Peak Heat Release Rate Value Research Articles

Investigation of nanocomposite system with long-chain phosphorus-containing intercalator-modified montmorillonite nanosheets

The biodegradable polyester polybutylene adipate-co-terephthalate (PBAT) is a synthetic material that can melt and ignite easily when exposed to fire. Herein, we synthesized a long-chain phosphorus-containing intercalator by grafting 9,10-dihydro-9-oxa-10-phos-phaphenanthrene10-oxide (DOPO) onto long-chain quaternary ammonium salts (BHMDAC). Then inserted it into the sodium-based montmorillonite (MMT) nanosheets at the ratio of 25.9 wt% to obtain organic modified nanosheets. Subsequently, they were mixed into the PBAT matrix, and a series of performance such as microscopic dispersion, thermal stability, flame retardancy, mechanism and mechanical properties of nanocomposite were investigated. Compared with PBAT (1138.42 kW/m2), PBAT/MMT-(DOPO-BHMDAC) 5 wt% exhibited the lowest peak heat release rate value (508.04 kW/m2), which was reduced by 55.37 %. After adding 1 wt% MMT/DOPO-BHMDAC, the tensile strength of the sample increased from 25.1 MPa to 32.0 MPa, and the elongation at break increased to 826 %. This work provides a new perspective for future research on high-performance degradable polyester materials.

Rationally designed lentinan outer layer to improve the comprehensive performance of flame-retardant cotton fabrics

As the most widely used natural fabric, cotton fabric is highly flammable with serious fire hazard concerns. The use of biomass materials to impart flame resistance to fabrics is always a hot topic of interest. In this work, a novel durable flame retardant cotton fabric (Cotton-APA/LNT) was fabricated by successively covalent bonding ammonium phytate (APA) and lentinan (LNT). The Cotton-APA/LNT fabric sample had a highly limiting oxygen index (LOI) value of 51.5 % and was self-extinguished in the vertical burning test (VBT) at 18.0 % weight gain. The peak heat release rate and total heat release values were decreased by 91.5 % and 46.0 %, respectively compared with those of the control cotton. Besides, after 50 laundering cycles (LCs), the fabric was still self-extinguished in the VBT with an LOI value of 34.2 %. APA fully strengthened the role of acid source by the presence of LNT. The constructed LNT outer layer showed comprehensive improvements in thermostability, flame retardancy, smoke suppression, durability, and breaking force. Specifically, the Cotton-APA/LNT sample had a higher LOI value (↑4.3 %), lower total heat release (↓23.8 %), lower total smoke production (↓29.1 %), higher thermostability (↑27 °C under air), better char formation ability (↑2.0 % under air), higher durability (self-extinguished in the VBT after 50 LCs), and higher breaking force (↑32.5 % in the warp direction and ↑33.9 % in the weft direction) compared with those of Cotton-APA sample. This work has proposed an advanced approach for fabricating eco-friendly durable fire-safety cotton fabrics.

Excellent thermal insulation and flame retardancy property of konjac glucomannan/sodium alginate aerogel reinforced by phytic acid

The growing social awareness of the green industry has driven the rapid development of eco-friendly insulation biomass aerogels to replace traditional ones. Natural polysaccharide aerogels have garnered significant research interest owing to their exceptional sustainability and safety. However, the challenges in achieving a harmonious combination of excellent thermal insulation and flame retardancy have impeded their practical application. In this study, a full biomass konjac glucomannan/sodium alginate aerogel was fabricated with phytic acid (PA) addition to strengthen its thermal insulation and flame retardancy properties. Results showed that the aerogel had a density of 11.8–49.2 mg/cm3 and a porosity of 95.1–98.7%. The physical cross-linking interactions of the components contributed to the formation of the pore structure. Although the analysis on the combustion, residual component, and char layer indicated a higher PA addition strengthened the flame retardancy property, it led to the appearance of micro holes on the pore wall, resulting in poorer thermal insulation properties and significantly weakened mechanical properties. Therefore the optimum PA addition was considered to be 0.25%, and the flame retardancy mechanism was proposed. The obtained aerogel exhibited a thermal conductivity as low as 0.032 W/(mK), compressive strength of 245.4 kPa, limiting oxygen index value of 29.3%, and peak heat release rate value of 21.79 W/g. These findings not only offered a kind of eco-friendly aerogel with excellent thermal insulation and flame retardancy but also contributed to the impact of PA addition on the polysaccharide aerogel structure.

