Peak Heat Release Rate Research Articles

Interfacial engineering of 0D–2D hierarchical MXene@PEI@AgNC nanohybrids to achieve flame retardant, mechanical and antibacterial properties of ABS nanocomposites

It is an intractable challenge that the hierarchical MXene-based nanohybrid fillers are intended to modify the inherent flammability and easily breeding bacteria property of ABS polymeric materials, thereby facilitating wide applicability of ABS composites. Here, an interface engineering strategy was proposed, wherein polyethyleneimine (PEI)-modified silver nanocubes (AgNCs) was firmly assembled on MXenes via electrostatic interaction to construct 0D–2D hierarchical MXene-based nanohybrids (MXene@PEI@AgNC). The MXene was protected and the interface compatibility between MXene-based nanohybrid and ABS matrix was enhanced. Results revealed that the unique hierarchical structure of the composite promoted enhanced dispersion of MXene@PEI@AgNC in the ABS matrix. Combustion tests showed that 1.0 wt%MXene@PEI@AgNC provided the ABS with effective fire safety. Moreover, ABS-1.0 wt%MXene@PEI@AgNC exhibited a 31.88 % decrease in peak heat release rate, a 39.60 % decrease in peak smoke release rate, a 41.50 % decrease in peak CO2 production rate, and a 50.04 % reduction in the smoke factor. Meanwhile, 1.0 wt%MXene@PEI@AgNC improved the tensile strength of ABS-1.0 %MXene@PEI@AgNC (+18.1 %) without reducing the elongation at break. They also enhanced the antibacterial properties of ABS-1.0 %MXene@PEI@AgNC. This study proposed a novel and feasible approach to address the interfacial stability of MXene and to construct MXene-based hierarchical nanoblends, thereby facilitating the wide practical applications of polymeric nanomaterials in industry.

Enhanced flame retardancy and mechanical properties of poly (lactic acid) composites via piperazine pyrophosphate and nanoscale cerium dioxide synergistic flame retarding and uniaxial pre-stretching

The simultaneous improvement of flame retardancy and mechanical properties (including strength, rigidity, and toughness) of PLA was achieved for the first time. A synergistic flame retardant system including PAPP and nano-CeO2 was used to enhance the flame retardant properties of PLA. Especially, uniaxial pre-stretching was further used to improve the mechanical properties of the flame-retardant PLA composites. With the addition of just 1 wt% nano-CeO2, the flame retardant properties of PLA composite were significantly enhanced. Relative to pure PLA, the limiting oxygen index (LOI) of PLA/14 wt%PAPP/1 wt% nano-CeO2 increased from 20.2 % to 28.8 %, achieving a V-0 rating in the UL-94 test. Moreover, the peak heat release rate (PHRR) was reduced from 461KW/m2 to 230KW/m2. Notably, the flame-retardant PLA composites with excellent mechanical properties were achieved using uniaxial pre-stretching for the first time. After pre-stretching, the tensile strength, elongation at break and impact strength of the flame-retardant PLA were significantly increased to 79.82 MPa, 103.8 %, and 9.7 kJ/m2, respectively. This work proposes an ingenious strategy for significantly enhancing both the fire safety and mechanical properties of PLA composites.

Full bio-based flame retardant towards multifunctional polylactic acid: Crystallization, flame retardant, antibacterial and enhanced mechanical properties

The preparation of flame-retardant high-performance polylactic acid (PLA) composites by adding green flame retardants have always been a challenge. In this work, an intumescent flame-retardant PCR based on phytic acid, chitosan, and resveratrol was successfully designed. Adding 4 wt% of PCR, the PLA-PCR composite was classified as UL-94 V-0 grade, with a LOI value increasing from 19.7 % (pure PLA) to 26.0 %, a peak heat release rate decreasing from 433 to 344 kW/m2. Owing to excellent compatibility of PCR, the mechanical strength and toughness of PLA-PCR composites have been improved, as reflected by a ~ 16 % increase in tensile strength, a ~ 73 % increase in impact strength and a ~ 57 % increase in toughness. In addition, PCR also presented plasticization effect on PLA, making it easier to process. This work provided a highly efficient and environmental-friendly modification approach for the development of multifunctional polymers.

