Combustion Tests Research Articles

Image Processing Technique for Enhanced Combustion Efficiency of Wood Pellets

The combustion efficiency of wood pellets is partly affected by their average length. The ISO 17829 standard defines the methodology for assessing the average length of sample pellets, but the method does not always lead to representative data. Furthermore, a standard analysis is time-consuming as it requires manual measurement of the pellets using a caliper. This paper, whilst evaluating the effect of pellet length on combustion efficiency, proposes a pending-patented dimensional image processing method (DIP) for assessing pellet length. DIP allows the dimensional data of grouped and stacked pellets to be obtained by exploiting the shadows produced by pellets when exposed to a light source, assuming that different-sized pellets produce different shadows. Thus, the proposed method allows for the extraction of dimensional information from non-distinct objects, overcoming the reliance of classical image processing methods on object distance for effective segmentation. Combustion tests, carried out using pellets varying only in length, confirmed the influence of length on combustion efficiency. Shorter pellets, compared to longer ones, significantly reduced CO emissions by up to 94% (mg/MJ). However, they exhibited a higher fuel mass consumption rate (kg/h), with an increase of up to 22.8% compared to the longest sample. In addition, longer pellets produced fewer but larger shadows than shorter ones. Further studies are needed to correlate the number and size of shadows with samples’ average length so that DIP could be implemented in stoves and programmed to communicate with the control unit and automatically optimize the setting in order to improve combustion efficiency.

Preparation and Performance of ATH-OPC-PEG Bilayer Microcapsules Based on Targeted Flame Retardation Against Spontaneous Coal Combustion

ABSTRACT In order to solve the problem of spontaneous combustion of coal in the air-mining area, ATH-OPC-PEG double-layer flame retardant microcapsules were prepared. The environmentally friendly flame retardant aluminum hydroxide (ATH) was selected as the core material of the microcapsules. Due to the high action temperature and late action time of ATH, sodium alginate-modified melamine-melamine resin was used as the first layer of shell material of microcapsules to coat ATH. Then molten polyethylene glycol (PEG) mixed with the environmentally friendly strong antioxidant proanthocyanidin (OPC) was used as the second layer of shell material for the secondary coating of microcapsules. Providing antioxidant properties to microcapsules. The surface morphology, dispersion, encapsulation, pyrolysis, and flame retardant properties of the microcapsules were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analyzer (TG), and cone calorimeter. On this basis, the microcapsules were mechanically mixed with coal samples, and four coal samples were prepared for combustion tests. The results showed that ATH-OPC-PEG microcapsules prolonged the water locking time and increased the TGA by 1.162%. According to the cone calorimeter analysis, the CO and CO2 release rates of microcapsule-treated coal were reduced by 27.90% and 13.98% compared with that of pure coal. This study provides directional solution ideas for solving different stages of spontaneous combustion of coal in the mining area, and enriches the technical means of fire prevention and extinguishing.

Low Thermal Conductivity Silicone Aerogels Tuned by Composite Surfactants.

The excellent flexibility of silicone aerogels has attracted attention. However, the thermal conductivity of silicone aerogels is higher than that of inorganic silicone aerogels. Thermal conductivity can be reduced by increasing the thermal insulation of silicone aerogels while maintaining their flexibility. Herein, we successfully propose an ultrasimple strategy to prepare thermally conductive silicone aerogels using composite surfactants. Cetyltrimethylammonium chloride and cetyltrimethylammonium bromide were selected as complex surfactants with effective emulsification ability. The synthesized cationic/cationic surfactant emulsion aerogels exhibited high porosity (93%), flexibility, remarkable adiabatic properties (0.021 W m-1 K-1 thermal conductivity at 25 °C), thermal stability (68.71% thermogravimetric residue at 0-800 °C), and excellent flame-retardant capacity (vertical combustion test grade = V-0; limiting oxygen index = 27.30%), which made cationic/cationic surfactant emulsion aerogels a candidate material in the field of thermal insulation.

