Limiting Oxygen Index Value Research Articles

Improving flame retardant and electromagnetic interference shielding properties of poly(lactic acid)/poly(ε-caprolactone) composites using catalytic imidazolium modified CNTs and ammonium polyphosphate

The flame retardants and electromagnetic interference (EMI) shielding performance were enhanced by using imidazolium-functionalized polyurethane (IPU) modified multi-walled carbon nanotubes (CNTs) and ammonium polyphosphate (APP) for polylactic acid (PLA)/polycaprolactone (PCL) composites. The PLA/PCL/10APP/8CNT/1.6IPU composite containing 10 wt% APP and 8 wt% imidazolium modified CNTs reached the limiting oxygen index (LOI) value of 30.3 % and passed the V-0 rating in UL-94 tests. Moreover, the peak of the heat release rate (pHRR) and total heat release (THR) for this composite reached around 302 kW/m2 and 64 KJ/m2, which were decreased by 39.1 % and 15.8 % compared with that of PLA/PCL/10APP composite. The improved flame retardancy was attributed to the interplay of catalytic, barrier, and condensed char forming of imidazolium-modified CNTs and APP. IPU catalyzed the charring effect of the polymer matrix during combustion and regulated the migration of more CNTs to disperse at the two-phase interface. The dispersion of imidazolium-modified CNTs and co-continuous phase structure of the composites can establish continuous conductive pathways. The PLA/PCL/APP/CNT/IPU composite obtained a higher conductivity compared to the PLA/PCL/APP/CNT composite and whose EMI SE reached 33.9 dB, which is a promising candidate for next-generation sustainable and protective plastics.

The Effect of Different Diluents and Curing Agents on the Performance of Epoxy Resin-Based Intumescent Flame-Retardant Coatings.

The epoxy resin-based (ESB) intumescent flame-retardant coatings were modified with 1,4-butanediol diglycidyl ether (14BDDE) and butyl glycidyl ether (BGE) as diluents and T403 and 4,4'-diaminodiphenylmethane (DDM) as curing agents, respectively. The effects of different diluents and curing agents on the flame-retardant and mechanical properties, as well as the composition evolution of the coatings, were investigated by using large-plate combustion, the limiting oxygen index (LOI), vertical combustion, a cone calorimeter, X-ray diffraction, FTIR analysis, a N2 adsorption and desorption test, a scanning electron microscope (SEM), a tensile strength test, and a viscosity test. The results showed that the addition of 14BBDE and T403 promoted the oxidation of B4C and the formation of boron-containing glass or ceramics, increased the residual mass of char, densified the surface char layer, and increased the specific surface area of porous residual char. When their dosage was 30%, ESB-1T-3 coating exhibited the most excellent flame-retardant properties. During the 2 h large-plate combustion test, the backside temperature was only 138.72 °C, without any melting pits. In addition, the peak heat release rate (PHRR), total heat release rate (THR), total smoke production (TSP), and peak smoke production (PSPR) were reduced by 13.15%, 13.9%, 5.48%, and 17.45%, respectively, compared to the blank ESB coating. The LOI value reached 33.4%, and the vertical combustion grade was V-0. In addition, the tensile strength of the ESB-1T-3 sample was increased by 10.94% compared to ESB. In contrast, the addition of BGE and DDM promoted the combustion of the coating, affected the ceramic process of the coating, seriously affected the formation of borosilicate glass, and exhibited poor flame retardancy. The backside temperature reached 190.93 °C after 2 h combustion. A unified rule is that as the amount of diluent and curing agent increases, the flame retardancy improves while the mechanical properties decrease. This work provides data support for the preparation and process optimization of resin-based coatings.