An organic-inorganic dual network built in fast-growing wood veneers to improve the flame retardant and mechanical properties of plywood

Fast-growing wood is widely used in plywood production due to its short growth cycle and low cost. However, its loose fiber structure, inferior material quality, and high flammability significantly limit the application range of plywood products and hinder high-value utilization. This paper reports a simple method for modifying fast-growing wood veneers. We modified phenolic resin with Mg(OH)₂@nano-silica composite particles and impregnated it into the veneers, constructing an organic-inorganic hybrid dual-network structure on both the surface and interior of the veneers. The plywood prepared from the modified veneers exhibited a bending strength of 115.6 MPa, a modulus of elasticity of 9.7 GPa, and a wet shear strength of 2.1 MPa, representing increases of 86.1%, 47.0%, and 90.9%, respectively, compared to plywood made from unmodified veneers. Additionally, the peak heat release rate decreased by 15.3%, and the ignition time was extended to 26 seconds. The uniformly distributed inorganic network effectively mitigated stress concentration and, together with the phenolic resin, formed an efficient thermal insulation layer, enhancing the flame retardancy of the material. This study offers a simple and effective treatment method for reinforcing fast-growing wood veneers, promoting the use of fast-growing wood in high-performance applications.

Hierarchical Nano/Micro-Array Structured CuMgAl-LDH/rGO Hybrids for Remarkably Improved Flame Retardancy and Smoke Suppression Performance of Flexible Polyvinyl Chloride.

In this study, we explored the rational integration of layered double hydroxides (LDHs) with reduced graphene oxide (rGO) to create a hierarchical nano/microarray structured CuMgAl-LDH/rGO hybrid aimed at enhancing the flame retardancy and smoke suppression properties of polymer nanocomposites. The results indicated that the limiting oxygen index (LOI) value of the G-CuMgAl/polyvinyl chloride (PVC) composite reached 35.8%, reflecting a 6.4% increase compared to pristine PVC (29.4%), and achieved a UL-94 V-0 rating. Furthermore, in comparison to pristine PVC, the peak heat release rate (PHRR) of the G-CuMgAl/PVC composite was significantly reduced by 40.2%; the total heat release rate (THR) decreased by 24.3%; the maximum average heat release rate (MARHE) diminished by 41.6%; the peak smoke production (PSPR) decreased by 37.8%; the total smoke production (TSP) was reduced by 31.3%; and the average effective heat of combustion (av-EHC) decreased by 15.2%. The enhanced flame retardancy and reduced smoke production can primarily be attributed to the multiple synergistic interactions among the highly dispersed constituents and the nano/microstructures, which effectively impede the transfer of heat, mass, and O2 from various directions while preventing further combustion of the underlying matrix by creating a tortuous path in the condensed phase. Additionally, this study provides a novel perspective on the design and synthesis of structured LDHs/rGO hybrids, with the potential to enhance flame retardancy and smoke suppression properties across a broad spectrum of polymer materials.

A reactive melamine-DOPO based flame retardant for superior thermal stability and flame retardancy in rigid polyurethane foam

The flame-retardant effect of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and its derivatives in reducing the flammability of polymeric materials are well known. In this study, flame-retardant rigid polyurethane foams (FR-RPUF) were synthesized using a melamine-DOPO-based flame-retardant (MDFR). Additionally, MDFR was also used for preparation of a flame-retardant elastomeric polyurethane (FR-PUE). The chemical structure and thermal properties of the FR-RPUF and FR-PUE samples were studied with Fourier transform infrared (FTIR), field emission-scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). TGA results revealed that the incorporation of MDFR into the PU matrix significantly increased the char residue. The char residue of FR-RPUF with 0.5 wt% MDFR increased from 4.75% to 44.36%, as compared to the pure RPUF. Results from the microscale combustion calorimeter (MCC) test illustrated that the peak of heat release rate (pHRR), total heat release (THR), and heat release capacity (HRC) of the FR-RPUF and FR-PUE samples were reduced, as compared to the pure PU samples. The pHRR value of FR-RPUF with 3 wt% of MDFR decreased 12%, as compared to the pure RPUF, while the pHRR was obtained 34% lower than of the pure PUE. Furthermore, FR-RPUFs successfully passed the UL94 testing, achieving a V-0 grade.