Processing of Pinus sylvestris L. into a heat-insulating, thermally stable, and flame-retarded material by combining the flame-retardant impregnation and densification treatment

Abstract Flame-retardant impregnation and densification are two major modification techniques to improve the fire safety of wood. Here, these two techniques were combined to prepare flame-retarded wood, aiming at further fire hazard reduction. The delignated Pinus sylvestris L. was impregnated with boric acid (BA) and graphene oxide (GO) solutions, then densified to prepare densified flame-retarded wood named BGO-DW sample. The results revealed that the BGO-DW sample obtained a limiting oxygen index (LOI) value of 47.4 %. Its backside temperature after 1200 s heating was 49 % lower than that of unmodified wood. Besides, the peak heat release rate (PHRR) and total heat release (THR) values of BGO-DW sample were 72 and 62 % lower than those of unmodified wood due to its shorter pyrolysis interval and lower peak mass loss rate (PMLR), as supported by thermogravimetric (TG) analysis. The flame retardancy of BGO-DW sample could be attributed to the formation of compatible char containing C=C aromatic structure, C–O–C cross-linked structure, and boron trioxide (B2O3) structure. These features of BGO-DW sample offer a new method to improve thermal stability, heat insulation, and flame retardancy for wood and wood-based products.

Bioinspired Hierarchical Multi-Protective Membrane for Extreme Environments via Co-Electrospinning-Electrospray Strategy.

Extreme environments can cause severe harm to human health, and even threaten life safety. Lightweight, breathable clothing with multi-protective functions would be of great application value. However, integrating multi-protective functions into nanofibers in a facile way remains a great challenge. Here, a one-step co-electrospinning-electrospray strategy is developed to fabricate a superhydrophobic multi-protective membrane (S-MPM). The water contact angle of S-MPM can reach up to 164.3°. More importantly, S-MPM can resist the skin temperature drop (11.2 °C) or increase (17.2 °C) caused by 0 °C cold or 70 °C hot compared with pure electrospun membrane. In the cold climate (-5 °C), the anti-icing time of the S-MPM is extended by 2.52 times, while the deicing time is only 1.45 s due to the great photothermal effect. In a fire disaster situation, the total heat release and peak heat release rate values of flame retarded S-MPM drop sharply by 24.2% and 69.3%, respectively. The S-MPM will serve as the last line of defense for the human body and has the potential to trigger a revolution in the practical application of next-generation functional clothing.

Fully bio-based coating for nylon/cotton blend fabrics with improved flame retardancy and smoke suppression properties

With the increasing requirements of eco-friendly flame retardant fabrics, fully bio-based flame retardants have attracted more and more attention. In this work, a fully bio-based flame retardant coating (PALC) was prepared by combining phytic acid and L-cysteine through ion exchange, which was then applied to nylon-cotton blends. The water contact angle (WCA) test indicates that the hydrophilicity of treated blend fabrics is significantly increased. The treated blend fabrics also exhibited excellent antibacterial property against E. coli and S. aureus. Besides, the limiting oxygen index (LOI) value of the treated blend fabric is increased to 27.2 % from 19.3 %, and the damage length is reduced to 5 cm from 30 cm. The analysis of cone calorimetry test results demonstrates that the total heat release (THR) and peak heat release rate (pHRR) values of the treated blend fabric are reduced by 62.6 % and 65.4 %, respectively, relative to CO/NY. At the same time, the PALC coating can also endow the blend fabric with smoke suppression properties. The total smoke production (TSP) and smoke production rate (SPR) values are reduced by 64.5 % and 67.6 %, respectively. The combination analysis of TG-FTIR, SEM and XPS proves that the phytic acid promotes the dense char layers forming, and L-cysteine generates non-combustible gases. This work provides an eco-friendly and organic solvent-free method for producing flame-retardant nylon/cotton blends with reduced smoke release.

