Intumescent Flame Retardant 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.

An eco-friendly and intumescent P/N/S-containing flame retardant coating for polyamide 6 fabric

This study focused on the construction of an eco-friendly and intumescent flame retardant (FR) coating for polyamide 6 (PA6) fabric. The intumescent FR coating, consisting of phytic acid, pentaerythritol and thiourea, was deposited onto PA6 fabric through dip-coating technique. The FR performance, anti-dripping ability, thermal stability, combustion behavior and mechanical property of the coated PA6 fabrics were explored. The severe dripping of coated PA6 fabric was totally eliminated, achieving an excellent FR performance at a low P (2.2%) and S (3.4%) content. Correspondingly, the LOI increased to 28.8% versus 23.2% of pristine one, displaying good flame retardancy. The char residue analyses confirmed the intumescent FR behavior of coated PA6 fabrics. The intumescent char layer played a major role in isolating the exchange of combustibles, oxygen and heat, leading to the significant reduction in heat release performance. The results of cone calorimetry test showed that the peak heat release rate and average effective heat of combustion of coated PA6 fabric decreased by about 36.5% and 34.4%, respectively versus pristine one. Meanwhile, the sulfur-based gases captured free radicals to interrupt the continuous combustion, leading to the significantly improved flame retardancy. Furthermore, the FR coating exerted little influence on the mechanical performance of PA6 fabric.

The piperazine pyrophosphate intumescent flame retardant of polypropylene composites prepared by selective laser sintering

AbstractA highly flame‐retardant PP composite powder suitable for selective laser sintering (SLS) was prepared successfully by mechanical blending, which was composed of pure PP, piperazine pyrophosphate (PPAP), melamine polyphosphate (MPP), and triazine‐based charring‐foaming agent (CFA). The results showed that the flowability of PP composite powder decreased by about 40% and the DSC data indicated the sintering window decreased by about 2°C. Although the flame retardants influenced the processing of SLS, the PP composite powder was still able to be used for printing. The LOI value of PP composites prepared by SLS was 29.2% and the UL‐94 grade was V‐0 rating at the filler loading (16wt% PPAP, 4wt% MPP, 4wt% CFA). The cone calorimeter testing (CCT) data represented that the heat and smoke release significantly decreased. The synergistic effect among flame retardants promoted high‐quality char layers, which is favorable for improving the flame retardancy and thermal stability of PP composites by the test of TGA, SEM, Raman spectra, and FT‐IR. However, the flame retardancy and mechanical properties of PP composites made by SLS were both in varying degrees of decline compared to the ones made by thermo‐compression (TC) because of the higher porosity. An air duct with complex structures was prepared by SLS at last.

Fabrication of P/N/B-Based Intumescent Flame-Retardant Coating for Polyester/Cotton Blend Fabric.

Polyester/cotton (T/C) blend fabrics are highly flammable due to the particular “scaffolding effect”. In this work, an intumescent flame retardant (IFR) agent containing P, N, and B was designed and synthesized using bio-based phytic acid, pentaerythritol, boric acid, and urea. The IFR compounds were deposited onto a T/C blend fabric by the surface-coating route. The chemical structure of IFR agent and its potential cross-linking reactions with T/C fibers were characterized. The morphology, thermal stability, heat-release ability, flame retardancy, and mechanism of coated T/C blend fabrics were explored. The self-extinguishing action was observed for the coated T/C blend fabric with a weight gain of 13.7%; the limiting oxygen index (LOI) value increased to 27.1% versus 16.9% for a pristine one. Furthermore, the intumescent flame retardant (IFR) coating imparted T/C blend fabrics with high thermal stability and significantly suppressed heat release by nearly 50%. The char residue analyses on morphology and element content confirmed the intumescent FR action for coated T/C blend fabrics. The prepared IFR coating has great potential to serve as an eco-friendly approach for improving the flame retardancy of T/C blend textiles.

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.