Comparison of different flame‐retardant agents for polylactic acid/fiber composites by a film‐stacking method: Flame‐retardant performance and mechanical properties

AbstractIn this investigation, characterization and comparison of the flame retardant performance were conducted for polylactic acid (PLA)/fiber composites featuring the incorporation of different flame retardants (APP, PAPP, and DMH). Based on the results obtained from the Limiting Oxygen Index (LOI) test and cone calorimeter test, it is evident that the intumescent flame retardants (IFR) such as APP and PAPP exhibit better efficacy on improving flame retardancy than DMH. The LOI value of the APP/PLA/F and PAPP/PLA/F composite reaches 35.5% and 27.4%, higher than that of DMH/PLA/F (23.0%). The pk‐HRR of APP/PLA/F and PAPP/PLA/F decreases 27% and 39% compared with PLA/F while the char residue at 500°C was higher than that of DMH/PLA/F (0.3 wt%) with the value of 51.4 and 44.1 wt%. It should be mentioned that the impact strength and tensile strength of PLA/fiber composite incorporating APP surpasses that of PAPP/PLA/F, which is caused by good dispersibility of fabrics among the PLA matrix, coupled with the strengthened interfacial adhesion between the fibers and the polylactic acid matrix. In summary, APP/PLA/F shows the most overall performance.Highlights Properties of PLA/fiber composites with various fire retardants were compared. APP/PLA/F obtained the best overall property while DMH/PLA/F had the worst. APP endows composites with excellent flame retardancy and mechanical property. The LOI value of APP/PLA/F was 35.3%, highest among four composites. Adding APP to PLA/F led to an increase in tensile strength and impact strength.

Bio‐based rigid polyurethane foam composites reinforced with flame retardants: From synthesis to performance evaluation

AbstractThe building and construction industry is under increasing pressure to make insulation materials greener, more sustainable, and less flammable. In this study, sugar beet pulp was liquified under the optimized liquefaction conditions and used as the source of bio‐polyol (SBpol) in the production of bio‐based rigid polyurethane foam (sPUF). In order to improve the flame retardancy, sPUF composites were prepared with the addition of flame retardants; expandable graphite (EG) and/or dimethyl methyl phosphonate (DMMP). The bio‐polyol was used at a fixed ratio of 50 php in sPUF composites whereas the total ratio of flame retardants was fixed at 20 php. The effects of the ratio of EG and/or DMMP on the morphological, physicomechanical, thermal, and flame retardant properties of sPUF composites were evaluated. Although the thermal conductivity values of flame retardant added sPUF composites were increased in comparison to the petroleum‐based foam, the compressive strength values were decreased as the amount of DMMP increased in the flame retardant formulation. Thermogravimetric analysis showed that the onset of decomposition of 20 php DMMP‐containing sPUF composite decreased to 168.3°C. Although the limiting oxygen index (LOI) value of the petroleum‐based PUF was as low as 19.7%, the LOI value of the sPUF/10E/10D foam increased to 24.9% (by about 26%). According to the cone calorimeter results, the peak heat release rate (pHRR) of sPUF was much higher than the petroleum‐based foam. The incorporation of both DMMP and EG could further improve the flame retardant properties. The pHRR value of sPUF/10E/10D was 28.1% lower than that of sPUF. The results have shown that flame retardancy of sPUF composites could be improved by the addition of EG which acts in the condensed phase and DMMP, which acts mainly in the gas phase during burning. Flame retardant incorporated sPUF composites are considered as promising materials for use in insulation applications.

Multifunctional polylactic acid sensing fabric based on biomass flame retardants for intelligent fire early-warning

Today, building materials emit many hazardous gases in the event of a fire, causing great harm to human health and the environment. Therefore, it is of great significance to develop bio-based flame retardant materials and to realize preventive measures to reduce fires or their damage. In this work, we fabricated a novel multifunctional fire early-warning polylactic acid-based fabric (MFR-PBF) by coating MXene nanosheet, phytic acid @ furfurylamine (PA@FA) and ammonium polyphosphate (APP) via an eco-friendly layer-by-layer assembly method. MFR-PBF showed outstanding flame retardancy including a limiting oxygen index value of 35 % and better char formation capacity. More importantly, MFR-PBF exhibited sensitive fire early-warning capability (∼1 s) and excellent cyclic alarm stability (>15 cycles) due to the excellent semiconductor responsiveness (light and heat) and the significant catalytic char formation effect. Moreover, MFR-PBF is comfortable, flexible and strong enough to sew onto firefighter uniform to detect a variety of human motions, which can be monitored in the internet by using a LoRa emitter and a gateway. In addition, the controllable heating performance rendered MFR-PBF as a potential portable heater. This work provides new insights into the preparation and application of intelligent fire early-warning fabrics in the smart fire protection and Internet of Things.

