Polymer Combustion Research Articles

Influence of metal ions on thermo-oxidative stability and combustion response of polyamide 6/clay nanocomposites

Combustion and thermo-oxidative properties of polyamide 6 (PA6)/montmorillonite (MMT) clay nanocomposites are studied with emphasis on the catalytic role of metal ions (Mg2+, Al3+ and Fe3+) present in MMT. Each metal ion uniquely influences condensed phase reactions (mechanism and/or kinetics) depending on its concentration in metal ion exchanged MMT, its ability to form metal-organic complexes, and confinement effect as determined by eventual dispersion of MMT in the matrix. Presence of Al3+ accelerated kinetics of PA6 decomposition during initial stages, Mg2+ rich composite displayed good thermo-oxidation stability and char yield, and Fe3+ prominently altered the chemical composition of condensed phase ultimately producing highest amount of smoke. Possible PA6 decomposition reaction mechanisms have been identified that are susceptible to metal ion catalysis in the presence of oxygen. These results provide important progress towards the understanding of widely reported yet poorly understood phenomena of catalyzing effect of clay during the combustion of polymer. The results are a definite step towards the realization of stand-alone clay based nanocomposites with superior fire retardancy.

Combustion characteristics of diesel and Jet-A droplets blended with polymeric additive

Recent experimental research has shown that the addition of long chain polymers to hydrocarbon fuel imparts non-Newtonian characteristics to the fuel which results in suppressed splashing behavior upon spilling over a surface and consequently improves fire safety. In this study, combustion of stationary fuel droplets of Diesel and Jet-A doped with different percentages of a long chain polymer (Polybutadiene) was examined and compared with the normal hydrocarbon behavior. In contrast with hydrocarbon droplets with no polymer addition, several zones of combustion including a slow and steady burning zone, a strong swelling zone and two fast and fairly steady combustion zone were also detected. It was found that combustion of polymer added fuel is controlled by the boiling point of more volatile component, i.e. base fuel. Therefore, initially the base fuel is transported to the droplet surface and evaporates. However, polymer addition turned out to slightly decrease burning rate in this stage. Viscosity was found to be the dominating factor that suppresses diffusion of volatile species to the surface and hence reduces evaporation rate at early stages of combustion. Increasing polymer content also resulted in stronger swelling behaviors as well as reduced burning time for both diesel and jet fuel droplets.

Evaluation of flammability and shear performance of layered-silicate-reinforced styrenic polymer

The current study focuses on overcoming the fire threat posed by styrenic polymer, widely used as electronic enclosures. Our detailed investigation majorly aimed at analyzing the influence of fire on the shear resistivity characteristics of polystyrene reinforced with Cloisite 20A. The increased viscosity in the case of nanocomposites owing to the restricted mobility of polymer chains and the tortuous path created by C20A prevented the escape of volatile by-products of polymer combustion, thereby substantially reducing the heat release rate. The improved moduli of nanocomposites further restricted the movement of combustion products to the flaming zone and reduced the mass loss rate too. X-ray diffraction spectra and transmission electron micrographs disclosed exfoliation of the nanoclays corroborating the improved fire, shear and thermal behavior.

Research on the Effects of Charring on the Polymer Combustion Process

PyroSim software was used to establish the combustion behavior of polymers in the cone calorimeter test, the char yield, the effects of thermal conductivity and the specific heat capacity of the char layer on the combustion process of polymer were analyzed. The results show that, the heat release rate curves show a single peak while the char yield is 0%. The heat release rate curves have three peaks when the char yield is larger than 0%. The charring of polymer significantly influences the shape of heat release rate curves. The heat release rate decreased with the increasing of char yield of polymer. Moreover, the heat release rate of charred polymer improved with the thermal conductivity of char layer. Moreover, the specific heat capacity of char layer plays no role in the heat release rate of polymer and the combustion behavior of polymer.