Informal settlements ablaze: decoding the combustible nature of building materials used in Bangladesh through experiments and numerical analysis

ABSTRACT Fire outbreaks in informal settlements pose severe threats to residents and their properties. Despite the frequent occurrence of fire events in Bangladesh, detailed studies on fire propagation behaviour remain limited. This study addresses this critical issue by comprehensive investigations into the ignitability and burning behaviour of different materials such as cardboard, polyurethane foam, plastic bags, wood, and structural timber that are commonly found in informal settlements. Additionally, an advanced numerical model based on the finite volume method was developed in Fire Dynamics Simulator and then employed to accurately predict the fire-reaction properties of materials under the cone calorimeter environment. The results revealed that cardboard ignites quickly, burns moderately, and does not produce flaming droplets or ignite the filter paper. PU foam burns vigorously, with a high burning rate, and emits dense black smoke and a toxic odour. Plastic bags ignite rapidly, burn intensely, and are greatly influenced by the presence of airflow. The numerical model successfully quantified fire-reaction properties such as ignition time, heat release rate (HRR), and flame spread characteristics. Notably, wood and structural timber demonstrate a distinct combustion pattern with a sharp HRR peak, while PU foam exhibits the highest peak HRR values followed by timber masonite.

Enhancing Flame Retardancy in Epoxy Resin with Clever Self-Assembly Method for Optimizing Interface Interaction via Well-Dispersed Cerium Oxide on Piperazine Pyrophosphate

Developing flame-retardant epoxy resins (EPs) is essential to broaden their industrial applications, as their inherent flammability restricts their widespread use. In this study, commercial cerium oxide (CeO2) nanoparticles were modified with oleic acid and successfully assembled onto the surface of pyrophosphate piperazine (PAPP) through a simple solvophobic effect, constructing an integrated superstructure flame retardant, CeO2@PAPP, with enhanced performance integration. Compared to traditional simple blends, the EP composite with 10 wt% CeO2@PAPP displayed superior flame retardancy, thanks to the more subtle synergistic effects between flame retardant components and their favorable interface interactions. The EP composite achieved a UL-94 V-0 rating and increased the limiting oxygen index (LOI) to 34.2%. Significant reductions of 56.3% in peak heat release rate (PHRR) and 38.2% in total heat release (THR) were observed. Furthermore, total smoke release (TSR), carbon monoxide yield (COPR), and carbon dioxide yield (CO2PR) decreased by 52.2%, 50.2%, and 67.3%, respectively. Through comprehensive and detailed characterization, it was discovered that the assembled integrated CeO2@PAPP flame retardant can perform better in both the gas phase and condensed phase, resulting in superior flame-retardant properties. This study offers an effective strategy for developing highly flame-retardant EPs, thereby expanding their potential applications across various industries.

Sustainable lignin-based high-efficiency flame-retardant epoxy resins with excellent mechanical properties

As an abundant natural aromatic polymer, how to realize the high-value utilization of lignin (LA) is still a difficult problem. Herein, a sustainable flame retardant (LA@APP) was synthesized through hydrogen bonding interactions between LA and ammonium polyphosphate (APP), then flame retarded alone epoxy resin (EP/LA@APP). With loading of 6 wt% LA@APP, the LOI of EP/LA@APP6 rose to 27.9 % and achieved UL-94 V0 rating. Meanwhile, EP/LA@APP6 presented a 63.5 % reduction in peak of heat release rate (pHRR) and an 51.3 % decrease in peak of smoke production rate (pSPR). LA@APP could promote the EP composites to form the denser and more continuous expanded charring residuals than APP during the combustion process, effectively shielding the underlying epoxy substrate and thus enhancing fire safety. Additionally, the shell layer of LA@APP, abundant in hydroxyl groups and methoxy groups, effectively improved the compatibility and interfacial interaction with EP. Therefore, the tensile, flexural and impact strength of EP/LA@APP6 reached 50.8 MPa, 86.1 MPa and 7.81 kJ/m2, higher than those of pure EP at 48.3 MPa, 81.5 MPa and 7.45 kJ/m2. This flame retardant with simultaneously enhanced fire safety and mechanical properties of epoxy resin was expected to realize the high-level utilization of lignin.

Polyaniline as a dual flame retardant and electrostatic dissipative additive in polyethylene nanocomposites

AbstractPolyolefins, such as polyethylene (PE), are highly flammable and electrically insulative, limiting their applicability. The study explored the flame‐retardancy and electrical conductivity of PE/polyaniline (PE/PANI) nanocomposites containing undoped PANI, PANI doped, and co‐doped with various acids and PANI modified with a double layered hydroxide or ammonium polyphosphate (APP). The nanocomposites were synthesized through in situ chemical oxidative polymerization of aniline and compression molding. Flame retardancy was evaluated using UL 94 tests and cone calorimetry. All nanocomposites, except the de‐doped PANI nanocomposite, attained a UL 94 V2 rating. Cone calorimeter results showed that PANI doped with H3PO4 reduced the peak heat release rate by 20% compared to neat PE, whereas co‐doping PANI with H3PO4 and phytic acid reduced it by 31%. The nanocomposites exhibited volume resistivity for suitable for electrotactic dissipation applications but showed marginally reduced mechanical properties. This study demonstrates the potential to develop electrostatic dissipative and flame‐retardant PE nanocomposites incorporating PANI.Highlights PE/PANI nanocomposites were synthesized. PANI doped with H3PO4 reduced the peak HRR by 20%. Co‐doping PANI with H3PO4 and phytic acid further reduced peak HRR. Nanocomposites attained a UL 94 V2 rating. PE/PANI nanocomposites were electrostatic dissipative.

