardant-modified continuous glass fiber-reinforced polypropylene composites (FR/GF/PP) in the field of electronic communication, the effects of four different kinds of flame retardants (Decabromodiphenyl ethane (DBDPE), halogen-free one-component flame retardant (MONO), halogen-free compound flame retardant (MULTI), and intumescent flame retardant (IFR)) on the properties of FR/GF/PP were compared, including the mechanical properties, dielectric properties and flame-retardant properties. The results showed that among the FR/GF/PP, IFR has the highest performance in mechanical properties, MULTI has better performance in LOI, DBDPE and IFR have better performance in flame retardant rating, and DBDPE and IFR have lower dielectric properties. Finally, gray relational analysis is applied to propose an approach for selecting the optimal combination (flame retardant type and flame-retardant content) of comprehensive performance. In the application exemplified in this paper, the performance of IFR-3-modified GF/PP is optimized.

Research on preparation and performance tests of the fire retardant coatings for special functionalized wires and cables

This study aimed to produce a new potential intumescent flame retardant system through the addition of titanium dioxide and alumina-silica fiber based on optimizing the traditional ammonium polyphosphate (APP) / melamine (MEL) / pentaerythritol (PER) intumescent flame retardant formula. The flame retardant capacity and the physical properties were fully analyzed and discussed. The produced flame retardant coating could resist the rapid rise in 1100 of high flame temperature, whereas 40 exceeded the national standards. Thus, the produced flame retardant coating in this study could be potentially further applied to the cables and wires that are frequently needed in petroleum, telecommunication, military, tunnel, and electric uses.

Review on Processing, Flame‐Retardant Properties, and Applications of Polyethylene Composites with Graphene‐Based Nanomaterials

AbstractThis paper presents recent developments in graphene‐based nanomaterial (GNM)‐containing flame‐retardant (FR) polyethylene (PE) composites for advanced applications and introduces knowledge gaps and potential solutions. Various nanomaterials have been used to improve the FR properties of PEs. Among these, GNMs score highly because of their superior performance and multifunctional characteristics. By offering a holistic overview of the fundamentals of the FR characteristics of GNMs, the processing and characterization of PE/GNM composites, and the critical aspects related to the development of FR PE/GNM composites for advanced applications, this review provides insights into advances in this area as well as prospects. Furthermore, the kinetics of the FR characteristics of PE and PE/GNM composites are critically discussed in the context of how the FR properties of PE/GNM composites can be tailored by modifying either the surface of the GNM, PE or both, an area seldom discussed in the literature. Moreover, the FR performance of PE/GNM composites is compared with PE/Expandable Graphite (EG) composites because EG has been recognized as a highly efficient and eco‐friendly intumescent FR. In summary, this review offers new insights into the design of advanced PE/GNM composites for automotive, construction, aerospace, and electronic packaging applications.

Modified lignin-based intumescent flame Retardant's effect on flame retardancy, mechanical and electrical properties of HDPE material for cable sheathing

High-density polyethylene (HDPE) is a commonly used material for cable sheathing, which is a flammable material. To ensure the safe transportation of electrical energy, it is necessary to enhance the flame-retardant properties of HDPE materials. In this work, ammonium polyphosphate (APP) with lignin (Lig) is used as an intumescent flame retardant, and the flame retardant properties of APP/Lig for HDPE with different ratios are analyzed. It is found that with 3/1 ratio of APP and Lig under 30 wt%, the best flame-retardant performance is achieved. To further improve its properties, chemical modification of Lig with hexachlorocyclotriphosphazene (HCCP) is conducted to introduce nitrogen and phosphorus, obtaining NP-Lig. Flame retardant, mechanical and electrical properties are tested for the prepared material. The flame retardant tests show that the LOI of HDPE is increased from 23.8 to 28.2 by the addition of APP/NP-Lig, compared to that of APP/Lig. Mechanical tests show that replacing Lig with NP-Lig slightly increases the tensile strength and elongation at break of HDPE. Electrical tests show that APP/NP-Lig flame retardant maintains the electrical properties of HDPE under the industry standards.

