Peak Heat Release Rate Research Articles

Enhanced mechanical property and flame resistance of phosphorylated cellulose nanofiber based‐aerogel combined with boric acid

AbstractAs for cellulose‐based aerogels, a feature of inadequate mechanics and easy‐flammability seriously restricts their practical applications. To address this issue, herein a lightweight, mechanical elastic and flame‐retardant phosphorylated lignin‐based cellulose nanofiber (PLCNF‐B) aerogel with the aid of boric acid was successfully obtained by freeze‐drying method. Due to the uniform and tough network structure benefitting by strong hydrogen bond between phosphorylated fibers and boric acid, the resultant aerogel showed excellent mechanical performance, that is, high compressive strength of 8.9 kPa (strain: 50%) and outstanding cyclic reliability (remain 90% after 10 cycles). Meanwhile, PLCNF‐B aerogel possesses highly improved flame‐retardant property, that is, a high LOI value (up to 46%), significantly reduced peak heat release rate (11.2 W/g) and total heat release rate (0.47 kJ/g). Based on structural observation and analysis, the flame‐retardant behavior should be attributed to the formation of PxOy/amorphous boron oxide protective layer, which is derived from the phosphorus containing group of PLCNF and boric acid. The splendid overall performance of aerogel material offers a potential material tactic for design and development of advanced bio‐based aerogels for practical applications.

A new application of MoS2@AG@PA prepared by irradiation: Synergizing with magnesium hydroxide to enhance fire safety and other key properties of EVA composites

AbstractTwo‐dimensional molybdenum disulfide (MoS2) nanosheets are seen as highly promising nanofillers for enhancing polymer properties, yet there is a need for methods that are low‐cost, simple, and environmentally friendly to facilitate the large‐scale production of MoS2 nanosheets. Furthermore, it is necessary to functionalize the MoS2 surface to ensure good interfacial compatibility with the polymer matrix. In this study, MoS2@Ag@PA hybrids were created by generating silver nanoparticles directly on the surface of MoS2 via radiation, followed by encapsulation on the surface of MoS2@Ag through the chelating properties of phytic acid. It is significant to note that, due to the excellent lubrication and physical cross‐linking effects of the MoS2@Ag@PA hybrids, adding one part of MoS2@Ag@PA hybrids can enhance the melt flow rate and elongation at break of the ethylene vinyl acetate copolymer (EVA)/MH composites by 140% and 17.3%, respectively. The simultaneous addition of one part of MoS2@Ag@PA hybrids decreased the peak heat release rate, total heat release, and total smoke release of the EVA composites by 48.7%, 42.7%, and 41.2%, respectively. Moreover, the toxic gasses (e.g., CO) generated by burning EVA composites were significantly reduced compared to pure EVA, indicating improved fire safety. This research not only provides significant opportunities for the green mass production of MoS2 nanosheets but also expands their potential applications in high‐performance nanocomposites.

Fire-resistant and mechanically-robust phosphorus-doped MoS2/epoxy composite as barrier of the thermal runaway propagation of lithium-ion batteries

Thermal runaway propagation (TRP) is an utmost safety issue in battery modules owing to its derivative accidents of fire or explosion. This study develops a novel flame-retardant epoxy resin (EP) board to prevent the battery TRP. The phosphorus doped MoS2 nanowires (PR-MoS2) is designed and incorporated into EP matrix to acquire EP/3.0 PR-MoS2 composite. The composite shows 159.4 % increase in char yield, 56.7 % decrease in peak heat release rate, 56.6 % reduction in peak CO production rate. By using EP/PR-MoS2-3 (EP/3.0 PR-MoS2 composite with thickness of 3 mm) between 103450-pouch cells, TRP can be effectively stopped. Meanwhile, the temperature of surviving battery remains below 100 °C. Of note, the minimum changes in internal crystal structure, chemical composition and electrochemical characteristics are discerned for the surviving battery. This research will offer inspirations for the design of TRP suppression materials, guaranteeing the safety the battery.

