Enhancement of fire retardancy properties of glass fibre–reinforced polyesters composites

This paper presents the results of an experimental investigation on the fire retardancy properties of glass fibre–reinforced polyester (GFRP) composites with bisphenol‐A vinylester and isophthalic polyester as matrices and low electrical conductivity E‐glass fibres as reinforcement. The fire protection systems tested were alumina trihydrate (ATH), decabromodiphenyl ether (DBDE), and antimony trioxide (Sb₂O₃). A mass loss cone calorimeter was used to obtain the properties of heat release rate (HRR), peak HRR, total heat released, total mass loss, time to ignition, and time of combustion. Moreover, limiting oxygen index (LOI), UL‐94, and glow‐wire tests were also performed. The fire tests were carried out in order to investigate if the combination of ATH and DBDE could have “additive,” “antagonistic,” or “synergistic” effects on the flame retardant properties of the GFRP studied in this work. In addition, the influence of the ATH content variation on flame retardant properties was also evaluated. The results indicate that the sole addition of ATH at 47.7 phr could lead to the complete inhibition of the composites ignition, while the materials containing DBDE exhibit ignition and flame propagation in the cone calorimeter test.     

Flame retardant flexible poly(vinyl chloride) compound for cable application

ZnO/MgO, ZnO/CaO, and ZnO/CaO/MgO can form solid solutions. The solid solution for we as flame retardant (SSFR) was obtained by annealing at 1023 K for 4.5 h in a muffle furnace. Flexible poly (vinyl chloride) (PVC) filled with SSFR and Sb₂O₃ was investigated by differential thermal analysis thermogravimetry. Limiting oxygen index (LOI), mechanical properties, and electrical properties were studied. The surface of the char formed after combusting of the PVC compounds was observed through scanning electron microscopy and the effect of the surface area to the LOI was also studied. The data suggested that a small amount of SSFR and Sb₂O₃ have good synergy and can greatly increase the LOI and the char yield, and that the thermal degradation temperature and the activation energy decreased. It can be concluded that the mechanism of SSFR is a condensed‐phase mechanism. Moreover, one can conclude that the surface area can enhance the LOI. All the results showed that SSFR is effective and safe as a flame retardant in flexible PVC. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3137–3142, 2003     

Zinc hydroxystannate and zinc stannate as flame‐retardant agents for flexible poly(vinyl chloride)

The flame‐retardant and smoke‐suppressant properties of inorganic tin compounds such as zinc hydroxystannate (ZHS) and zinc stannate (ZS) were investigated in a comparison with alumina trihydrate, magnesium hydroxide, and Sb₂O₃ through the limiting oxygen index test and smoke density test. The flame‐retardant mechanisms were studied through the char yield test, SEM, quantitative analysis, thermogravimetry and differential thermal analysis. The thermal degradation in air of flexible PVC treated with the above compounds was studied by thermal analysis from ambient temperature to 800°C. The results showed that tin compounds such as ZHS and ZS could be used as a highly effective flame retardant for flexible PVC, and it appears that the tin compound may exert its action in both the condensed and vapor phases, but mainly in condensed phases as a Lewis acid. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1469–1475, 2005     

Application of chlorinated waste rubber as a flame retardant of low density polyethylene

For the reuse of the abundant waste rubber (WR), chlorinated waste rubber (Cl‐WR) was prepared by a water‐based chlorination method using chlorine gas as the chlorinating reagent. The resultant Cl‐WR was used as a flame retardant of low density polyethylene (LDPE) matrix. The properties of WR and Cl‐WR were characterized by thermogravimetric (TG) and Fourier transform infrared (FTIR) spectrometer. The results indicated that the Cl‐WR with a 42% chlorine content had a higher char residue than WR. The limiting oxygen index (LOI) value can be increased up to 27.2 and the flame retardancy reached to the maximum (V‐0) grade for the LDPE/Cl‐WR‐Sb blends with mass ratios of Cl‐WR/LDPE and Cl‐WR/Sb₂O₃ being 80/100 and 1.5/1, respectively. The improvement of the flame retardancy and thermal properties of the LDPE/Cl‐WR‐Sb blends were attributed to the char formation and synergistic effect between Cl‐WR and Sb₂O₃ in a high temperature region, although the mechanical properties of the said blend decreased in comparison with that of the neat LDPE. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Tin‐containing layered double hydroxides: Synthesis and application in poly(vinyl chloride) cable formulations