Adsorption charring flame retardant effect of phosphaphenanthrene derivate intercalated micro-expanded graphite composite system in rigid polyurethane foams

Phosphaphenanthrene derivate molecule (DT) was synthesized by a simple method, and exploring the flame retardant effect of DT, micro-expanded graphite (MEG) with different combination modes compounded dimethyl methylphosphonate (DMMP) in polyurethane foam rigid polyurethane foams (RPUFs). The results showed that the properties of an intercalated DT-MEG system was better than a DT blended MEG system. Specific data of DT-MEG/DMMP were as follows: the LOI value of the 6DT-8MEG/16D sample reached 30.3%, the peak heat release rate (PHRR) value decreased by 70.4%, the total smoke release value decreased by 42.4%, the total heat release (THR) value was the lowest at only 14.9 MJ/m2, and the residue yields reached 31.6%. According to the test results, the flame retardant mechanism of the DT-MEG/DMMP compounded system was also explored. DMMP of DT-MEG/DMMP can exert flame retardant effects by releasing phosphorus free radicals in the gas phase to inhibit flame intensity at the beginning of combustion. Then, when the DT-MEG structure was heated, it expanded to form a caged char layer to exert adsorption charring flame retardant effects to filter and absorb the smoke particles. Meanwhile, the intercalated DT-MEG structure produced stronger adhesion with MEG during combustion, which generated more phosphoric acids to carbonize more RPUF matrix. Therefore, DT-MEG/DMMP compound flame retardant system can endow RPUFs with excellent synergistic flame retardant effects in both the gas and condensed phases. This exerts adsorption charring flame retardant effects in the DT-MEG microscopic form, and decreases the combustion intensity and obtains a compacted char layer.

Aromatization of residue caused by group aggregation of hyperbranched ester macromolecule capped with benzene rings improved flame retardancy of epoxy resin

To investigate the effect of the distribution state of phosphophenanthrene groups within the branched structure on the flame retardant efficiency, the hyperbranched ester macromolecules Bz-DQMC-n (n = 1, 2, 3) capped with benzene rings were synthesized. The aggregation effect of phosphaphenanthrene groups in Bz-DQMC-n enhanced the flame retardancy of epoxy resins (EPs). At the same phosphorus contents of EPs, the Bz-DQMC-n/EP passed the V-0 rating, except for 2-(6-oxid-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)-1,4-benzenediol (DOPO-HQ)/EP without aggregated phosphaphenanthrene groups, which only reached the V-1 rating in UL 94 test. The Bz-DQMC-2 showed a better flame inhibition effect. The limiting oxygen index (LOI) value of the Bz-DQMC-2/EP reached to 39.3%, and the peak heat release rate (pk-HRR) value was 563 kW/m2, which decreased by 62.5% compared to neat EP. In addition, the total heat release (THR), and average effective heat of combustion (av-EHC) values of EP with Bz-DQMC-2 were also lower than that with Bz-DQMC-1 and Bz-DQMC-3 in the cone calorimetry test. The mechanism demonstrated that the aggregated phosphophenanthrene groups and benzene rings in Bz-DQMC-2 jointly promoted the formation of high-quality residue with more aromatic structures. Meanwhile, the concentrated release feature caused by group aggregation slightly enhanced the quenching effect in the gas phase. The aggregation effect of phosphophenanthrene groups in specific structures provides guidance for the development of high-efficiency DOPO-based flame retardants.

A highly efficient, colorless phosphorus–nitrogen synergistic flame retardant for durable flame retardancy in wood pulp paper