A Study of Fire Retardant Effect in Natural Fiber Composite Panels with Magnesium Hydroxide and Zinc Borate as Additives

The objective of this study is to investigate the fire retardancy effect of coconut coir, rice husk and sawdust panels which are incorporated with magnesium hydroxide (Mg (OH)2) and zinc borate (2ZnO∙3B2O3∙3.5H2O) as additives. The natural fiber and additives are mixed and cured for one week, with polyester resin and hardening catalyst as binders. Fire retardancy of these panels are tested according to American Society for Testing and Materials (ASTM) Horizontal (D 365) and Vertical Burning (D 3801) tests. Principle of fire retardants and mechanism of polymer combustion are shown in this study too. The study revealed that the sawdust panels with both additives have the highest fire retardancy compared to rice husk and coconut coir panel with both additives.

Role of PVA in synthesis of nano Co3O4‐decorated graphene oxide

Polymeric materials have been found to be ideal candidates for the synthesis of organic–inorganic nanomaterials. We have obtained Co3O4‐decorated graphene oxide (GO) nanocomposites by a simple polymer combustion method. Polyvinyl alcohol (PVA) of two different molecular weights, 14,000 and 125,000, was used for the synthesis. The pristine sample was annealed at 300, 500, and 800°C. PVA has played an important role in the formation of GO and Co3O4 nanoparticles. Synthesized Co3O4–GO nanocomposites were characterized by X‐ray diffraction, Fourier transform infrared, Raman, electron paramagnetic resonance, transmission electron microscopy, and vibrating sample magnetometry. Reflection peaks at 12° and 37° in an X‐ray study confirm the formation of Co3O4–GO. Raman study validates the presence of GO in nanocomposites of Co3O4–GO. Room temperature ferromagnetism was observed in all annealed samples. The highest coercivity of 462 G was observed for 300°C annealed samples as compared with bulk Co3O4. On the basis of the results obtained, a mechanism of formation is proposed. Copyright © 2015 John Wiley & Sons, Ltd.

Low-cost formation of bulk and localized polymer-derived carbon nanodomains from polydimethylsiloxane.

We present two simple alternative methods to form polymer-derived carbon nanodomains in a controlled fashion and at low cost, using custom-made chemical vapour deposition and selective laser ablation with a commercial CD-DVD platform. Both processes presented shiny and dark residual materials after the polymer combustion and according to micro-Raman spectroscopy of the domains, graphitic nanocrystals and carbon nanotubes have successfully been produced by the combustion of polydimethylsiloxane layers. The fabrication processes and characterization of the byproduct materials are reported. We demonstrate that CVD led to bulk production of graphitic nanocrystals and single-walled carbon nanotubes while direct laser ablation may be employed for the formation of localized fluorescent nanodots. In the latter case, graphitic nanodomains and multi-wall carbon nanotubes are left inside microchannels and preliminary results seem to indicate that laser ablation could offer a tuning control of the nature and optical properties of the nanodomains that are left inside micropatterns with on-demand geometries. These low-cost methods look particularly promising for the formation of carbon nanoresidues with controlled properties and in applications where high integration is desired.

COMBUSTION AND PERFORMANCE STUDIES OF GLYCIDYL AZIDE POLYMER AND ITS MIXTURES AS HYBRID ROCKET FUEL

The combustion of glycidyl azide polymer (GAP) was investigated. The GAP fuel tests were conducted in a strand burner with nitrogen gas purge and in a lab-scale hybrid rocket with gas oxygen as oxidizer. In the strand burner, at intermediate pressure range 3−6 MPa, burning rates of both cured and uncured GAP were nearly the same and strongly depend on the chamber pressure. At pressure larger than 6 MPa, uncured GAP shows less dependence on pressure, and the GAP ratio of mixtures begins to have dominant role on burning rate. Transition pressure region was observed, which was in between the pressure dependence to composition dependence. The fluctuating burning rate was the main appearance in the transition pressure region. The Zel'dovich formula shows good prediction for burning rate at intermediate pressure range, but has much deviation at high pressure due to the surface instability. A smaller sample tube can restrict the burning surface from twisting, and the resulting burning rate shows good agreement with Zel'dovich formula prediction. Uncured 100% GAP can reach its maximum burning rate at certain pressure less than 10 MPa. Based on the assumption that condensed phase reaction is the only heat source which dominates the burning rate, the prediction of maximum burning rate of GAP mixture is also possible. In a lab-scale hybrid rocket test, GAP/PEG solid fuel demonstrated a very good burning rate under mild chamber pressure and oxygen flux. Instantaneous burning rate was successfully measured by ultrasonic techniques, and the results implied complex internal ballistic behavior.

