Total Heat Release Research Articles

Synthesis of P-decorated polysiloxane for good flame retardancy and toughness of epoxy thermosets

Polysiloxanes are modifiers that can enhance the fire safety and toughness of epoxy thermosets. However, the design of high-efficiency polysiloxane modifiers remains a formidable challenge, due to their indefinite structures as well as the complexity and high costs of the preparation process. A phosphorous-containing epoxy-functionalized polydimethylsiloxane (PDMS-DGE) has been prepared by a three-step process using octamethylcyclotetrasiloxane (D4), 2,4,6,8-tetramethylcyclotetrasiloxane (D4H), 1,1,3,3-tetramethyldisiloxane (TMDS), allyl glycidyl ether (AGE), and 9,10-dihydro-9-oxo-10-phosphaphenanthrene (DOPO). Incorporation of 15 wt% PDMS-DGE strongly improved the flame retardancy of epoxy thermosets. There was 38.2 % increase in limiting oxygen index value (LOI), 54.4 % decline in total heat release (THR), and 27.2 % decrease in total smoke production (TSP) as compared to the same values for combustion of unmodified epoxy thermoset. This could be ascribed to the generation of phosphorus/silicon-containing char layers, which effectively reduced the formation of combustible gases, smoke, and heat during burning. Compared to neat EP thermoset, the flexural strength and impact strength of the 15 wt% PDMS-DGE modified epoxy thermoset was increased by 51.1 % and 107.8 %, respectively. This is due to the existence of epoxy groups, rigid phosphaphenanthrene structures, and flexible polydimethylsiloxane chains in PDMS-DGE. Further, the presence of PDMS-DGE provides epoxy thermosets with good moisture resistance. A facile strategy to develop polysiloxanes for epoxy thermosets with both flame retardant properties and toughness, which has vast potential for industrial applications has been proposed.

Preparation and properties of bio‐based flame‐retardant rigid polyurethane foams with soybean oil polyols containing phosphorus

AbstractTwo types of bio‐based RPUFs (RPUF‐P and RPUF‐PPOA) were prepared that contained ethanol‐modified polyols (Polyol‐E) and one contained an epoxidized polyol modified with phosphoric acid (Polyol‐P), and the other contained epoxidized polyol modified with phenylphosphonic acid (Polyol‐PPOA). The cell morphologies, thermal and mechanical properties, and flame retardancy characteristics of the RPUF, RPUF‐P, and RPUF‐PPOA were studied by scanning electron microscopy (SEM), thermogravimetric analysis(TGA), compression tests, limiting oxygen index (LOI), and cone calorimetry test (CCT). The porous structures revealed that the cell sizes of both RPUF‐P and RPUF‐PPOA increased first and then decreased, and the number of pores decreased first and then increased. Furthermore, the apparent density showed a similar trend of increasing before decreasing. The compressive strengths of the RPUF‐P and RPUF‐PPOA were higher than that of the RPUF, and the compressive strength of the RPUF‐P was better than that of the RPUF‐PPOA, because the hydroxyl value of the Polyol‐P was much higher than that of the Polyol‐PPOA. The crosslinking density of the RPUF‐P prepared by the PM‐200 reaction was much higher than that of the RPUF‐PPOA. The LOI values of the RPUF‐P4 and RPUF‐PPOA4 were 21.68 and 23.10, respectively. Furthermore, the value of the peak of the heat release rate (HRR) was reduced by 40.3% compared with that of pure RPUF. The total heat release (THR), smoke produce rate (SPR), and total smoke release (TSR) decreased with increased Polyol‐P and Polyol‐PPOA addition. The flame‐retardancy residues micrographs showed that the carbon layers generated from the combustion of the RPUF‐P4 and the RPUF‐PPOA4 lacked perforated structures and exhibited better densification than the pure RPUF. Based on the analysis and discussion, the flame retardancy of RPUF‐P and RPUF‐PPOA were improved mainly through a condensed and gas phases mechanism.