Tannic acid coated ammonium polyphosphate: For flame retardant and UV resistant of polypropylene

Polypropylene (PP) has the advantages of excellent mechanical properties and easy molding, but its shortcomings such as high flammability and poor ultraviolet (UV) resistance cannot be ignored. In this paper, APP was used as the core, 1, 10-diamino-decane (DA) was used as a "bridge" to connect TA to the surface of APP, obtaining TAPP through oxidation self-polymerization. The addition of TAPP greatly improved the flame retardancy and UV resistance of PP matrix. The limiting oxygen index of the PP/22.5 %TAPP sample was increased to 31.0 %, and it was able to pass the UL-94 V-0 rating without droplet produced. Compared with PP samples, the peak heat release rate and peak smoke release rate of PP/22.5 %TAPP sample were reduced by 65.0 % and 44.7 %, respectively. In addition, the tensile strength and impact strength of PP/22.5 %TAPP samples decreased by only 2.7 % and 15.0 % after 60 h UV irradiation. The results showed that the addition of TAPP effectively improved the flame retardancy and UV aging resistance of PP. This study provides a feasible method for the preparation of anti-UV aging and flame-retardant PP composites.

Self-crosslinking phosphorus-containing durable flame retardants for cotton fabrics

The phosphorus-containing flame retardant that can enter the interior of cotton fiber and has self-crosslinking ability was designed and synthesized. The flame retardant contains two components, 2-(1-(dimethoxy phosphoryl)-2,5, 8-Triazectridecyl) phosphonate starch (PTPS) and 4-(hydroxymethyl)-10-((3-((5-(hydroxymethyl)-10-((3-((tris(hydroxymethyl)phosphonio)methyl)ureido)methyl)-2,6,8,12,14,18-hexaaza-4,10,16-Triphosphanonadecane (BPTP). The structure of PTPS and BPTP were detected by NMR and FTIR, and the results showed that the synthesis of PTPS and BPTP was successful. During the treatment, cellulose was first endowed with -NH groups. Then PTPS molecule and BPTP molecule were grafted onto cellulose through the reaction of P-CH2OH groups and -NH groups. After 50 laundering cycles (NFPA2112–2012 standard), the limiting oxygen indexes (LOIs) of the fabrics treated with 35 wt% CFN-PB and 30 wt% CFN-PB were 28.80% and 27.30%, respectively, and passed the vertical flame test (VFT). Compared with the raw cotton, the peak heat release rate (PHRR), the total heat rate (THR) and the flame growth rate (FGR) of the CNF-PB treatment fabric were reduced by 62.90 %, 29.43 % and 62.91 % respectively. These indicate that the flame retardant PB could be firmly fixed on the fibers and show good flame retardancy durability. In the VFT, and cone calorimetry test, the CFN-PB treated fabric showed the condensed phase flame retardant mechanism.

The intrinsic flame retardant multifunctional composite phase change material with phosphorus pentoxide for battery thermal safety system

The temperature distribution has severely affected the performance of lithium-ion battery modules in electric vehicles (EVs), composite phase change material (CPCM) with excellent temperature controlling function as a passive battery thermal management system is essential to ensure the safety of battery module. In this study, the polyethylene glycol phosphate ester (PEGP) has been synthesized by esterification of phosphorus pentoxide and polyethylene glycol through the reaction of PEGP and melamine (MA), the network crosslinking structure has been built to greatly improve the anti-leakage performance. The flame-retardant CPCM containing PEGP/expanded graphite /epoxy resin/MA (PPEM) has been successfully designed and prepared. The results indicate that PPEM2 containing 20 wt% melamine and 7 wt% epoxy resin exhibit excellent antileakage and prominent flame retardant properties comprehensively. It should be noted that the peak heat release rate of PPEM2 has been reached to 352.41 KW/m2, which is obviously decreased by 47.55 % comparing with pure PEG. The main reason is that the grafting flame retardant elements (P) and melamine onto polyethylene glycol molecular chain by chemical reaction. In addition, it can maintain the operating temperature below 36 °C at 23 A discharge current. The battery module with PPEM2 can transfer the heat timely and promptly, exhibiting outstanding flame-retardant effect to avoid thermal runaway. With these prominent performances, this intrinsic flame-retardant CPCM can not only exhibit an excellent thermal management effect but also provide a promising approach to inhibit the thermal runaway propagation.

