Kind Of Flame Retardant Research Articles

Mechanical, Dielectric and Flame-Retardant Properties of GF/PP Modified with Different Flame Retardants.

With the rapid development of electronic information technology, higher requirements have been put forward for the dielectric properties and load-bearing capacity of materials. In continuous glass fiber-reinforced thermoplastic composites, polypropylene matrix is a non-polar polymer with a very low dielectric constant and dielectric loss, but polypropylene is extremely flammable which greatly limits its application. Aiming at the better application of flame retardant-modified continuous glass fiber-reinforced polypropylene composites (FR/GF/PP) in the field of electronic communication, the effects of four different kinds of flame retardants (Decabromodiphenyl ethane (DBDPE), halogen-free one-component flame retardant (MONO), halogen-free compound flame retardant (MULTI), and intumescent flame retardant (IFR)) on the properties of FR/GF/PP were compared, including the mechanical properties, dielectric properties and flame-retardant properties. The results showed that among the FR/GF/PP, IFR has the highest performance in mechanical properties, MULTI has better performance in LOI, DBDPE and IFR have better performance in flame retardant rating, and DBDPE and IFR have lower dielectric properties. Finally, gray relational analysis is applied to propose an approach for selecting the optimal combination (flame retardant type and flame-retardant content) of comprehensive performance. In the application exemplified in this paper, the performance of IFR-3-modified GF/PP is optimized.

STUDY ON THE MOST EFFECTIVE COMBINATION OF FLAME RETARDANT AND ANTI-AGING AGENT FOR BAMBOO MODIFICATION

In order to promote the universal application of bamboo materials as well as to provide reference for the study of the performance of bamboo, four kinds of flame retardants (boric acid (BA), borax (BX), ammonium polyphosphate (APP), disodium octaborate tetrahydrate (DOT)), two kinds of ultraviolet light absorbers (UV-531, nano TiO2) were added into waterborne polyurethane (WPU) to synthesize 5 kinds of modified coatings and coated on the surface of bamboo to make test materials. The flame-retardant analysis of the coated samples comprehensively explored the changes in flame retardancy of the test material after treatment. And the anti-aging test was carried out to investigate the color difference and adhesion change of the coating sample. The results show that the optimum flame retardant and anti-aging coating composition was obtained as 20% solid content of WPU, 8g coating amount of modifier, with the mass ratio of BA/BX/APP /DOT/water being 75:75:7:42:600, and the amount of UV-531 added being 1%.

Fabrication of NiO and TiO2 supported nano calcium carbonate and its effect on the flame retardancy and thermal stability of epoxy resin composites

Nano calcium carbonate (CaCO3) was successfully treated by tetrabutyl titanate sol together with nickel hydroxide, followed by calcination to form a new kind of flame retardant (Ni-TiO2@CaCO3). After study of the Ni-TiO2@CaCO3 structure, it was then introduced into epoxy resin (EP) to improve the flame retardancy and thermal stability. The results shown that NiO and TiO2 were supported on the surface of the CaCO3, and 5 wt% CaCO3 could enhance the flame retardancy and Ni-TiO2@CaCO3 further increased the flame retardancy of the EP composites. In the cone calorimeter test (CCT), the values of the peak heat release rate (pHRR) and smoke production rate (pSPR) were reduced to 769 kW/m2 and 0.32 m2/s by CaCO3 from 1101 kW/m2 and 0.39 m2/s of the raw EP respectively. Moreover, pHRR and pSPR values were further decreased to 511 kW/m2 and 0.25 m2/s by Ni-TiO2@CaCO3 respectively. Although the degradation temperature values were lower than that of the control EP, the temperature values at 5 and 50% mass loss for Ni-TiO2@CaCO3/EP composites were improved compared to the EP. In addition, the char residues value of the Ni-TiO2@CaCO3/ EP composite (23.5%) was obviously improved compared to that of the EP (13.0%) and CaCO3/ EP composite (16.4%). In addition, the flame retardancy mechanism of the Ni-TiO2@CaCO3/ EP composite was thoroughly analyzed by TGA-FTIR, FITR and Raman methods. This work provides a promising evaluation strategy for utilizing CaCO3 and its derivatives for possible treatment of EP to enhance its flame retardancy and thermal stability.