Synthesis of Triazole-functionalized Phenolic Resin and its Inherent Flame Retardant Property

A novel triazole-functionalized phenolic resin was developed, and its thermal and flame-retardant properties were investigated. The triazole group was incorporated as a pendant unit on the phenolic resin via copper- mediated click chemistry between propargylated phenolic resin and benzyl azide. The newly-developed triazole-functionalized phenolic resin showed higher thermal stability and char yield, together with a reduced total heat release (THR), than the non-functionalized bare phenolic resin, indicating enhanced flame retardancy for the triazole-functionalized phenolic resin. and superior mechanical and ablative properties. 1,2 Phenolic resins are generally prepared by reactions bet- ween formaldehyde and phenol in the presence of acid or base. When prepared by acid catalysis, they are normally called novolac-type resins. In these resins, the molar ratio of formaldehyde to phenol is less than 1, and substitution occurs mostly at the ortho position of the phenol. In contrast, base-catalyzed pathways produce more cross-linked struc- tures, and are called resole-type phenolic resins, with sub- stitutions at both ortho- and para-positions. Phenolic resins with improved thermal and pyrolysis characteristics are desirable for producing composites for thermo-structural applications. 3,4 Although conventional phenolic resins are already considered to be temperature- resistant polymers and are currently in use for the above- mentioned applications, some of the properties of phenolic resins need further improvement for meeting the ever- increasing performance requirements. With sufficient heat and oxygen, most organic polymers will burn. Fundamentally, four processes are involved in the polymer combustion cycle: heating, decomposition, ignition, and combustion. In order to increase its flame resistance, the polymer system should function to interrupt this cycle. 5 A

Plasma-based determination of inorganic contaminants in waste of electric and electronic equipment after microwave-induced combustion

A systematic study was performed for the determination of inorganic contaminants in polymeric waste from electrical and electronic equipment (EEE) for achieving an efficient digestion to minimize interferences in determination using plasma-based techniques. The determination of As, Br, Cd, Co, Cr, Cu, Ni, Pb, Sb, and Zn by inductively coupled plasma mass spectrometry (ICP-MS) and also by inductively coupled plasma optical emission spectrometry (ICP OES) was carried out after digestion using microwave-induced combustion (MIC). Arsenic and Hg were determined by flow-injection chemical vapor generation inductively coupled plasma mass spectrometry (FI-CVG-ICP-MS). Dynamic reaction cell inductively coupled plasma mass spectrometry (DRC-ICP-MS) with ammonia was also used for Cr determination. The suitability of MIC for digestion of sample masses up to 400mg was demonstrated using microcrystalline cellulose as aid for combustion of polymers from waste of EEEs that usually contain flame retardants that impair the combustion. The composition and concentration of acid solutions (HNO3 or HNO3 plus HCl) were evaluated for metals and metalloids and NH4OH solutions were investigated for Br absorption. Accuracy was evaluated by comparison of results with those obtained using high pressure microwave-assisted wet digestion (HP-MAWD) and also by the analysis of certified reference material (CRM) of polymer (EC680k—low-density polyethylene). Bromine determination was only feasible using digestion by MIC once losses were observed when HP-MAWD was used. Lower limits of detection were obtained for all analytes using MIC (from 0.005μgg−1 for Co by ICP-MS up to 3.120μgg−1 for Sb by ICP OES) in comparison to HP-MAWD due to the higher sample mass that can be digested (400mg) and the use of diluted absorbing solutions. The combination of HNO3 and HCl for digestion showed to be crucial for quantitative recovery of some elements, as Cr and Sb. In addition, suitable agreement of Cr to CRM value was only obtained by mixing NH4Cl to samples before combustion. No statistical difference (95% confidence level) was observed between the results obtained for As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, and Zn by MIC and HP-MAWD methods. Agreement with certified values was better than 96% using MIC for all inorganic contaminants. Particularly for Br, MIC was the method of choice for digestion due to the possibility of using diluted alkaline solutions for analyte absorption. Based on the obtained results, MIC can be considered as a suitable method for digestion of polymers from waste of EEEs for further plasma based determination of inorganic contaminants.

