Ammonium Polyphosphate Research Articles

Combination effect of ADP‐intercalated kaolinite and ammonium polyphosphate on simultaneously enhancing the flame retardancy and smoke suppression of epoxy resins

AbstractIn this article, ammonium dihydrogen phosphate (ADP) was successfully intercalated into kaolinite (Kaol) to prepare a novel synergist named ADP‐intercalated kaolinite (K‐ADP). The chemical structure of K‐ADP was thoroughly characterized using various analytical methods, and then K‐ADP was combined with ammonium polyphosphate (APP) to enhance the fire safety of epoxy resins (EPs). The flammability results indicate that the combination of K‐ADP and APP exerts super positive effects on reducing the heat release and smoke emission of EPs than the mixture of Kaol and APP. Especially, the EP/8 wt% APP/2 wt% K‐ADP has a super LOI value of 33.2% and reaches a UL94 V‐0 rating accompanying with a 29.1% reduction in total heat release (THR) and a 72.7% reduction in total smoke production (TSP) compared to pure EP. The morphology and component analyses show that the combination of K‐ADP and APP facilitates the formation of more phosphorus‐rich crosslinking and aromatic structures in the condensed phase to enhance the compactness and intumescence of char layer, which effectively segregates heat, combustible compounds and smoke particles. Thermogravimetric analysis shows that the combination of K‐ADP and APP exerts super char‐forming ability in EPs, and the residual weight of EP/8 wt% APP/2 wt% K‐ADP at 800°C increases from 7.8% of pure EP to 19.7%. Mechanical test shows that the addition of K‐ADP displays the less adverse effect on the mechanical properties of EP composites compared to Kaol due to the better compatibility of K‐ADP and epoxy matrix with DSC analysis support.Highlights A novel ammonium dihydrogen phosphate‐intercalated kaolinite (K‐ADP) was synthesized. APP/K‐ADP system exerts super positive effect on reducing fire hazards of EPs. APP/K‐ADP system takes effect in both gas phase and condensed phase. APP/K‐ADP has a satisfying balance between fire safety and mechanical properties in EPs.

A multi-functional polyurethane elastomer with high damping, water resistance and flame retardancy

Polyurethane elastomer has become a current focal point in the field of damping materials due to superior comprehensive properties. However, its effective damping temperature range is limited, and existing methods often lead to a reduction in mechanical performance. Moreover, polyurethane exhibits poor water resistance and flame resistance, constraining its applications. In this study, we introduce a small amount of dangling chain and aromatic dynamic disulfide bond into polyurethane to achieve a balance between damping and mechanical performance. Notably, the fluorinated dangling chain improves water resistance of the material synchronously and effectively. Additionally, ammonium polyphosphate modified by melamine and diethyl bis(2-hydroxyethyl)aminomethylphosphonate are introduced into polyurethane to improve flame resistance. The prepared polyurethane elastomer exhibits excellent comprehensive performance, featuring an effective damping (tanδ≥0.3) temperature range of 153.2 °C (−53.2 °C ∼ 100 °C), V-0 level flame resistance and excellent water resistance. Meanwhile, the heat stability of the polyurethane elastomer has been significantly enhanced, while maintaining a certain level of mechanical performance (9.72 ± 0.25 MPa, 602.4 ± 30.1%). These improvements extend the service life of polyurethane and expand its range of potential applications.

Synthesis of DOPO Derivatives for the Fabrication of Flame Retardant Epoxy Composites