Layered double hydroxides (LDHs) and Sn‐containing LDHs have been synthesized using a co‐precipitation method, and the resulting products have been characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), Fourier‐transform infrared spectroscopy (FTIR) and Brunauer‐Emmett‐Teller(BET) surface area measurement, clearly showing that Sn‐containing LDH hybrids have been successfully prepared. TEM shows the ‘house‐of‐cards’ structure of the Sn‐LDHs produced, resulting from the edge‐to‐face interaction of the LDH layers. Higher tin levels lead to an additional magnesium hydroxystannate, MgSn(OH)₆, (‘MHS’) phase that is present in the form of approximately 40‐nm cubic particles in an LDH/MHS hybrid structure. FTIR and XRD suggest that, at low levels of Sn, the Sn⁴⁺ may exist in the form of amorphous hydrated tin(IV) oxide rather than being incorporated into the LDH lattice. These powders have been compounded into poly(vinyl chloride) (PVC), and their fire performance has been evaluated using limited oxygen index and cone calorimeter techniques. Peak rate of heat release and smoke parameter can be reduced by 64% and 81%, respectively, when replacing 10 wt% of the primary ATH fire‐retardant filler by the synthesized Sn‐LDHs, while keeping the total fire‐retardant loading at 100 phr. Thermogravimetric analysis indicates that Sn‐LDH is an effective char promoter for PVC. Copyright © 2011 John Wiley & Sons, Ltd.     

Tin dioxide coated calcium carbonate as flame retardant for semirigid poly(vinyl chloride)

The flame retardant and smoke suppressant properties of semirigid PVC treated with calcium carbonate (CaCO₃), tin oxide (SnO₂), the mixture of CaCO₃/SnO₂ and SnO₂‐coated CaCO₃ have been studied through the limiting oxygen index, char yield, and smoke density rating (SDR) methods. The thermal degradation in air of the treated semirigid PVC was studied by thermogravimetry (TG) and differential thermal analysis (DTA) from ambient temperature to 1073 K. The morphologies of the additives and the char formation were studied through SEM. The mechanical property was also studied. The results showed that the semirigid PVC treated with SnO₂‐coated CaCO₃ has a higher limiting oxygen index and char yield, lower SDR and MSDR, a more compact structure of char formation than the semirigid PVC without flame retardant and the semirigid PVC with the equivalent CaCO₃, or SnO₂, or the mixture of CaCO₃/SnO₂, a similar tensile property and greatly improved impact strength compared with that of the semirigid PVC without flame retardant. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 731–738, 2006     

Flame retardation of polypropylene: Effect of silane treated antimony compounds

Flame retardation of polypropylene was accomplished by blending with antimony compounds (Sb₂O₃ and SbPO₄) in conjunction with polyvinyl chloride (PVC) or ferric oxide. The compatibility and dispersion of antimony compounds in the polymer matrix was enhanced by using silane coupling agents, viz., vinyltriethoxysilane (A-151) and γ-aminopropyltriethoxysilane (A-1100). Rheological properties of filled polypropylene were studied in the temperature range 180 to 220°C at shear rates of 29.5 to 119.5 sec^?1. An increase in the melt viscosity was found in the filled polypropylene as compared to virgin polymer. Silanation of antimony compounds also influenced the melt rheology of flame retardant polypropylene. Incorporation of 6 phr Sb₂O₃ and 19 phr PVC raised the oxygen index of polypropylene to 22.9 and this sample was found to be self extinguishing in 65 s with a burning rate of 0.06 mm/s as compared to 1.1 mm/s for unfilled polypropylene. Though silanation of antimony compounds slightly reduced the oxygen index of flame retardant polypropylene, yield strain and flexural rigidity of injection molded samples was improved over unsilanated flame retardant polymer.     

Effect of nitrogen–phosphorus fire retardant blended with Mg(OH)2/Al(OH)3 and nano‐SiO2 on fire‐retardant behavior and hygroscopicity of poplar

The aim of the study was to screen any possible synergistic effects related to the combination of nitrogen–phosphorus fire retardant and Mg(OH)₂/Al(OH)_3. This combination is used to improve fire performance, especially smoke suppression of poplar through ultrasonic wave impregnation after microwave treatment. In this study, nano‐SiO₂ was used to impregnate poplar treated with nitrogen–phosphorus fire retardant and form a hydrophobic layer on wood cells in order to improve hygroscopicity and reduce water uptake. Cone tests and thermal analysis showed that poplar treated with blended fire retardant had improved behavior. Results show that a 20% and 25% nitrogen–phosphorus fire‐retardant solution (blended by adding 10% Mg(OH)₂/Al(OH)₃ based on the dry weight of nitrogen–phosphorus fire retardant) was more effective for smoke suppression. The heat release rate, total heat release, and total smoke production of a 25% nitrogen–phosphorus fire‐retardant solution blended by adding 10% Mg(OH)₂/Al(OH)₃ showed significant reduction. The char residual yield showed a marked increase to 35.5%. Fourier transform infrared analysis suggested a –CH₂–Si–CH₂– and Si–O–C stretching vibration in nano‐SiO₂ treated poplar, which greatly decreased the hygroscopicity of fire‐retardant‐treated poplar. Copyright © 2014 John Wiley & Sons, Ltd.     