Ultralean Combustion Mechanism of Methane–Air Swirling Premixed Flame

ABSTRACT This study investigated a methane – air premixed flame in a partially tapered swirl burner. Experimentally, we succeeded in forming almost steady ultralean flames with an equivalence ratio as lean as 0.465. On the other hand, a numerical simulation of the flame with detailed chemistry revealed that the flame head existed in a large recirculation zone under ultralean conditions. In addition, high-value peaks of temperature, heat-release rate (HRR), and concentrations of OH, O, and H radicals were formed at the flame head, enabling ultralean combustion. Subsequently, to identify the formation mechanism of these peaks, adiabatic swirl burner flames were simulated with and without the effect of thermal-diffusive imbalance (a Lewis number effect). The results show that a Lewis number of less than unity caused a temperature increase in the flame located in the recirculation zone owing to the thermal-diffusive imbalance, which increased the peak heights of the HRR and the three radicals. The results also showed that even in a flame unaffected by thermal-diffusive imbalance, the backward convective transport could accumulate CO and OH at the flame head thus enhancing the chemical reactions at the head. (185 words)

Assessing the Fire Properties of Various Surface Treatments on Timber Components in Ancient Chinese Buildings: A Case Study from the Xianqing Temple in Changzhi, Shanxi, China

Traditional and modern coatings play a key role in enhancing the fire resistance of ancient Chinese buildings. However, further comparative analysis is needed on the fire properties of the two coatings and their effects on different timber structural components. This study focuses on the main hall of the Shanxi Changzhi Xianqing Temple, a typical traditional column and beam construction built between the Song and Jin periods. Firstly, the combustion characteristics of various timber structural component samples with different surface treatments (traditional “Yi-ma-wu-hui” and modern flame retardants) were analyzed using cone calorimeter. Secondly, the fire development process of the Xianqing Temple building model was analyzed by a fire dynamics simulator (FDS), and the effect mechanism of different surface treatments on the burning process was further studied. The results show that the fire resistance of timber structural components is significantly improved after modern and traditional surface treatments. The traditional method is more effective in delaying the peak heat release rate and reducing the surface temperature during combustion, while the modern surface treatment significantly prolongs the ignition time of the timber structural components. The FDS results confirm that modern and traditional surface treatments significantly improve the fire resistance of the building, delaying the flashover time by about 300 s, with no collapse occurring within 800 s. In addition, the fire resistance of buildings after traditional surface treatment is better compared to traditional methods. The above research results can provide direct data support for the selection and optimization of fireproof coatings and treatment methods for ancient buildings.

Co Hybrids modified piperazine pyrophosphate towards efficient flame retardancy, smoke suppression, and high mechanical properties of styrenic thermoplastic elastomer

The highly flammable nature of thermoplastic elastomers (TPE) results in poor fire safety performance. The large addition of flame retardants leads to a significant decrease in mechanical properties. To solve above challenges, we design a multilayer core-shell flame retardant, piperazine pyrophosphate@ tannic acid@ Co amorphous hybrids (PAPP@TA@Co-2-MIM) and add it to TPE to enhance the fire safety and mechanical performance simultaneously. It was found that the addition of 32 wt% PAPP@TA@Co-2-MIM achieved a UL-94 V-0 rating of TPE composites, with a limiting oxygen index of 27 %. Compared to pure TPE, the peak heat release rate, total heat release, total smoke production, and peak CO release rate of TPE/PAPP@TA@Co-2-MIM were reduced by 79.8 %, 37.1 %, 42.9 %, and 82.5 %, respectively, effectively suppressing the release of heat, smoke, and toxic gases. Besides, the flame-retardant mechanism was also explained. In terms of mechanical performance, benefiting by the bridging effect of the core-shell structure, the tensile strength of TPE/PAPP@TA@Co-2-MIM increased by 52.7 %, compared to TPE/PAPP. This study designed a TPE composite material that showed good thermal stability, high fire safety performance and enhanced mechanical properties.