Four flame retardant DOPO derivatives were succesfully synthesized by Pudovik reaction, including 6,6'-(([1,1'-biphenyl]-4,4'-diylbis(azanediyl))bis (thiophen-2-ylmethylene))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) 5a, 6,6'-(((sulfonylbis(4,1-phenylene))bis(azanediyl)) bis(thiophen-2-ylmethylene))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) 5b, 6,6'-((1,4-phenylenebis(azanediyl))bis(furan-2ylmethylene))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) 5c and 6,6'-((oxybis(4,1-phenylene))bis(1-(thiophen-2-yl)ethane-2,1-diyl))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) 5d. Among them, flame retardants 5a and 5d were synthesized for the first time. DOPO derivatives were combined with functionalized ammonium polyphosphate using polyethyleneimine (PEI-APP) as flame retardant systems for epoxy composites. The combination of compound 5a and PEI-APP gave the materials with the best flame retardancy. 6wt% of PEI-APP/6% of 5a promoted the composite material to V-0 rating in UL-94 vertical burning test and the limiting oxygen index reached 28.9%. The impact of flame retardants towards the mechanical and physical properties of epoxy resin was also evaluated. The combination of 5a with PEI-APP showed the least decrease in mechanical strength of epoxy composite.

Core–Shell Structured Flame‐Retardant Separator Mediated with Metal–Organic Framework Armor Enables Self‐Acceleration Mechanism for Dendrite‐Free and Safer Lithium Metal Batteries

AbstractDeveloping an optimal multifunctional flame‐retardant separator is crucial for enhancing lithium metal battery (LMB) safety. However, this task poses challenges due to the inferior electrochemical stability and limited ion transport of most fire retardant‐based coatings. In this work, the core–shell structured flame‐retardant matrix is elaborated by in situ growing a thin layer of MOF armor onto flame‐retardant ammonium polyphosphate (APP) bulk materials to further manufacture a multifunctional separator (APP@ZIF‐8@PP). The MOF armor acts as both a protector and ion transport regulator, effectively safeguarding APP from side reactions and optimizing the efficiency, selectivity, and deposition behavior of ion flux. Notably, such separator demonstrates a self‐acceleration mechanism, i.e., APP and ZIF‐8 can promote the decomposition of each other mutually, activating the flame‐retardant effect at lower temperatures. Additionally, APP@ZIF‐8 aids in forming a dense char layer during pyrolysis, which can insulate against the transfer of oxygen and heat. Finally, the LMBs assembled with such a multifunctional separator exhibit heightened safety and optimized electrochemical performance. This work provides valuable insights into the development of advanced porous materials‐based flame‐retardant separators, contributing to safer and more reliable energy storage devices.

N‐methylmorpholine‐N‐oxide molecules coated ammonium polyphosphates for dope spinning of flame‐retardant lyocell fiber

AbstractLyocell fiber, hailed as the “verdant filament of the 21st century,” boasts elevated tensile strength, environmentally conscientious production practices, and innate biodegradability. Nonetheless, its intrinsic combustibility constitutes a noteworthy impediment to its pervasive utilization across textile and industrial domains. In a concerted effort to surmount this challenge, ammonium polyphosphate (APP) underwent modification through the infusion of N‐methylmorpholine‐N‐oxide (NMMO) molecules, amplifying its dispersibility within lyocell solutions. The resultant NMMO‐coated ammonium polyphosphate (NAPP) underwent meticulous characterization of both its structure and properties. Remarkably, lyocell fiber impregnated with 30% NAPP exhibited exemplary flame retardancy, enduring through 30 laundering cycles. Notably, its tensile strength remained notably robust at 139 MPa, demonstrating a mere 6.1% reduction in comparison to its pristine lyocell counterpart. This study delineates a promising trajectory for the fabrication of mechanically resilient lyocell fibers endowed with commendable flame‐retardant attributes.Highlights The raw material is waste cotton textiles, prepared on a green basis. The use of ultrasonic mixing and low‐speed stirring defoaming method and the use of room temperature spinning advantage of the production of flame retardant lyocell fiber. The amount of flame retardant is small, and the mechanical strength is reduced to a lesser extent. Good flame‐retardant effect and excellent water washing resistance.