P/N synergistic integrated flame retardants with instant cross-linking at high-temperature for flame retardancy and impact resistance of epoxy resins

With the development of flame retardant technology, intumescent flame retardant (IFR) systems, and instant cross-linking in case of fire have become important directions for epoxy resin (EP) flame retardancy. A carbonized matrix containing a benzoxazine structure was constructed with the triazine structure, and the integrated flame retardant (TRBPO) was constructed by introducing the phosphorus source through a partial ring-opening reaction. It can maintain its structural characteristics during the curing process of EP. When EP materials are exposed to fire, TRBPO will cross-link in the EP matrix and work as the P/N synergistic IFR system to achieve excellent flame retardancy. The results showed that 5 wt% of TRBPO could make EP composites reach UL-94 rating of V-0 with a PHRR of 303.7 kW/m2, and the TSP and TSR were reduced by 48.5 % and 48.9 %, respectively, compared with pure EP. The introduction of TRBPO has a impact resistance effect on EP, and its excellent stress dispersion effect made the impact strength of 5-TRBPO/EP reached 36.49 KJ/m2. The analysis of the flame retardant mechanism proved that the rapid carbon formation function of IFR and the self-crosslinking flame retardancy of TRBPO in the fire are the main reasons for flame retardancy. In addition, the capture of flammable groups in the gas phase is an important source of flame retardant effect.

Mechanical, Flame-Retardant and Dielectric Properties of Intumescent Flame Retardant/Glass Fiber-Reinforced Polypropylene through a Novel Dispersed Distribution Mode.

The application of continuous glass fiber-reinforced polypropylene thermoplastic composites (GF/PP) is limited due to the inadequate flame retardancy of the polypropylene (PP) matrix. Apart from altering the composition of the flame retardants, the distribution modes of flame retardants also impact material performance. In this study, an alternative approach involving non-uniform distribution is proposed, namely, dispersed distribution, in which non-flame-retardant-content layers (NFRLs) and/or low-flame-retardant-content layers (LFRLs) are dispersed among high-flame-retardant-content layers (HFRLs). The mechanical, flame retardant and dielectric properties of GF/PP with intumescent flame retardant (IFR/GF/PP) are investigated comparatively under uniform, gradient, and dispersed distributions of the flame retardants. The results demonstrate that non-uniform distribution exhibits superior flame retardant performance compared to uniform distribution. Dispersed distribution enables IFR/GF/PP to attain enhanced mechanical properties and reduced dielectric constants while maintaining excellent flame-retardant properties.

A macromolecular intumescent flame retardant with thermal cross-linking groups for poly(ethylene terephthalate) with enhanced fire safety

To improve the flame retardancy of poly(ethylene terephthalate) (PET) without loss of its mechanical properties, a macromolecular intumescent flame retardant (SPPO) with thermal-responsive groups was developed in an effective way. As 8 wt% of SPPO was melt-blended into PET, the prepared PET/SPPO composite achieved a V-0 rating during UL-94 tests without melt-dripping, and exhibited substantial reduction in the total heat release (THR), peak heat release rate (PHRR), total smoke production (TSP) and average carbon monoxide yield (av-COY) by 44.8 %, 39.0 %, 63.3 % and 45.8 %, respectively, in comparison with pure PET. The improved flame retardancy of this composite was considered to be ascribed to the formation of intumescent residues of SPPO. The generated physical barrier increased the melt viscosity by triggering the cross-linking reactions of the C≡N groups in SPPO, effectively inhibiting the melt-dripping of PET during burning. The tensile strength was also well-retained for PET composites when different contents of SPPO were added into PET, demonstrating the good compatibility between SPPO and PET matrix, which can meet the requirements of industrial application.