Wood pulp paper (WPP) is an exemplary substrate material, yet its flammability impedes the widespread application in diverse functional fields. Herein, a highly effective, colorless and transparent phosphorus–nitrogen flame retardant, namely ammonium salt of tris(hydroxymethyl)aminomethane diphosphonic acid (AMPAP-NH4+) without halogen and formaldehyde, has been synthesized for WPP. Chemical grafting was employed to confer highly durable flame retardancy to the WPP, enabling it to maintain excellent fire resistance after functionalization. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) analysis demonstrated that AMPAP-NH4+ was directly linked to cellulose fibers via POC bonds, effectively introducing P and N elements into the WPP without altering the surface morphology of the fibers. Results from thermogravimetric analysis, vertical burning test, limiting oxygen index test, cone calorimeter test and thermogravimetric-Fourier infrared spectrometer test demonstrated that the treated WPP exhibited outstanding flame retardancy. The peak heat release rate (pHRR) and total heat release (THR) values decreased by 80.8% and 70.9%, respectively, and the limiting oxygen index (LOI) increased to 41.4%. Furthermore, due to the stability of the POC bond, the treated samples remained unignited after 168 h, with a high LOI value of 35.3%. In summary, AMPAP-NH4+ serves as a phosphorus–nitrogen synergistic transparent flame retardant that can effectively and durably impart paper with flame retardancy without altering its surface morphology.

Solvent-free intumescent fire protection epoxy coatings with excellent smoke suppression, toxicity reduction, and durability enabled by a micro/nano-structured P/N/Si-containing flame retardant

The development of solvent-free intumescent fire protection epoxy (EP) coatings with excellent durability is an extremely important issue for the protection of storage tanks and structural steels in the coating industry. In this work, a micro/nano-structured phosphorus/nitrogen/silicon-containing flame retardant (APP@Si) was synthesized by silica nanoparticles-modified ammonium polyphosphate, which was utilized to prepare high-performance intumescent fire protection epoxy resin (EP) coatings via a solvent-free method. APP@Si enhanced fire protection, smoke suppression, toxicity reduction, mechanical properties, and durability of solvent-free EP coatings. APP@Si with a 10 wt% loading level endowed solvent-free EP coating (EP/10APP@Si) with a limiting oxygen index value of 32.4 % and a UL-94 V-0 rating. Meanwhile, APP@Si declined the peak heat release rate, smoke factor, and peak CO production rate values of EP/10APP@Si by 77.5 %, 92.6 %, and 56.4 %, respectively, compared with those of pure EP. Moreover, the maximum back temperature of EP/10APP@Si was as low as 126.4 °C under heating for 1200 s in the back temperature test, which was 221.5 °C lower than that of pure EP. The increase in fire protection of EP/APP@Si coating was mainly attributed to forming an intumescent and dense char layer with strong strength and high expansion degree during combustion. In addition, APP@Si enhanced the flexural strength and impact strength of EP/10APP@Si by 12.0 % and 24.6 % compared with those of EP/10APP. Moreover, APP@Si also increased the water contact angles of EP/APP@Si coatings from 87.9° for pure EP to 93.3° for EP/10APP@Si. And the weight change rate of EP/10APP@Si was the lowest among all coatings after immersing in the deionized water for 20 days. Therefore, this work presented a feasible strategy for fabricating multifunctional solvent-free intumescent fire protection epoxy coatings, which was expected to be applied in the coating industry.

Copper phenyl phosphonate for epoxy resin and cyanate ester copolymer with improved flame retardancy and thermal properties

Abstract Epoxy resin (EP)/cyanate ester (CE) copolymer, an important structural material with high temperature resistance and low dielectric constant in aerospace, microelectronics, and related fields, is still of great flammability danger. In this work, copper phenyl phosphonate (CuPP), a flame retardant used in EP/CE copolymer was synthesized by the reaction of phenyl phosphonic acid and copper nitrate trihydrate. The fire and thermal behavior of EP/CE/CuPP composites were studied in detail. The results suggested that the UL-94 rating and limiting oxygen index of EP/CE composite with 5 wt% CuPP (EP/CE/CuPP5) reach V-1 level and 30.6%, respectively. Compared with pure EP/CE copolymer, the peak heat release rate and total heat release values of EP/CE/CuPP5 decreased by 34.5% and 18.9%, respectively. The glass transition temperature of EP/CE/CuPP composite is higher than that of pure EP/CE copolymer, suggesting that the fire-retardant composite has higher work temperature and better heat resistance.

Mechanical, Thermal, and Fire Retardant Properties of Rice Husk Biochar Reinforced Recycled High-Density Polyethylene Composite Material.