Green synthesis of a P/N/B-containing aggregate for boosting fire-retardancy of PA6/aluminum diethylphosphinate composites

The intrinsic flammability of polyamide 6 (PA6) has significantly impeded its broad application regardless of its balanced physical properties. Aluminum diethylphosphinate (ADP), as a P-containing fire retardant, has been demonstrated to be effective in reducing flammability of PA6 because of its dual-phase modes of action by creating an intact protective char layer and inhibiting the burning process. However, the efficiency of ADP needs to be further improved for creating cost-effective fire-retardant PA6, in addition to its relatively high cost. To boost its efficiency, we, here, report a P/N/B-containing aggregate (MBA) as an effective synergist via green self-assembly of melamine (MA), boric acid (BA) and amino trimethylene phosphonic acid (ATMP) in an aqueous medium. The results show that the inclusion of 5 wt% MBA and 10 wt% ADP leads to a significantly reduced peak heat release rate (PHRR) by 52.5% compared to neat PA6, in addition to a desired UL-94 V-0 rating. A synergistic effect of 55.4 % is observed between MBA and ADP in terms of the PHRR value. This work provides a facile green strategy for developing eco-friendly multiple elements-containing fire retardants, which can be used as fire retardants alone or high-efficiency synergists for other fire retardants.

Composite silica aerogel based on HNTs-modified APP with enhanced thermal insulation and flame retardancy performance for organosilicon resin

Efficient thermal insulation and flame-retardant materials are crucial in reducing energy consumption and minimizing fire hazards. This work presents a novel method for preparing a composite aerogel: a silane coupling agent was used as a chemical bridge to synthesize a new flame retardant AKH (modified APP with HNTs). AKH was incorporated into the silica sol to fabricate the SA-AKH composite aerogel. SA-AKH features a dense three-dimensional network skeletal structure, excellent thermal stability, and a high specific surface area. When integrated into organosilicon resin, SA-AKH significantly enhances the flame resistance of composite materials. During cone calorimetry testing (CCT), SSAKH4 exhibited a peak heat release rate (PHRR) of 281.88 kW/m2 and total smoke production (TSP) of 5.52 m2, representing a decrease of 30.8 % and 4.5 %, respectively, compared to SSA4. The composite material, derived from the unique mesoporous structure of aerogel combined with the flame retardant and hollow characterization of AKH, demonstrates exceptional flame retardancy and smoke suppression. SA-AKH is expected to make novel advancements in the field of high-efficiency insulation and flame-resistant composites.

Vanillin-based flame retardant enables polylactic acid high-efficiency fireproof, anti-UV and oxygen barrier for food packaging

Polylactic acid (PLA) is widely known for its biocompatibility, biodegradability, and high transparency. However, it still has varied limitations such as flammability, UV sensitivity, and poor oxygen barrier properties. To address these issues, a bio-based compound, hexasubstituted cyclotriphosphazene (HVP), was synthesized by using vanillin and hexachlorocyclotriphosphazene to enhance the overall performance of PLA. The resulting PLA/HVP composites demonstrated improved mechanical strength and UV resistance. Specifically, PLA/3HVP, with a 3 wt% HVP loading, achieved a UL-94 V-0 rating and a high limiting oxygen index of 26.5 %. Cone calorimeter tests revealed that PLA/3HVP possessed a significantly longer ignition time and a lower peak heat release rate compared to pure PLA. These burning testing results indicated the enhanced fire resistance. Additionally, the oxygen transmission rate of PLA/3HVP was reduced by 81.1 % compared to pure PLA. When used as food packaging, the weight loss of mangoes covered with PLA/3HVP film was 2.2 % after 7 days, compared to 2.5 % with pure PLA film, highlighting its potential for food preservation applications.