Highly efficient flame retardancy and fire spread behavior of rigid polyurethane foams with extremely low content of flame retardant

In recent years, flame-retardant rigid polyurethane foam (RPUF) has once again captured the scholars’ attention due to the growing the growing demands in the field of building energy efficiency. However, the inherent flammability of RPUF is high and the complexities of its flame-retardant mechanisms remain inadequately understood. In this study, a modified biomass material, amino starch phosphate ester was successfully synthesized which was then combined with expandable graphite (EG) and incorporated into RPUF. The research delved into the optimal ratio and minimal flame-retardant additive required to achieve the stringent UL-94 V-0 rating, while also thoroughly investigating the flame retardancy and thermal properties of the composite system. The findings revealed that with just 6 wt.% of flame retardants, the RPUF achieved the UL-94 V-0 rating, with a 41.1 % reduction in peak heat release rate (pHRR) and a 23.7 % decrease in total heat release (THR). Additionally, it diminishes the flame's size and width, leading to quicker extinction, while also lowering the internal combustion temperature of the polyurethane, thereby delaying both preheating and combustion times. The synergistic interaction between amino starch phosphate ester and EG during combustion results in the formation of a dense, continuous char layer, effectively inhibiting the pyrolysis and combustion of RPUF. This study provides a theoretical foundation for the development of efficient flame-retardant systems for RPUF.

Synergistic Effect of GO and MXene Enables Ultrasensitive, Reversible, and Self-Powered Fire Warning of a GO/MXene/Chitosan Aerogel.

Graphene oxide (GO)-based fire alarm materials have garnered extensive attention because the thermal reduction of GO to reduced GO (RGO) enables rapid fire warning. However, they suffer from poor flame retardancy, irreversible fire warning, and dependence on an external power supply. Herein, a GO/MXene/chitosan aerogel with a low density of 0.018 g cm-3 and good compressibility has been developed. The experimental results demonstrate that (i) MXene effectively reduces the peak and mean heat release rate of GO, while RGO nanosheets compensate for the structural instability of MXene in the flame due to thermal oxidation into TiO2; as such, long-lasting fire warning (>120 s) has been achieved; (ii) the reducibility and conductivity of MXene contribute to the ultrasensitive response of GO, with a fire response time of 1 s; and (iii) notably, the thermoelectric effect of MXene enables the reversible and self-powered fire warning of the GO/MXene/CS aerogel without an external power supply. Compared to pure MXene/CS aerogel, the presence of GO improves the sensitivity and stability of self-powered fire warning, owing to the formation of the highly conductive RGO nanosheets. The results of this work highlight the cooperation between GO and MXene in realizing ultrasensitive, long-lasting, reversible, and self-powered fire warning.

Optimised prediction of tunnel fire heat release rate using the ResNet18_2CLSTM model with bagging for multimodal data

Accurate predictions of HRR will improve preparedness and response strategies, enhance safety, and minimise damage in tunnel fires. In this study, a deep learning prediction model for HRR under multimodal data fusion is proposed. A multimodal dataset is first established to obtain flame images and flue gas time series data through model-scale tunnel fire experiments. During the model training process, ResNet18 was used to extract features from the flame image, and 2CLSTM was employed to understand the time series of the flame image features and flue gas features to establish the correlation with the HRR. It was evaluated that the error analyses of the measured and predicted values of the validation set yielded R2 greater than 0.85, with errors and standard deviations less than 4 kW. And the model predicted better in the flame growth and decay phases. However, there is some deviation in the predictions near the peak HRR. To address this issue, the Bagging algorithm was introduced to optimise the model. The results show that the ResNet18_2CLSTM model with Bagging reduces the RMSE by 20.47 % and increases the R2 by 4.64 % compared to the original model, and the accuracy is greatly improved.