3D Printed hybrid rocket fuels with μAl core-shell particles coated with polyvinylidene fluoride and polydopamine: enhanced combustion characteristics

3D printing technology enhances the combustion characteristics of hybrid rocket fuels by enabling complex geometries. However, improvements in regression rate and energy properties of monotonous 3D printed fuels have been limited. This study explores the impact of poly (vinylidene fluoride) and polydopamine-coated aluminum particles on the thermal and combustion properties of 3D printed hybrid rocket fuels. Physical self-assembly and anti-solvent methods were employed for constructing composite μAl particles. Characterization using SEM, XRD, XPS, FTIR, and μCT revealed a core-shell structure and homogeneous elemental distribution. Thermal analysis showed that PVDF coatings significantly increased the heat of combustion for aluminum particles, with maximum enhancement observed in μAl@PDA@PVDF (denoted as μAl@PF) at 6.20 kJ/g. Subsequently, 3D printed fuels with varying pure and composite μAl particle contents were prepared using 3D printing. Combustion tests indicated higher regression rates for Al@PF/Resin composites compared to pure resin, positively correlating with particle content. The fluorocarbon-alumina reaction during the combustion stage intensified Al particle combustion, reducing residue size. A comprehensive model based on experiments provides insights into the combustion process of PDA and PVDF-coated droplets. This study advances the design of 3D-printed hybrid rocket fuels, offering strategies to improve regression rates and energy release, crucial for enhancing solid fuel performance for hybrid propulsion.

Optimization Design of Flame-Retardant Rigid Polyurethane Foam Modified by Piperazine pyrophosphate/ Zinc Tailings/ Sodium Ligninsulfonate based on Orthogonal experiment

The flammability of rigid polyurethane foams (RPUF) is a significant concern for application. This study introduces a novel flame-retardant RPUF modified by piperazine pyrophosphate (PAPP), zinc tailings (ZTs), and sodium lignosulfonate (LS). The result of cone calorimeter test reveals that the peak heat release rate (p-HRR) and total heat release (THR) of the RPUF doped with 18wt.% PAPP, 10wt.% ZTs and 2.5wt.% LS decreases by 49.4% and 58.3% respectively. The Fire Resistance Index (FRI) achieved a value of 10.17, and vertical combustion tests indicated V-0 rating, signifying improved flame retardancy. Furthermore, the TG/DTG analysis shows that the decomposition activation energy (Eα) increased from 132.85kJ·mol-1 to 222.12kJ·mol-1 in the main stage of decomposition (249~342 ℃), representing enhanced thermal stability. Subsequently, the orthogonal experiments and regression analysis reveal that LS has the most significant impact on p-HRR, followed by ZTs. The combination of ZTs and LS exerts the most significant synergistic influence on p-HRR, whereas the combination of PAPP and LS has the most insignificant impact. The introduction of LS provides carbon and gas source, and improve the dispersion of PAPP and ZTs in the whole system. The optimal experimental ratio of modified RPUF is obtained through regression optimization. Consequently, the flame-retardant RPUF represents a sustainable bio-based composite material that effectively utilizes industrial and biowaste resources.

A recyclable, toughening, extreme-condition resistant flame retardant for unsaturated polyester: Bridging performance and sustainability