Preparation of P/N/Si‐containing covalent organic framework‐based flame retardants and their application in epoxy resins

AbstractBalancing the enhancement of flame retardancy of epoxy resin while maintaining its mechanical capacities intact poses a significant challenge in the realm of flame‐retardant epoxy resins. To reach the above objectives, a COF‐based synergistic flame retardant with phosphorus, nitrogen, and silicon (PA‐COF@MT) was synthesized using phytic acid (PA), montmorillonite (MT), and covalent organic framework (COF). When PA‐COF@MT was added at 4 wt%, EP/PA‐COF@MT exhibited a reduction of 42.1% in peak heat release rate (PHRR), 45.84% in total heat release (THR), and 59.8% in total smoke production (TSP) compared with the pure EP. LOI increased by 30.5% and UL‐94 tested to V‐0 grade. flame‐retardant index (FRI) value of 3.03, achieving a “good” rating. Fire growth indices and mean effective combustion heat were increased while mechanical properties also improved. These findings suggest that the flame retarding mechanism of PA‐COF@MT is mainly through vapor phase and condensed phase actions. The combined effects of phosphorus, nitrogen, and silicon make the surface of carbon residue solid and dense, resulting in excellent heat insulation and smoke suppression effects. In simple terms, this study provides new insights into COF‐based flame retardants. Combining low‐cost and simple preparation methods, PA‐COF@MT has broad application prospects in flame‐retardant epoxy resin systems.

Enhancing the flame retardancy of polycarbonate through the synergistic effect of 1,3‐Benzenedisulfonate acid dipotassium salt and phenyl polysiloxanes

AbstractAs the application of polycarbonate (PC) in various fields continues to expand, the requirements for its flame retardancy are becoming increasingly stringent. To enhance the flame retardancy of PC, employing multi‐element synergistic effects and developing novel flame retardants are considered as vital strategies. This work introduces a blend of 1,3‐Benzenedisulfonic acid dipotassium salt (KSP) and three types of phenyl polysiloxanes, namely Octaphenylcyclotetrasiloxane (P4), Octaphenylsilsesquioxane (OPS), and ladder‐like Polyphenylsesquioxane (L‐PPSQ), into PC to create composites. The thermal stability and combustion properties of these composites were characterized using thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 vertical burning, and cone calorimetry tests. Composites with phenyl polysiloxanes achieved a UL‐94 V‐0 flame retardant rating for 1.6 mm thickness sample and reduced the peak heat release rate by 30%–45%. PC composites with 3% OPS and 0.03% KSP achieved optimal performance, howing a LOI of 34.5%, a 45.4% reduction in peak heat release, and a 40.5% reduction in total smoke release. The flame‐retardant mechanism was analyzed using scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and pyrolysis‐gas chromatography‐mass spectrometry (Py‐GC‐MS).

Sustainable castor oil-based microcellular polyurethane foam with desirable flame retardancy, vibration damping performance and recyclability

