Limiting Oxygen Index Results Research Articles

Comparative study of flame retardancy in polyimine vitrimers and composites: Evaluating additive and reactive flame retardants acting via gas-, solid-, and combined-phase mechanisms

We developed flame retarded polyimine type vitrimers and carbon fibre reinforced composites using two additive and a reactive flame retardant containing phosphorus: ammonium polyphosphate (APP), resorcinol bis(diphenyl phosphate) (RDP); and N,N',N’’-tris(2-aminoethyl)-phosphoric acid triamide (TEDAP). We characterised the vitrimer matrix materials by differential scanning calorimetry (DSC), thermal analysis (TGA), limiting oxygen index (LOI), UL-94 test and mass loss calorimetry (MLC), while the vitrimer composites by LOI, UL-94 test, MLC and dynamic mechanical analysis (DMA). We compared the performance of the vitrimer systems to a benchmark pentaerythritol-based aliphatic epoxy resin system (PER). The vitrimer reference had higher thermal stability but lower fire performance than the PER aliphatic reference epoxy. At lower phosphorus content, the vitrimer systems exhibited a melting above their vitrimer transition temperature, which negatively affected their LOI and UL-94 results. From 2% phosphorus content, rapid charring and extinguishing of vitrimers prevented the softening and deforming. The superior performance of these same flame retardants in vitrimer systems could be attributed to the high nitrogen content of imine-based vitrimers in combination with phosphorus flame retardants, exploiting nitrogen-phosphorus synergism. In both matrices, flame retardants with solid phase action lead to better fire performance, while in composites, the lowest peak heat release rates (152 kW/m2 in vitrimer composite) were achieved with RDP acting predominantly in the gas phase, as carbon fibres hindered the intumescent phenomenon.

Preparation and properties of bio-based intumescent flame retardant containing chitosan functionalized ammonium polyphosphate for polyurethane

In this study, chitosan (CS) from fish waste was used to prepare bio-based environmentally friendly flame retardants. After the hydroxyl group (−OH) of CS and the ammonium group (NH4+) of ammonium polyphosphate (APP) underwent reactions, they were filtered and dried to obtain CS-APP. The amino group of CS-APP then reacted with the epoxy group of 4,4′-methylenebis(N,N-diglycidylaniline) (NDY) to form CS-APP-NDY. Isophorone diisocyanate, polyol, and 3-aminopropyltriethoxysilane reacted to form silicon polyurethane. CS-APP-NDY was then mixed with Si-PU to prepare polymer composites. To determine the structure, thermal properties, flame retardancy, and mechanical properties of the composites, Fourier-transform infrared spectroscopy, thermogravimetric analysis, limiting oxygen index (LOI), cone calorimetry, UL-94, thermal analysis-FTIR (TA-FTIR) spectroscopy, universal machine testing, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy were performed. The TGA results revealed that, after the addition of CS-APP-NDY, char yield increased from 0.5 wt% to 25.8 wt%, and the thermal stability of pristine PU also improved. In addition, the LOI and UL-94 results indicated that, after the addition of CS-APP-NDY, the LOI increased from 18.2% to 26.3%, and the UL-94 level improved from “Fail” to V-1. Overall, these results indicated that the addition of CS-APP-NDY to pristine PU increased its flame-retarding performance.

Investigation of flame retardancy properties of polypropylene-colemanite and intumescent flame retardant additive blends

Polypropylene (PP) represents a considerable proportion of polyolefins (PO) used in different industrial applications such as automobile components, textiles, packaging, insulation, medical devices, various housewares and household appliances due to its efficient cost, desirable mechanical, thermal and electrical properties, easy processability and recyclability. Because of its carbonaceous structure, PP is a highly flammable material with a LOI value of 18 that presents serious fire hazard. In this research, Intumescent flame retardant (IFR) and colemanite were added to polypropylene to compose 30% of the total mass of the polymeric compounds and the synergistic effect of colemanite with intumescent flame retardant (IFR) additive in PP was investigated by limiting oxygen index (LOI), glow wire test (GWT), UL-94 test and mechanical properties measurements. The LOI, UL 94 and glow wire test results showed that colemanite had a significant effect on flame retardancy and LOI value which can reach to 37.6 % with loading level of 2 wt.% colemanite at the total amount of flame retardant additives kept constant at 30 wt.%. Additionally, the PP/IFR compounds passed UL 94 V0 rating and both 750 °C and 850 °C glow wire tests and with 2-8 wt.% colemanite loading. According to TGA analyses, the results indicated that colemanite improved the thermal stability of PP/IFR compounds and also promoted the formation of char layer. When colemanite mineral added to polypropylene without IFR system, it has no effect on flame retardancy properties of polypropylene. When all properties have been taken into consideration, colemanite can be used up to 6 wt% in IFR.