An Evaluation of the Fire Safety of Waste Paper-Based Internal Finishing Materials Combined with Expandable Graphite According to Changes in Magnesium Hydroxide Content

Inflammable building finishing materials act as a major cause of fire propagation, and they, therefore, pose significant risks to life and can lead to property damage. To replace such flammable building finishing materials, many countries have established regulations limiting their use, which has led to extensive research on the development of flame-retardant building finishing materials. Such methods have included adding flame retardants to construction materials to reduce the heat release rate and total heat release. The present study aimed to enhance the fire performance of cellulose-based architectural finishing materials by creating a dual flame-retardant mixture using expandable graphite and magnesium hydroxide added to recycled paper waste. Specimen fabrication involves using a pressing method to apply uniform pressure to compress the mixture in a mold. The total heat release (THR), CO, and CO2 production of the produced specimens were measured using a cone calorimeter while varying the magnesium hydroxide additive ratio. The combustion gases were measured through NES 713 experiments to determine any changes in the Toxic Index corresponding to variations in the magnesium hydroxide content. The experiment results established a correlation between the magnesium hydroxide additive ratio and the total heat release, as well as the existence of variations in CO and CO2 production for the dual flame-retardant recycled paper material. A database for combustion gases was also obtained. It was confirmed that the fire performance was improved by confirming that the total heat release decreased by 52% from the previous one in the magnesium hydroxide content of 30 g, and it was confirmed that the inflection points of the Toxic Index value due to the change in CO and CO2 gas production occurred in the magnesium hydroxide content of 20 g due to the improvement of the fire performance. Through the ISO 5660-1 experiment data, we have secured data that can be used as foundational information for performance-oriented fire risk assessments, thereby ensuring the fire safety of cellulose materials that are vulnerable to fire.

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

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

Characterization of oxygen initiation process in the autothermic pyrolysis in-situ conversion of Huadian oil shale

The oxygen initiation process, one of the key processes in the early stage of the autothermic pyrolysis in-situ conversion technology, has not been deeply investigated, which seriously limits its development. In this study, the reaction behaviors, kinetic parameters, heat and product release characteristics during the isothermal oxygen initiation process of Huadian oil shale in O2/N2 mixtures with different oxygen concentrations and initiation temperatures were investigated via TG/DSC-FTIR. The results show that the samples exhibit three different reaction behaviors during the initiation stage, consisting of two main parts, i.e., the oxidative weight-gain and the oxidative reaction phases. The former phase is mainly characterized by the oxygen addition reaction that produces oxidizing groups which increase the sample mass. And the latter stage consists of two main subreactions. The first subreaction involves the oxidative cracking and pyrolysis of oxidizing groups and kerogen to produce fuel deposits such as residual carbon, while the second subreaction focuses on the oxidation of the resulting fuels. Furthermore, increasing the oxygen concentration significantly promotes the above reactions, leading to an increase in the reaction intensity and reaction rate. Owing to the combined effect of oxygen concentration and residual organic matter content, the total heat release increases with the increasing initiation temperature and reaches its maximum at 330–370 °C. In addition, the preheating stage primarily produces hydrocarbon gases, while the initiation stage predominantly generates CO2. As the preheating temperature increases, the CO2 output intensifies, the required reaction time shortens, and the release becomes more concentrated. Based on these findings, a reaction mechanism for the oxygen initiation process of Huadian oil shale was proposed, and recommendations were provided for optimizing the construction process.

Construction of composite self-assembly coating based on chitosan for enhancing the flame-retardant and antibacterial performances of cotton fabric

In this work, the step-by-step dip-coating (SBS) method was used to effectively improve the drawback of LBL by reducing the construction of a multilayer polyelectrolyte. Bio-based flame retardants, phytic acid (PA), and chitosan (CS) were further self-assembly on the surface of cotton fabric treated by epichlorohydrin-modified aramid nanofibers (AEP), ionic liquid (IL), and Cu ion. The pure cotton fabric was immersed in each dipping liquid only once, improving fire safety and antibacterial performance. The treated cotton self-extinguished with a 59 mm char length in the vertical flammability test, and the limiting oxygen index (LOI) value increased from 18.5 % to 38.5 %. The result of the cone calorimeter test (CCT) revealed that the fire hazard of flame-retardant cotton noteworthy declined (e.g., ~44.1 % and 55.4 % decline in peak heat release rate (pHRR) and total heat release rate (THR)). Conspicuously, the treated cotton exhibited a remarkably inhibiting effect on E. coli and S. aureus activity. The cotton fabric after flame-retardant finishing exhibited excellent fire safety and antibacterial performance.