Polybrominated diphenyl ethers and bromophenols in paired serum, hair, and urine samples of e-waste dismantlers: Insights into hair as an indicator of endogenous exposure

Polybrominated diphenyl ethers (PBDEs) are important pollutants during dismantling activities of electronic waste (e-waste) in China due to its large production and usage. Bromophenols (BPs), which are a kind of flame retardants and diphenyl ether bond cleavage metabolites of PBDEs, are often neglected in the assessment of human exposure to e-waste. Herein, 22 PBDEs and 19 BPs were determined in paired serum, hair, and urine samples collected from workers and residents of a typical e-waste dismantling site in southern China. Both PBDE and BP congeners were more frequently detected in hair than serum and urine samples. The medians of ΣPBDEs and ΣBPs were 350 and 547 ng/g dw in hair internal (hair-In) of occupational population, respectively, which were significantly higher than non-occupational population. However, a non-significant difference was found in levels of ΣPBDEs and ΣBPs in serum and urine between occupational and non-occupational populations, suggesting that hair analysis could easily differentiate between the exposure intensities of PBDEs and BPs to populations than serum and urine analyses. Moreover, levels of BPs in hair-In were 1–2 orders of magnitude higher than those in hair external (hair-Ex), while a non-significant difference was found in the levels of PBDEs. This result indicated that BPs might have originated from endogenous contribution. Notably, as the predominant congeners, the level of 2,4,6-tribromophenol (2,4,6-TBP) in hair-In was 3–8 times higher than that of BDE-209, while level of 2,4,6-TBP in hair-Ex was 1–3 times lower than that of BDE-209. Furthermore, in vivo experiments performed on Sprague–Dawley rats following a 28-day oral treatment with BDE-209 and 2,4,6-TBP verified that endogenous accumulation of 2,4,6-TBP in hair could be attributed to the metabolism of BDE-209 and exposure to 2,4,6-TBP. In conclusion, compared with PBDEs, biomonitoring phenolic compounds or metabolites with hair could better reflect human endogenous exposure.

Legacy and novel brominated flame retardants in animal-derived foods from China Total Diet Study (CTDS): Temporal trends, evidence of substitution, and dietary exposure assessment.

Based on the 6th China Total Diet Study (CTDS) conducted in 2016-2019, the occurrence of both legacy and novel brominated flame retardants (BFRs) was measured in animal-derived foods collected across China. Most BFRs could be frequently detected in food samples, indicating their ubiquity in the environment. Decabromodiphenyl ethane (DBDPE), a typical novel BFR, presented the highest contamination level, whereas legacy BFRs, including decabrominated diphenyl ether (BDE-209), tetrabromobisphenol A (TBBPA), and hexabromocyclododecane (HBCDD), still presented high detection frequencies and relatively abundant proportions in total BFRs. Compared with previous CTDSs conducted from 2007 to 2011, the levels and estimated dietary intakes (EDIs) of most BFRs showed a significant downtrend, which suggested that flame retardant consumption in China has transferred from legacy BFRs to novel BFRs (mainly DBDPE) and from BFRs to other kinds of flame retardants. Based on probabilistic estimation, the median EDIs of mainly used BFRs for the Chinese population ranged from 41.0 to 1.67×103 pg/kg bw/day, and meat consumption was the primary source in dietary BFR intake. By conducting the margin of exposure (MOE) approach or comparing with the reference dose (RfD), it can be concluded that daily dietary intakes of BFRs were still unable to cause significant health risks to the general population in China.

Recent advances in fire-retardant rigid polyurethane foam

• This review reports the state-of-the-art design of flame-retardant RPUF. • The reactive, additive and coating type flame retardants for RPUF are discussed. • The flame-retardant and thermal conductive properties of RPUF are compared. • Key challenges and opportunities for future flame-retardant RPUF are described. Driven by global environmental concerns, many efforts have been made to develop halogen-free flame retardants for rigid polyurethane foam (RPUF). These environmentally benign flame retardants are mainly divided into (i) reactive, (ii) additive, and (iii) coating types. The last decade has witnessed great progress of these three strategies, which enhance the fire safety of RPUF and maintain even improve the thermal insulation properties. This comprehensive review focuses on the up-to-date design of the reactive, additive, and coating flame retardants, and their effects on flame retardancy and thermal conductivity of RPUF. Moreover, the practical applications of the as-prepared flame-retardant RPUFs are highlighted. Finally, key challenges associated with these three kinds of flame retardants are discussed and future research opportunities are also proposed.