Microcellular polyurethane foam (MPUF) is extensively utilized as a vibration dampening material. However, its long chain and porous composition render it highly susceptible to combustion. Herein, we grafted the flame retardant 9,10-dihydro-9-oxa-10-phospha-phenanthrene-10-oxide (DOPO) onto the castor oil by a simple method to obtain a bio-based flame-retardant polyester polyol (COBH). Then, a bio-based flame-retardant MPUF was synthesized by one-pot synthesis of COBH, polyether polyol, and isocyanate. The target MPUF exhibits excellent flame retardancy, with the limiting oxygen index (LOI) sharply increasing from 19.3 % to 27.6 % and the peak of heat release rate (PHRR) decreasing significantly by 60.1 % as compared to MPUF prepared using unmodified castor oil. In addition, the MPUF shows good vibration dampening performance with a maximum loss factor of 5.2 and a maximum Sc-factor of 250. Moreover, the MPUF can be processed into MPU film by compression molding. The MPU film has adjustable mechanical properties and reusability. This study provides a feasible method for the preparation of flame-retardant, recyclable, bio-based MPUF with good vibration damping properties, thus expanding the practical applications of MPUF in the automotive, aerospace, and packaging and transportation industries.

DOPO chemically modified mesoporous silica composites: Preparation, flame retardancy, and thermodynamic properties

AbstractOrganic flame retardant 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide (DOPO) was used to decorate the pores of mesoporous silica (m‐SiO2) nanospheres to prepare a new composite flame retardant (DK‐SiO2). The content of DOPO in DK‐SiO2 is about 17 wt%. Due to the chemical bonding, DK‐SiO2 not only enhances the flame retardant performance, but also effectively avoids adverse effects of DOPO on the glass transition temperature and mechanical properties of epoxy resin (EP). At 9 wt% loading, the limiting oxygen index of the EP increased from 25.7 to 31.2, and successfully passed the UL‐94 V‐0 rating. Besides, DK‐SiO2 can significantly reduce the peak heat release rate, total heat release, and total smoke production of EP, with reductions of 26%, 32%, and 20.8%, respectively. Compared with the simple blended sample, DK‐SiO2 not only has better flame retardant performance but also shows significant advantages in thermodynamic properties. The glass transition temperature, impact, and tensile strength, as well as storage and flexural modulus have been improved. This excellent flame retardant performance is mainly attributed to the gas‐condensed synergistic flame retardant mechanism between DOPO and m‐SiO2. The good thermodynamic performance is due to the excellent dispersion of DK‐SiO2 nanospheres in the EP.

Fabrication of Flame-Retardant Ammonium Polyphosphate Modified Phytic Acid-Based Rigid Polyurethane Foam with Enhanced Mechanical Properties.

Ammonium polyphosphate (APP) and self-made nickel phytate (PANi) were used as modified materials to prepare green biomass rigid polyurethane foam (RPUF). The flame retardancy, thermal stability, smoke toxicity and mechanical properties of the modified RPUF were investigated by limiting oxygen index (LOI), a cone calorimetry (CONE) test, thermogravimetric analysis and a compression test. The results showed that the RPUF with 10 wt% APP (PANi/APP10) had the highest LOI of 26.5%. Its peak heat release rate (PHRR) and total heat release (THR) were reduced by 29.64% and 24.05% compared with PANi/APP0 without APP. And its smoke production rate (SPR) and total smoke release (TSR) decreased by 33.14% and 19.88%, respectively. Compared with pure RPUF, the compressive strength of PANi/APP10 was increased by 50%, mainly because APP itself was an ultra-fine powder, which was better compatible with the matrix and improved the hardness of the material. The results showed that the synergistic effect of the gas phase and the condensed phase mechanism could effectively improve the flame-retardant effect. The current research results provided a new strategy for the preparation of green and low-toxicity RPUF.

Enhanced Fire Safety of Energy-Saving Foam by Self-Cleavage CO2 Pre-Combustion and Phosphorus Release Post-Combustion.

