Char Residue Research Articles

Synthesis and Viscoelastic Properties of Polycaprolactone/Polyvinylidene Fluoride/Nanohydroxyapatite Composite Scaffolds

AbstractObtaining a polymer nanocomposite with optimum viscoelastic, thermal, and biocompatibility properties is the main objective when designing nanocomposite systems with potential applications in tissue engineering. For this purpose, a blend of Polycaprolactone (PCL) and Polyvinylidene fluoride (PVDF) in an 85/15 weight ratio, along with a nanocomposite reinforced by nanohydroxyapatite (nHA) particles, is fabricated using a solution casting method in a mold. The impact of nHA content on crystallinity, viscoelastic properties, thermal stability, and the properties–structure relationship of nanocomposites is evaluated using scanning electron microscopy (SEM). Dynamic mechanical thermal (DMTA) analysis is used to determine the William–Landel–Ferry (WLF) constants and the effect of nHA on the nanocomposite's viscoelastic behavior. The PCL/15PVDF/0.5 wt% nHA exhibits the maximum thermal stability (40% residual char value) and 95% increase in storage modulus at 90 °C (rubbery region) in comparison with PCL/15PVDF blend. Water contact angle (WCA) and biocompatibility tests are conducted on the PCL/15PVDF blend and nanocomposite scaffolds to design appropriate nanocomposite systems with potential applications in tissue engineering. The high hydrophilic properties are assigned to PCL/15PVDF/0.5 wt% nHA with a WCA of 67.5°. Finally, in vitro cell culture confirmed 0.5 wt% nHA significantly improves cell adhesion and cytotoxicity with MG‐63 cells.

Development of carbon composite coatings for fire retardancy and electromagnetic interference shielding

This study has effectively showcased the feasibility of employing a carbon composite coatings, comprised of various carbon nanomaterials including carbon nanodots, carbon nanotubes, and graphene nanosheets integrated within a matrix of sodium metasilicate + gypsum, for applications in both flame retardancy and electromagnetic interference (EMI) shielding. The resulting carbon composite coatings, when applied to wooden substrates, demonstrate remarkable fireproof performance, as validated through fire injections at temperatures as high as 1050 °C. This underscores the pivotal role plays by the design of carbon composites in suppressing flame propagation and charring, leading to reduced carbonization areas. Thermogravimetric analysis further reveals that the carbon composite coating generates substantial char residue at 800 °C, signifying enhanced thermal insulating properties derived from the robust composite carbon architecture. Furthermore, the carbon composite coatings show a significant decrease in electromagnetic fields (electric field around 50 % and magnetic field around 44 %), indicating their efficient EMI shielding properties. This improved EMI shielding performance may be due to the deliberate insertion of CNs into the composite materials, which fine-tunes resistance and dielectric loss while allowing effective electromagnetic absorption by the carbon composites. The breakthroughs made in flame retardancy and EMI shielding highlight carbon composites as superior strengthens to flame-retardant and EMI-absorbing building coatings.

A Novel Intumescent MCA-Modified Sodium Silicate/Acrylic Flame-Retardant Coating to Improve the Flame Retardancy of Wood.

The incompatibility between inorganic flame retardants and organic acrylic coatings represents a significant challenge that requires resolution. This work selected environmentally friendly organic aqueous acrylic coatings as the substrate, sodium silicate hydrate as the inorganic flame retardant, and melamine cyanurate (MCA) as the flame-retardant modifier and the flame-retardant co-modifier, with the objective of improving the dispersion and flame-retardant properties of sodium silicate hydrate in the aqueous acrylic coatings. Subsequently, the sodium silicate/MCA/waterborne acrylic acid flame-retardant coating was prepared. The flame-retardant treatment was then applied to poplar veneer in order to create a flame-retardant poplar veneer. The dispersion of the flame-retardant coating was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), and X-ray diffractometry (XRD). Furthermore, the flame-retardant properties of the flame-retardant poplar veneer were analyzed by thermogravimetry (TG), limiting oxygen index (LOI), and cone calorimeter. The results demonstrated that the MCA-modified sodium silicate flame retardant was well dispersed in aqueous acrylic coatings. The results of the flame-retardant properties of the poplar veneer indicated that the ignition time of the 9% flame retardant-treated poplar veneer was increased by 122.7%, the limiting oxygen index value was increased by 43.0%, and the peak heat release rate (pHRR), the peak total heat release rate (pTHR), and the peak mass loss rate were decreased by 19.9%, 10.8%, and 27.2%, respectively, in comparison to the non-flame retardant-treated poplar veneer. Furthermore, the residual char mass increased by 14.4%, and the residual char exhibited enhanced thickness, density, and regularity. The results demonstrated that MCA was an effective promoter of sodium silicate dispersion in acrylic coatings. Furthermore, the sodium silicate/MCA/waterborne acrylic flame-retardant coating significantly enhance the flame retardancy of wood, and its flame retardant mechanism was consistent with the synergistic silicone-nitrogen expansion flame-retardant mechanism. This work presents a novel approach to enhancing the dispersion of inorganic flame retardants in organic coatings, offering a valuable contribution to the advancement of research and application in the domains of innovative flame retardant coatings and flame retardant wood.