Recycling thermosets presents significant economic benefits and social implications, and to date, a series of controllable recycling strategies have been proposed. However, prior research has primarily focused on neat polymers, neglecting the impact of the recycling process on composites whose additives may lose performance post-recycling. The paradigm shift towards sustainability necessitates the development of additives that not only exhibit high performance but also endure recycling conditions. Herein, taking flame-retardant unsaturated polyester (FRUP) as an example, we designed a new flame retardant (DPPONSi) with multiple flame-retardant elements and a low phosphorous oxidation state. FRUP with 16.7 wt% of DPPONSi achieves a V-0 rating in the UL-94 vertical burning test, and its limiting oxygen index (LOI) reaches 27.1%. Moreover, its peak heat release rate and total heat release are distinctively reduced by 65% and 42%, respectively. The high flame-retardant efficiency structure also protected DPPONSi from by-reactions. Without complex separation processes, FRUP degradation products were integrated with polyvinyl alcohol (PVA) to create flame-retardant aerogels with high flame retardancy. Additionally, we systematically studied the influence of flame retardants with varying oxidation states on FRUP, the corresponding flame-retardant mechanisms, and the degradation process of FRUP. This work realizes the organic combination of strategies to enhance the high efficiency of flame retardants with design methods for flame retardants that are resistant to existing unsaturated polyester degradation systems.

Insight into the production factors influencing the physicochemical properties of densified briquettes comprising wood shavings and rice husk

The present work aims at elucidating the impact of various densification parameters on the physicochemical and combustion properties of fuel briquettes issued from the co-processing of wood shavings (W) and rice husks (RH) using a mechanical piston press machine. To that end, a design of experiments integrating three feeding speeds (15.76, 18.56, and 21.73 mm·s−1), two wood particle sizes (< 7 mm and between 7 and 10 mm) and six different RH contents ranging from 0 to 100 wt% was built. The obtained results showed that all the above operating factors influence the apparent density of the produced briquettes. Values ranging from 1143 to 1247 kg·m−3 were notably measured, with the highest one determined when considering a low feeding speed, small wood particles and an RH proportion of 80 wt%. While increasing the RH content led to an increase in the briquette density, the obtained results also showed that the higher the RH content, the lower the water resistance index. Measured values indeed went from 94 % on average for pure wood to ⁓85 % for pure RH, attesting to the potential challenge associated with the storage of briquettes containing high RH contents. As for the net calorific value, it was shown to rise from ⁓11 to ⁓ 16 MJ·kg−1 when varying the proportion of wood between 0 and 100 wt%. This trend was especially traced to an increase of the wt% of volatile matters in the produced briquettes accompanied by a decrease of their ash content. Combustion tests performed with different briquette samples then allowed inferring burning rates between 10.9 and 13.4 g·min−1, specific fuel consumptions ranging from 115.8 to 138.4 g·l−1 and combustion efficiencies of around 12 %. As highlights, these tests demonstrated that the higher the wood content, the higher the burning rate, the lower the specific fuel consumption and the higher the combustion efficiency. Finally, two tested briquette formulations containing 80 and 100 wt% of wood were shown to have better combustion properties than a commercial firewood used for comparison. Total greenhouse gas (CO2 and CH4) emissions were even found to be reduced by 9.4 % when burning the RH-containing sample instead of firewood, while providing the same amount of sensible heat to a 3-l volume of water. These findings thus highlight the potential interest of beneficiating biomass wastes into briquettes for heat generation, further noting that the development of this type of alternative energy carrier offers multiple advantages in terms of waste management, reduction of the deforestation induced by the intensive use of firewood and mitigation of climate change through a potential reduction greenhouse gas emissions.

Thermal stability and combustion properties of polyurethane foam modified with manganese phytate and expandable graphite

Manganese phytate (MnPa) was prepared and synergistically combined with expandable graphite (EG) flame retardant modified polyurethane foam (PUF). Utilizing thermogravimetric (TG), pyrolysis kinetic analysis, CONE analysis, smoke toxicity analysis, limiting oxygen index (LOI), and UL-94 horizontal combustion test procedures, the thermal stability and combustion parameters of the modified PUFs were examined. The flame retardancy and smoke suppression of the modified PUFs were analyzed based on the heat release rate (HRR), total heat release (THR), smoke production rate (SPR), and total smoke release (TSR). The results showed that MEPUF3 had the highest thermal decomposition rate temperature, initial thermogravimetric temperature, and activation energy (E). It was shown that MEPUF3 had the lowest HRR of 17.68 kW/m2, the lowest THR of 1.15 MJ/m2, the lowest SPR of 0.0046 m2/s, the lowest TSR of 19.58 m2/m2, the lowest Ds of 32.1, the highest transmittance of 57.7%, and the highest LOI of 23.0%. The present study showed that MEPUF3 possessed good thermal stability and flame retardant properties, which provided useful references for subsequent phytate and EG-modified PUFs.