Polybrominated diphenyl ethers quinone-induced intracellular protein oxidative damage triggers ubiquitin-proteasome and autophagy-lysosomal system activation in LO2 cells

Polybrominated diphenyl ethers (PBDEs), a kind of flame retardants, were widely used in the furniture, textile and electronics industries. Because of their lipophilic, persistent and bio-accumulative properties, PBDEs were listed on the Stockholm Convention as typical persistent organic pollutants (POPs). We have previously reported that a highly active, quinone-type metabolite of PBDEs (PBDEQ) causes DNA damage and subsequently triggers apoptosis. However, it is remaining unclear whether PBDEQ provokes protein damage and stimulates corresponding signaling cascade. Using human normal liver (LO2) cells as an in vitro model, we demonstrated that PBDEQ causes oxidative protein damage through excess reactive oxygen species (ROS). Consistently, we found PBDEQ exposure causes the depletion of protein thiol group, the appearance of carbonyl group and the accumulation of protein aggregates. Endoplasmic reticulum (ER) stress was involved in the repair of oxidized proteins. Under the scenario of severe damage, LO2 cells degrade oxidized proteins through ubiquitin-proteasome system (UPS) and autophagy. The blockage of these protein degradation pathways aggravates PBDEQ-induced cytotoxicity in LO2 cells, whilst antioxidant N-acetyl-cysteine (NAC) rescues PBDEQ-induced oxidative protein damage conversely. In summary, our current study first demonstrated PBDEQ-induced protein oxidative damage in LO2 cells, which offer a better understanding of the cytotoxicity of PBDEs and corresponding metabolites.

The potential relationship between neurobehavioral toxicity and visual dysfunction of BDE-209 on zebrafish larvae: a pilot study

BackgroundAlthough listed in the Stockholm Convention, commercial Decabromodiphenyl ether (c-DecaBDE) is still being produced in many factories and used as a kind of flame retardants primarily in plastic polymers and textiles. Widespread use offered many exposure ways of its major ingredient, BDE-209, to humans and the environment. Most current studies of BDE-209 focused on the health effects and toxicity of thyroid disruption, oxidative stress, neurotoxicity, and reproductive function, but seldom spread light on the relationship between neurobehavioral toxicity and visual dysfunction. Using zebrafish larvae model, we hope to uncover the potential relationship between the neurobehavioral and visual effects after exposure to BDE-209.ResultsBDE-209 exposure could not induce the changes of locomotion and path angle in 5 days post fertilization (dpf) larvae; however, 5 μg/L BDE-209 exposure caused locomotor hyperactivity and more responsive turns at 7 dpf. The social activity of 50 μg/L exposure group was significantly higher than the control group at 6 dpf. Besides, 5 and 50 μg/L exposure caused the upregulation and downregulation of four cone opsin genes, respectively. The expression of rhodopsin gene was not influenced by both concentration exposures.ConclusionThe neurobehavioral effects induced by 5 μg/L BDE-209 exposure were consistent with the upregulation of four cone opsins in 7 dpf larvae. The low concentration of BDE-209 exposure caused the hyperactivity and more responsive turns of larvae possibly contributing to the disruption on the cone opsin expressions of larvae. Our results would provide the mechanism cue of neurobehavioral toxicity after BDE-209 exposure and call for more attention on the ecotoxicology studies of BDE-209.

Classification-based material decomposition method for photon counting-based spectral radiography: Application to plastic sorting

Dual-energy X-ray radiography has been commonly used for materials separation. However, its performance is limited, especially for the separation of close materials or the identification of multiple materials. To cope with this problem, we propose to investigate the material decomposition ability of spectral radiography based on photon-counting detector. The latter having energy resolving capability can provide spectral information of several energy bins and thus enables selective imaging of multiple materials. In this framework, a classification-based patchwise regularized decomposition method was proposed to gain better differentiation between materials. It consists of performing several decompositions with reduced number of materials in the basis and classifying these decompositions using their cost function values. The results on simulations showed that, in the presence of Poisson noise, the method without classification can separate acrylonitrile-butadiene-styrene (ABS) from three kinds of flame retardants (FRs: brominated FR, chlorinated FR and phosphorus FR), but that the type of FR cannot be identified. With the classification technique, ABS and three kinds of FRs can be both separated and identified at the same time when the thickness was as large as 2 mm or 4 mm. The results on real data from physical photon-counting detector further confirm that the ABS, Br and Cl can be separated from each other.