Fire-Retardant Property of Hexasubstituted Cyclotriphosphazene Derivatives with Schiff Base Linking Unit Applied as an Additives in Polyurethane Coating for Wood Fabrication.

A series of new hexasubstituted cyclotriphosphaze derivatives containing Schiff base linkages were successfully synthesized and characterized. The series contains different terminal substituents of pentyl and tetradecyl. Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and carbon, hydrogen, and nitrogen (CHN) elemental analysis were used to characterize the intermediates and final compounds, while the thermal stability of the final compounds is evaluated with a thermogravimetric analysis (TGA) test. The final compounds are physically added to the polyurethane coating formulation and then applied to the wood panel using a brush and the compound’s fire-retardant properties are evaluated using the limiting oxygen index (LOI) test. In this research, compound 3b showed good thermal stability compared to compound 3a. In terms of LOI results, polyurethane with an LOI value of 21.90% was employed as a matrix for wood coating and the value increased to 24.90% when this polyurethane is incorporated with 1 wt.% of the compound 3b. The increase in the LOI value indicates that the wood coating containing hexasubstituted cyclotriphosphazene compounds exhibits excellent fire-retardant properties as additives.

Synthesis and characterization of flame‐retardant polyurethane based on new chain extenders

AbstractA series of novel flame‐retardant waterborne polyurethanes (FWPU) were synthesized with tris(hydroxymethyl)phosphine (THPO) obtained from the reaction of tetrakis(hydroxymethyl)phosphonium sulfate and bis(2‐hydroxyethyl)terephthalate from the alcoholysis of waste poly(ethylene terephthalate) as flame‐retardant chain extenders. Influences of THPO on flame retardancy and bonding properties of FWPU were investigated using limiting oxygen index (LOI) measurement, vertical burning test, cone calorimeter test (CCT), thermogravimetric analysis and shear tensile test. The results of LOI, vertical burning test and CCT indicated that flame retardancy of FWPU was improved with the introduction of THPO. The peak of heat release rate of FWPU with 1.5 wt% THPO was 401 kW m−2. After hard segment flame‐retardant modification, the initial bonding strength of FWPU adhesive increased by 150%, and the final bonding strength decreased slightly. A new way is provided for the design of novel reactive FWPU which maintained better flame retardancy and adhesive properties after hard segment flame‐retardant modification. © 2022 Society of Industrial Chemistry.

Role of Copper Oxide on Epoxy Coatings with New Intumescent Polymer-Based Fire Retardant.

Epoxy resins (EP) have been used as a thermos-setting material in the field of coating, casting, bonding agent, and laminating. However, a major drawback associated with its use is the lack of good flaming properties, and it is responsible for heavy smoke along with hazardous gases considerably limiting its uses in various fields. In this study, N-ethanolamine triazine-piperizine, a melamine polymer (ETPMP), was established as a new charring-foaming agent and was successfully synthesized with ethanolamine, piperizine, cyanuric chloride, and melamine as precursor molecules via the nucleophilic substitution reaction method. Elemental analysis and Fourier transform infrared (FTIR) spectroscopy analysis were applied to approve the synthesis of ETPMP and confirmation of its structure and characterization. The epoxy coating of intumescent flame retardant (IFR) was equipped by introducing ETPMP, ammonium polyphosphate (APP), and copper oxide (CuO) in multiple composition ratios. CuO was loaded at various amounts into the IFR-coating system as a synergistic agent. The synergistic action of CuO on IFR coatings was scientifically examined by using different analytical tests such as vertical burning test (UL-94V), limited oxygen index (LOI), thermal gravimetric analysis (TGA), cone calorimeter, and scanning electron microscope (SEM). The results showed that small changes in the amount of CuO expressively amplified the LOI results and enhanced the V-0 ratings in the UL-94V test. The TGA data clearly demonstrate that the inclusion of CuO can transform the thermal deprivation behavior of coatings with a growing char slag proportion with elevated temperatures. Information from cone calorimeter data affirmed that CuO can decrease the burning factors by total heat release (THR) together with peak heat release rate (PHRR). The SEM images indicated that CuO can enrich the power and compression of the intumescent char that restricts the movement of heat and oxygen. Our results demonstrate a positive influence of CuO on the epoxy-headed intumescent flame retardant coatings.