This study concentrated on the influence of rice husk biochar on the structural, thermal, flammable, and mechanical properties of recycled high-density polyethylene (HDPE). The percentage of rice husk biochar with recycled HDPE was varied between 10% and 40%, and the optimum percentages were found for the various properties. Mechanical characteristics were evaluated in terms of the tensile, flexural, and impact properties. Similarly, the flame retardancy of the composites was observed by means of horizontal and vertical burning tests (UL-94 tests), limited oxygen index, and cone calorimetry. The thermal properties were characterized using thermogravimetric analysis (TGA). For detailed characterization, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) tests were performed, to elaborate on the variation in properties. The composite with 30% rice husk biochar demonstrated the maximum increase in tensile and flexural strength, i.e., 24% and 19%, respectively, compared to the recycled HDPE, whereas the 40% composite showed a 22.5% decrease in impact strength. Thermogravimetric analysis revealed that the 40% rice husk biochar reinforced composite exhibited the best thermal stability, due to having the highest amount of biochar. In addition, the 40% composite also displayed the lowest burning rate in the horizontal burning test and the lowest V-1 rating in the vertical burning test. The 40% composite material also showed the highest limited oxygen index (LOI), whereas it had the lowest peak heat release rate (PHRR) value (52.40% reduced) and total heat release rate (THR) value (52.88% reduced) for cone calorimetry, when compared with the recycled HDPE. These tests proved that rice husk biochar is a significant additive for enhancing the mechanical, thermal, and fire-retardant properties of recycled HDPE.

Simulation Study on Suppressing Shielded Fires by Water Mist Systems

This article presents a numerical analysis of the performance of three water mist fire suppression systems, with different characteristics, on shielded fires as representing more realistic fire scenarios in an enclosure. A diesel pool fire with a peak heat release rate (HRR) value of 75 kW is covered by an obstacle above it with different shielding conditions to investigate the influence of the obstacle size and the vertical distance between the obstacle and the nozzle on the efficiency of the water mist systems. The obstacle prevents a large number of droplets from directly reaching the fuel surface and flames. The modeling and numerical analysis of this study were carried out by the fire dynamics simulator (FDS) programming tool, and the designed model was validated against the experimental data for both dry and wet tests. The results show that two of the analyzed mist sprays could successfully extinguish the shielded fires in a short time with an obstacle size of 25 cm × 25 cm and 50 cm × 50 cm, placed at two heights. However, the third mist system had a longer extinguishing time compared to the first two nozzles. All three nozzles failed to suppress the fire covered by the largest obstacle (1 m × 1 m). The shielding conditions and nozzle characteristics can affect the performance of water mist systems to some extent.

Preparation and properties of APP flame-retardant ramie fabric reinforced epoxy resin composites

Ramie fabrics (RFs) as natural fibers have shown promising potential in the field of fiber reinforced composites, but flammability of RFs limits their application in composites. In this study, ammonium polyphosphate (APP) was first coated on the surface of RFs, and then the flame-retardant RF reinforced epoxy resin composites were obtained. When the weight gain rate of APP in RFs was about 20 %, the limiting oxygen index of the flame-retardant composites reached 33.8 %, and achieved UL-94 V-0 rating. At the same time, the peak heat release rate and total heat release values of the flame-retardant composites were reduced by 26 % and 41 % respectively, and the total smoke production was reduced by 43.9 %. In terms of mechanical properties, the presence of APP had a certain negative effect on the internal compatibility of composites. In this work, the flame-retardant composites show excellent flame retardancy and provide a feasible solution to improve the flammability of natural fiber reinforced composites.