An Efficient Composite Modifier Prepared for Enhancing the Crystallization and Flame-Retardancy of Poly(m-xylylene adipamide)

Poly(m-xylylene adipamide) (MXD6) has good gas barrier properties and high mechanical strength. However, in nature, this resin has a low rate of crystallization. In order to overcome this obstacle in its applications, this study prepares a new, efficient modifier for MXD6 by combining the synthesized DOPO derivative (DT) and P22. It is found that the use of the binary modifier exhibits obvious effects on the crystallization of MXD6. When 11.0 wt.% DT is added together with 0.1 wt.% P22 (DT/P22), the crystallization temperature of MXD6 shifts to a higher temperature of 19.7 °C, and the crystallinity degree of MXD6 is significantly increased by 60%. Meanwhile, this modifier exhibits obviously intumescent flame-retardancy on MXD6 by increasing the limited oxygen index (LOI) from 26.4% to 33.4%. The results of the cone calorimeter test (CCT) reveal that the peak heat release rate (PHRR), total heat release (THR) and average effective heat release (av-EHC) are obviously suppressed due to the use of this modifier. Moreover, the influences of this modifier on the crystal structures, mechanical and rheological properties of MXD6 are analyzed in detail. This study can provide an efficient modifier for MXD6.

To improve the flame retardancy, mechanical properties and degradation rate of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) by divinybenzene-maleic anhydride microsphere

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB), as a bio-originated and biodegradable polyester, is expected to be developed to substitute traditional petroleum-based plastics. However, its flammability restrains its application, intumescent flame retardant (IFR) has been used in P34HB. Herein, a rigid microsphere divinylbenzene-maleic anhydride (DM) copolymer was used as a synergistic agent with IFR together in P34HB. The LOI of the 83wt% P34HB/16wt% IFR/1wt% DM reached 30.0%, and the composite also passed the UL-94V-0 rating. In the cone calorimeter test, the peak heat release rate (PHRR) of the control P34HB was 727 kW/m2, which was reduced to 281 kW/m2 for the 83wt% P34HB/16wt% IFR/1wt% DM. The total smoke production (TSP) of the control P34HB was 12.1 m2, however, the TSP value of 83wt% P34HB/16wt% IFR/1wt% DM was reduced to 8.4 m2. The results showed that DM acted as an ideal synergist flame retardant. For the 75wt% P34HB/25wt% IFR, the tensile strength and impact strength were 13.7 MPa and 4.2 KJ/m2, respectively and for the 83wt% P34HB/16wt% IFR/1wt% DM, they were increased to 18.1 MPa and 9.1 KJ/m2, respectively. In the degradation process, the weight loss rate of control P34HB was 0.1 mg/h, and that was 0.56 mg/h for 83wt% P34HB/16wt% IFR/1wt% DM, which indicated that the IFR/DM accelerated the degradation of P34HB. All the work documented that DM improved the flame retardant, mechanical properties, and degradation rate of P34HB.

Synthesis and properties of a new halogen-free flame-retardant epoxy resin flame retardant

PurposeThis paper aims to study a new halogen-free fame-retardant curing agent 1-aminoethylidenediphosphonate (AAEDP).Design/methodology/approachThe AAEDP was synthesized by phosphoric acid, acetonitrile and ammonia. The chemical structures of AAEDP were characterized by proton nuclear magnetic resonance, mass spectrometry and Fourier transform infrared spectrometer. Thermal gravimetric analysis (TGA) and scanning electron microscope (SEM) would study the thermal properties and the char residues of AAEDP/EP. The thermal stability, mechanical and flame properties and morphology for the char layer of composite materials were separately investigated using TGA, tensile and charpy impact tests, limiting oxygen index (LOI), UL-94 HB flammability standard (UL-94) and SEM.FindingsThe results showed that the AAEDP had been prepared successfully. When the intumescent flame retardant was added into the EP, the LOI of composite material was improved.Research limitations/implicationsThe AAEDP can be prepared successfully and can improve the flame resistance of composite material.Practical implicationsThe AAEDP has excellent flame-retardant properties and produce no toxic fumes when burnt in case of fire.Originality/valueThe results showed that the phosphorus content of AAEDP was 2.958 Wt.%; the impact and tensile strength of the composite material were 6.417 kJ m−2 and 38.0 MPa, respectively; and the LOI and UL-94 were 29.7% and V-0 ranking, respectively. The TGA results indicated that the carbon residue ratio can be increased by 1000°C in air. The denser and more uniform structure of residual carbon prevents heat transfer and diffusion, restricts the production of combustible gas and reduces the rate of heat release.