Thermal Decomposition Process of Fireproof Sealant Measured with Thermogravimetric and Fourier Transform Infrared Spectroscopy Analysis and Estimated Using Shuffled Complex Evolution

Fireproof sealing technology is widely used in industrial, commercial, and other public buildings, so the performance of fireproof sealing materials in high temperatures or fire environments must be taken into account as an important factor. Fireproof sealant is considered to be a highly effective adhesive for sealing and fireproofing purposes. To explore its thermal decomposition mechanism and estimate its pyrolysis behaviors, a series of thermogravimetric experiments from 10 K/min to 60 K/min coupled with Fourier transform infrared spectroscopy analysis technology were performed. The results indicated that the thermal decomposition of the fireproof sealant could be divided into three reactions: the degradation of ammonium polyphosphate, melamine, and acrylic acid. In addition, the pyrolysis behavior of the fireproof sealant was compared under two kinds of atmosphere (nitrogen and air). Furthermore, the initial kinetic parameters in the nitrogen atmosphere were calculated based on model-free methods including the Friedman, KAS, and Starink methods. The average activation energy of three reactions obtained by the three methods was 108.32 kJ/mol, 200.46 kJ/mol, and 177.10 kJ/mol, respectively, while these obtained parameters were hard to regenerate, the thermogravimetric curves were accurately based on the established pyrolysis reaction scheme, with the existence of clear deviations. Therefore, a global heuristic optimization algorithm, Shuffled Complex Evolution (SCE), was selected to optimize 14 parameters (including activation energies and the pre-exponential factors) and the optimized pyrolysis results agreed well with the experimental data, even at the extra heating rate, with the correlation coefficient for the mass loss and mass loss rate being reaching up to 0.9943 and 0.9019, respectively. The study indicated that the SCE algorithm showed an appropriate potential to estimate the pyrolysis behavior of an unknown thermogravimetric experiment group.

Improving flame retardant and electromagnetic interference shielding properties of poly(lactic acid)/poly(ε-caprolactone) composites using catalytic imidazolium modified CNTs and ammonium polyphosphate

The flame retardants and electromagnetic interference (EMI) shielding performance were enhanced by using imidazolium-functionalized polyurethane (IPU) modified multi-walled carbon nanotubes (CNTs) and ammonium polyphosphate (APP) for polylactic acid (PLA)/polycaprolactone (PCL) composites. The PLA/PCL/10APP/8CNT/1.6IPU composite containing 10 wt% APP and 8 wt% imidazolium modified CNTs reached the limiting oxygen index (LOI) value of 30.3 % and passed the V-0 rating in UL-94 tests. Moreover, the peak of the heat release rate (pHRR) and total heat release (THR) for this composite reached around 302 kW/m2 and 64 KJ/m2, which were decreased by 39.1 % and 15.8 % compared with that of PLA/PCL/10APP composite. The improved flame retardancy was attributed to the interplay of catalytic, barrier, and condensed char forming of imidazolium-modified CNTs and APP. IPU catalyzed the charring effect of the polymer matrix during combustion and regulated the migration of more CNTs to disperse at the two-phase interface. The dispersion of imidazolium-modified CNTs and co-continuous phase structure of the composites can establish continuous conductive pathways. The PLA/PCL/APP/CNT/IPU composite obtained a higher conductivity compared to the PLA/PCL/APP/CNT composite and whose EMI SE reached 33.9 dB, which is a promising candidate for next-generation sustainable and protective plastics.

Investigation on the battery thermal management and thermal safety of battery-powered ship with flame-retardant composite phase change materials

Pure battery-powered ships have attracted much attention because of its unique advantages of zero-emission. However, the problems of adaptability to extreme working conditions and thermal safety risks restrict the development of battery-powered ships. In this study, a novel flexible flame-retardant composite phase change materials (CPCM) with paraffin (PA)/EVA grafted on maleic anhydride (EVA-g-MAH)/expanded graphite (EG)/ammonium polyphosphate (APP)/triphenyl phosphate (TPP)/Na2SiO3 has been proposed and utilized in battery module. Among them, the sample ATPCM2 with APP/TPP/Na2SiO3 ratio of 5/10/10 achieved the optimal thermal properties and flame-retardant effect. The designed multifunctional CPCM harmonizes the competition between flame retardancy, mechanical properties and phase change latent heat by the synergistic effect. Besides, the ATPCM2-Module shows a good temperature control performance during charge-discharge cycles, such as the maximum temperature of battery module can be still controlled below 50 °C at 2C discharge rate and the corresponding temperature difference was effectively maintained within 4.1 °C. This is owing to the constructed stable three-dimensional heat conductive skeleton formed by synergistic flame retardancy effect, which could improve the dissipation heat capacity and thermal safety. With these prominent performances, the designed flexible CPCM with desired flame-retardant and thermal management performance can provide insights into the passive thermal management and thermal safety improvement of both battery-powered ships and high-power battery module under extreme conditions.