A microscale combustion calorimeter study of gas phase combustion of polymers

A microscale combustion calorimeter (MCC) was modified to study gas phase combustion of polymers and flame-retardant plastics by adding carbon monoxide (CO) and carbon dioxide (CO2) analyzers to the standard oxygen (O2) analyzer. Experiments were conducted on 22 hydrocarbon, heteroatom and halogen-containing polymers of known composition over a wide range of combustion temperatures and oxygen concentrations. At high temperatures and excess oxygen when combustion was complete, the oxygen consumed (ΔO2) and CO2 produced by combustion of the pyrolysis gases were in quantitative agreement with theoretical values for all of these charring and non-charring polymers. At lower combustor temperatures, halogen-containing polymers exhibited significantly reduced fuel oxidation rates, as evidenced by a shift in maximum ΔO2, CO and CO2 yields to much higher temperatures.

Assessment of the impact of fire retardants on the combustion of natural polymers employing DTG and LOI

SummaryThermal analysis is widely used for the investigation of the thermal decomposition of polymeric/lignocellulosic materials. Differential thermogravimetry (DTG) curves have been used for the assessment of fire retardants employing a mathematical technique, based on the observation that the DTG profile peaks become less pronounced and are shifted to lower temperatures when a fire retardant is added. The efficiency of a fire retardant is proposed to be assessed from a formula comprising of the following: (i) the depth of the main peak; (ii) the main decomposition peak temperature; (iii) the temperature range of the DTG curve; and (iv) the area above the curve. Initially, four well‐known fire retardants have been assessed for their efficiency on a lignocellulosic matrix (Olea europaea). All the results deriving from the mathematical technique have been compared with the mass residue criterion and a limiting oxygen index test (Relative Limiting Oxygen Index). Both are commonly used as reliable tools for the assessment of a fire retardant. Secondly, the impact of fire retardant concentration on efficiency was investigated. In addition, using mathematical routines, an optimum concentration zone was proposed; further, an optimum concentration value (%) has been estimated. Copyright © 2014 John Wiley & Sons, Ltd.

FTIR–PCFC coupling: A new method for studying the combustion of polymers

Gases released from pyrolysis and partial combustion of various polymers (low-density polyethylene, polystyrene, poly(parabromostyrene), pure and flame-retarded polypolyamide 6, cellulose, and chloroprene) were studied using a new coupling between Fourier transform infrared spectrometry (FTIR) and pyrolysis combustion flow calorimetry (PCFC). Combustion in PCFC was monitored by modifying the combustion temperature between 600 and 900°C. Decreasing the combustion temperature in PCFC leads to partial combustion and the evolution of CO, but also of methane, acetylene, or ethylene when temperature is very low. The evolution of these gases depends also on the polymer and on the presence of a flame inhibitor, demonstrating that flame inhibition can be studied using this method. A correlation between FTIR–PCFC and FTIR–cone calorimetry coupling was attempted via the CO/CO2 ratio. The first results show that an “isoconversion temperature” in the cone calorimeter test may be estimated. Polar gases such as chlorinated or brominated gases are not fully observed using this method due to possible adsorption in the transfer line before they reach the FTIR gas cell.