Effects of intumescent flame retardant based on THEIC-based oligomeric ester as char forming agent on thermal，mechanical and flame retardant properties of HDPE composites

In this study, a new phosphor-ester (TPE) was prepared by one-spot polycondensation of tris (2-hydroxyethyl) isocyanurate (THEIC) and phenyl phosphonic dichloride (PPDC) and used as a charring agent in combination with ammonium polyphosphate (APP) to develop new intumescent flame retardant (IFR) for high-density polyethylene (HDPE). The thermal and flame retardant properties of composites were investigated by thermogravimetric analysis (TGA), limiting oxygen index measurement (LOI), and cone calorimetry (CCT). At the same time, the morphology and chemical structure of the char residue were analyzed by scanning electron microscopy, Fourier transfer infrared spectroscopy, and laser Raman spectroscopy. The results showed the LOI value of the composite HD/APP/TPE containing 25 wt. % of APP/THE reaches 28.2 %. The CCT test suggested that the peak heat released rate (PHRR) of the flame retardant composite is decreased by 37 % compared to that of pure HDPE. The use of IFR based on APP and TPE produces a compact char residue that acts as a barrier for heat, oxygen, and volatile combustibles and protects the underlying polymer. Besides TPE can produce the PO-type radicals that show some gas phase flame retardant action. However, the tensile strength of the composites is still lower than that of pure polymer.

A semi-global reaction mechanism for the thermal decomposition of low-density polyethylene blended with ammonium polyphosphate and pentaerythritol

A semi-global reaction mechanism has been developed to capture the decomposition of a polymer, i.e. low-density polyethylene (LDPE) that contains a condensed-phase-active intumescent flame retardant, i.e. ammonium polyphosphate (APP) mixed with pentaerythritol (PER) with ratio 3:1 (wt/wt). The methodology combines thermogravimetric analysis (TGA) in anaerobic environment over a wide range of heating rates and inverse modeling of these experiments based on the Shuffled Complex Evolution (SCE) optimization algorithm. The decomposition of neat LDPE can be described by a single first-order reaction. In contrast, the decomposition of the APP/PER additive is characterized by strong interactions between the reactants and a 5-step reaction mechanism was designed driven by the mechanisms of the intumescence process. The direct coupling of the 1-step reaction mechanism for LDPE and the 5-step reaction mechanism for APP/PER was found to provide decent predictions for the decomposition of the 90%LDPE/10% APP/PER blend. The slight interactions between the LDPE matrix and the APP/PER additive were taken into account by updating the kinetic parameters of two reactions, leading to a final robust and accurate 6-step reaction model.

Influence of glycidyl methacrylate grafted poly (butylene succinate) (PBS‐g‐GMA) on flame retardancy and mechanical properties of water hyacinth fiber/ammonium polyphosphate/poly (butylene succinate) composites

AbstractIn this study, water hyacinth fiber (WHF) was used as a carbon source in combination with ammonium polyphosphate (APP) to formulate an environmentally friendly intumescent flame retardant for poly (butylene succinate) (PBS) composites. Glycidyl methacrylate grafted poly (butylene succinate) (PBS‐g‐GMA) was prepared via a reactive melt grafting reaction to serve as a compatibilizer for WHF/APP/PBS composites. Effects of incorporating APP and WHF, and PBS‐g‐GMA on mechanical properties, thermal properties and flame retardancy of PBS composites were investigated. Results showed that the addition of PBS‐g‐GMA greatly improved tensile strength, flexural strength and crystallization rate of WHF/APP/PBS composites. According to UL‐94 and limiting oxygen index (LOI) tests, the presence of 15 wt% WHF, 30 wt% APP, and 15 wt% PBS‐g‐GMA enabled the WHF/APP/15PBS‐g‐GMA/PBS composite to achieve a V‐0 rating and the maximum LOI value of 29.2%. Char residue analysis revealed that the combination of APP and WHF promoted the formation of an expanded char layer, whereas the addition of PBS‐g‐GMA induced the formation of compact, highly graphitized residues. Findings will contribute to the development of biodegradable flame‐retardant polymer composites for engineering applications.