Multifunctional polyester-cotton fabrics with excellent flame retardancy, superhydrophobicity, antibacterial property and UV resistance

In this study, multifunctional polyester-cotton fabrics (PTCO) were constructed by gradually assembling polyethyleneimine phenyl phosphonate (POI) and different hydrophobic agents, respectively. The effect of different hydrophobic agents including tetraethyl orthosilicate, perfluorooctyltriethoxysilane (PFDTES), and hexadecyltrimethoxysilane on the thermal stability, flame retardancy, hydrophobic property, UV resistance and antibacterial property of PTCO/POI was investigated in detail. PTCO/POI-SiF had better flame retardancy due to the flame-retardant effect of PFDTES and POI, and the limiting oxygen index increased from 29.8 % to 31.2 %. The thermal oxidation stability of PTCO/POI-SiH and PTCO/POI-SiF was significantly improved in high temperatures, and the char residues at 700 °C were increased from 4.1 % to 7.6 % and 7.4 %. And PTCO/POI-SiH and PTCO/POI-SiF had excellent superhydrophobic properties with water contact angles of 151° and 162° and sliding angles of 4° and 3°. The ultraviolet protection factors of them were increased to 56.9 and 63.3, respectively, which had a good UV resistance. And both PTCO/POI-SiH and PTCO/POI-SiF had excellent antibacterial effects for E. coli and S. aureus. The breaking force, whiteness and moisture permeability of the finished fabrics had not been changed. Therefore, it is believed that PTCO/POI-SiH and PTCO/POI-SiF are promising for application in multifunctional fabrics.

A thermogravimetric analysis of residual char formation by gilsonite-filled, polyfurfuryl alcohol composites: acid treatment of gilsonite

Gilsonite (GLS), a natural bitumen containing a considerable amount of asphaltenes, is expected to leave heavy char after pyrolysis; however, its high potential as an efficient filler to enhance the thermal properties of composite materials is surprisingly neglected throughout the literature. On the other hand, polyfurfuryl alcohol (PFA) has attracted much attention as a thermosetting resin due to its excellent char-leaving characteristics, the renewable nature of the monomer(s), and high accessibility at an affordable cost. This study aimed to investigate the thermal stability and char-forming performance of composites made of a PFA resin matrix filled with chemically modified GLS. To modify the ash and sulfur contents of GLS, the nitric acid leaching process was performed according to a D-optimal experimental design approach. The nitric acid concentration (10, 20, and 30 wt.%), treatment time (30, 75, and 120 min), and reaction temperature (30 °C, 50 °C, and 70 °C) were set as the input variables. The morphology (SEM), chemical structure (FTIR), thermal stability (TGA), sulfur content, and ash content of the GLS particles were characterized before and after acid treatment. Thermogravimetric analysis revealed the lowest ash content for GLS after treatment with 10 wt.% acid conc. at 75 °C for 75 min. The nitric acid concentration, reaction temperature, and time were the most influential parameters for improving the ash content of GLS according to their order of appearance. In addition, the inorganic form of sulfur, pyrite, was separated through the acid leaching process. Then, the PFA resin matrix was filled with modified GLS particles at different weight percentages (5, 10, 15, and 20 wt.%) and cured in the presence of an acid catalyst. The thermal stability of the PFA resin was negatively affected by the presence of GLS, probably due to oxidation reactions and disruption of the integrity of the resin structure.