Chitosan-regulated inorganic oxyacid salt flame retardants: preparation and application in PVC composites

A series of chitosan-modified inorganic oxyacid salt flame retardants (IOS-CS) were synthesized and used as flame retardants to improve the fire resistance of poly(vinyl chloride) (PVC) composites while improving the mechanical properties of the materials. The thermal stability of the material was analyzed by TG test; the flame-retardant and smoke suppression properties were evaluated by limiting oxygen index (LOI) and cone calorimeter test, and the mechanical properties were analyzed by tensile test and impact test. The TG results showed that the addition of flame retardant can promote the early cross-linking decomposition of PVC composites, not only advance the decomposition temperature of the material but also promote the formation of char layer and increase the char residual content. LOI and cone calorimeter test results showed that stannate chitosan (Sn-CS) can improve flame retardant and smoke suppression more effectively than other samples. Compared with pure PVC, the addition of Sn-CS increased its LOI from 26.6 to 30.5% and reduced the total heat release value and total smoke release by 18.23% and 52.55%, respectively. At the same time, the addition of the flame retardants had no large deterioration effect on the mechanical properties of the material. The tensile properties of flame-retardant PVC were slightly reduced compared with pure PVC, and the impact resistance was even improved to some extent.

Bio-Based Polyamide 1010 with a Halogen-Free Flame Retardant Based on Melamine-Gallic Acid Complex.

This work aims at developing polyamide 1010 (PA1010) composites with improved fire behavior using a halogen-free flame-retardant system based on melamine (Me) and gallic acid (GA) complexes (MA). The MA complexes were formed by hydrogen bonding, starting from 1:2, 1:1, 2:1 Me:GA molar ratios. PA1010 composites were obtained by melt mixing, followed by compression molding. MA provided a plasticizing effect on the PA1010 matrix by decreasing the glass transition temperature. The influence of MA on PA1010 chain packaging was highlighted in the X-ray diffraction patterns, mainly in the amorphous phase, but affected also the α and γ planes. This was reflected in the dynamic mechanical properties by the reduction of the storage modulus. H-bonds occurrence in MA complexes, improved the efficiency in the gaseous form during fire exposure, facilitating the gas formation and finally reflected in thermal stability, thermo-oxidative stability, LOI results, and vertical burning behavior results. PA1010 containing a higher amount of GA in the complex (MA12) displayed a limiting oxygen index (LOI) value of 33.6%, much higher when compared to neat PA1010 (25.8%). Vertical burning tests showed that all the composites can achieve the V-0 rating in contrast with neat PA1010 that has V-2 classification.

Preparation and properties of melamine-formaldehyde rigid closed-cell foam toughened by ethylene glycol/carbon fiber

Toughing melamine-formaldehyde (MF) rigid closed-cell foams were prepared by using ethylene glycol (EG) and carbon fiber (CF) as composite toughening agents. The pulverization rate, compressive strength, bending strength, cellular structure, closed-cell ratio, water absorption ratio, thermal conductivity, thermal stability, limiting oxygen index (LOI), and char yield were characterized to study the morphology, mechanical, thermal, and fire-retardant properties of as-prepared toughing MF rigid foams. The pulverization rate result showed that introduction of composite modifier can obviously improve the toughness of MF rigid foams. The cellular structure, closed-cell ratio, and water absorption results showed that the addition of EG/CF can increase the closed-cell ratio and control the cell size of MF rigid foams. The compressive strength and bending strength results showed that the incorporation of composite modifier of MF rigid foams dramatically improved the mechanical properties. The LOI, char yield, and thermal stability results showed that the toughing MF rigid foams remained more intact char skeleton with flame-retardant effect, thus reducing the fire hazards. The as-prepared toughing MF rigid foams showed the best comprehensive performance with pulverization rate of 5.21%, compressive strength of 355.3 kPa, bending strength of 0.44 MPa, closed-cell ratio of 79.1%, water absorption of 9%, thermal conductivity of 0.031 W m−1 K−1, and LOI of 39.6%. Compared with unmodified MF rigid foams, toughing rigid closed-cell MF foams possess excellent pulverization rate, compressive strength, bending strength, cellular structure, thermal insulation, and flame retardancy.