Strength enhancement of a flame‐retardant hybrid composite by incorporating graphene nanoparticles for structural applications

AbstractHybrid composite's flame retardancy properties play a dynamic role in structural applications. When inorganic nanomaterials form organic/inorganic nanocomposites, they exhibit superior flame‐retardant effects. Therefore, the current work investigates the combined effects of halogen‐free fire‐retardant ammonium polyphosphate (APP) and graphene (GR) nanofillers on the mechanical, and fire‐resistant behavior of hybrid composite fabricated using a vacuum bag process. Mechanical study affirmed that the concurrent incorporation of APP and GR hybrid composite improved the hardness, flexural, and tensile properties by 7%, 26%, and 16%, respectively. Scanning electron microscopy (SEM) confirms that the dispersion of 0.75 wt% GRs improved the mechanical properties by preventing crack propagation and strong binding between fiber‐matrix in the hybrid composite. The vibrational analysis reveals an improved natural frequency (NF) value was obtained with 0.75 wt% GR; further addition of GR increased the damping due to an increase in nanoparticle agglomeration. The combined effect of APP and GR decreased the hybrid composite's water uptake and porosity by 52% and 80%, respectively. The flammability study (Vertical burning) affirmed that the composite's grade score was improved from V‐1 to V‐0. Therefore, the current study emphasizes that this optimized hybrid composite can be utilized in fire‐sensitive structural applications.Highlights UL‐94 VB test reveals the flammability of the hybrid composite. Examine the combined effect of APP and GR in strength and flame‐retardant properties. GR and APP added sample shows better mechanical and flame resistance properties. The optimized wt% of GR and APP for better results is 0.75% and 9.25%. The prepared composite may suitable fire‐sensitive structural applications.

Flame retardant, mechanical, and hot air aging properties of ethylene‐propylene‐diene monomer/ammonium polyphosphate/nano‐silic composite rubber

AbstractIn this work, effect of the ratio of nonhalogenated flame retardants (ammonium polyphosphate [APP] and nano‐silica [nano‐SiO2]) on the mechanical, thermal, and flame retardant properties of ethylene‐propylene‐diene monomer (EPDM) composite rubber were investigated. Vulcanization characteristics, high temperature compression permanent deformation, thermal oxygen aging, dynamic thermodynamic analysis, thermal stability, cone calorimetry, limiting oxygen index (LOI), horizontal vertical combustion (UL‐94), and scanning electron microscopy were carried out. The experimental results showed that the mechanical properties of the composite rubber decreased with the addition of APP. However, the addition of nano‐SiO2 was found to significantly improve the mechanical properties of the composite rubber when it was incorporated. In terms of flame retardant properties of EPDM composite rubber, the combination of APP and nano‐SiO2 has a synergistic flame retardant effect in comparison to the use of single APP flame retardant. The heat release rate of EPDM composite rubber decreased by 34%, the total heat release decreased by 19%, the LOI increased by 76%, and the flame retardant grade of EPDM composite rubber reached V‐0. The EPDM composite rubber fabricated in the present study showed excellent fire resistance and desirable mechanical properties, which are of practical significance for further expanding the application ranges of EPDM rubbers.