High fire-safety epoxy thermosets with a macromolecular phosphorus-nitrogen containing flame retardant at a low loading

In this article, a macromolecular phosphorus-nitrogen containing flame retardant defined as PDPSB was incorporated into epoxy resins (EP). The fire safety, flame-retardant mechanism and mechanical properties of EP/PDPSB thermosets were systematically investigated. The EP-5 sheets containing 5 wt% PDPSB passed V-0 level in the vertical burning tests (UL-94) with a high limiting oxygen index (LOI) value of 30.9%. The results of cone calorimeter tests (CCT) revealed that both the emission of heat and smoke for EP/PDPSB thermosets was substantially suppressed. Compared to pure EP, the values for peak of heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) of EP-5 were dropped by 19.4%, 31.5% and 33.0%, respectively. Remarkably, the char residue mass of EP-5 was enhanced by 87.7%. The maximum smoke density (Ds, max) was slashed by 18.9%. Furthermore, the tensile, flexural and charpy impact strength of EP-5 were maintained to 97.3%, 95.1% and 86.9%, respectively. The investigation of flame-retardant mechanism demonstrated PDPSB exerted flame retardant effect both in condensed and gaseous phase by the scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectra (XPS), laser Raman spectra (LRS) and thermogravimetric-Fourier transform infrared spectroscopy (TG-FTIR). As PDPSB was a one-component multifunctional additive renowned for its exceptional efficiency, it was anticipated to facilitate the advancement of high-performance epoxy thermosets via researching on EP/PDPSB thermosets.

Functionalized Zr‐MOFs for Enhancing Flame Retardancy and Smoke Suppression Performance on TPU

AbstractMetal‐Organic Framework (MOF) materials can be used as flame‐retardants and smoke suppressants for polymers. As a MOF material, UIO‐66(Zr) possesses higher thermal stability and controllable pore size. In this paper, UIO‐66(Zr), NH2‐UIO‐66(Zr), and SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) was fabricated to improve the flame retardant and smoke suppression performance of thermoplastic polyurethanes (TPU). The experimental results show that compared with neat TPU (LOI value 19.1 %), 2 % usage of UIO‐66(Zr) and NH2‐UIO‐66(Zr) can endow TPU with 26 % LOI value and vertical combustion rating of V‐1. Moreover, SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) provide TPU with above 27.8 % LOI value and vertical combustion rating of V‐0. Meanwhile, the CCT results showed that the peak heat release rate and total heat release of TPU‐U5 (added 2 % GO‐modified NH2‐UIO‐66(Zr)) are 299.52 Kw ⋅ m−2 and 68.21 MJ m−2, much lower than that of neat TPU, which are 1180.05 Kw ⋅ m−2and 104.87 MJ m−2, respectively. The TGA, char residue EDS and XRD analysis show that SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr) could generate zirconium metal oxide during the combustion process, which acts as a physical barrier to prevent the TPU matrix by promoting the generation of carbonization layer. The zirconium metal oxide and carbonization layer also can confine flammable gases, which can delay the ignition time and hinder the overflow of gas. In addition, NH2‐UIO‐66(Zr) could generate non‐flammable N2 diluting the concentration of flammable gases. The mechanical properties of TPU composites can maintain more than 87 % of the neat TPU after the addition of 2 % SiO2, MWCNT, and GO functionalized NH2‐UIO‐66(Zr). These results indicate that functionalized Zr‐MOFs composites could act as excellent flame‐retardants in TPU.