The synergistic flame retardancy of modified expandable graphite and metal hydroxides on HDPE/EVA composites

In this article, the flammable behaviors and synergistic effects of modified expanded graphite (MEG) with zinc borate (ZB) on flame-retardant high-density polyethylene/ethylene vinyl acetate (HDPE/EVA) composites containing magnesium hydroxide (MH) and aluminum hydroxide (ATH) are investigated by the Underwriters Laboratories-94 (UL-94) test, limiting oxygen index (LOI), cone calorimeter test (CCT), thermal gravimetric analysis (TGA), Fourier transform infrared (FTIR), differential scanning calorimetry, and tensile tests. The LOI, UL-94, and CCT results show that the synergistic effect of MEG and ZB can improve the flame retardancy of the composites. With the addition of ZB and MEG, the LOI value increases, and the UL-94 reaches the V-0 rating. The heat release rate and total heat release decrease, respectively. The data obtained from the TGA indicate that the synergistic effects of ZB with MEG increase the decomposition temperature when 2 phr ZB and 8 phr MEG are added into the composites. The data from FTIR show that HMEG8 and HMEG10 composites produce phosphate at high temperatures, which promotes the formation of stable and compact charred layer. All the results show that ZB and MEG have positive synergistic effects on HDPE/EVA composites containing MH and ATH. However, ZB and MEG play a negative role in the tensile properties of the HDPE/EVA composites.

Synthesis of a novel polyphosphazene/triazine bi‐group flame retardant in situ doping nano zinc oxide and its application in poly (lactic acid) resin

A novel polyphosphazene/triazine bi‐group flame retardant in situ doping nano ZnO (A4‐d‐ZnO) was synthesized and applied in poly (lactic acid) (PLA). Fourier transform infrared (FTIR), solid state nuclear magnetic resonance (SSNMR), X‐ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), transmission electron microscope (TEM), and energy dispersive spectrometer (EDS) were used to confirm the chemical structure of A4‐d‐ZnO. The thermal stability and the flame‐retardant properties of the PLA composites were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), limiting oxygen index (LOI), vertical burning test (UL‐94), and micro combustion calorimeter (MCC) test. The results of XPS showed that A4‐d‐ZnO has been synthesized, and the doping ratio of ZnO was 7.2% in flame‐retardant A4‐d‐ZnO. TGA results revealed that A4‐d‐ZnO had good char forming ability (40 wt% at 600°C). The results of LOI, vertical burning test, and MCC showed that PLA/5%A4‐d‐ZnO composite acquired a higher LOI value (24%), higher UL94 rating, and lower pk‐HRR (501 kW/m2) comparing with that of pure PLA. It indicated that a small amount of flame‐retardant A4‐d‐ZnO could achieve great flame‐retardant performance in PLA composites. The catalytic chain scission effect of A4‐d‐ZnO could make PLA composites drip with flame and go out during combustion, which was the reason for the good flame‐retardant property. Moreover, after the addition of A4‐d‐ZnO, the impaired mechanical properties of PLA composites are minimal enough.

Synergistic flame-retardant effects of aluminum phosphate and Trimer in ethylene–vinyl acetate composites

A series of flame-retardant ethylene–vinyl acetate (EVA) composites with different contents of aluminum phosphate (AHP) and Trimer were prepared. The synergistic flame-retardant effects of the Trimer with AHP in EVA/AHP blends were studied by limiting oxygen index (LOI) tests, UL-94 tests, cone calorimeter tests, thermogravimetric analysis, and scanning electron microscopy (SEM). The LOI and UL-94 results showed that the system containing AHP and Trimer was very effective in improving the flame retardancy of EVA. When the mass ratio of AHP and Trimer was 3:1, the highest flame retardancy could be obtained, and when the flame-retardant loading was 30 wt%, the EVA/AHP/Trimer (7.5%) sample could achieve the V-0 rating in UL-94 tests, at the same time, its LOI value was 24.4%. The TG and DTG results showed that the addition of flame retardants catalyzes EVA decomposition in the first stage and generates a more stable char residue in the second stage. Consequently, an efficient reduction in the flammability parameters, such as heat release rate, total heat release, smoke production rate, and total smoke production could be observed. In addition, it was observed from the SEM observations of the morphological features that the AHP and Trimer combination, at the optimum proportion, could promote the formation of compact charred layers and prevent their cracking, which effectively protected the underlying materials from burning.