Synergism of polysiloxane and zinc borate flame retardant polycarbonate

Abstract Liquid polysiloxane (PSI) and zinc borate (ZB) were combined for the flame retardance of polycarbonate (PC). During polymer combustion, for the PC flame-retarded with PSI only, PSI can form char residue containing silica on the material surface. But the liquid silicone tends to drip with melting polymer and volatilize in high temperature, thus decreasing the charring performance. In the case of only ZB flame retardant involved, this inorganic flame retardant and possible some of its decomposition products (B2O3) more difficultly move to the surface and it appears that they do not effectively contribute to the char formation. Present study suggests that the existing synergism between PSI and ZB is the result of chemical reaction via forming cross-linking B–O–Si structure. As results, the loss of Si/silicone is reduced by eliminating the melt dripping. Meanwhile, boron species can be “dragged” by PSI (in the form of borosiloxane) to the surface of the char residue. Consequently, Si and B elements together contribute to the integrity of char residue layer with better quality, achieving obviously improved flame retardance compared with only PSI and only ZB flame retardant systems.

Combustion of polymers in the electrostatic field

The paper presents the results of the experimental study of the influence of an external electrostatic field on the mass burning rate and flame temperature of PMMA, SKD-2, SKN-26, SKMS-30, SKEPT localized in different parts of the combustion zone.

Effect of zinc borate on flammability/thermal properties of ethylene vinyl acetate filled with metal hydroxides

In this work, zinc borate was used as a flame retardant in ethylene vinyl acetate/magnesium hydroxide or aluminum hydroxide flame-retardant formulations. High content zinc borate leads to significant improvements of flame retardancy through limiting oxygen index, UL-94 and cone calorimeter experiments. The protective char formation revealed significant structural modifications due to the presence of zinc borate. It was demonstrated that during polymer heating, aluminum hydroxide and magnesium hydroxide decomposed to Al2O3 and MgO which resulted an increase in ignition time. Moreover, formation of Al2O3 or MgO in situ from aluminum hydroxide or magnesium hydroxide during polymer combustion is the first event. Concurrently, zinc borate degraded and formed a vitreous protective coating, which yielded the substrate with an efficient char which acted as a physical barrier and a glassy cage for better protection of polymer substrate.

Effects of Acidic Sites in HA Zeolite on the Fire Performance of Polystyrene Composite

A Lewis acid has been considered as a char promoter during the combustion of polymers. The acidified 4A zeolites (HA zeolite) containing Lewis acid sites (4A-L zeolite) and Bronsted-acid sites (4A-H+ zeolite) were prepared and their crystallinity and acidic site structure were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The thermal behavior and flammability of a polystyrene (PS) composite containing different types of zeolite were investigated by thermogravimetric analysis (TGA), volatile gas and condensed phase FTIR analysis, limiting oxygen index (LOI), and cone calorimeter. Both 4A-L and 4A-H+ zeolite could enhance the flame retardancy of a PS composite significantly. The heat release rate (HRR) of a PS composite could be decreased by 48% after adding 2% 4A-L. It is suggested that Lewis acidic sites in HA zeolite can alter the degradation route and enhance the char formation of a PS composite.

불화수소(HF)의 독성에 관한 병리학적 분석 연구

현대의 건축 재료는 각종 고분자 화합물의 비중이 커지고 있어 건축 재료 연소 시에 발생하는 가스의 성분비가 천연재료를 이용하던 과거의 건축물과 차이를 보인다. 실제로 근래의 건축재료 연소가스의 정성분석결과를 살펴보면, 천연재료의 연소가스에 포함되어있는 CO, <TEX>$CO_2$</TEX>외에도 HF, HCN, HBr, HCl, NO, <TEX>$NO_2$</TEX>, <TEX>$SO_2$</TEX>등의 화학종이 포함되어 있음을 알 수 있다. 이러한 화학종들은 고분자 화합물에서 발생하는 것으로 분석되며, 건축 재료에서 그 비중이 높아지는 만큼 향후 이러한 화학종들이 건축물 화재에서 대피의 주요 방해요인으로 작용할 수 있을 것으로 예상된다. 이에 본 연구에서는 연소가스중 HF가 실험동물의 생체에 미치는 영향을 병리학적으로 분석하기 위하여, HF의 표준가스를 실험동물에 노출시켜 조직 병리 검사, 유전 독성 평가실험을 실시하였다. 이를 통하여 HF에 노출된 실험동물은 폐와 간에서의 광범위한 출혈과 괴사가 발생함을 확인하였으며, 이로 인한 혈액과 장기별 DNA손상은 Comet assay를 이용하여 정량적으로 분석하였다. Polymer materials are well-used for Modern building constructions. Combustion gas of construction material has different components between natural and polymer. Recently research shows, Apart from combustion gas of natural construction material contain CO. <TEX>$CO_2$</TEX> species. Also polymer combustion gas include HF, HCN, HBr, HCl, NO, <TEX>$NO_2$</TEX>, and <TEX>$SO_2$</TEX> additionally. It analyzed that species product from Polymer compounds. These species can act as major disturbance factors in the evacuation from the building's fire. Because, polymer will increase the proportion in building materials. In this research, effects from HF gas are analyzed by pathological method. Histopathologic examination, DNA toxicity evaluation experiments were conducted for mouse exposed by HF standard gas. Exposing HF gas were caused extensive hemorrhage and necrosis in the liver and lung from experimental animals. and blood and DNA damage were analyzed quantitatively by comet assay.