Rigid polyurethane foam (RPUF) is widely utilized in construction and rail transportation due to its lightweight properties and low thermal conductivity, contributing to energy conservation and emission reduction. However, the inherent flammability of RPUF presents significant challenges. Delaying the time to ignition and preventing flame spread post-combustion is crucial for ensuring sufficient evacuation time in the event of a fire. Based on this principle, this study explores the efficacy of using potassium salts as a catalyst to promote the self-cleavage of RPUF, generating substantial amounts of CO2, thereby reducing the local oxygen concentration and delaying ignition. Additionally, the inclusion of a reactive flame retardant (DFD) facilitates the release of phosphorus-oxygen free radicals during combustion, disrupting the combustion chain reaction and thus mitigating flame propagation. Moreover, potassium salt-induced catalytic carbonization and phosphorus derivative cross-linking enhance the condensed phase flame retardancy. Consequently, the combined application of potassium salts and DFD increases the limiting oxygen index (LOI) and reduces both peak heat release rate (PHRR) and total heat release (THR). Importantly, the incorporation of these additives does not compromise the compressive strength or thermal insulation performance of RPUF. This integrated approach offers a new and effective strategy for the development of flame retardant RPUF.

In-situ polymerization of phosphorus/nitrogen flame-retardant coating for polyester/cotton blend fabrics with superior durability

The durable flame-retardant functional coating of polyester/cotton (T/C) blend fabrics is both interesting and challenging. In this study, a novel in-situ polymerization strategy for phosphorus/nitrogen-based flame-retardant on T/C blend samples was developed through the polycondensation of tetramethylolphosphonium sulfate, dicyandiamide, and anionic cyclic phosphate ester. The chemical structure of the polycondensation compounds, as well as the surface morphology, combustion behavior, flame-retardant capacity, washing durability and flame-retardant mechanism of the coated T/C blend fabrics, were investigated. The coated T/C blend fabrics demonstrated excellent self-extinguishing performance, with the damaged length decreasing to as low as 8.0 cm and the LOI reaching 28 %. Moreover, the peak heat release rate of the coated T/C blend fabrics decreased by 39.7 %. The superior flame retardancy can be attributed to the enhanced dehydration and carbonization by phosphate groups in the condensed phase, as well as the quenching effect and diluting effect in the gas phase. Additionally, the coated T/C blend fabrics exhibited remarkable washing durability and still achieved self-extinguishing after 65 washing cycles, and the in-situ deposition of insoluble three-dimensional polycondensation compounds onto the T/C blend fabrics was beneficial. The flame-retardant coating had a minor impact on the whiteness, tensile strength and breathability of the T/C blend fabrics.

Enhancing diesel engine performance and emission reduction through hydrogen enrichment in algal biodiesel blends.

The introduction of hydrogen into the engine could enhance its combustion efficiency and emission characteristics. The current study examines the attributes of compression ignition (CI) engines by introducing hydrogen into a biodiesel blend derived from algae. The improved thermal properties of hydrogen, when combined with algae biodiesel, significantly affect the performance, combustion, and emissions of dual-fuel engines. A study was conducted to evaluate the impact of hydrogen enrichment levels of 5%, 10%, 15%, and 20% of the nozzle volume on a biodiesel blend fuel. In comparison to diesel, algal biodiesel reduces emissions of unburned hydrocarbons (HC), carbon monoxide (CO), and oxygen (O2) by 5.19%, 3.61%, and 2.83%, respectively, while increasing nitrogen oxide (NO) emissions by 4.73%. In contrast to biodiesel, diesel demonstrated superior brake thermal efficiency (BTE) and lower specific energy consumption (SEC). Injecting hydrogen into A20 blend fuel at volumes of 5%, 10%, 15%, and 20% results in a respective increase in brake thermal efficiency of 2.65%, 2.97%, 3.50%, and 4.15%. The addition of hydrogen gas to biodiesel blends further enhances their combustion qualities, leading to elevated peak cylinder pressure, temperature, and heat release rate. The results indicate that A20H5, A20H10, A20H15, and A20H20 fuel reduced CO emissions by 3.75%, 8.75%, 12.5%, and 16.25%, respectively, compared to the A20 blend. In the same vein, HC emissions decreased by 5.76%, 10.29%, 15.52%, and 18.98%, respectively, as compared to A20 fuel. However, NO emissions rose by 5.36%, 10.20%, 15.28%, and 23.23%, respectively, for A20H5, A20H10, A20H15, and A20H20 test fuels. Ultimately, the utilization of algal biodiesel and hydrogen enrichment in diesel engines was proven to substantially reduce pollutants while increasing efficiency. This study contributes valuable insights into the intersection of renewable fuels, hydrogen enrichment, and engine technology, with the potential to drive significant advancements in sustainable transportation and environmental conservation.