Self-assembled coatings with durable flame retardancy for EPS foam

Layer by layer (LBL) self-assembly coatings upon expandable polystyrene (EPS) surface play an important role in improving its flame retardancy. However, a large number of layers is needed to achieve a satisfied fire performance, and the coatings are difficult to adhere on the inert EPS surface, resulting in the poor durability. In this work, the surface of EPS was activated by ultraviolet ozone (UVO) with the appearance of oxygen contained groups, then a LBL coating with only two bilayers (branched polyethyleneimine (BPEI)-kaolinite (kaol)-BPEI-diethylene triamine penta (methylene phosphonic acid)) was covalently connected on the EPS surface. Compared with neat EPS, the obtained E-K5D30 sample increased the value of limiting oxygen index (LOI) from 18.8 % to 37.7 %, improved the ignition time from 59 s to 95 s, reduced the peak heat release rate (pHRR) value from 282.0 kW/m2 to 220.9 kW/m2, and enhanced the char residues from 6.3 % to 32.3 % after the combustion. Moreover, an ultraviolet (UV) curing layer with P/N elements was prepared upon E-K5D30 sample to maximize the flame retardant durability. A novel amino-intercalated kaol was used to play a smoke suppression role. The results showed that E-K*5D30-P8N3 sample further increased the LOI to 39.2 %. Even after 12 h washing, the E-K*5D30-P8N3 sample exhibited a slight LOI reduction to 37.8 %, and fire performance index (FPI) value of 0.405 m2·s/kW, showing the successful construction of coatings with good fire safety and flame retardant durability.

Frequency-Dependent Dielectric Permittivity and Water Permeability in Ordered Mesoporous Silica-Grafted Fluorinated Polyimides.

Polymers with a low dielectric constant (Dk) are promising materials for high-speed communication networks, which demand exceptional thermal stability, ultralow Dk and dissipation factor, and minimum moisture absorption. In this paper, we prepared a series of novel low-Dk polyimide films containing an MCM-41-type amino-functionalized mesoporous silica (AMS) via in situ polymerization and subsequent thermal imidization and investigated their morphologies, thermal properties, frequency-dependent dielectric behaviors, and water permeabilities. Incorporating 6 wt.% AMS reduced the Dk at 1 MHz from 2.91 of the pristine fluorinated polyimide (FPI) to 2.67 of the AMS-grafted FPI (FPI-g-AMS), attributed to the free volume and low polarizability of fluorine moieties in the backbone and the incorporation of air voids within the mesoporous AMS particles. The FPI-g-AMS films presented a stable dissipation factor across a wide frequency range. Introducing a silane coupling agent increased the hydrophobicity of AMS surfaces, which inhibited the approaching of the water molecules, avoiding the hydrolysis of Si-O-Si bonds of the AMS pore walls. The increased tortuosity caused by the AMS particles also reduced water permeability. All the FPI-g-AMS films displayed excellent thermooxidative/thermomechanical stability, including a high 5% weight loss temperature (>531 °C), char residue at 800 °C (>51%), and glass transition temperature (>300 °C).

Facile preparation and application of ternary hybrid of POSS/DOPO/F macromolecular as highly-effective epoxy modifier

In order to easily achieve the multifunctionality of epoxy resin, this paper designs and synthesizes a ternary hybrid copolymer containing POSS/DOPO/F. This method not only facile combines POSS with DOPO, but also introduces F element to further reduce the surface energy of epoxy composite materials. Research has found that the POSS/DOPO/F ternary hybrid copolymer can achieve a UL-94 flame retardant rating of V-0 with just 5 wt% of the modifier, and the limit oxygen index of epoxy composites is 32% (23.1% higher than pure epoxy resin). The residual char after combustion is denser and the carbonization rate is higher. Furthermore, we conducted an in-depth analysis of the flame retardant mechanism of POSS/DOPO/F ternary hybrid copolymer epoxy composites using TGA-FTIR technology and EDS. In addition, the introduction of ternary hybrid polymers effectively improves the mechanical properties of epoxy composite materials and significantly reduces the surface energy of the composite materials.

A novel conductive nano-based flame-retardant coating: Preparation and its application for cotton fabric

A novel coating consisting of polyvinyl alcohol (PVA), folic acid (FA), and polyaniline nanoparticles (PANI) was applied to cotton fabric (CF) to enhance its flame retardancy, thermal stability, and electrical properties. The results from different flammability tests indicated a synergistic effect between FA and PANI to enhance the flame retardancy of CF at low weight gain percentages. The rate of burning data displayed that the new coating stopped the flame propagation in CF. The limiting oxygen index (LOI) of CF increased from 18 % to 26.9 % in the sample coated with PVA/FA/PANI. The new coating improved the thermal stability and char residue formation of CF at high temperatures. Moreover, it succeeded in decreasing the smoke density, and the production of toxic gases during treated CF combustion. The tensile strength and colour strength of CF were improved after the addition of PVA/FA/PANI coating. The surface resistance and the AC conductivity of the coated CF were measured. The addition of PVA/FA/PANI to CF increased the AC electrical conductivity due to the growth of conductive paths between the CF and the new coating material.