Explosion characteristics of wood dust and its suppression in typical powder-related environments

To reduce the explosion hazard caused by wood dust, the effects of dust concentration and ammonium polyphosphate (APP) on the explosion of wood dust were carried out in a vertical combustion pipeline and the suppression mechanism was revealed. The explosion intensity of the wood dust increased and then decreased with increasing concentration, and the bottom of the pipeline remained bright due to continuous ignition. APP could effectively suppress the propagation of wood dust explosion flame. When the mass fraction of APP was 10%, there was no obvious flame, and the flame pressure dropped by up to 98%. The effect of APP on wood dust pyrolysis was analyzed using TG-DSC, and the explosion products were characterized by physicochemical analysis using EDS. The results showed that APP could improve the stability of the carbon layer on the surface of wood dust particles, and its decomposition products could enhance the thermal shielding and oxygen isolation effects of the particle surface protective layer. In addition, the APP significantly suppressed wood dust explosion by absorbing heat from the reaction zone, capturing and consuming free radicals, and reducing the oxygen concentration per unit volume.

Flexural and Flammability Characteristics of Woven Jute Fabric Reinforced Vinyl Ester Treated with Ammonium Polyphosphate

The work aims to determine the optimum fire-retardant treatment for the jute/vinyl ester composites on the composites' flexural and flammability characteristics. Ammonium polyphosphate deposition in composite samples increased the thickness and weight, which led to an increase in their sample densities. The deposition of 10% ammonium polyphosphate (APP) resulted in the highest flexural strength. However, APP significantly increased the flexural modulus of all samples to the untreated sample. In terms of flammability properties, the deposition of APP increased composites' performance against fire. Incorporating 10% of APP provides good flexural and fire-retardancy properties for the woven jute/vinyl ester composites

Study on the inhibition of explosion and combustion of coal dust based on the structure of core-shell microencapsulated polyurethane

In order to study the effect of core-shell microencapsulated ammonium polyphosphate modified materials on the suppression of explosion and combustion of different metamorphic coal, a core-shell microencapsulated ammonium polyphosphate explosion inhibitor was prepared using in-situ polymerization method. Through experiments on flame suppression and overpressure suppression during explosive combustion, the inhibitory effect of core-shell microencapsulated ammonium polyphosphate explosion suppressant on coal dust explosion was studied, revealing the coupling inhibition mechanism of thermal propagation isolation obstruction effect and group reaction reduction of key atoms. The experimental results show that when 60 wt% core-shell microencapsulated ammonium polyphosphate explosion suppressant is added, the suppression effect on the explosion and combustion of different metamorphic coal is significant, and the flame propagation and pressure rise of coal dust explosion can be basically achieved. By analyzing the substances before and after the explosion through characterization experiments, the inhibitory mechanism of core-shell microencapsulated ammonium polyphosphate explosion suppressant on different metamorphic coal was obtained. Expanding the application field of microcapsule materials provides important methods and theoretical basis for developing core shell microcapsule flame retardant and explosion suppression materials to prevent coal dust explosion disasters.

Development of a Sustainable Biobased Flame-Retardant Microcapsule and Its Flame-Retarding Mechanism on Asphalt Combustion.

To develop an efficient, sustainable, and eco-friendly biobased flame-retardant microcapsule suitable for the working environments of tunnel asphalt pavement and reveal its flame-retarding mechanism on asphalt combustion, microencapsulated amylopectin (MAMP) was first prepared using an in situ polymerization method. Changes in the basic properties of amylopectin (AMP) and its compatibility with asphalt after microencapsulation were studied. Then, the flame retarding efficiency and improvement effects of MAMP on the flame retardancy of asphalt were investigated. Results show that melamine formaldehyde (MF) resin is evenly coated on the AMP surface without changing the chemical composition of AMP, increasing the thermal stability of AMP and the compatibility between AMP and asphalt. MAMP reacts with ammonium polyphosphate (APP) to release a number of incombustible gases to delay asphalt combustion at early stages and subsequently dehydrates to form a stable starch-based charring layer to suppress heat and mass transfer during asphalt combustion, improving the fire safety of asphalt materials. The added 3% MAMP can reduce the total enthalpy value of all exothermic peaks of the 10% APP-modified asphalt by 43.6%. As a carbonization agent, MAMP produces a charring layer with higher heat capacity during asphalt combustion, exerting an excellent inhibition effect on heat release. This study provides a reference for the application of biobased materials in flame-retarded asphalt pavements.