FLAME RETARDANCE AND MECHANICAL PROPERTIES OF EPOXY RESIN: EFFECTS OF ADDED INORGANIC FLAME RETARDANTS

Effects of ammonium polyphosphate (APP) in combination with zinc borate (ZnB), zirconium oxide (ZrO2), and nanoclay on flame retardance and mechanical properties of epoxy resin have been explored. Data listed from UL-94, limiting oxygen index, and cone calorimeter tests convey that the addition of flame retardants improved the fire behavior of epoxy composites significantly. The EP/APP/ZnB/ZrO2 composite having 10% APP, 5% ZnB and 2% ZrO2 by weight attained the best V-0 rating in the UL-94 test, 29.1% limiting oxygen index value and 42.8% decrease in peak heat release rate in cone calorimeter test. A significant decrease of 48.1% in the total smoke release is observed owing to the smoke suppressant action of ZnB/ZrO2. TGA data of epoxy composite reported 25.8 and 36.7% char yield at 600℃ in air and nitrogen atmospheres, respectively. Also, a significant increase in storage modulus is observed for the EP/APP/ZnB/ZrO2 composite loaded with 2 wt% ZrO2 in dynamic mechanical analysis.

Optimization of flame retardancy and mechanical properties of cotton fabrics with d-glucosamine hydrochloride and phosphorus-containing polyol coating

This study investigates the utilization of d-glucosamine hydrochloride (DGH) as a carbon donor in intumescent coating systems and as a nitrogen-based flame retardant, leveraging its ability to release ammonia under elevated temperatures to inhibit combustion. The use of phosphorus-containing polyol (PPO) complements the formulation by promoting the formation of char and further inhibiting combustion. The flame retardancy and thermal stability were assessed by using the Vertical Flame Test (ASTM D6413), Limiting Oxygen Index (LOI) Test and Cone Calorimeter Test. A substantial improvement in the treated fabric was reported when a ratio of 1:2 wt/wt. (DGH:PPO) was used in the coating formulation, reporting an LOI value of 30 % and a reduction in the peak heat release rate (p-HRR) of around 88 % compared to the control sample. Additionally, an improvement in the fabric flexibility was attained when concentrations between 5 wt% to 7.5 wt% of DGH were added.

Synthesis and characterization of non-ionic flame-retardant waterborne polyurethane.

Waterborne polyurethane (WPU) offers many advantages and is widely used in coatings, leathers, adhesives, biomaterials, and other consumer products. However, WPU is highly flammable. Many reactive flame retardants have been developed, but their char formation efficiency is still unsatisfactory, and the melt dripping during combustion has not been effectively suppressed. In this paper, a novel phosphorus-containing flame retardant with dihydroxy groups, (6-((4-hydroxyphenyl)((4-hydroxyphenyl)amino)methyl) dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (PHAD), was successfully synthesized and incorporated into WPU molecular chain as a chain extender, thereby synthesizing a series of non-ionic flame-retardant waterborne polyurethane (NFRWPU) emulsions. The chemical structure of NFRWPU was successfully characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance. With the help of a thermogravimetric analyzer, scanning electron microscope and other instruments, some key performance parameters of NFRWPU in applications were investigated, including: physical, mechanical, and thermal stability and flammability. Some important experimental results include: both the particle size and viscosity of the emulsion increase gradually with increasing PHAD content, and when the PHAD content reaches 12%, the average particle size of emulsion increases to 106.6 nm with a viscosity of 89 mPa s; with the addition of PHAD, the tensile strength of NFRWPU initially increased and then decreased, while the elongation at break showed a continuous downward trend. The maximum tensile strength reached 22.63 MPa, and the minimum elongation at break dropped to 1060%; the addition of PHAD improved the thermal stability and flame retardancy of the film, with the highest limiting oxygen index value reaching 25.6% and the maximum carbon residue increasing to 6.5%. All these results indicate that NFRWPU is a promising flame retardant WPU considering the comprehensive performance.