Mechanical and adhesive properties of RTV silicone rubber blended with silicone polyurethane modified epoxy resin

To enhance mechanical, adhesive, and thermal properties of Room Temperature Vulcanized (RTV) silicone rubber, a silicon-containing polyurethane/epoxy resin modifier (ESiPU) was developed. A three-phase system of polyurethane/epoxy resin/silicone rubber was prepared through blending, modification, and co-curing. FT-IR and 1H-NMR were employed to characterize the chemical structure of ESiPU. Microscopic analysis revealed improved compatibility between modified epoxy resin and silicone rubber. Mechanical testing showed significant enhancements in tensile strength, elongation at break, and adhesive strength, with RTV-20phr exhibiting increases of 236, 266, and 259%, respectively. Thermogravimetric analysis indicated higher initial decomposition temperature compared to pure RTV. At the same time, the char residue at 800 °C increased to 8.67%. TG-IR analysis demonstrated ESiPU’s ability to delay thermal degradation. Contact angle test confirmed improved hydrophobicity. Overall, the developed silicone rubber system exhibits promising mechanical and thermal properties, suggesting potential for aerospace heat protection applications.

Eco-friendly, efficient and durable flame retardant lyocell fabrics prepared via a feasible grafting of taurine

Inspired by alkaline oxidative degradation of cellulose, a novel eco-friendly scenario for preparation of flame retardant lyocell fabrics was developed by the chemical grafting of biomass taurine. FTIR and XPS results verified the establishment of a covalent bond between taurine and lyocell fabric. Thermogravimetric analysis and vertical combustion test proved the improved char-forming ability and flame resistance of the grafted fabric. The THR and pHRR of the finished fabric were successfully reduced by 67.3 % and 89.9 % respectively after modification. In addition, after 50 wash cycles, the LOI value of the grafted fabric was maintained at 29.5 %. The gas-phase and condensed-phase flame retardant mechanisms were proposed from the analyses of pyrolysis gaseous products and char residue of the modified fabrics. The modification process is simple to operate and provides a feasible green flame retardant strategy for flammable lyocell fabrics.

Thermal stability and flame retardancy of cotton fabric coated with PVA-boric acid-cellulose nanofiber hybrid: Role of chemical interactions

An ecofriendly, polymer coating to impart fire retardancy to cotton fabric is introduced in the current study. Polyvinyl alcohol-boric acid-cellulose nanofiber (PVA-BA-CNF) hybrid coating with different compositions of boric acid and 2.5 wt% cellulose nanofiber (CNF) were coated over cotton fabric. The CNF used in the study was extracted from onion skin, an agricultural waste. The nanofibrous morphology of extracted CNF was confirmed from Transmission Electron Microscopic (TEM) images. The surface morphology of treated cotton was compared with that of bare cotton using scanning electron microscope (SEM) and optical microscope (OM). The dispersion of the coating formulation over the cotton fabric and the porosity after coating were confirmed. Chemical interactions developed in the coating formulations were characterized by Fourier transform infrared spectroscopy (FTIR). In addition to hydrogen bonding established between the coating formulation and cotton fabric, the existence of chemical bonding (B-O-C) between the components of the coating formulation and between the crosslinked coating and cotton fabric has been evident. The thermal stability of the coated cotton fabrics was evaluated using thermogravimetric analysis (TGA). The high char residue recorded for PVA-BA-CNF coated fabric, especially with 17phr BA content indicated the efficiency of crosslinked coating matrix in enhancing the thermal stability of the cotton fabric. The coated cotton degraded in two stages and with a different degradation kinetics than that of uncoated cotton fabric. Flame retardant performance of the coated fabric has been evaluated by vertical flammability tests and pyrolysis combustion flow calorimetry (PCFC). The peak temperature of heat release rate (pHRR) showed 32 % reduction for PVA-BA-CNF coating with 17phr BA content compared with pure cotton indicating a decreasing flame spreading rate due to the inhibition of oxygen diffusion by chemically crosslinked PVA-BA-CNF coating.