Synthesis of a charring agent containing triazine and benzene groups and its intumescent flame retardant performance for polypropylene

A novel linear triazine-based charring agent, N-Ethanolamine Triazine-4,4-diaminodiphenylsulfone-piperazine copolymer hybrids (ETDPCs), was successfully synthesized and was combined with fire-retardant (FR) (mass ratio 2:1 of ammonium polyphosphate (APP) and melamine pyrophosphate (MPP)) to fabricate intumescent flame-retard PP composites at a 20 wt% loading, which exhibited excellent char-forming capacity and thermostability. The value of the limiting oxygen index (LOI) reached 30.4% and the vertical burning test (UL-94) passed V-0 grade for the PP2 sample with a mass ratio of FR to ETDPCs being 3:1. The cone calorimeter test revealed that the total heat release (THR) and total smoke release (TSR) of PP2 were significantly decreased by 61.8% and 87.9% compared with that of pure PP. The flame retardancy index (FRI) of PP2 was 12.2, showing an “Excellent” grade of flame retardancy. The thermogravimetric results showed that ETDPCs presented good char formation ability, and it would greatly increase the charring yield of PP when combined with FR due to the synergistic effect. The investigation of the structures and properties of char residues indicated that the continuous and compact char layer with high mechanical stability and low thermal conductivity, containing benzene and triazine derivatives, was formed for PP2 during combustion, which acted as a good barrier against the transmission of heat and volatiles and movement of high-temperature melt. This work expanded the avenue in the synthesis of high-efficiency charring agents and improved the intumescent flame retardancy of PP.

Ultra-light polylactic acid/combination composite foam: A fully biodegradable flame retardant material

In this study, low-density polylactic acid (PLA) flame retardant foams were prepared using lignin fiber (LF), ammonium polyphosphate (APP), resorcinol bis(diphenyl phosphate) (RDP) and SiO2 aerogel. LF, RDP and SiO2 aerogel alone did not improved the flame retardancy of PLA composites; however, APP alone required a higher addition of amount to achieve a better flame retardancy. The synergistic effect between the four can improve the flame retardancy of PLA at a lower addition level. The intumescent flame retardant system composed of LF/APP/RDP/SiO2 aerogel can not only form a dense carbon layer on the surface of the material when burning to improve the flame retardant performance, but also improve the thermal stability of PLA, increase the degradation temperature and reduce the thermal weight loss rate. The final PLA flame retardant foam (density: 0.022 g/cm3) prepared by supercritical foaming can reach V-0 rating in UL-94 vertical combustion test, and the limiting oxygen index (LOI) can reach 30.5 %.

High efficient fire-retardant coatings on wood fabricated by divalent metal ion cross-linked multilayer polyethyleneimine and ammonium polyphosphate polyelectrolytes

In this work, to endow wood with efficient flame retardancy, polyethyleneimine (PEI) and ammonium polyphosphate (APP) as an intumescent flame retardant system was deposited on wood via layer-by-layer (LbL) self-assembly approach combined with divalent metal ions cross-linking treatment. Scanning electron microscopy equipped with energy-dispersive (SEM-EDX) and Fourier transform infrared spectroscopy (FT-IR) analysis demonstrated that divalent metal ions cross-linked PEI-APP coatings were successfully constructed on wood surface. Thermogravimetric analysis (TGA) indicated that PEI-APP modification could improve the thermal stability of coated wood by decreasing the maximum degradation rate and increasing the char residue, while Cu2+ and Co2+ cross-linking treatments could further enhance these properties. What's more, the fire resistance of the modified wood was also significantly improved, proved by limiting oxygen index (LOI) and cone calorimeter characterizations. When coated by PEI-APP, the LOI was increased to 37.5 from the pristine uncoated 23.5. Further, when cross-linked by Cu2+ and Co2+, the LOIs were increased to 47 and 42.5, respectively. In addition, the heat release rate (HRR) and total heat release (THR), especially the total smoke release of the PEI-APP and metal ions cross-linked coated wood, were also obviously decreased. The improvement of thermal stability and fire-retardant performance was mainly due to the synergistic effect of APP and metal ions, which could accelerate the char-forming process and increase the amount of carbon formed, thus effectively preventing the spread of heat and flame into the inner wood and protecting the wood from fire attacking. The green and low-cost flame-retardant treatment approach reported in this study is likely to improve the added value of modified wood and promote its wide application.