Fully biobased thermal insulating aerogels with superior fire-retardant and mechanical properties

Biomass-based aerogels offer a promising potential as alternatives to plastic-based foams for thermal insulation applications. However, their inherent flammability has hindered their practical usage. In this work, we addressed this issue by employing a layer-by-layer assembly technique to deposit two oppositely charged biobased materials, namely phytic acid and chitosan, onto a fully biobased aerogel system. These aerogels were fabricated using cellulose filaments and chitosan and cross-linked with citric acid, resulting in a mechanically robust 3D structure. The synergistic effects of phytic acid and chitosan in the layer-by-layer deposited aerogels significantly enhanced their fire resistance and mechanical strength. The developed aerogel with six bilayer depositions (LBL6), showed an outstanding peak heat release rate (pHRR) of 6.0 kW.m−2, and total heat release (THR) of 0.4 MJ.m−2, substantially lower than the previously developed cellulose-based aerogels and foams. LBL6 also demonstrated immediate self-extinguishing behaviour, boasting an impressive limiting oxygen index (LOI) value of 63 %, which is the highest reported for a biobased aerogel. Furthermore, the developed aerogels exhibited a superior Young’s modulus of up to 4.5 MPa, surpassing previously developed flame-retardant aerogels. Additionally, they excelled in thermal insulation properties, with a thermal conductivity of less than 38.2 mW·m−1·K−1, placing them in the same range as, or even lower than, commercially available thermal insulators. Given the simplicity of the aerogel development process and the well-known advantages of a completely biobased system, our developed aerogels present a sustainable and environmentally friendly alternative to current commercial thermal insulators that are derived from petroleum-based materials.

Construction of Fire Safe Thermoplastic Polyurethane/Reduced Graphene Oxide Hierarchical Composites with Electromagnetic Interference Shielding.

Incorporating outstanding flame retardancy and electromagnetic interference shielding effectiveness (EMI SE) into polymers is a pressing requirement for practical utilization. In this study, we first employed the principles of microencapsulation and electrostatic interaction-driven self-assembly to encapsulate polyethyleneimine (PEI) molecules and Ti3C2Tx nanosheets on the surface of ammonium polyphosphate (APP), forming a double-layer-encapsulated structure of ammonium polyphosphate (APP@PEI@Ti3C2Tx). Subsequently, flame-retardant thermoplastic polyurethane (TPU) composites were fabricated by melting the flame-retardant agent with TPU. Afterwards, by using air-assisted thermocompression technology, we combined a reduced graphene oxide (rGO) film with flame-retardant TPU composites to fabricate hierarchical TPU/APP@PEI@Ti3C2Tx/rGO composites. We systematically studied the combustion behavior, flame retardancy, and smoke-suppression performance of these composite materials, as well as the flame-retardant mechanism of the expansion system. The results indicated a significant improvement in the interface interaction between APP@PEI@Ti3C2Tx and the TPU matrix. Compared to pure TPU, the TPU/10APP@PEI@1TC composite exhibited reductions of 84.1%, 43.2%, 62.4%, and 85.2% in peak heat release rate, total heat release, total smoke release, and total carbon dioxide yield, respectively. The averaged EMI SE of hierarchical TPU/5APP@PEI@1TC/rGO also reached 15.53 dB in the X-band.

Influence of ground granulated blast furnace slag on recycled concrete powder-based geopolymer cured at ambient temperature: Rheology, mechanical properties, reaction kinetics and air-void characteristics

In this paper, ground granulated blast-furnace slag was used to enhance the properties of recycled concrete powder based geopolymer cured at ambient conditions. The rheology, workability, strength, hydration reaction kinetics, microstructure, and air-void characteristics of the geopolymer were investigated. The results showed that adding the slag accelerated the setting process and reduced the water absorption and porosity of the geopolymer mixtures. Excellent mechanical properties were achieved when the slag content exceeds 30 %. The 28-d compressive and flexural strength of the geopolymer with 50 % slag addition reached 61.2 and 5.17 MPa, respectively. The yield stress and plastic viscosity of the geopolymer increased as the slag content increased. A quantitative model between the slag content, resting time, and rheological parameters was established, with high accuracy, realistically reflecting the rheological properties of the geopolymer. The addition of the slag provided nucleation sites for the C-S-H gel, which promoted the hydration reaction, increased the hydration products and the total heat release, and formed a denser and more uniform microstructure, thereby increasing the strength of the geopolymer. The slag addition was also found to reduce the air content, spacing factor, and average chord length of the geopolymer matrix. As the slag content increased, the air bubbles became smaller and more stable, and exhibited a more uniform distribution.