Iron ore reduction using agricultural waste biochar with different carbon to oxygen ratios

BackgroundDuring iron production ferric oxide is reduced to iron, with carbon used as the reducing agent. Traditionally, coke was used as the carbon component, which became a crucial raw material in the iron and steel industry after the industrial revolution. However, coke is the most significant contributor to CO2 emissions due to the source of heat and reducing agent. Thus, shifting to low carbon energy systems, such as those based on biomass, is challenging. Therefore, in this study, we employed the mushroom cultivation residue char (MCRC) as a reducing agent to investigate the feasibility of replacing coke in the production of metallic iron. MethodsAfter carbonization at different temperatures (500 °C, 700 °C and 900 °C), mushroom cultivation residue char (MCRC), were used as a reducing agent in the production of metallic iron. To create the composite pellets, the MCRCs were individually mixed with iron ore at different carbon to oxygen ratios (C/O) (0.7, 0.8 and 0.9) and 1 % of bentonite. The reduction process was undergoing in the electric muffle furnace at different high temperatures (1,000 °C, 1,200 °C and 1,300 °C) to investigate the biomass C/O ratios required for efficient iron production. Significant findingsThe results show that 0.8 was selected as the optimal C/O ratio for mushroom cultivation residue char (MCRC) to be used as a reducing agent. Its metallization rate can reach 31.99 %. The results also indicate that the carbon and volatiles in MCRC play a key role in iron making production using such biochar pellets. In conclusion, MCRC can be used as a reducing agent to increase the sustainability of iron production and reduce agricultural waste.

Preparation and properties investigation of flame‐retardant rigid polyurethane foam composites based on alkylphosphate oligomer

AbstractIn this work, FR‐PNX, an alkylphosphate oligomer was introduced into rigid polyurethane foam (RPUF) to fabricate FR‐PNX/RPUF composites. The flame retardancy, thermal stability, and combustion properties of composites were investigated by limiting oxygen index (LOI), thermogravimetric (TG), microcalorimetry (MCC), scanning electron microscopy (SEM), et al. The flame retardancy tests demonstrated that the incorporation of 50 phr of FR‐PNX yielded composites that the highest LOI of 23.6 vol% and achieved a V‐0 rating in the UL‐94 test. TG results indicated that FR‐PNX promoted the decomposition of FR‐RPUF in the process, but enhanced the high‐temperature stability of the composites. MCC analyses revealed that the addition of FR‐PNX suppressed the heat release during combustion, and FR‐PNX50/RPUF exhibited the lowest total heat release of 17.3 MJ/m2, a 35% reduction compared to the pure sample. Moreover, the peak heat release rate was decreased to 83.1 W/g, representing a 46.9% reduction compared to pure RPUF. SEM and Raman analyses of the char residue demonstrated that the incorporation of FR‐PNX facilitated the formation of a dense and continuous char layer in the FR‐RPUF, with increased graphitization degree of the char layer, thereby enhancing the composite's fire resistance through the development of a more stable fire barrier.

Biomass phytate salt-based flame-retardant polyurethane coating for outdoor polyester fabric: A long-lasting solution

Polyurethane (PU)-coated polyester fabrics are commonly used in outdoor settings, but their flame-retardant properties are somewhat lacking. In this study, biomass phytate salt was applied to improve the flame retardancy and anti-dripping properties of PU-coated polyester fabrics. This study also explored the hydrostatic pressure, mechanical performance, heat release capacity, flame retardancy, washing durability, and mode of action of coated polyester fabrics. The polyester fabric coated with 4 % phytate salt-modified PU exhibited impressive self-extinguishing properties without any dripping. Additionally, the coated polyester fabric showed a low damaged length of 12.2 cm and a high LOI of 33.8 %, satisfying the requirements for the B1 level. The coated polyester fabric proved to withstand 50 washing cycles, highlighting its remarkable flame retardancy efficiency and durability. It also exhibited a significant reduction in heat release, suggesting the fire safety performance. Analysis of the thermal resistance and char residue revealed a condensed flame-retardant mechanism attributed to the phytate-based system. Overall, phytate salt shows promising potential as a long-lasting flame-retardant system for outdoor PU-coated polyester fabrics.