Facile fabrication of efficient flame retardant-modified wool fabrics with antibacterial properties by zinc‐based coating

Flame retardant and antibacterial applications of wool are attracting increasing scientific attention. Herein, we report a facile method to deposit a zinc-based coating on the surfaces of wool fabric and fabricate functional fabrics with flame retardant and antibacterial properties. The wool fabrics with 9.9 % weight add-on could reach a limit oxygen index value of 33.7%. Compared to the control sample, the coated sample exhibited better fire safety properties, with peak heat release rate and total smoke production values decreased by 46.5% and 33.7% during a cone calorimeter test. The obtained wool fabrics also demonstrated excellent antibacterial properties, with Staphylococcus aureus and Escherichia coli killing rates of 99.4% and 96.9%, respectively. These results proved that the treated wool samples had excellent flame retardancy and antibacterial properties. Additionally, the flame-retardant coating had minor negative effects on the whiteness and strength of the wool fabrics.

Synthesis of a vanillin-derived bisDOPO co-curing agent rendering epoxy thermosets simultaneously improved flame retardancy, mechanical strength and transparency

To prepare transparent and flame-retardant epoxy thermosets, a vanillin-derived bisDOPO co-curing agent (DVD) was synthesized from vanillin and DOPO. The influence of DVD on the curing kinetics of the epoxy systems was investigated by non-isothermal differential scanning calorimetry (DSC). The introduction of DVD increased the activation energy of the curing process. Compared with pure epoxy, the storage modulus at 30 °C and tensile strength of EP/DVD-5% increased by 35.7% and 145%, respectively. Additionally, the epoxy thermosets still maintained excellent transparency. The addition of DVD improved the flame-retardant performance of epoxy thermosets by promoting the formation of char and reducing the thermal decomposition rate. Most importantly, DVD showed high flame retardant efficiency for the resulting epoxy thermosets. Specifically, with the incorporation of 5 wt% DVD (only 0.42 wt% phosphorus loading), the resulting epoxy thermoset exhibited a limiting oxygen index (LOI) value of 30.5% and reached a UL-94 V-0 rating. The cone calorimetry results showed that the total heat release (THR), peak value of heat release rate (PHRR), and total smoke production (TSP) of EP/DVD-5% decreased by 32%, 42%, and 21%, respectively, compared with the unmodified EP. The modes of action of flame retardant analysis indicated that DVD exhibited high flame retardant efficiency by serving as a charring promotor in the condensed phase and acting as a radical scavenger in the gaseous phase. The above results demonstrate that DVD is a promising flame retardant agent to render epoxy thermosets simultaneously improved flame retardancy, mechanical strength and transparency.

Development of ductile green flame retardant poly(lactic acid) composites using hydromagnesite&huntite and bio‐based plasticizer

AbstractTurning brittle poly(lactic acid) (PLA) to ductile form via plasticizer inclusion is an effective option in the case of processing with high amounts of additives. Additionally, the integration of natural flame retardants to PLA involving bio‐based plasticizer enables to use of environmentally friendly composites in conditions where fire resistance performance is required. In the current study, ductile green fire retardant PLA composites were manufactured using hydromagnesite&huntite (HH) as a natural fire retardant additive and acetyl tributyl citrate as a bio‐based plasticizer. The influences of plasticizer and HH contents on the fire retardant, thermal and mechanical performances of the composites were explored. According to test results, the limiting oxygen index (LOI) value of PLA reduced from 29.2 to 28.0 and the UL‐94 V rating changed from V2 to BC with the addition of 20 wt% plasticizer owing to the reduction in melt viscosity. The peak heat release rate (pHRR) and average heat release rate (avHRR) values increased steadily as the concentration of plasticizer increased due to the formation of a more porous residue structure stemming from the increased transportation rate of gases. In order to produce ductile flame retardant material, the plasticizer content was required to 20 wt% of HH. The highest LOI value (36.2) and UL‐94 rating of V0 were achieved with the inclusion of 70 wt% HH in the presence of 20 wt% plasticizer. Improvement in impact resistance and reduction in tensile strength were observed as the added amount of plasticizer increased.