Electrostatic assembly of metal organic frameworks nanocubes on electrochemically exfoliated graphene nanoflakes: Superior role in flame retardance

The extensive usage of epoxy resin (EP) is facing the head-scratching challenge of high fire hazard. As such, the electrostatic assembly of metal organic frameworks (MOFs) nanocubes on electrochemically exfoliated graphene nanoflakes is performed to acquire the hybrid of PG@UIO. The corresponding role and behavior in flame retardance are explored in detail. By adding 2.0 wt% PG@UIO, the reductions in peak heat release rate, total heat release, peak smoke production rate, peak CO yield, peak CO2 yield reach 49.2 %, 44.3 %, 56.1 %, 57.7 % and 51.3 %. The in-situ volatiles analysis points out the reductions of 35.1 %, 29.4 %, 50.8 %, 32.5 % in the maximal intensities of aromatic compounds, ethers, CO and HCN. The mechanical interlocking area between PG@UIO nanostructures and EP molecular chains contributes to the enhanced mechanical performances. Specifically, by adding 2.0 wt% PG@UIO, the flexural strength is increased by 50.3 %. This work enables a new paradigm for fabricating fire-safe polymer composites with the judicious design of MOFs based flame retardant.

Layer-by-layer coated cellulose reduces the fire risk of polyurethane foam biocomposites

Cellulose implementation as filler in polyurethane foams (PUF) often leads to an increased the fire risk associated to the prepared biocomposite. To address this problem, this paper presents a novel approach where the cellulose filler is coated by a nanostructured layer-by-layer (LbL) assembly with flame retardant characteristics before its addition to the biocomposite. During PUF production, the presence of cellulose led to a reduced cell size distribution with improved thermal insulation properties. By forced combustion tests, the use of neat cellulose produced a detrimental effect by increasing the PUF heat release rates (up to +21 %). Conversely, the coated cellulose simultaneously decreased the peak of heat release rate (-22 %) and the total smoke release (-32 %) if compared with the reference PUF. The proposed approach represents a viable strategy for the production of PUF biocomposites where sustainability and fire protection are optimized.

High-performance epoxy resin with flame-retardant, transparent, and ultraviolet shielding properties based on a vanillin-based multifunctional macromolecule

Flame-retardant epoxy resins with tough, transparent, ultraviolet shielding, and low dielectric properties have fascinating prospects in electronic and electrical applications, but it is still challenging at present. In this work, a bio-based macromolecule was synthesized from vanillin (a lignin derivative), phenyl dichlorophosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO), and poly(propylene glycol) bis(2-aminopropyl ether). The bio-based macromolecule, namely, MFR, was designed and added to the epoxy resin (EP). The cured EP containing 15 wt% MFR (i.e., EP/MFR15) exhibits excellent flame retardancy with an Underwriter Laboratory 94 (UL-94) V-0 rating and a limiting oxygen index (LOI) of 29.2 %. Furthermore, the peak heat release rate (PHRR) and total heat release rate (THR) are drastically reduced by 59.5 % and 40.7 %, respectively. Meanwhile, EP/MFR15 shows 20.3 % and 43.8 % improvements in tensile strength and toughness, respectively. Moreover, MFR simultaneously endows EP with accessional ultraviolet shielding performance and low dielectric constant without sacrificing transparency. This work provides a promising strategy for fabricating a bio-based macromolecular flame retardant and preparing a high-performance EP composite with versatile properties.