Co-combustion of straw and waste rubber thermolysis char in a moving grate boiler

The study investigates the co-combustion of straw with waste rubber thermolysis char and the addition of 4% lime in a small-scale pellet-fired boiler. Char content in the fuel was set at 10, 15, 25, and 49%. During combustion tests, flame visual were inspected, gas and particulate emissions were measured, individual losses and boiler efficiency were determined, and the amount and chemical composition of particulate depositions on boiler surfaces were estimated. Results indicate that burning fuel with char requires burner design modification to increase primary air relative to secondary air. Blends with up to 25% char content can be combusted while maintaining high boiler efficiency of approximately 87%, comparable to straw-only combustion. Significant fly ash deposits on boiler walls were observed, with K, Zn, Ca, and Si being predominant in the composition. Although there are risks of slagging and corrosion during co-combustion, these risks decrease with a higher char proportion. SO2 was detected in the flue gases, with high levels of particulate emissions, while NOx emissions stayed within permissible limits for small boilers. A marked increase in unburned carbon in bottom ash suggests the need for grate modifications and an extended combustion zone when co-combusting biomass with waste rubber thermolysis char.

Boosting the efficiency of water-based intumescent coatings with fumed silica nanoparticles: A synergistic approach

This research looked into how well the water-based intumescent coating (WBIC) with fumed silica nanoparticles (FSNs) worked to keep steel parts safe from cellulose fire. The adhesion strength of the coatings was evaluated using the pull-off test according to ASTM D4541. Flame retardant performance was studied by a lab-scale simulated big panel test at 950 °C for 1 hour. Thermogravimetric analysis (TGA) and the UL94 test were used to study the thermal stability and burning characteristics of the WBIC. An FESEM, an X-ray diffraction (XRD), and a Fourier transform infrared spectroscopy (FTIR) analysis were used to fully characterize the residual chars of the optimized formulation and the control coating. Adhesion strength test results showed that adding 0.2 wt% of FSNs increased paint adhesion strength from 0 to 2 MPa and changed the failure mode from adhesive to cohesive. It was found that at the optimal FSNs content (0.2 wt% SiO2), the lowest steel backside temperature of 181℃ after 1 hour of fire testing was obtained. Adding fumed silica from 0.1 to 0.3 wt% has resulted in a reduction of the char layer's intumescent factor by 5.3–42.1 %. The SEM images indicated that fumed silica enhanced the formation of dense, crack-free char layers with small pore sizes. Thermogravimetric analysis revealed that intumescent coatings' thermal stability and residual weight increased with the addition of 0.2 wt% fumed silica. Additionally, the coating contained 0.2 wt% SiO2 passed the V0 rating in the UL94 vertical burning test. The XRD and FTIR tests also revealed that the leftover chars had rutile titanium oxide, aluminum metaphosphate, and titanium pyrophosphate in them. At high temperatures, these ceramic compounds exhibit thermal insulation performance, preventing heat and oxygen penetration into the char layer.