Preparation and Evaluation of Composite Flame Retardant Asphalt in Tunnel

Asphalt pavement becomes more and more popular in tunnel engineering, while its flammability is a serious problem that limits its development. In order to obtain a flame retardant asphalt, orthogonal design was utilized to investigate the best flame retardant content of magnesium hydroxide (MH), phosphorus (P) and decabromodiphenyl ethane (DBDPE). Limiting oxygen index (LOI), penetration, softening point and ductility tests were employed to evaluate the flame retardancy and pavement performance of asphalt. The results show that three kinds of flame retardants have positive influence on the low temperature performance and flame retardancy of SBS modified asphalt but not good for its high temperature performance. The best flame retardant content is determined as: 4% MH, 6% P and 8% DBDPE.

New formulation and characterization of enhanced bulk-organic phase change materials

The main drawbacks faced by researchers to successfully implement organic-PCM as materials to improve the thermal performance of building systems are their low thermal conductivity, their high flammability, and their low thermal cycling stability. In the present work, authors present a new enhanced PCM formulations aimed to solve the stated disadvantages in organic bulk-PCM. The new enhanced PCMs were prepared by adding high thermal conductivity particles and two kinds of flame retardants into organic PCM (paraffin and fatty acid eutectic mixtures). In the first stage, the effective thermal conductivity of organic-PCM was increased by using two different methods: directly dispersion of powder graphite (PG) bulk-PCM and vacuum impregnation of PCM into expanded graphite (EG). In the second stage, the fire reaction behaviour of the thermal conductivity enhanced PCM formulations was improved by adding two kind of flame retardants: magnesium hydroxide and ammonium phosphate (APP). Their fire reaction behaviour, thermal conductivity and thermophysical properties were measured by adapting the dripping test (UNE 23727-90), the hot-wire method and Differential Scanning Calorimetry (DSC), respectively. The enhanced PCM composites show a self-extinguished behaviour in terms of fire performance mechanism. The EG working with endothermic and phosphates flame retardants improve the fire performance of PCM by acting as a synergic system and the thermal conductivity is increased. However, their thermal storage capacity is significant decreased due to the large amount of flame retardant added (up to 40%). The thermal reliability was also tested, the enhanced PCM composites were stable up to 1000 thermal cycles.

Experimental study on the influence of the flame retardants on the flammability of R1234yf

R1234yf has been considered as an alternative refrigerant with the low global warming potential (GWP), but it is flammable. Therefore, it is necessary to study the reduction or inhibition of flammability of R1234yf by different flame retardants. This paper mainly contributed to the influence of two kinds of flame retardants on the flammability of R1234yf. Firstly, the flammability limits of R1234yf and the mixtures of R1234yf/R227ea and R1234yf/R134a were tested out. Then the relationship between their flammability limits characteristics with the ratio of the flame retardants to R1234yf were evaluated by the fitted equations. The critical suppression ratios of R227ea/R1234yf and R134a/R1234yf were obtained. The results indicated that the inhibitory effect of R227ea on R1234yf was better than that of R134a by comparative analysis. Finally, the flame colors and flame propagation velocity characteristics of R1234yf before and after the addition flame retardants were researched and analyzed. The research achievement will be of universal guiding significance for the security application of R1234yf.

Synergistic effect on flame retardancy and thermal behavior of polycarbonate filled with α‐zirconium phosphate@gel‐silica

ABSTRACTA new kind of flame retardant (ZS) with layered α‐zirconium phosphate disks (α‐ZrP) as the core and inorganic flame retardant (gel‐silica, GS) to shield solid acid sites on the surface of α‐ZrP as the shell, was synthesized via a facile method. The incorporation effects of ZS with silicone resin on the thermal properties and flame retardance of PC composites were investigated. The presence of ZS could improve the thermal stability of PC matrix. With the addition of ZS contents increased to 3 wt %, the limiting oxygen index (LOI) of the composite was 32.3% and the vertical burning (UL‐94) test reached a V‐0 rating. However, with more contents of ZS, the LOI value decreased, and without the GS layer, the LOI value was decreased significantly as well. The synergism between the α‐ZrP core and gel‐silica shell, also with the silicone resin were found. Based on these results, the flame‐retardant mechanism was proposed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44829.