Microcapsule Modification Strategy Empowering Separator Multifunctionality to Enhance Safety of Lithium-Metal Batteries.

The uncontrollable growth of lithium dendrites and the flammability of electrolytes are the direct impediments to the commercial application of high-energy-density lithium metal batteries (LMBs). Herein, this study presents a novel approach that combines microencapsulation and electrospinning technologies to develop a multifunctional composite separator (P@AS) for improving the electrochemical performance and safety performance of LMBs. The P@AS separator forms a dense charcoal layer through the condensed-phase flame retardant mechanism causing the internal separator to suffocate from lack of oxygen. Furthermore, it incorporates a triple strategy promoting the uniform flow of lithium ions, facilitating the formation of a highly ion-conducting solid electrolyte interface (SEI), and encouraging flattened lithium deposition with active SiO2 seed points, considerably suppressing lithium dendrites growth. The high Coulombic efficiency of 95.27% is achieved in Li-Cu cells with additive-free carbonate electrolyte. Additionally, stable cycling performance is also maintained with a capacity retention rate of 93.56% after 300 cycles in LFP//Li cells. Importantly, utilizing P@AS separator delays the ignition of pouch batteries under continuous external heating by 138s, causing a remarkable reduction in peak heat release rate and total heat release by 23.85% and 27.61%, respectively, substantially improving the fire safety of LMBs.

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.

Dual function of carboxymethyl cellulose scaffold: A one-stone-two-birds strategy to prepare double‐layer hollow ZIF-67 derivates for flame retardant epoxy composites

Aluminum hypophosphite (AHP) has been used as a flame retardant for a long time. Previous studies about AHP employed in flame retardant materials mostly focus on coating, modification, and complex system. It is valuable to explore simple experimental steps to prepare nano hybrids with AHP and metal–organic frameworks (MOFs). We found acidic substances could etch zeolitic imidazolate framework-67 (ZIF-67) to obtain MOF derivatives. Unfortunately, AHP and ZIF-67 could not directly form a hybrid. Therefore, carboxymethylcellulose (CMC) is introduced as a dual function layer (buffer and support). The CMC resists the complete conversion of ZIF-67 etched by phosphoric acid to amorphous cobalt phosphate hydrate (ACP). Meanwhile, CMC containing hydroxyl groups combines with AHP through electrostatic interaction and coordination bonds. A double-layer hollow MOF derivative is synthesized through this one-stone-two-birds strategy. Due to multiple flame retardant elements and unique nanostructure, this MOF derivative endows epoxy (EP) resin with excellent flame retardancy. With 2.0 wt% addition, the peak heat release rate (pHRR) and total heat release (THR) of EP/AHP/ACP@CMC are decreased by 47.8 and 21.0 %, respectively. This study proposes a novel scheme that converts AHP into MOF derivatives as high-performance FRs.

Production and characterization of flame-retardant poly (butylene terephthalate) composites containing boron compounds

ABSTRACT Within the scope of this work, flame retardant polybutylene terephthalate (PBT) was produced using boron compounds, namely, anhydrous borax (BX), colemanite (C), and zinc borate (ZnB) in three different concentrations of 40, 50, and 60 wt%. The thermal, flame retardant, and tensile properties of PBT composites were systematically investigated using thermogravimetric analysis (TGA), limiting oxygen index (LOI), vertical UL 94 test (UL-94V), mass loss calorimeter (MLC), and tensile tests. The thermal stability of PBT slightly enhanced with the use of BX, whereas the use of C and ZnB reduced the thermal stability. Improvement in LOI value, a reduction in peak heat release rate (pHRR), and total heat release (THR) values were observed with the use of all boron compounds. The improvement in UL-94V rating was observed only with the use C. The addition of all boron compounds deteriorates the tensile strength of the composites. In brief, the highest flame retardant performance with V0 rating (UL-94 V), 33.5% (LOI), and 48 Kw·m−2 (pHRR) was achieved with the use of C.

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.