Preparation and fire resistance modification on tannin-based non-isocyanate polyurethane (NIPU) rigid foams

Non-isocyanate polyurethane (NIPU) as a new type of polyurethane material has become a hot research topic in the polyurethane industry due to its no utilization of toxic isocyanates during the synthesis process. And the developing on recyclable biomass materials has also much attention in the industrial sector, hence the preparation and application of bio-based NIPU has also become a very meaningful study work. So, in this paper, tannin as a biomass material was used to synthesize tannin based non-isocyanate polyurethanes (TNIPU) resin, and then successfully prepared a self-blowing TNIPU foam at room temperature by using formic acid as initiator and glutaraldehyde as cross-linking agent. The compressive strength of this foam as high as 0.8 MPa, which is an excellent compressive performance. Meanwhile it will return to the state before compression when removing the pressure. This indicating that the foam has good toughness. In addition, formic acid can react with the amino groups in TNIPU to form amide substances, and generated enough heat to initiate the foaming process. Glutaraldehyde, as a crosslinking agent, reacts with the amino group in TNIPU to form a network structure system. By scanning electron microscope (SEM) observation of the cell shapes, it can be seen that the foam cells were uniform in size and shape, and the cell pores showed open and closed cells. The limiting oxygen index (LOI) tested value of this TNIPU foam is 24.45 % without any flame retardant added, but compared to the LOI value of polyurethane foam (17 %–19 %), TNIPU foam reveal a better fire resistance. It has a wider application prospect.

Bio-based alginate and Si-, P- and N-containing compounds cooperate toward flame-retardant modification of polyester fabrics

Imparting flame retardancy to polyester fabrics is still a pressing issue for the textile industry. To this end, a composite coating was developed by phosphite, pentamethyldisiloxane, urea and sodium alginate, and then applied together with calcium chloride to prepare flame-retardant polyester fabrics. The optimized polyester fabrics named PF-HUSC exhibited a rough surface with P, Si, N and Ca element distributions, as observed by scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDX). Flame retardancy evaluations showed that the damaged length of PF-HUSC with a limiting oxygen index (LOI) value of 35.3 ± 0.3 % was reduced from the contrastive 17.6 ± 0.4 cm to 4.6 ± 0.2 cm after vertical burning test. Thermogravimetric (TG) test confirmed that PF-HUSC retained a char residue as high as 35.1 % at 700 °C. Cone calorimetry test displayed that the total heat release (THR) and total smoke production (TSP) values of PF-HUSC were reduced to 3.1 MJ/m2 and 1.1 m2, respectively, as compared to those of pure polyester fabrics. More importantly, PF-HUSC still exhibited higher LOI value than that of pure polyester fabrics after 25 washing cycles. Hence, the coating scheme is considered as a new method to expand the preparation of flame-retardant polyester fabrics.

Phosphorus‐containing benzoxazine modified epoxy resin: High flame retardancy, low dielectric, and low water absorption

AbstractA phosphorous‐containing benzoxazine, (3‐(4‐hydroxyphenyl)‐3,4‐dihydro‐2H‐benzo[e][1,3]oxazin‐4‐yl)diphenylphosphine oxide (DPOBH), was synthesized and used as flame retardant and co‐curing agent in the presence of 4,4′‐diaminodiphenylsulfone (DDS) for diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin. The flame retardancy, thermal stability, Tg, dielectric properties, and water absorption properties of epoxy resins (EP) were investigated and compared. The incorporation of DPOBH results in ca. 40%–45% increase of limiting oxygen index (LOI) values. UL‐94 V‐0 rating could be achieved for EP/DPOBH1.2 sample with the LOI value of 35.1%. Compared with EP, ca. 47% decrease of peak heat release rate (PHRR) could be obtained for EP/DPOBH1.2. According to the results of cone calorimetry tests (CCT), DPOBH could play roles in both gas and condensed phases. Moreover, the incorporation of DPOBH could reduce the water absorption rate, dielectric constant, and dielectric loss. All results suggest that DPOBH is a type of flame retardant suitable for EP used in electronic fields.

Synergistic Effects of 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-Based Derivative and Modified Sepiolite on Flame-Retarded Poly (Ethylene Oxide)-Poly (Butylene Adipate-Co-Terephthalate) Composites.