Effect of DOPO-containing flame retardants on poly(lactic acid): Non-flammability, mechanical properties and thermal behaviors

The flame retardancies of three kinds of 9,10-dihydro-9-oxa-10-phosphaphenan-threne 10-oxide(DOPO)-containing flame retardant(A1, A2, A3)/poly(lactic acid)(PLA) composites[PA-n/(Ax-y), n=1—12; x=1, 2, 3, denoting three kinds of flame retardants; y=10%, 20%, 30%, 40%, denoting the mass fraction of Ax] were greatly enhanced by melt blending of flame retardant Ax with PLA, including twin-screw extrusion and injection-molding processes. With only 10%(mass fraction) of Ax added to PLA, good flame retardancy with limiting oxygen index(LOI) values of more than 33% was achieved. As the Ax mass fraction was further increased to 20%, PA-n/(Ax-20%) composites showed much better flame retardancy(LOI≥35% and UL-94 V-0 rating). Moreover, the thermal degradation behaviors and mechanical properties of PA-n/(Ax-y) composites were investigated via thermogravimetric analysis(TGA), differen-tial thermal analysis(DTA), tensile testing, notched impact-bar testing, and dynamic mechanical analysis(DMA). TGA results show that PA-n/(Ax-y) composites have slower rate of mass loss and much higher char yield, compared to neat PLA. With the addition of Ax to PLA, the DTA and DMA results indicate slight variations in glass transition tempe- ratures(Tg) of PA-n/(Ax-y) composites. Based on TGA results under nonisothermal conditions, the thermal degrada-tion kinetics of PA-n/(Ax-y) composites were studied by Kissinger’s and Ozawa’s methods. These thermal degrada-tion dynamic analyses show lower activation energies(EK or EO) for PA-n/(Ax-y) composites, corresponding to higher mass fractions of Ax(from 10% to 40%). The PA-n/(Ax-y) composites with good flame retardancy and good mecha- nical properties obtained in this study could be potential candidates for fire- and heat-resistant applications in auto-motive engineering and building fields with more safety and excellent performance.

Flame retardancy and toughness modification of flame retardant polycarbonate/acrylonitrile-butadiene-styrene/AHP composites

A kind of flame retardant polycarbonate/acrylonitrile-butadiene-styrene copolymer (FR PC/ABS) composite was prepared by melt extrusion blending using aluminum hypophosphite (AHP) as a flame retardant and ethylene-co-acrylic ester-co-glycidyl methacrylate (EMA) as a compatibilizer. The thermal behavior and flame retardancy of FR PC/ABS composites were investigated by thermogravimetric analysis, the UL-94 vertical burning test, the limiting oxygen index, and the cone calorimeter test. The FR PC/ABS composites showed good flame retardancy, from no vertical rating for PC/ABS, to V-0 rating for FR PC/ABS containing 15 wt% AHP in the UL-94 test. PC/ABS/15wt%AHP/6wt%EMA composite was more efficient in decreasing the peak heat release rate (PHRR) of FR PC/ABS composite in the cone calorimeter test. The same amount of AHP provided equally strong flame inhibition and increased char flame retardancy in PC/ABS/AHP and PC/ABS/AHP/EMA composite. Whereas, the protective compact char layer of PC/ABS/AHP/EMA composite efficiently improved the flame retardancy that of PC/ABS/AHP composite. With the addition of 6 w% of EMA copolymers, the elongation yield at break of the FR PC/ABS composite increased by 6.7 times compared to that of the PC/ABS/AHP composite; and the notched impact strength and unnotched strength improved by approximately 250% and 710%, respectively, compared to those of the PC/ABS/AHP composite. Fourier transformed infrared (FT-IR) and scanning electron measurements (SEM) results indicated that EMA could effectively enhance the interfacial interaction of FR PC/ABS composite.

Use of Polishing Alumina as Flame Retardant in Orthophthalic Polyester Resin Matrix Composites

The field of Civil Engineering Materials has found a use for a range of industrial waste products as substitutes, that are as effective as standard construction materials but which have the bonus of providing an ecologically sound alternative for materials that would otherwise become an environmental concern. The use of waste materials in polymer composites is a prime example of this practice. These composites display excellent mechanical properties but must be adapted to the combustibility properties. This study aimed to produce polymer concrete composites using waste alumina from metallurgic industrial processing. The composites have an ortophtalic polyester resin as a binder, river sand as aggregates and fly ash as filler. Two kinds of flame retardants were used: a residue, polishing alumina and the other virgin, commercial alumina which were used in four different percentages 15, 30, 45 and 60% in mass in relation to the resin. The samples were subjected to testing of flexural strength, temperature changes of 125, 225 and 325°C and porosity by mercury addition. The results received statistical treatment in order to evaluate the variable significance in relation to the studied properties. In this study the composites displayed flexural strength values around 30 MPa. The statistical analysis showed that the factors temperature changes, addition percentage and the interaction among these factors posed great influence on the studied compositions in relation to the heat resistance testing. In general terms, it can be said that the flame retardant waste, polishing alumina, is an efficient alternative to substitute the trihydrated commercial alumina in the polymer concrete composites with the other components proposed in this study.Key words: polishing alumina, recycling, polymer concrete, fly ash, combustibility