Fabrication of thermoplastic composites using fly-ash a coal and hollow glass beads to study their mechanical, thermal, rheological, morphological and flame retradency properties

Thermoplastic polycarbonate (PC) and nylon 6 (NY) composites with cenosphere and hollow glass beads were prepared and their mechanical, rheological, thermal and flame retardency properties were studied. The flexural behavior of the composites increased after loading with cenosphere and hollow glass beads. The tensile strength of the PC composites was enhanced up to 80 N mm–2 as compared to pure PC while no remarkable change was observed in case of nylon 6 composites. Study of thermogravimetric Analysis (TGA) showed that the thermal stability of all the composites (Polycarbonate/cenosphere, Polycarbonate/hollow glass beads, Nylon 6/cenosphere and Nylon 6/hollow glass beads) increased. It was concluded that both the fillers enhanced the non-flammability of the polymers. Limiting oxygen index (LOI) value of all the composites showed an increase with increase in the concentration of filler. The optimal results of LOI and UL 94 were observed in composites with 8% cenosphere and 12 % cenosphere in case of Nylon 6. Cenosphere led to superior mechanical properties of polycarbonate and nylon 6 in comparison to hollow glass beads which suggested the composites can find use in automotive, industrial, pump component and for manufacturing of light weight parts in aeronautic industry at lower economic value.

The synergistic effect of hollow glass microsphere in intumescent flame-retardant epoxy resin

A series of flame-retardant epoxy resin (EP) composites, with different mass ratio of intumescent flame-retardant (IFR) and hollow glass microspheres (HGM), have been prepared. The synergistic flame-retardant effects of HGM between IFR in EP blends have been examined through several conventional methods, such as limiting oxygen index (LOI) test, UL-94 test, cone calorimeter test (CCT), scanning electron microscopy (SEM), and thermogravimetric analysis (TG), respectively. The LOI and UL-94 results show that when 2.0 mass% IFR is replaced by HGM, the LOI value can be increased to the maximum value of 34.7 among all samples. The data obtained from the CCT test indicate the peak value of heat release rate of EP/IFR/HGM sample with 2.0 mass% HGM reduced to 177.6 from 851.1 kW m−2 (pure EP). The digital photographs and SEM of char residues after CCT give positive evidence of the synergistic flame-retardant effects between HGM and IFR. Firstly, HGM could promote the formation of dense and compact charred layers. Secondly, it could prevent the charred layers from cracking. The TG results reveal that EP/IFR/HGM samples show higher thermal stability at high temperature than EP/IFR sample.

Effect of nano‐titanium nitride on thermal insulating and flame‐retardant performances of phenolic foam

ABSTRACTIn this work, titanium nitride (TiN) nanoparticles were employed to achieve enhanced thermal insulation and flame retardance of phenolic foam (PF)/TiN nanocomposites (PFTNs) viain situpolymerization. The morphologies of PFTNs were observed by scanning electron microscope and the images showed that the PFTNs have more uniform cell morphologies compared with pure PF. Thermal insulating properties of PFTNs were evaluated by thermal conductivity tests. The introduction of TiN obviously decreased the thermal conductivities of PF over a wide temperature range (−20 to 60 °C). Significantly, the thermal conductivity of PFTNs gradually decreased as the temperature increased from 30 to 60 °C, showing a contrary tendency with that of pure PF. Moreover, the thermal stability and flame‐retardant properties of PFTNs were estimated by thermogravimetric analysis (TGA), UL‐94 vertical burning and limited oxygen index (LOI) tests, respectively. The TGA and LOI results indicated that PFTNs possess enhanced thermal stabilities and fire‐retardant performances with respect to the virgin PF. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2016,133, 43765.

Ammonium Polyphosphate/Melamine Cyanurate Synergetic Flame Retardant System for Use in Papermaking

A new synergetic flame retardant system (SFRS) using ammonium polyphosphate/melamine cyanurate (APP/MCA) core-shell particle was synthesized and applied to papermaking. Cationic polyacrylamide (CPAM) was added to improve the adsorption of SFRS in pulp. Higher amounts of SFRS led to higher adsorption by pulp. Handsheets were produced with different amounts of SFRS. Thermal gravimetric analysis (TGA) and limiting oxygen index (LOI) were employed to test fire retardation in these handsheets. TGA and LOI results showed that this new core-shell SFRS is an effective flame retardant that improves the thermal stability of handsheets.