A 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-based derivative (PN-DOPO) combined with aluminium phosphates-coated sepiolite (Sep@AlPO4) was used to improve the flame retardance, thermal stability and mechanical performances of poly (ethylene oxide) (PEO)/poly (butylene adipate-co-terephthalate) (PBAT) blends. The synergistic effects of PN-DOPO and Sep@AlPO4 on flame-retarded PEO/PBAT composites were systematically discussed. Results indicated that introducing 5 wt% Sep@AlPO4 with 10 wt% PN-DOPO into PEO/PBAT achieved a V-1 rating for the UL-94 test and increased the limiting oxygen index value to 23.7%. Moreover, the peak heat release rate (p-HRR), average HRR and total heat release values of PEO/PBAT/PN10%/Sep5% composites decreased by 35.6%, 11.0% and 23.0% compared with those of PEO/PBAT, respectively. Thermogravimetric analysis (TGA) results confirmed that PN-DOPO/Sep@AlPO4 enhanced the initial thermal stability and char yield of PEO/PBAT matrix, and TGA/Fourier transform infrared spectrometry results revealed that the composites exhibited the characteristic absorption peaks of phosphorous-containing groups and an increase in gas-phase volatiles during thermal degradation. The morphological structures of the residues indicated that PN-DOPO and Sep@AlPO4 mixtures produced a more dense and continuous char layer on the composite surface during burning. Rheological behaviour revealed that higher complex viscosity and modulus values of PEO/PBAT/PN-DOPO/Sep@AlPO4 sample could also promote the crosslinking network structure of condensed phases during combustion. Furthermore, the PEO/PBAT/PN-DOPO/Sep@AlPO4 composites exhibited superior elongation at break and flexural performance than the PEO/PBAT system. All results demonstrated that the PEO/PBAT system modified with PN-DOPO/Sep@AlPO4 showed remarkable flame retardance, and improved thermal stability and mechanical properties, indicating its potential application in areas requiring fire safety.

A novel bio‐based charcoal‐forming agent based on chitosan and phytate@Mg to improve the flame retardancy of poly(lactic acid)

AbstractA novel bio‐based carbon forming agent (Mg@PA‐CS) containing P and N elements was were synthesized using the complexation characteristics of chitosan (CS) and phytate (PA). The flame retardant behavior of poly(lactic acid) (PLA)/Mg@PA‐CS/APP composites (addition of 20 wt% of different ratios of Mg@PA‐CS and APP to polylactic acid composites) were investigated by the limiting oxygen index (LOI), vertical burning test (UL‐94), cone calorimetry test (CCT), and thermogravimetric analysis (TGA). Due to the biphasic flame retardant and synergistic effect, since the 20 wt% flame retardant system (Mg@PA‐CS:APP = 1:2), PLA composites passed the UL‐94 test V‐0 rating, reached 34% LOI value. The peak heat release rate (PHRR) and total heat release rate (THR) were reduced to 1/2 of the pure PLA, char residue could be as high as 11.49% at 800°C. Moreover, the flame‐retardant mechanism of PLA composites during thermal decomposition was analyzed using a scanning electron microscope (SEM) and the coupling techniques of TGA linked with FT‐IR (TG‐FTIR).

Synthesis of a graft‐functionalized flame retardant based on DOPO and its application on the surface of terylene/cotton fabrics

AbstractTerylene/cotton (TC) fabrics are widely used in the textile industry because of their superior softness and durability. In addition, its high combustibility leads to a great safety hazard, and the droplet phenomenon during combustion is particularly serious. 9‐oxa‐10‐phospha‐9,10‐dihydrophenanthrene 10‐oxide (DOPO) and its derivatives are frequently used as eco‐friendly flame retardants in large quantities in substrates. It would be difficult to apply to the surface of the fabric, and the addition of large amounts would lead to a decrease in the mechanical properties. Therefore, it is necessary to design a strategy for graft‐functionalized flame retardants that can be applied to surfaces. Here, this study reported a washing‐fastness flame‐retardant coating (DOPO‐p) synthesized from DOPO and p‐hydroxybenzaldehyde (p‐HBA), coatings with a low weight growth and high flame‐retardant efficiency are prepared by the strategy of dissolving with organic solvents. Water and dry‐cleaning tests showed excellent washing fastness of TC fabrics. In the limiting oxygen index (LOI) test, the finished fabric achieved a LOI value of 22.9%. In the cone calorimetry test, the peak of heat release rate of the finished fabric is decreased by 27% and CO2 release is reduced by 29% when the coating weight growth was only 3.3 wt%.