Fabrication and Performance Investigation of Flame Retardant Flexible Polyurethane Composites via Polyethyleneimine/Phytic Acid LBL Self‐Assembly Coatings

ABSTRACTTo bolster the fire resistance of flexible polyurethane foam (FPUF), and a series of FPUF/polyethylenimine/phytic acid (FPUF/PEI/PA) composites were prepared by layer‐by‐layer self‐assembly strategy. Furthermore, the thermal stability, flame retardancy, combustion properties, and char layer were comprehensively evaluated via thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 vertical combustion test, microcalorimetry (MCC), scanning electron microscopy (SEM), Raman spectroscopy, and tensile testing. TG analysis revealed that the PEI/PA coatings markedly diminished the initial decomposition temperature (T‐5wt%) and char residue at 800°C. FPUF‐6 extended the burning duration by 20 s, a 80% improvement compared with unmodified FPUF, with an LOI value increased to 19.2 vol%. SEM and Raman analyses of the char residues indicated that the PEI/PA coating promoted graphitization degree of the char layer. This work offered novel insights for the development of high‐performance FPUF composites.

A green synthesis strategy for liquid microcapsule flame-retardant polyurethane foam: Lowering consumer health risks from flame retardant inhalation and ensuring long-lasting fire safety

Dimethyl methylphosphonate (DMMP), is widely used in the production of commercial flexible polyurethane foam due to its excellent fire-retardant properties and the low addition levels required. However, in daily use, the volatility and migration of this liquid fire retardant reduce its fire safety performance and pose significant health risks. To address this issue, we employed interfacial polymerization facilitated by ultraviolet light-induced triallyl isocyanurate (TAIC) cross-linking at the water-oil interface to rapidly encapsulate DMMP. Incorporating TAIC@DMMP microcapsules into FPUF composites effectively suppressed DMMP emissions, maintaining low health and fire safety risks. These microcapsules act as sprinkler heads within each FPUF cell, rupturing during flame propagation. This release of phosphorus-containing radicals significantly enhances fire safety, reducing the peak heat release rate (PHRR) and total heat release (THR) by approximately 47% and 33%, respectively. The TAIC@DMMP microcapsule FPUF composite material exhibited excellent fire safety performance after 28 years of long-term aging simulated in an oven, passing the vertical burning test. In an environment simulating a 60 °C heat source, the TAIC@DMMP microcapsule FPUF composite material significantly reduced the release of DMMP, lowering the carcinogenic risk and non-carcinogenic risk by approximately 80 times and 100 times, respectively. This study presents a method for preparing FPUF composites that balance fire safety and environmental health, offering a valuable reference for further research on flame-retardant materials in environmental safety.

The Electrochemical and Combustion Properties of HAN‐ECSP Using Cu2O/Cu Electrode

AbstractElectrically controlled solid propellant based on hydroxyammonium nitrate (HAN‐ECSP) cause extensive research by scientists. Nevertheless, research on the performance of ECSP is currently focused on the formulation of propellants, and few studies have been published on the design of electrodes and the influence of electrochemical properties on the combustion performance of propellant. Metal have been reported as one of potential electrodes in HAN‐ECSP, but it has many drawbacks, such as being prone to corrosion during electrochemical and ignition combustion testing. Hence, modifying metal electrodes is one of the best ways to improve their adaptability in the HAN‐ECSP system. In this work, Cu2O/Cu and Cu2O/CF electrodes were prepared by oxidation methods and subsequent calcination with tube furnace. It can be seen from the experimental results that the Cu2O/Cu and Cu2O/CF have positive effect on the overpotential and corrosion resistance. Furthermore, the ignition delay time at 210 V of the propellant decreases from 3.28 s (Cu) to 2.05 s (Cu2O/Cu), 3.89 s (CF) to 1.85 (Cu2O/CF), respectively. Thus, Cu2O/Cu electrode is more suitable in the HAN‐ECSP system, and the electrochemical performance of HAN‐ECSP is an important factor that evaluate its ignition performance. Lower overpotential and higher current retention rate in the system will improve the ignition and combustion performance of the propellant. In general, this work reveals the influence of the electrochemical performance of propellants on their combustion performance, and provides data support and advices for improving the combustion performance of HAN‐ECSP.