Preparation of an integrated P–N–Si tube containing phosphazene-triazine-silica structure: An efficient flame retardant agent for epoxy resin

To reduce the fire risk of EP, an amino-silica functionalized triazine-rich polyphosphazene tube (MTP@NH2–SiO2) was designed and prepared. With low addition of MTP@NH2–SiO2 (0.5 wt% and 1.5 wt%), the peak value of heat release rate (PHRR) of EP/MTP@NH2–SiO20.5 and EP/MTP@NH2–SiO21.5 decreases by 55.1% and 72.4%, respectively. The total smoke production (TSP) of EP/MTP@NH2–SiO21.5 is of 52.8% reduction. And the fire growth index (FGI) and the fire performance index (FPI) of EP/MTP@NH2–SiO21.5 are 2.74 kW/(m2s) and 0.19 (m2s)/kW, which means EP/MTP@NH2–SiO21.5 is of the lowest fire risk properties. Therefore, the fire safety properties of EP/MTP@NH2–SiO2 can be improved by designed MTP@NH2–SiO2 indeed. MTP@NH2–SiO2 is with high-efficiency of condensed phase flame retardant effect on EP. EP/MTP@NH2–SiO2 can form a glass-like protective char layer rich in phosphorus-nitrogen-silicon (P–N–Si), so as to suppress the transmission of volatile products, oxygen and heat in combustion zone of EP, thus improving the fire safety of EP.

Simultaneously improving the hydrophobic property and flame retardancy of aluminum hypophosphite using rare earth based coupling agent for epoxy composites

AbstractA novel hydrophobic rare earth‐based aluminum hypophosphite (AHP) was prepared using rare earth aluminate coupling agent (REA) in a ball mill with a one‐step mechanochemistry method, and used as flame retardant for epoxy resin. It has been found that RaAHP‐4 (AHP was modified by 4 wt% REA) exhibited excellent hydrophobic properties with the water contact angle of 94.58°. The effect of RaAHP‐2 (AHP was modified by 2 wt% REA) and RaAHP‐4 on the flame retardancy, thermal stability, and hydrophobic properties of EP/6RaAHP‐2 and EP/6RaAHP‐4 composites were investigated. It has been found RaAHP‐2 and RaAHP‐4 can significantly improve the flame retardant performance of EP/6RaAHP‐2 and EP/6RaAHP‐4 composites. And the peak heat release rate (PHRR) and total heat release (THR) values of EP/6RaAHP‐4 were reduced by 50.44% and 35.59% compared with pure EP, respectively. Moreover, the maximum peak value of CO production rate from EP/6RaAHP‐4 decreased by 62.64% compared with that from EP/6AHP. The excellent flame retardant effect of EP/6RaAHP‐4 composites was obtained because RaAHP‐4 changed the formation of the char residue layer during the combustion process. In comparison, the compactness, expansion degree, and carbonization quality of the char residue layer from the samples with RaAHP‐2 or RaAHP‐4 have been significantly improved, which acted as a valuable barrier for heat and mass transfer. The above results showed that the one‐step synthesis method had high potential application in the large‐scale production of hydrophobic AHP.

Effect of diesel/PODE/ethanol blends coupled pilot injection strategy on combustion and emissions of a heavy duty diesel engine

Ethanol has limited solubility in diesel. Polyoxymethylene dimethyl ethers (PODE) can enhance the miscibility of ethanol/diesel blends. The application of pilot injection strategy can improve combustion noise and NOx emissions. Thus, the effects of different diesel/PODE/ethanol blends coupled various pilot injection strategies on the combustion, performance and emissions were conducted in a six-cylinder heavy duty diesel engine. As renewable alternative fuel, PODE has the characteristics of high cetane number, high oxygen content and no CC bond, while ethanol has the characteristics of high volatility and high oxygen content. The results show that the significant differences in heat release rate (HRR) and maximum pressure rise rate (MPRR) among DP20, DPE5, DPE10 and DPE15 can be reduced by using the pilot injection, in that the differences in HRR timing and peak value of HRR are weakened. Both the brake and indicated thermal efficiency of blends can be improved by appropriately optimizing the pilot strategy, when compared with the case of single injection. The thermal efficiency of blends is more sensitive to the pilot injection quantity, while the CO and HC emissions are more sensitive to the pilot-main interval. For single injection, blending ethanol into PODE/diesel blends causes adverse effects of increasing hazardous gas emissions, while optimizing pilot injection strategy can reduce the hazardous gas emissions of the blends to the best level of diesel and significantly reduce soot emissions when compared to diesel.