Multifunctional MXene-based fire alarm wallpaper with sandwich-like structure for enhanced fire safety and prevention

Design and development of multifunctional fire-resistant and fire alarm wallpaper (FAW) that can simultaneously hold early fire warning function and the ability to inhibit flame propagation is urgently required to boost the fire safety of combustible materials in public security. Herein, a flexible sandwich-like and nacre-biomimetic FAW was fabricated by using renewable lignocellulose nanofibrils (LCNF) and MXene thermosensitive sensor via a vacuum-assisted alternate self-assembly method. The FAW achieved ultrasensitive fire early warning response because of the synergistic effect of the insulating LCNF layers and highly conductive MXene with hierarchical structure sandwiched between LCNF layers. Furthermore, owing to the ultrafast catalytic char formation and intumescent flame retardant effect of ammonium polyphosphate (APP), the trigger sensitivity and thermal oxidation capacity of the FAW (LCNF-15) were greatly optimized by adding 15 % APP in the LCNF layer, resulting in a superior fire alarm response (0.32 s) and a continuous alarm signal (about 3073.0 s) under a flame attack. Besides, the LCNF-15 also exhibited good flexibility, ideal cyclic warning performance, excellent heat insulation ability and strong char-forming properties in a fire. The sandwich-like strategy offers a new platform for the construction of MXene-based multifunctional FAW, which is of great value in broadly addressing the fire hazard problem of traditional wallpapers.

Growth of biobased flakes on the surface and within interlayer of metakaolinite to enhance the fire safety and mechanical properties of intumescent flame-retardant polyurea composites

In this work, meta-kaolinite has been successfully multidimensionally modified by growing melamine-phytate nanoflakes within the interlayer and on the surface of metakaolinite via facile and green supramolecular self-assembly technology. Then, multidimensionally modified metakaolinite (Mul-K0) along with intumescent flame retardant (IFR) has been incorporated into polyurea (PUA)The incorporation of Mul-K0 together with IFR into PUA has simultaneously enhanced both the fire safety and mechanical property. Flame retardancy and smoke suppression of Mul-K0 based PUA/IFR composite have been evaluated by oxyacetylene ablation test, limiting oxygen index, UL-94 vertical burning and conventional or modified cone calorimeter tests. The underlying mechanism of Mul-K0 responsible for enhancing the fire safety and mechanical properties were explored. This work offers a new strategy for improving the flame-retardancy efficiency utilizing the synergistic effect of IFR and modified meta-kaolinite and provides a promising opportunity for fabricating long-life flame retardant PUA composites.

A bio-based intumescent flame retardant with biomolecules functionalized ammonium polyphosphate enables polylactic acid with excellent flame retardancy

A bio-based intumescent flame retardant (IFR) was designed and synthesized by employing a simple and environment-friendly strategy. Via electrostatic interaction, chitosan (CS) and amino trimethylphosphonic acid (ATMP) as organic shells are deposited on the inorganic core of ammonium polyphosphate (APP) to form the core–shell flame retardant (APP@CS@ATMP). Then, agar (AG) is used as a charring agent candidate that combines with APP@CS@ATMP to fabricate a bio-based IFR. The application of APP@CS@ATMP and AG in polylactic acid (PLA) is effective in improving its flame retardancy and anti-dripping properties. The PLA composite including 20 wt% APP@CS@ATMP/AG (APP@CS@ATMP:AG = 3:1) can achieve the optimal flame-retardant effect and a UL-94 V-0 rating with a slight melt-dripping phenomenon. Furthermore, the peak heat release rate and total heat release significantly decrease in the cone calorimetric tests contrasted with those of pure PLA. The flame-retardant mechanism of APP@CS@ATMP/AG is revealed by analyzing the pyrolysis gaseous products during the thermal decomposition and the morphology and structure of char residues. This work provides a facile and sustainable route to construct bio-based polymer composites with excellent fire-safety properties.