Biogas Production from Tofu Processing Waste and Corncobs with the Addition of Clam Shell Lime

Tofu production process waste has the potential to become raw material in producing biogas because its organic components, but it has a very low pH, which is not suitable for biogas production. Therefore, it is necessary to increase the pH and maintain it to be neutral during fermentation. The number of treatments given were two treatments. The first treatment by adding 3% of NaOH and the second treatment by adding clam shell lime as much as 3 levels (6%, 7% and 8%). From the research, it was found that the highest value of parameters tested was found in the treatment of adding clam shell lime as much as 6% which produced biogas as much as 1633.33 ml with a pressure of 1.0184 bar. The biogas production rate was 842 ml /day. After the combustion test, the resulting flame was blue and can burn for 38.63 seconds.

Ignition and Combustion Performance of B@HMX Composite Microunit Prepared by Recrystallization of Solvent Evaporation.

Fuel boron (B) has the advantage of a high calorific value. However, a coating of boron oxide (B2O3) is present on the outermost layer of the B particles, which will greatly hinder the oxidation of B. In this study, the high-energy 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) is used to increase the activity of B powder, so as to enhance the ignition and combustion performance of B. Samples with various HMX contents are successfully prepared by recrystallization of the solvent evaporation method. The study of morphology and composition reveals that HMX is coated on the surface of B particles to form composite microunits. Interestingly, the heat and gas released during the decomposition of HMX facilitated the evaporation and destruction of the oxide film. Consequently, this promotes the oxidation reaction of B and results in a reduction in its initial oxidation temperature to 762.45 °C. The results of ignition and combustion tests show that the shortest ignition delay time of the sample with the mass ratio of B to HMX of 1:5 is 1.11 s, which is 0.38 s earlier than that of the physical mixed sample. In addition, the maximum height and width of the combustion flame are the largest. These results show that B@HMX composite microunits with a high energy activation effect provide an effective strategy for better application of B powder.

Application of high-temperature and high-pressure processes in the flame-retardant finishing of polylactic acid nonwovens

This study examined the flame-retardant stability of polylactic acid (PLA) nonwovens after treatment with high-temperature and high-pressure finishing technology. Flame-retardant properties of PLA nonwovens were measured using a limiting oxygen index (LOI) and vertical combustion test. Surface morphology, elemental content, and thermal stability were measured by scanning electron microscope, energy dispersive spectroscopy, and thermogravimetric analysis. The LOI of the finished PLA nonwovens was 37.5%, which is 29.3% higher than that of the original nonwovens. The combustion length is reduced to 12.3 cm, the melting droplet phenomenon is significantly improved. After washing once, the LOI of the nonwovens decreased by 7.5%, and the vertical burning length increased by 13%. The finished PLA nonwovens have certain flame-retardant property. After finishing, the flame retardant was evenly distributed on the surface of PLA fiber, and the mass fraction of phosphorus reached 5.69%. Thus, the finished PLA showed improved flame-retardant property.

Proposed shorter duration protocols for measuring resting energy expenditure utilizing whole-room indirect calorimetry.

Sixty minutes is currently the shortest testing duration for 24-h resting energy expenditure (24-h REE) utilizing whole-room indirect calorimetry. Show that recalculated 30-min extrapolated 24-h REE from previously published 60-min metabolic data are valid. Propane consumption linearity was determined through an 8-h combustion test. Thereafter, metabolic data for 24-h extrapolated ventilation rates of oxygen (VO2; l/d), carbon dioxide (VCO2; l/d), respiratory quotient (RQ; VCO2/VO2), and REE (MJ/d) from ten 60-min propane combustion tests were recalculated to reflect a 30-min testing duration. A similar analysis was performed utilizing data from 60-min subject metabolic measurements within a whole-room indirect calorimeter (4597 liters) specific for measuring resting energy expenditure (REE). Statistical (p < 0.05) comparisons between recalculated and original 60-min metabolic data were determined by SPSS (version 29). Propane consumption during a combustion test was found to be linear for up to 8-h. Furthermore, no differences existed between propane stoichiometry and combustion for any of the extrapolated 24-h metabolic parameters when recalculated from 60-min propane combustion data to reflect a 30-min duration. Finally, similar results were obtained for all recalculated subject metabolic data. Recalculated extrapolated 24-h metabolic data derived from a 30-min testing duration appear to be valid. This suggests that whole-room indirect calorimetry could be an adjunct for various weight loss or other programs where accurate metabolic measurements are required.