Real-time monitoring of charcoal layer resistance for investigating the synergistic flame retardant mechanism of zinc oxide and intumescent flame retardants in SBS

Metal oxides as synergists of intumescent flame retardant (IFR) lead to an extremely complex formation process of intumescent char layers. The lack of means to detect the evolution of the char layer in real time makes it challenging to investigate the synergistic flame retardant mechanism between metal oxides and IFR. Herein, an innovative method of detecting real-time changes in the resistance of the char layer under flame ablation is used to investigate its changes in morphology, thus assisting in revealing the synergistic flame retardant mechanism of zinc oxide (ZnO) in IFR/SBS. ZnO showed a significant synergistic flame retardant effect with IFR without MEL and no synergistic effect with MEL-containing IFR. The analysis of the char layer structure revealed that ZnO played a role in promoting gas release and char layer formation and increasing the viscosity of the molten char layer regardless of the presence or absence of MEL.The difference in the morphology of the char layer could not reveal the experimental phenomenon that there is no synergistic flame retardant effect between ZnO and MEL-containing IFR. The analysis of the real-time resistance of the charcoal layer reveals that ZnO achieves its synergistic flame retardation with the MEL-free IFR by increasing the expansion of the charcoal layer at the initial stage of its formation. For MEL-containing IFR, 0.5% ZnO inhibits the rupture of the char layer by promoting its formation in the early stages of ablation, and 1% ZnO leads to the rupture of the char layer instead, due to the promotion of gas release. Excess ZnO (2%) caused pyrolysis gases to escape from the voids of the char layer rather than allowing it to expand. The analysis of the real-time resistance of the charcoal layer can help to accurately reveal the flame retardant mechanism.

Fully bio-based intumescent flame retardant hybrid: A green strategy towards reducing fire hazard and improving degradation of polylactic acid

Polylactic acid (PLA) is a promising renewable polymer material with excellent biodegradability and good mechanical properties. However, the easy flammability and slow natural degradation limited its further applications, especially in high-security fields. In this work, a fully bio-based intumescent flame-retardant system was designed to reduce the fire hazard of PLA. Firstly, arginine (Arg) and phytic acid (PA) were combined through electrostatic ionic interaction, followed by the introduction of starch as a carbon source, namely APS. The UL-94 grade of PLA/APS composites reached V-0 grade by adding 3 wt% of APS and exhibited excellent anti-dripping performance. With APS addition increasing to 7 wt%, LOI value increased to 26 % and total heat release decreased from 58.4 (neat PLA) to 51.1 MJ/m2. Moreover, the addition of APS increased its crystallinity up to 83.5 % and maintained the mechanical strength of pristine PLA. Noteworthy, APS accelerated the degradation rate of PLA under submerged conditions. Compared with pristine PLA, PLA/APS showed more apparent destructive network morphology and higher mass and Mn loss, suggesting effective degradation promotion. This work provides a full biomass modification strategy to construct renewable plastic with both good flame retardancy and high degradation efficiency.

Effect of foaming behavior of polypropylene foams on flame retardant properties under different weight reduction methods

AbstractIn previous studies, the effect of cell structures of polypropylene (PP) foam materials on flammability behavior had been largely overlooked. In this work, ammonium polyphosphate and pentaerythritol were used as intumescent flame retardants (IFR) for PP, and then the PP‐IFR flame retardant foams were prepared by using injection foaming technology with two different weight reduction methods (same mold volume before foaming and after foaming). The results showed that the average cell size of all the PP‐IFR flame retardant foams in the 10% to 30% weight reduction was less than 100 μm. The PP‐IFR flame retardant foams with an average cell diameter of 26.22 μm and cell density of 7.88 × 106 cells/cm3 had the best limiting oxygen index (LOI) of 27.9%. In addition, the PP‐IFR flame retardant foams with better foaming quality had a higher LOI and a denser foam carbon layer whatever the weight reduction methods, resulting in better flame retardant properties. The escape of gases from the foamed and un‐foamed areas not only reduced the concentration of flammable gases but also led to the collapse and rupture of the foam carbon layer during the combustion process. Hence, it provides guidance for preparing PP foam materials with excellent flame retardancy.