Multifunctional polylactic acid sensing fabric based on biomass flame retardants for intelligent fire early-warning

Today, building materials emit many hazardous gases in the event of a fire, causing great harm to human health and the environment. Therefore, it is of great significance to develop bio-based flame retardant materials and to realize preventive measures to reduce fires or their damage. In this work, we fabricated a novel multifunctional fire early-warning polylactic acid-based fabric (MFR-PBF) by coating MXene nanosheet, phytic acid @ furfurylamine (PA@FA) and ammonium polyphosphate (APP) via an eco-friendly layer-by-layer assembly method. MFR-PBF showed outstanding flame retardancy including a limiting oxygen index value of 35 % and better char formation capacity. More importantly, MFR-PBF exhibited sensitive fire early-warning capability (∼1 s) and excellent cyclic alarm stability (>15 cycles) due to the excellent semiconductor responsiveness (light and heat) and the significant catalytic char formation effect. Moreover, MFR-PBF is comfortable, flexible and strong enough to sew onto firefighter uniform to detect a variety of human motions, which can be monitored in the internet by using a LoRa emitter and a gateway. In addition, the controllable heating performance rendered MFR-PBF as a potential portable heater. This work provides new insights into the preparation and application of intelligent fire early-warning fabrics in the smart fire protection and Internet of Things.

Study on flame retardancy of EPDM reinforced by ammonium polyphosphate.

Currently, the most widely used material for solid rocket motor (SRM) insulation is ethylene propylene diene monomer (EPDM) filled with flame-retardant and ablation-resistant fillers. Researchers have been working hard to find a flame-retardant filler that can simultaneously meet the complex requirements of mechanical strength, density, flame retardancy and ablative performance of the insulation layer. This requires research on the flame retardant properties of flame retardants in oxygen-poor environments. In this paper, ammonium polyphosphate (APP) is used as a flame retardant filler, which is filled into an EPDM premix (p-EPDM) containing fumed silica and aluminum hydroxide to prepare composite materials. By creating an anoxic environment, the flame retardant behavior of APP under anoxic conditions on EPDM was studied. The results show that composites prepared with APP show better flame retardant properties in tests such as limiting oxygen index and UL-94, with less impact on mechanical strength and density. The surface morphology and elemental composition of the composite combustion residues were studied using Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). In an oxygen-depleted environment, APP will thermally decompose to form ammonia, water vapor and phosphorus-containing acidic substances. These gases dilute the flammable gas and reduce the thermal conductivity. The acidic substances containing phosphorus are concentrated on the surface of the pyrolysis layer to promote the formation of the carbon layer. This provides guidance for us to design insulation layer materials with properties that are more in line with actual use requirements.

Effects of different water‐soluble phosphorus on the distribution and utilization of phosphorus in maize in Xinjiang, China

AbstractPhosphorus (P) is the main limiting nutrient in agriculture. Most of the P fertilizers applied to the soil remain ineffective because of the weak movement and transfer of P in the soil. Current agricultural production requires large amounts of P fertilizers, leading to the accumulation of residual P in the soil and serious ecological problems. Fixation of P is a vital reason for limited fertilizer effectiveness. Therefore, improving soil P effectiveness is the key to reducing soil P accumulation. This study explored the effects of different water‐soluble P fertilizers on maize yield and economic benefits by comparing the relationships between soil P distribution and P absorption and utilization of maize in calcareous soil of Xinjiang province in China. The main results indicated that (1) the drip application of ammonium polyphosphate (APP) and urea phosphate (UP) was more beneficial for increasing the total P content in the deep soil layer; the drip application of APP was beneficial in increasing the available P content of the deep soil layer. (2) Dripping acid fertilizer was more conducive to reducing soil acidity and alkalinity (pH). (3) The application of different P fertilizers favoured the accumulation of P in all organs of maize, among which APP and UP were the most effective since they increased accumulation by 75.8% and 60.4% (at the flowering stage) and 98.2% and 62.3% (at the maturity stage), respectively, compared with CK (without P fertilizer). (4) pH was the main factor affecting P uptake and transformation, and the drip application of P fertilizer had the most significant effect on pH. (5) The application of different water‐soluble P fertilizers increased maize yield and economic benefits. Among the five water‐soluble P fertilizers selected in this study, APP had the greatest economic benefits, followed by UP and monoammonium phosphate (MAP); they increased yields by 31.6%, 24.5%, and 22.0%, respectively, compared with CK.