Expanded charring flame retardant effect of caged polysilsesquioxane containing Schiff base structure on poly(ethylene terephthalate) combustion

Via a hydrolytic condensation reaction, we successfully synthesized polyhedral oligomeric silsesquioxane containing Schiff base structures (NSPOSS). These were then incorporated into the PET matrix through melt blending, aiming to bolster the flame retardancy of poly(ethylene terephthalate) (PET). The interaction force between NSPOSS and PET was analyzed by simulation of NSPOSS pulling out in PET via MS8.0. Additionally, NSPOSS exhibits excellent flame retardancy and smoke suppression. For PET-10wt%NSPOSS, the peak heat release rate (pk-HRR), the total heat release (THR), the total smoke release (TSR), peak smoke release rate (pk-RSR), and the highest smoke density peak (Ds max) decreased by 60%, 14%, 57%, 42% and 59%, respectively, compared to neat PET. Moreover, PET-NSPOSS composites exhibit char expansion during combustion, for which we propose a charring mechanism. The newly prepared NSPOSS can be applied in various resin matrices, offering promising prospects for practical applications.

Fire Properties of Paper Sheets Made of Cellulose Fibers Treated with Various Retardants.

This article presents the results of flame-retardancy tests conducted on cellulose sheets produced using a Rapid Köthen apparatus treated with retardants. The agents used were potassium carbonate (PC) K2CO3 (concentrations of 20; 33.3; and 50% wt/wt), monoammonium phosphate (MAP) NH4H2PO4 (concentrations of 35% wt/wt), diammonium phosphate (DAP) (NH4)2HPO4 (concentrations of 42.9% wt/wt), and bisguanidal phosphate (FOS) C2H10N6 (concentrations of 22.5% wt/wt). The agents were used to improve Kraft cellulose-based sheets' flame-retardant properties and compare their performances. As part of the study, the flammability of the materials was determined by the following methods: an oxygen index (OI) test, a mass loss calorimeter (MLC) test, and a mini fire tube (MFT) test. All formulations showed an increase in flame retardancy compared to the control test. All protected samples were non-flammable for OI determinations, and DAP-protected samples showed the highest OI index. For the MLC test, DAP-protected and MAP-protected samples showed the best heat-release rate (HRR), total heat release (THR), and average heat-release rate (ARHE) (samples did not ignite for 600 s). In the MFT test, all treated samples had comparably reduced weight loss. The best parameter was achieved for MAP and DAP (15% weight loss).

Enhancement of mechanical and flame‐retardant properties of PLA composites through the combined action of flexible chain segments and hydrogen bonding interactions

AbstractThe development of high toughness as well as flame‐retardant polylactic acid (PLA) materials is important for expanding the practical applications. Herein, a type of high toughness PLA composites with improved flame retardancy was developed through combining modified carbon nanotubes (CNT) and polysiliconoxaborane (PBSi) with PLA matrix. The optimal PLA composite (PLA/PBSi/CNT‐3.0) exhibited excellent crystallization degree (18.7%), thermal stability (the Ea significantly increased), flame retardancy (the values of peak heat release rate (PHRR) polarized optical microscopy and total heat release (THR) decreased to 287.1 W/g and 15.5 kJ/m2, respectively), and mechanical properties (the elongation at break increased to 149.5%, with an increasement of 1745.7%) due to the combined action of flexible chain segments and hydrogen bonding interactions. Furthermore, the toughening mechanism of the PLA/PBSi/CNT composites was illustrated and attributed to the combination of flexible SiOBO segments and two dominant energy dissipation processes (the breakage of hydrogen bond and the destruction of microcrystals). Overall, this work provided a facile approach for improving the toughness and flame retardancy of PLA, which was conducive to expanding the application range of PLA.

Multifunctional nanocomposite coating for aluminium alloy: Corrosion resistance, flame retardancy, and mechanical enhancement for automotive components