Comparing the Effect of Micro- and Nano-Scale Silica on the Rheological, Dynamic Mechanical Properties and Flame Resistance of Nylon 6,6

Nylon 6,6 micro- and nano-silica composites were prepared by melt processing using a twin-screw extruder. Three nanocomposites containing 4, 8, and 12 wt.% of nanosilica were prepared. In order to compare the effect of size, a microcomposite containing 4 wt.% of micron-size silica was also prepared. The effects of particle type (micro- and nano-size) on the dynamic thermomechanical and rheological properties, morphology, and flame resistance of the composites were examined. The dynamic thermomechanical properties (DMTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic rheometry, thermogravimetry analysis (TGA), and limiting oxygen index (LOI) data are reported. The particles were observed to be dispersed uniformly, but with a different level of coalescence, by means of SEM and TEM. The DMTA results showed that the damping factor peak positions of the nanocomposites at low content of nanofiller shifted more to higher temperature compared to those of nanocomposites containing high concentrations of nanofiller. Dynamic rheometry, using a parallel plate rheometer, showed that the rheological moduli of the nanocomposites increased with increase in nanofiller concentration; however, this increase was greater in the high-frequency region. These results showed that increasing the concentration of nanofiller, and the consequent coalescence effect within the nanocomposites, led to rheological moduli values similar to those of the microcomposite. The TGA and LOI results of the microcomposite and nanocomposite containing 4wt.% of nanosilica showed that nanosilica had a more significant effect to enhance the heat and flame resistance of nylon 6,6 compared to that of micron-sized silica.

Synergistic flame retardant effects between hollow glass microspheres and magnesium hydroxide in ethylene-vinyl acetate composites

Abstract A series of flame retardant ethylene-vinyl acetate (EVA) composites, with different content of magnesium hydroxide (MH) and hollow glass microspheres (HGM), have been prepared. The synergistic flame retardant effects of HGM with MH in EVA/MH blends have been studied by limiting oxygen index (LOI), UL-94 tests, cone calorimeter test (CCT), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), respectively. The LOI and UL-94 results show that when 2.00 wt% magnesium hydroxide (MH) is substituted with HGM, the LOI value can be raised to the maximum value of 42.1 among all samples. The data obtained from the CCT test indicate the heat release rate (HRR) of EVA/MH/HGM sample with 1.00 wt% HGM reduced by 37% when compared with EVA/MH sample without HGM. The digital photo graphs and scanning electron microscope (SEM) of char residues after CCT give positive evidence that the synergistic flame retardant effects between HGM and MH can be described that HGM mixed with MH can decrease the melt viscosity of EVA/MH/HGM, and promote the homogeneous dispersion of MH. HGM also can promote the formation of compact charred layers and prevent the charred layers from cracking, which effectively protects the underlying materials from burning. The TGA results reveal that EVA/MH/HGM samples show higher thermal stability at high temperature than EVA/MH sample.

Comparative study of boron compounds and aluminum trihydroxide as flame retardant additives in epoxy resin

The aim of this study was to investigate and compare the flame retardant properties of boron compounds with respect to aluminum trihydroxide (ATH) in an epoxy system based on bisphenol A epichlorohydrin-based epoxy resin and cycloaliphatic polyamine-based hardener. Six different boron compounds including colemanite (C), ulexite (U), boric acid (BA), boric oxide (BO), melamine borate (MB) and guanidinium nonaborate (GB) were used as flame retardant additive. The flame retardant properties of epoxy-based composites were investigated using limiting oxygen index (LOI), UL 94 standards both in vertical and horizontal position, thermogravimetric analysis, cone calorimeter and scanning electron microscopy. According to flammability test results, boron compounds except for C and U showed better performance than ATH. According to the LOI results, 40% BA containing sample had the highest LOI value of 28.5, while 30% MB, 35% GB and 40% BA containing samples had the highest UL 94V rating (V0). According to the cone calorimeter test results, all boron containing samples had better fire performances than ATH containing sample; 40 wt% BO containing sample showed the lowest peak heat release rate, average heat release rate and total heat release values. Copyright © 2014 John Wiley & Sons, Ltd.

Effect of fire retardants on thermal conductivity and limited oxygen index of high density fiberboard

In this study, Fire Retardant (FR) chemicals with different proportions were added into fibers and high density fiberboards (HDF) were produced using fibers from Scots pine and beech (50:50). HDF panels containing 3%, 6%, and 9% borax, boric acid, ammonium polyphosphate and alpha-x chemicals powders were manufactured. Limiting oxygen index (LOI) and thermal conductivity properties of HDF panels were determined. FR chemicals improved the LOI and thermal conductivity. However, this improvement was affected by the type and the concentration of the FR chemicals used. The best thermal conductivity result was obtained with 9% boric acid concentrations (0.2815 W/moK) while the best LOI results were obtained from 6% and 9% ammonium polyphosphate concentrations (45%). Keywords: HDF, Borax, Boric acid, Thermal conductivity, LOI