Constructing cross-functional intumescent flame retardants with UV resistance for polypropylene composites

Cross-functional additives were carefully designed for polypropylene (PP) composites to enhance the flame retardancy, UV resistance, and mechanical properties. In this work, first, ammonium polyphosphate (APP) was coated with polysiloxane to avoid the pyrolysis of APP under UV irradiation; second, the charring formation agent (CFA) with triazine groups was selected to enhance the absorbance of UV radiation. Hindered amine light stabilizer (TEMP) was reacted with sodium lignin sulfonate (SLS) to obtain SLS-TEMP. By using 19 wt.% (SiAPP/CFA)/2 wt.% SLS-TEMP, the limiting oxygen index of the PP composite was increased to 33.5 and the UL-94 grade was achieved to V-0. The peak heat release rate and peak smoke release rate were reduced by 76% and 74% compared with that of the control PP sample, respectively. Moreover, the aging process of the PP composite sample was delayed. The tensile and impact strength of the PP/19 wt.%(SiAPP/CFA)/2 wt.%SLS-TEMP sample was decreased by 13.4% and 27.8%, respectively after 60 h UV irradiation, which was significantly lower than that of control PP (50.9% and 68%). The change of limiting oxygen index before and after aging was minimal, and the sample still passed UL-94 V-0 grade after 100 h UV-aging test. It was proved that the SLS-TEMP has an excellent synergy effect on improving the flame retardancy and UV resistance of PP. This cross-functional additive strategy provides a good solution for obtaining high-performance PP composites.

Effect of layered double hydroxide on the flame retardancy of intumescent flame retardant thermoplastic polyurethane composites prepared by selective laser sintering

AbstractPresently, layered double hydroxides (LDHs) are pervasively adopted as part of flame retardant polymer composite materials due to its favorable synergism effect with certain flame retardants. In addition, it is environmentally friendly. Meanwhile, selective laser sintering (SLS) is a powder‐based three‐dimensional (3D) printing technology, providing a novel path to manufacturing polymer composite materials with complex shapes. In this research, flame retardancy of thermoplastic polyurethane (TPU) was enhanced based on LDHs and intumescent flame retardant (IFR). Being prepared by SLS technology. First, TPU composite powders based on LDHs and IFR were obtained using a two‐stage mixing method. Morphology analysis revealed that IFR and LDHs were dispersed uniformly in TPU powder. Subsequently, flame retardant TPU composites were prepared with TPU composite powders using the SLS process under appropriate 3D printing parameters, thereby enabling flame retardant TPU parts to be obtained. With 23 wt% IFR and 2 wt% LDHs filler, the limiting oxygen index of TPU composite was reached to 31.7%, while passing the UL‐94 V‐0 level during the vertical burning test. The cone calorimeter test showed that the heat release rate, smoke production rate, as well as production of carbonic oxides, all decreased significantly following the addition of LDHs. Thermogravimetric analysis indicated that LDHs and IFR were characterized by a favorable synergism effect, with the TPU/23IFR/2LDHs possessing good thermal stability. Char residue analysis, including SEM, energy dispersive X‐ray, Fourier transform infrared, and Raman spectra, further testified that a synergism effect existed between LDHs and IFR in the TPU composite. Overall, in this study the TPU composites fabricated by SLS technology exhibited excellent flame retardant ability.

Improving the safety of oil and gas facilities by improving flame retardants

Introduction. One of the ways to reduce the fire hazard at industrial facilities is the application of intumescent coatings. It is known that intumescent compositions are multicomponent composite materials, whose effectiveness is due to complex chemical transformations of the components of the studied flame retardant exposed to high temperatures. In this regard, the problem of studying the physicochemical processes and thermophysical characteristics of flame retardant thermal expansion materials is in demand and relevant.The purpose of this article is to analyze the thermophysical properties of water- and acrylic compound-based intumescent flame retardants to improve the safety of oil and gas facilities.To accomplish this purpose, the following objectives were attained:studying acrylic dispersion-based intumescent flame retardant materials using methods of thermal analysis;analyzing aqueous dispersion-based intumescent flame retardant materials using methods of thermal analysis;making a comparative analysis of the thermo-oxidative degradation of the studied flame retardant materials.Methods. During the study, thermogravimetric analysis, differential thermogravimetric analysis, differential scanning calorimetry, and quadrupole mass spectrometry were chosen as the main methods.Results. As a result of the studies performed using methods of synchronous thermal analysis of water- and acrylic compound-based intumescent flame retardants, the similarity of ongoing physicochemical processes was identified, including the presence of four main stages of mass loss and a high exothermic effect. This high thermal effect has proven high flammability of the studied flame retardant materials.Conclusions. Following the analysis, the authors have concluded that intumescent flame retardants, containing acrylic vinyl acetate emulsion and aqueous dispersion, begin to lose their performance characteristics, necessary for a flame retardant material, when the temperature reaches approximately ~600 °C.