Low phosphorus-containing hydrophobic silica aerogels with high thermal stability and outstanding flame retardancy

To enhance the thermal safety of hydrophobic silica aerogel (SA), we synthesized a high thermal safety SA utilizing phytic acid (PA) as a catalyst. Tests confirmed that the SA/PA maintain low density (0.09 g/cm3) and low thermal conductivity (23.2 mW/m/K). The thermal stability and combustion characteristics of SA/PA were evaluated by thermogravimetric analysis (TG), gross calorific value (GCV) and cone calorimeter. The TG data clearly show that the addition of PA can greatly increase the decomposition temperature of silylmethyl by 208.1 °C and the residual char content to 92.6%. The GCV results show that a small amount of PA could greatly reduce the GCV of SA, with a maximum decrease of 51.6 %. Information from cone calorimeter data affirmed that PA can decrease the burning factors by decreasing the total heat release and peak heat release rate by 63.6% and 28.7%, respectively. The flame retardant mechanism of PA against SA was scientifically examined by thermogravimetric-infrared-mass spectrometry analysis and residual char analysis. In the gas phase, PA by capturing radicals produced during the combustion process of the material, the combustion chain reaction is quenched. In the condensed phase, PA promotes the rapid dehydration and carbonization of SA to establish a physical barrier and achieve flame retardancy. Our findings highlight the beneficial impact of PA on SA. The aerogel exhibited enhanced thermal stability and effective flame retardancy after PA treatment.

A novel flame retardant epoxy thermoset based on renewable honokiol and furfuryl alcohol

In this study, honokiol epoxy resin was directly functionalized by bio-based material honokiol, which was combined with furfuryl alcohol-derived flame retardant by Diels-Alder reaction to prepare bio-based epoxy cross-linking system. After curing with 4,4′-diaminodiphenyl methane, HE1/FP0.5/DDM (121.37 °C) offered higher glass transition temperature than EP/DDM (91.75 °C). Meanwhile, the HE1/FP0.5/DDM exhibited excellent thermal stability and flame retardancy compared to EP/DDM. The char residue of HE1/FP0.5/DDM was obviously increased from 12.8% (EP/DDM) to 35.6% at 700 °C. Notably, the HE1/FP0.5/DDM achieved a limiting oxygen index value of 37.4% and UL-94 V-0 rating. Cone calorimeter demonstrated that the peak heat release rate, total heat release and fire growth rate of HE1/FP0.5/DDM were 400.29 kW/m2, 33.45 MJ/m2 and 4.40 kW/m2·s, reduced by 57.47%, 63.39% and 41.1% compared with EP/DDM, respectively. The satisfactory flame retardancy and smoke suppression were attributed to the flame-retardant function of FP in the condensed and gas phases. Thus, this work not only provided a simple but also eco-friendly approach to achieve flame retardant thermosets from honokiol to replace bisphenol A epoxy.

Innovative multifunctional fire retardance of poly(butylene adipate-co-butylene terephthalate)-based bio-composite formulation

Poly(butylene adipate-co-butylene terephthalate) (PBAT), a biodegradable aromatic-aliphatic copolyester, has been widely applied in various fields, but it shows the flammability, resulting in serious fire risk. The flame retardancy of some PBAT/polymer blend systems have been studied, but that of neat PBAT was seldom reported. In particular, the research and development of the bio-based green flame retardant agent is highly desired. In this work, fully bio-derived modified chitosan particles (C-CS), were synthesized and used to prepare a novel PBAT-based multifunctional flame-retardant composite. The PBAT/3%C-CS composite (PC3) exhibited an excellent anti-dripping and self-extinguishing performance and achieved the highest fire safety rating (V-0). Peak of heat release rate and total heat release reduced by 39.8 % and 14.9 %, respectively. The char residue yield of the PC3 increased by 211.6 % in the PC3, compared with that of neat PBAT. Both condensed- and gas-phase played dual roles on increasing the flame-retardant performance of the PC3. The PC3 showed a relatively compact and continuous char layer which acted as a physical barrier to suppress the heat exchange and O2 entry (into the matrix) in the combustion process. Meanwhile, the concentration of O2 and H·/HO· free radicals were diluted by a small portion of non-flammable gas products in the pyrolysis process. Also, the PC3 presented elevated crystallizability and anti-bacterial effect, and reduced UV-transmittance characteristic.