Evaluation of combustion system for organically bound tritium analysis using dried fish samples.

The combustion process of the organically bound tritium (OBT) analysis method is difficult and requires sophisticated techniques. For ease, safety, and reproducibility a semi-automatic combustion system was developed. An arbitrary combustion program that prevents sudden ignition was devised and combustion tests were conducted. Analytical test runs were conducted using fish standard samples to confirm the validity of the developed system. The test values were compared with values obtained with another analysis method, and the recovery rate of the combustion water was evaluated. The results confirmed that the analytical values obtained with this combustion system were equivalent to those obtained with another analytical method and were valid for OBT analysis.

Preparation of Activated Carbon- and Graphite-Coated Banana Fibers as Flame-Retardant Materials

In polymer studies, biocomposite now draws attention as an exciting material obtained from combining natural fiber and matrix, which is an environmentally friendly material with biodegradable properties. One of the natural fibers often used in polymer filler is banana stem fiber. This study aims to prepare carbon-coated waste-dried banana fiber. The waste of banana stems was used as raw material for preparing cellulose-rich banana stem fiber. The banana fiber was soaked in an alkaline solvent, 1% NaOH, to remove the lignin content. The dried banana fiber was then coated with activated carbon and graphite by immersion in the carbon dispersion in ethanol with PVA glue binder added. Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) spectra show different profiles on raw and carbon-coated banana fibers, indicating successful carbon coating. The burning test and thermal analysis results show that carbon-coated banana fibers have better thermal properties than raw banana fiber. This suggests that carbon covered on the fiber surface could enhance its thermal property due to intramolecular bonds between fibers and carbon particles. Graphite-coated banana fibers have the longest burning time and are concluded to have the best fire-retardant properties among all samples. The findings confirmed the potential use of carbon-coated banana fiber as filler material for reinforcing conventional composites.

Synergistic flame retardancy of poly(cyclotriphosphazene-co-piperazine) particle with aluminum diethylphosphinate in epoxy resin

Hexachlorocyclotriphosphazene (HCCP) was reacted with piperazine to obtain poly(cyclotriphosphazene-co-piperazine) particle (PCPS), which was used as the flame retardant for epoxy resin (EP). The structure of PCPS was determined by various methods. When PCPS was used alone and the addition amount of PCPS in the prepared flame-retardant EP (FR-EP) reached 4%, the obtained FR-EP cannot even pass the V-1 level in the Vertical burning (UL-94) test. However, PCPS showed a synergistic flame retardancy with aluminum diethylphosphinate (ADP). When the mixture of ADP and PCPS in EP was 4% and the weight ratio of ADP and PCPS was 3:1, the prepared FR-EP, EP-ADP/PCPS3:1, reached the V-0 level in the UL-94 test. The limiting oxygen index (LOI) value of EP-ADP/PCPS3:1 was 29.7%. Compared with pure EP, the peak heat release rate of EP-ADP/PCPS3:1 obtained by the micro-combustion calorimetry (MCC) test was reduced by 20.6%. Thermogravimetric analysis (TGA) result showed that, with the addition of ADP and PCPS, the char residual of EP-ADP/PCPS3:1 increased about 5.1% compared with EP. The combination of ADP and PCPS showed significant advantage in promoting the flame retardancy of EP. Compared with pure EP, the mechanical properties of EP-ADP/PCPS3:1 was hardly decreased with the addition of ADP and PCPS.