Aerosols emitted by the combustion of polymers containing nanoparticles

The fire behavior and the characterization of solid and gaseous fire effluents of polymers [polymethyl methacrylate (PMMA) and polyamide-6 (PA-6)] filled with nanoparticles (silica, alumina, and carbon nanotubes) used to improve their flame retardancy were investigated. To determine the impact of these composites on the emission of airborne particles produced during their combustion in accidental fire scenarios, an experimental setup was developed to measure the mass distribution in the 30 nm–10 μm range, and the concentrations of submicrometric particles in the aerosol. Comparisons were made between unfilled and filled polymers, and the influence of filler surface treatments (silane-based), as well as combinations with a flame retardant [ammonium polyphosphate (APP)], was investigated. The presence of nano-oxides in PMMA shows a significant effect on the rate of particle emission with a decrease in the concentration of the emitted submicrometric particles. APP in PMMA led to a decrease in the mass fraction of ultrafine particles and an increase in the rate of submicrometric particle emission compared to filled compositions with nano-oxides. Atomic force microscopy was used as a complementary tool for the characterization of the particles emitted during combustion, allowing direct observation of nanoparticle morphology, detection of carbon nanotubes in the aerosol, and visualization of the effect of APP on nanoparticle morphology.

In vitro cytotoxicity and morphological assessment of smoke from polymer combustion in human lung derived cells (A549)

The application of polymer and composites in building and modern transport interiors raises concerns of potential health hazards during combustion. Cytotoxicity and morphological assessment of smoke from polymer combustion in human lung derived cells (A549) has been investigated. A laboratory scale vertical tube furnace was used for the generation of combustion products. A range of materials used in the building and transport industry including high density-polyethylene (HDPE), polypropylene (PP), polycarbonate (PC), and polyvinyl chloride (PVC), fiberglass reinforced polymers (FRPs), and melamine faced plywood (MFP) were studied. The exposure of combustion toxicants to human lung cells (A549) at the air/liquid interface was acquired using a Harvard Navicyte Chamber. Cytotoxic effects on human cells were assessed based on cell viability using a selected in vitro cytotoxicity assays, including NRU (neutral red uptake) and ATP (adenosine triphosphate). Morphological assessment on the effects of combustion products in human lung cells from selected materials including PVC, FRP and MFP was assessed using scanning electron microscopy (SEM). The volatile organic compounds from thermal decomposition products were identified using ATD-GCMS (Automatic Thermal Desorption Gas Chromatography Mass Spectrometry). NOAEC (No Observable Adverse Effect Concentration), IC(10) (10% inhibitory concentration), IC(50) (50% inhibitory concentration), and TLC (Total Lethal Concentration) values (mg/l) were generated. The following toxicity ranking was observed from the most toxic material to the least toxic using the NRU assay: PVC>PP>HDPE>PC >FRP-10>MFP>FRP-16; and the ATP assay: PVC>HDPE>PP>FRP-10>FRP-16>MFP>PC. The method described here could potentially be an alternative to current fire toxicity standards.