Aluminium alloys are utilized in the automotive industry for components such as engine blocks, wheels, chassis, and body panels. Their lightweight nature helps reduce vehicle weight, leading to improved fuel efficiency and lower emissions. The development of nanocomposites incorporating impermeable two-dimensional materials holds significant promise for safeguarding metals against corrosion. By introducing N-aminoethyl-3-aminopropyltrimethoxysilane (AAMS) functionalized molybdenum nitride (MoN) into a coating matrix, the barrier effect can be significantly enhanced owing to its remarkable chemical and thermal stability. This enhancement is further amplified through the incorporation of functionalized MoN into graphitic carbon nitride (GCN) within a polyurethane (PU) matrix, resulting in improved corrosion protection and fire-retardant properties. Through electrochemical techniques conducted in marine environments, the protective efficacy of aluminium coated with polyurethane, alongside varying concentrations of functionalized MoN/GCN, was assessed. The resulting PU composite exhibited superior flame-retardant capabilities, manifesting in substantial reductions in peak heat release rate (PHRR), total heat release (THR), and total smoke production (TSP) compared to pure PU formulations. Electrochemical impedance spectroscopy (EIS) measurements revealed a notable enhancement in coating resistance (5.65 × 1011 Ω. cm2), even following 500 h of exposure to the electrolyte. Furthermore, the newly formulated PU composite, featuring functionalized MoN/GCN, demonstrated exceptional water repellency with a water contact angle (WCA) of 157°. This remarkable hydrophobicity underscores its potential for applications requiring protection against moisture ingress. Additionally, the PU composite exhibited commendable mechanical properties, boasting an adhesive strength of 19.1 MPa within the PU substrate. This enhanced adhesive strength ensures the coating's integrity even after prolonged immersion periods. Given its multifaceted benefits, the PU composite incorporating functionalized MoN/GCN emerges as a promising candidate for integration into automotive industries as a viable coating component. Its ability to concurrently provide corrosion protection, flame retardancy, water repellency, and mechanical robustness underscores its potential to enhance the durability and longevity of automotive components, thereby contributing to improved performance and longevity in harsh operating environments.

Preparation of a Highly Flame-Retardant Urea-Formaldehyde Resin and Flame Retardance Mechanism.

Urea-formaldehyde (UF) resin is the most widely used adhesive resin. However, it is necessary to improve its flame-retardant performance to expand its applications. In this study, exploiting electrostatic interactions, anionic phytic acid and cationic chitosan were combined to form a bio-based intumescent flame-retardant, denoted phytic acid-chitosan polyelectrolyte (PCS). The molecular structure of the urea-formaldehyde resin was optimized by crosslinking with melamine and plasticizing with polyvinyl alcohol-124. Thus, by combining PCS with the urea-formaldehyde resin and with ammonium polyphosphate and ammonium chloride as composite curing agents, flame-retardant urea-formaldehyde resins (FRUFs) were prepared. Compared to traditional UF resin, FRUF showed excellent flame retardancy and not only reached the UL-94 V-0 level, but the limit of oxygen index was also as high as 36%. Compared to those of UF, the total heat release and peak heat release rate of FRUF decreased by 86.44% and 81.13%, respectively. The high flame retardancy of FRUF originates from the combination of oxygen and heat isolation by the dense carbon layer, quenching of phosphorus free radicals, and dilution of oxygen by a non-flammable gas. In addition, the mechanical properties of the FRUF remained good, even after modification. The findings of this study provide a reference for the flame-retardant application of FRUF for applications in multiple fields.

Joint Exfoliation of MXene by Dimensional Mismatched SiC/ZIF-67 Toward Multifunctional Flame Retardant Thermoplastic Polyurethane.

The single-layer MXene fully demonstrates the advantages of 2D materials, especially catalytic, conductive, and mechanical properties. However, the high energy consumption and low efficiency faced by MXene in the divestiture process are still challenges that need to be solved urgently. In this article, dimension mismatch and collaborative stripping strategies are skillfully combined to easily realize the transformation from multi-layer MXene to single layer. In addition, the functionalized MXene@SiC@polyaniline (MXene@SiC@PANI) nano-hybrid materials are used as fillers to improve the thermal conductivity, flame retardant, and antibacterial properties of thermoplastic polyurethane (TPU). The surface temperature of TPU/MXene@SiC@PANI composites increased from 33.4°C to 59.8°C within 10 s. In addition, the antibacterial efficiency of TPU composites against Escherichia coli and Staphylococcus aureus is 69.6% and 88.9%, respectively. Compared with pure TPU, the peak heat release rate and total heat release are reduced by 71.4% and 34.6%, respectively. The flame-retardant mechanism of MXene hybrid materials is systematically discussed. It is worth noting that the introduction of PANI enhances the compatibility between the filler and the polymer, effectively maintaining the mechanical properties of the TPU itself. This work provides a convenient method for the multi-functional practical application of TPU.