The flame retardancy and mechanical properties of waste polyester fabric/hemp stalk composites modified with piperazine pyrophosphate and ammonium polyphosphate

The piperazine pyrophosphate (PAPP) and ammonium polyphosphate (APP) were employed to enhance the flame retardancy of waste polyester/hemp stalk composites. And the impact of PAPP/APP flame retardants on the flame retardancy and mechanical properties of waste polyester/hemp stalk was investigated. The results indicated that the PAPP/APP combination offered superior flame retardancy, with minimal impact on the composites’ bending property. Notably, when the total addition of PAPP/APP was 25%, with a mass ratio of 1 to 1, the limiting oxygen index (LOI) value of the PAPP/APP/waste polyester/hemp stalk composite material increased significantly from 18.8% to 27.1%, achieving the flame retardant level. Correspondingly, the vertical combustion level attained V-0 level, and the charring rate at 600°C escalated from the initial 25.8% to 32.5%. Remarkably, both the bending strength and modulus of PAPP/APP/waste polyester/hemp stalk composites remained stable.

FLAME RETARDANCE AND MECHANICAL PROPERTIES OF EPOXY RESIN: EFFECTS OF ADDED INORGANIC FLAME RETARDANTS

Effects of ammonium polyphosphate (APP) in combination with zinc borate (ZnB), zirconium oxide (ZrO2), and nanoclay on flame retardance and mechanical properties of epoxy resin have been explored. Data listed from UL-94, limiting oxygen index, and cone calorimeter tests convey that the addition of flame retardants improved the fire behavior of epoxy composites significantly. The EP/APP/ZnB/ZrO2 composite having 10% APP, 5% ZnB and 2% ZrO2 by weight attained the best V-0 rating in the UL-94 test, 29.1% limiting oxygen index value and 42.8% decrease in peak heat release rate in cone calorimeter test. A significant decrease of 48.1% in the total smoke release is observed owing to the smoke suppressant action of ZnB/ZrO2. TGA data of epoxy composite reported 25.8 and 36.7% char yield at 600℃ in air and nitrogen atmospheres, respectively. Also, a significant increase in storage modulus is observed for the EP/APP/ZnB/ZrO2 composite loaded with 2 wt% ZrO2 in dynamic mechanical analysis.

Construction of a flame retardant three-dimensional network structure in sisal/polypropylene composites

Due to the high flammability of lignocellulose filler and plastic matrix, wood-plastic composites are easily ignited with large amounts of heat and smoke, which has the potential risk of causing fire. In this study, sisal fiber was modified with ammonium polyphosphate, polyethyleneimine and nano-silica based on the attraction between oppositely charged polyelectrolytes. FTIR, XPS and SEM indicated that the flame retardant was successfully introduced into the lumen and surface of fiber, and its content increased with the increase of modification times. Then, the modified fibers with different contents of flame retardants were dispersed into polypropylene and a three-dimensional flame retardant network was constructed. The results of TG, LOI and combustion testing showed that the fire retardance of the fiber and composites improved with the increase of fiber modification times. After 4 cycles of modification, the LOI of fiber and composites increased from 20.7% and 18.9% to 37.8% and 22.8%, respectively. The morphology of the fiber and composites after combustion illustrated that the modified fiber can act as network skeleton and promote the construction of char layer. Consequently, the combustion and heat release of fiber were inhibited by flame retardant modification, and the flame retardant network also hindered the combustion of the polypropylene matrix, which effectively improved the fire retardance of composites.