Effect of three flame retardants on the performance of PE wood plastic composites flooring.

To improve application of wood-plastic composites （WPC）, a new type of environmental material, and to promote safety, the effects of three kinds of flame retardants （A, B, and C） on mechanical properties and combustion performance of PE wood plastic composite flooring were compared to unprocessed wood plastic composite flooring and analyzed. Results showed that after adding flame retardants, the 24 h water absorption rate, the bending failure load, and the smoke density of WPC flooring met the GB/T 24508-2009 and GB 8624-2006 standards. Compared to unprocessed WPC flooring, the oxygen index increased from 25.2% to 34.4%, the 24 h water absorption rate increased from 47.0% to 152.0%, and the bending failure load decreased from 10.5% to 27.4%. Retardant C had the maximum oxygen index and bending failure load for treated WPC flooring; retardant B had the minimum 24 h water absorption rate and smoke density. Overall, flame retardants improved the flame retardation properties of WPC flooring but negatively influenced mechanical properties; meanwhile, smoke from fire with WPC flooring was the main cause of casualties, so this toxic smoke requires further study. ［Ch, 4 fig. 1 tab. 19 ref.］

Fire Performances, Hot Properties and Decomposition Kinetics of Sb<sub>2</sub>O<sub>3</sub>/DBDPE/RTV

Fire and hot properties of title composite were taken by the method of vertical burning, OI, and TG. Fire performance experiments demonstrated that the scale of flame retardant property of Sb2O3/ DBDPE/RTV was FV-0, OI was 46. Hot decomposition temperature is about 400 oC to 520 oC with the amount of 20wt% as additives. The kinetic parameters of the decomposition reaction of the title composite have been studied by means of DSC. The data are fitted to the integral, differential and exothermic rate equations by linear least-squares, iterative, combined dichotomous and least-squares methods, respectively. The study leads the reader to the conclusion that the empirical kinetic model functions in differential form, the values of and of this reaction were , -1857.20 kJ/mol and 244.9 s-1 respectively. Sb2O3/ DBDPE are a kind of flame retardant which own its flame retardant function to higher activation energy but the release of halogen. It is a usable retardant during the lifetime.

Flammability properties of PI fabric coated with montmorillonite

In this study, polyimide (PI) fabric was coated with montmorillonite (MMT) which performed as a kind of flame retardant. Thermogravimetric analysis showed that PI coated with MMT left as much as 69 % char after heating to 700 °C, about 15 % more than uncoated PI fabric. Cone calorimeter testing (heat flux: 60 kW m−2) showed that coated fabric reduced the total heat release and showed resistance to degradation from direct flame. Post-burn residues of samples were examined with SEM and revealed that the weave structure and fiber shape in all coated fabrics were preserved. In addition, heat-insulting test showed that the temperature difference of coated PI could reach 400 °C after 10 min at 800 °C. These results demonstrate that MMT coating is relatively effective for improving flame-retardant behavior to PI fabric.

The flame retardancy of blob-like multi-walled carbon nanotubes/silica nanospheres hybrids in poly (methyl methacrylate)

Multi-walled carbon nanotubes (MWNTs) were grafted with poly (acrylic acid), and subsequently coated with a close-packed layer of silica nanospheres, namely SiO2-g-MWNTs. Such blob-like MWNTs/silica nanospheres hybrids were introduced into poly (methyl methacrylate) (PMMA) as a kind of flame retardant. From determinations of thermogravimetric analysis and cone calorimeter tests, it was indicated that the SiO2-g-MWNTs not only increased the initial degradation temperature and the maximum weight loss rate temperature of PMMA, but also decreased the peak of heat release rate. Observation using scanning electron microscopy revealed that the silica nanospheres on the surface of MWNTs strengthened the protective network layer during combustion.