A durable phosphorous-based flame retardant containing double reactive groups for cotton fabrics

Ammonium acryloyl phosphite (AAP) flame retardant with multiple reactive functional groups has been synthesized for use in cotton textiles. Nuclear magnetic resonance was utilized to analyze the structure of AAP flame retardant. The scanning electron microscopy images indicated that some flame retardants penetrated the amorphous region of cotton fibres. The energy-dispersive X-ray and Fourier transform infrared (FTIR) spectroscopy spectra suggested that AAP flame retardant was grafted with cellulose through forming the -N-P(=O)-O-C- connection. The laundering cycles (LCs), limiting oxygen index (LOI), cone calorimetry, and vertical flame test (VFT) suggested that AAP-treated cotton (CF/AAP) possessed exceptional flame retardance and durability. The CF/AAP3 demonstrated an initial LOI value of 47.2 %, which remained at 40.7 % even after undergoing 50 LCs following the washing standard (AATCC 61–2013 3A). The thermogravimetric and infrared spectroscopy, thermogravimetric, and VFT analyses showed that AAP grafting groups underwent a condensed-phase flame retardance mechanism. The X-ray diffraction patterns indicated that the AAP flame retardant affected the diffraction peak structure of cotton fibres crystal a little during the finishing process. After finishing, the cotton fabrics retained their breaking strength and softness effectively. The overall results indicated that incorporating reactive groups such as -N-P(=O)-(ONH4)2 and CH2CH- into flame retardants could reinforce the durability of flame-retardant cotton fabrics.

Melamine resin coordinated cobalt@piperazine pyrophosphate microcapsule: An innovative strategy for imparting long-lasting fire safety to rigid polyurethane foams

The persistent challenge of maintaining fire safety in flame retardant modified rigid polyurethane foams (RPUF) under humid conditions continues to be a concern. To address this challenge, a microcapsule named MF-Co@PAPP has synthesized, composed of melamine resin (MF, shell) and piperazine pyrophosphate (PAPP, core). This microcapsule was developed to enhance the long-lasting flame retardancy and smoke suppression of RPUF. These composites demonstrated a significant reduction in total heat release and total smoke release compared to pure samples, with decreases of 44% and 29%, respectively. The MF-Co@PAPP facilitated the carbonization process of RPUF, leading to the formation of a more stable char layer. The RPUF/MF-Co@PAPP composites exhibited the highest limiting oxygen index values, even after a 14-day immersion in water. This study introduces a target-driven design approach to enhance the fire safety of RPUF, offering inspiration for future development of tailored flame retardants.

Preparation and flame retardant properties of organic montmorillonite synergistic intumescent flame retardant polypropylene

Ammonium polyphosphate (APP) and aluminium diethylphosphonate (ADP) were mixed according to the mass ratio of 4:1, compounded with dipentaerythritol (DPER) to construct a novel intumescent flame retardant (IFR), and organo-montmorillonite (OMMT) as a synergistic flame retardant, then melt blended to prepare intumescent flame retardant polypropylene (PP) composites. The flame retardancy, thermal stability, and mechanical properties of flame retardant polypropylene composites were examined using the limiting oxygen index (LOI), vertical combustion test, thermogravimetric analysis, and cone calorimetry test. The results showed that the LOI value of the flame retardant composite PP3 reached 31.3%, UL-94 reached V-0 level, the peak heat release rate (pHRR) and the total heat release (THR) decreased by 87.8% and 33.7%, respectively, compared with the original sample of PP, and the break elongation increased by 216.4% compared with that of the sample PP1 without the addition of OMMT. The findings demonstrated that adding OMMT to IFR in the right dosage can have a positive synergistic flame retardant impact.