Effects of Diesel Pre-Injection Time on Combustion Process and Emission Characteristics of Diesel/Methanol Dual Fuel Engine

ABSTRACT The traditional diesel engine not only causes the reduction of nonrenewable energy but also aggravates environmental pollution. The utilization of renewable fuels in engine can not only effectively reduce the dependence on oil sources but also effectively reduce emissions. As a renewable oxygen-containing fuel with low production cost and widely sourced, methanol holds vast potential for application in engine. The dual-fuel combustion of diesel and methanol has emerged as an important research issue in the internal combustion engine industry. This paper conducted a study on the combustion and emission characteristics of the diesel/methanol dual fuel based on the optical engine test platform and 3D numerical simulation software. The results show that the change in cylinder pressure is relatively small and the heat release rate increases with the advance of diesel pre-injection time. The pre-injection time of diesel mainly affects the mixture distribution of pre-injection diesel, and the mixture is more evenly mixed with the advance of the pre-injection time. The degree of premixed combustion becomes higher, premixed combustion will lead to more rapid combustion, so the peak heat release rate shows an increasing trend. The pre-injection time of diesel is advanced, resulting in a leaner mixture in the early stage, and the fuel is not easy to burn, so CA10 and CA50 are delayed. The soot formation decreases as the mixture becomes more uniform, and the number of pixels of KL factor in each range also decreases. The average temperature in the cylinder is reduced and the NOX shows a decreasing trend with the advance of the pre-injection time. The change in CO generation is relatively small with the advance of pre-injection time.

Improving poly(lactic acid) fire performances via blending with benzoxazine

Improving the mechanical performance of PLA via reactive blending with thermosets is an interesting approach, however, not well explored for its fire performance improvement. With our approach, the fire performances of PLA were improved by blending PLA with a commercially available bisphenol-F-based benzoxazine. To establish the proof of concept, the benzoxazine was initially pre-cured at either 100 °C or 150 °C for a pre-selected time i.e. 60′, 80′, or 120′. The benzoxazine samples were then blended with PLA matrix via an extrusion process at 10 wt.% or 20 wt.% loadings. Detailed thermal and chemical investigations via Differential Scanning Calorimetry (DSC) and Size Exclusion Chromatography (SEC), and the evaluation of the mechanical properties, confirmed that the addition of benzoxazine does not influence the intrinsic properties of PLA. The fire performance was tested by Mass Loss Cone (MLC) calorimetry. PLA formulation with 20 wt.% of the benzoxazine cured 80′ at 150 °C, lead to a 43 % reduction of the peak of heat release rate compared to neat PLA. This was attributed to increased char formation during the combustion process. Also, the char formation permits a significant delay in the temperature increase of the sample.

Effect of ambient pressure on the fire characteristics of lithium-ion battery energy storage container

As lithium-ion battery energy storage gains popularity and application at high altitudes, the evolution of fire risk in storage containers remains uncertain. In this study, numerical simulation is employed to investigate the fire characteristics of lithium-ion battery storage container under varying ambient pressures. The findings reveal that the peak heat release rate of fires at normal pressure is significantly higher than at lower pressure. Specifically, the heat release rate at 100 kPa is 9215 kW, exceeding the value at 40 kPa by 42%, which is only 3900 kW. This peak heat release rate also demonstrates a power function relationship with ambient pressure. In addition, fires tend to last longer in lower pressure, where high-temperature areas expand and spread rates increase. Moreover, higher pressures produce elevated peak concentrations of CO and CO2, while smoke spreads faster in lower pressure, despite lower peak smoke concentrations. The study findings can serve as a foundation for assessing the fire hazards and designing fire protection measures for lithium-ion battery storage containers exposed to varying ambient pressures.

A P/Si-containing flame retardant towards simultaneous improvement of the toughness, transparency and fire safety of polycarbonate

Polycarbonate (PC) is a commonly used engineering plastic, but its poor flame retardancy limits its use. In this study, a DOPO-based flame-retardant (DOPO-TMTA) containing P and Si elements was synthesized via a simple method involving 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and 2, 4, 6-trivinyl-2, 4, 6-trimethylcyclotrisiloxane (TMTA). The PC/mDOPO-TMTA (m = 4, 6, 8) composites were prepared by melt blending PC with different loadings of DOPO-TMTA. The prepared PC/DOPO-TMTA composites had excellent flame retardancy while maintaining good transparency. The limiting oxygen index (LOI) of PC/8DOPO-TMTA reached 32.5 % and achieved a UL-94 V-0 rating. Moreover, cone calorimetry tests revealed that, compared with those of pure PC, the peak heat release rate (PHRR) and total heat release (THR) of PC/8DOPO-TMTA decreased by 39.0 % and 38.1 %, respectively. Compared with pure PC, PC/mDOPO-TMTA also maintained good mechanical properties, and the tensile and impact strengths were slightly improved. The synergistic flame retardancy of DOPO-TMTA on P/Si elements for the PC matrix was revealed by condensed phase and gas phase product analysis. This work provides a good reference for the preparation of PC composites with high transparency and excellent comprehensive properties.