Enhance the fire safety of epoxy resin using ammonium polyphosphate flame retardant with the sandwich structure containing catalytic carbon formation function

AbstractAmmonium polyphosphate (APP) is often used to construct intumescent flame retardant systems together, but it is faced with the problem of adding too much flame retardant. This paper envisions the construction of a modified APP flame retardant (TR@ZIFAPP) with a sandwich structure by the method of covering, which, in order to endow APP flame retardant with better flame retardant effect. By constructing a metal catalytic layer and a triazine carbon formation layer, the modified APP flame retardant has both catalytic carbon formation and phosphorus–nitrogen synergistic flame retardant functions. TR@ZIFAPP is expected to be used in flame‐retardant polymer composites with low addition requirements, adding it to epoxy resin (EP) reveals that the TR@ZIFAPP flame retardant could achieve the optimal flame retardant effect when the addition amount was only 3 wt%. The UL‐94 rating reached V‐0 grade, and the two off‐fire auto‐ignition time levels were only 0.7 s. The analysis of its flame retardant mechanism showed that the flame retardant in EP was mainly through the rapid formation of carbon to isolate oxygen and dilute the flammable gas to reach a strong flame retardant effect.

Preparation and application of halogen-free and efficient Si/P/N-containing flame retardants on cotton fabrics

Cotton fabric is extensively utilized due to its numerous applications, but the flammability associated with cotton fabric poses potential security risks to individuals. A halogen-free efficient flame retardant named poly [(tetramethylcyclosiloxyl spirocyclic pentaerythritol)-piperazin phosphate] (PCPNTSi) was developed to consolidate the fire retardance of cotton fabrics. After PCPNTSi treatment, the limiting oxygen index (LOI) of cotton fabric with 30 % weight gain (CP3) was raised to 32.8 %. In the vertical flammability test (VFT), CP3 has self-extinguished performance with a char length of 8.7 cm. The heat release rate (HRR) of cotton fabric with 20 % weight gain (CP2) is 78.8 % lower than that of pure cotton fabric (CP0). In addition, the total smoke release (TSP) of CP2 is 41.7 % lower than that of CP0, indicating PCPNTSi gives cotton fabric a good capability to inhibit smoke release. Finally, the possible flame retardant mechanism was discussed by the data of scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared spectroscopy (FT-IR) and thermogravimetric infrared spectroscopy (TG-IR). The results show that PCPNTSi is an intumescent flame retardant acting in both gas phase and solid phase.

Improved flame resistance and thermal insulation properties of steel fireproof coatings based on polyvinyl alcohol @ expandable graphite

Intumescent fireproof coating (IFC) can effectively slow down the temperature rise of base materials by constructing intumescent heat isolation chars. Expandable graphite (EG), combined with a typical intumescent flame-retardant system, shows an excellent expansion effect. However, it is difficult to be evenly dispersed in the coating system due to its low surface energy, thus limiting its application in IFC. In this research, EG encapsulated by polyvinyl alcohol (PVA) film was used in combination with conventional intumescent flame retardants to prepare a fireproof coating. Due to the increased hydrophilicity caused by the hydroxy groups of the PVA, both the dispersion and adhesion of EG can be greatly improved in the coating. Additionally, PVA also plays the role of a charring agent to further upgrade the quality of the produced carbon layer. The prepared IFC displays a satisfying synergistic effect. The experimental results showed that the back-surface temperature of the steel plate coated by PVA@EG was reduced to 232 °C after 20 min, far lower than the 250 °C of the unmodified EG system, and the thermal insulation performance was enhanced significantly. Compared with the untreated EG coating, the HRR, THR, and TSR decreased by 79.5 %, 86.0 % and 24.8 %, respectively, and combustion and smoke suppression performance were improved greatly. All in all, PVA@EG endows the coating with superior flame-retardant and thermal insulation performance and greatly improves the safety of steel structures in buildings.