Ionic liquids modified MXene as a flame retardant synergist for the unsaturated polyester resin

AbstractI‐MXene with excellent dispersibility was successfully prepared using the chemical grafting method with 1‐butyl‐3‐methylimidazole hexafluorophosphate ([BMIM]PF6) onto MXene. It was characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM), which was added to unsaturated polyester resin (UPR) as a synergistic agent, combined with ammonium polyphosphate (APP) to improve the flame retardancy of composites. Tensile strength of the composites was measured using the electronic universal material testing machine. The results showed that the incorporation of I‐MXene was able to increase the tensile strength and elongation at break of the composites. The flame retardancy and thermal stability of the composites were investigated through limiting oxygen index (LOI), cone calorimeter test (CCT), TG and Fourier‐infrared spectroscopy (FT‐IR). The experimental data showed that the LOI values of I‐MXene/APP/UPR composites increased to 29.1%, complying with UL‐94V‐0 rating. Its peak heat release rate (pHRR) and total heat release (THR) were 19.35% and 16.35% lower than those of APP/UPR composites, and the total smoke production (TSP) was reduced by 10.78%. When heated to 800°C, the amount of residual carbon increased by 7.71%. The catalytic effect of I‐MXene contributed to the formation of a compact and expanded carbon layer, resulting in further suppression of heat and smoke release.Highlights A new type of modified MXene is obtained. It has good dispersivity and synergistic effects. It has good flame retardancy and smoke suppression effects.

Combination of bio-based tannic acid, sophora flower extract and metal salts: A facile route towards improving durable flame retardancy and UV resistance of silk fabrics

Environmental engineering placed green demands on the functional modification of textiles. Here, the combination of bio-based tannic acid, sophora flower extract and metal salts was used to manufacture silk fabrics with flame retardancy and UV resistance via a facile impregnation strategy. With different metal salts treated, the modified silk fabrics named silk/TA/SFE-TE, silk/TA/SFE-Fe and silk/TA/SFE-Cu achieved self-extinguishing in the vertical burning test, with limiting oxygen index values of 31.7 ± 0.4 %, 30.2 ± 0.2 % and 30.9 ± 0.3 %, respectively. In the cone calorimetry test, the peak heat release rate values of the three silk fabrics modified with metal salts were all significantly suppressed, and the total smoke production values of silk/TA/SFE-TE and silk/TA/SFE-Fe were reduced from the original 0.178 m2 to 0.126 m2 and 0.138 m2, respectively. Furthermore, silk/TA/SFE-TE, silk/TA/SFE-Fe and silk/TA/SFE-Cu displayed high ultraviolet protection factor values and thus had good UV resistance, owing to the presence of tannic acid and sophora flower extract. Most importantly, the flame retardancy and UV resistance of the three silk fabrics modified with metal salts were still superior to those of the original silk fabrics after 30 washing cycles. In short, this facile route for the preparation of functionalized silk fabrics provides a novel idea for the development of advanced textiles.

The synergistic flame retardant effect of biobased phytic acid arginine salt and hydroxylated montmorillonite in polybutylenes succinate

In this research, hydroxylated nano montmorillonite (DK2) was used as a synergistic agent in combination with phytic acid arginine salt (PaArg). The flame retardancy and mechanical properties of PBS with different amounts of PaArg and DK2 were studied. Furthermore, the synergistic effect and mechanism of PaArg and DK2 in PBS were explored. The results showed that adding 23.5 % PaArg and 1.5 % DK2 increased the limiting oxygen index value (LOI) of the composite to 31.4 %, passing the UL 94 V-0 rating. By adding 25 % PaArg alone, the LOI value of the composite is 26.2 %, and the vertical burning test result is only V-2 rating. The cone calorimetry test results show that the peak heat release rate, total heat release rate, and total smoke production of PBS/23.5 % PaArg/1.5 % DK2 composite are 55.8 %, 17.1 %, and 44.7 % lower than those of PBS/25 % PaArg composite, respectively. All the results showed that PaArg and DK2 exhibited good synergistic flame retardancy in PBS. In addition, the impact strength and bending strength test results show that the impact strength and bending strength of PBS/23.5 %PaArg/1.5 %DK2 composite are higher than those of PBS/25%PaArg composite. This work improved the flame retardant efficiency of biobased flame retardants in PBS.