The flame retardant and smoke suppression effect of fullerene by trapping radicals in decabromodiphenyl oxide/Sb2O3 flame‐retarded high density polyethylene

To improve the large release of smoke and heat for brominated flame retardants (BFRs) in fire hazard, fullerene (C₆₀) had been introduced in high density polyethylene (HDPE)/bromine flame retardant (Deca/Sb₂O₃, BFR in short) system in this study. The effects of C₆₀ on the thermal properties, flame retardant properties, rheological behaviors, and smoke release behaviors in HDPE/BFR blends were researched. During polymer thermal degradation, C₆₀ and BFR exhibited the trapping radical ability in condensed phase and gaseous phase, respectively. The intergrated effects of C₆₀ and BFR on the thermal stability and flammability of HDPE were studied by thermo‐gravimetry and cone calorimeter. It was indicated that the introduction of C₆₀ improved the thermal and thermo‐oxidative stability of HDPE/BFR blends. A remarkable advantage of adding C₆₀ was to reduce the peak heat release rate and the average specific extinction area, especially at higher concentration of C₆₀. The analysis of rheological behaviors and pyrolysis products revealed that C₆₀ can capture alkyl radicals, chain radicals, and bromine radicals in the condensed phase, which was in favor of terminating the thermo‐oxidative decomposition and inhibiting the heat and smoke release of HDPE/BFR blends during combustion.     

Thermal stability and mechanical properties of room temperature vulcanized silicone rubbers

Based on much of the importance of RTV on the field of self-cleaning application for its nontoxic, tasteless, and thermal stability, the effects of D₄-SiO₂ on mechanical properties, Al(OH)₃ and decabromodiphenyl oxide ethyl(DBDPE) on flame retardant property of RTV matrix were investigated firstly. Then, a new kind of complex fire retardants was compounded. The morphology of additives and fracture appearance of composites were demonstrated by SEM. The hot property of RTV-based composites was outlined by TG. It is found that D₄-SiO₂/Al(OH)₃/DBDPE/Sb₂O₃/RTV composites were of better comprehensive performances in mechanical property, hot property, fire resistance property, and insulating property, which presented tear 26.73 kN/m of strength, 279.8% of elongation at break, 2.81 MPa of tensile strength, FV-0 at the level of flame retardant property, 46 of Oxygen index (OI) 3.03 × 10¹⁵ Ωm of Volume electric resistivity, the range of decomposition temperature was 370°C to 650°C, and the percentage of remain weight was 26.4%. Those properties was acquired on the condition of 11 wt % D₄-SiO₂ + 20 wt % Al(OH)₃ + 15 wt % DBDPE+ Sb₂O₃ at the amount of 3.0 wt % to 3.7 wt %. This investigation leads the authors to a conclusion that D₄-SiO₂/Al(OH)₃/DBDPE/Sb₂O₃ is a kind of better combination modifier than anyone kind of which in comprehensive properties for RTV. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synergistic effects of organically modified montmorillonite in combination with metal oxides on the fire safety enhancement of intumescent flame-retarded epoxy resins

Synergistic effects of organically modified montmorillonite (OMMT) in combination with different metal oxides (Bi₂O₃, Sb₂O₃, and MoO₃) on the fire safety enhancement of the intumescent flame-retarded epoxy resins (EPs) were systematically evaluated. The results from X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses show that the OMMT and metal oxides acquire a uniform distribution in the EP matrix, and OMMT platelets exhibit a fully exfoliated state. The flammability and thermogravimetry (TG) tests show that the intumescent flame retardant (IFR)-OMMT-metal oxide ternary system can endow EPs with the higher synergistic efficiencies on the enhancement of flame retardancy, smoke suppression properties, and charring ability compared to those of IFR or IFR-OMMT system, and the synergistic efficiency is the following order: IFR/OMMT/Sb₂O₃ > IFR/OMMT/MoO₃ > IFR/OMMT/Bi₂O₃. In particular, the sample, filled with 1.5 wt% OMMT, 1.5 wt% Sb₂O₃, and 27 wt% IFR, passes the UL94 V-0 rating and acquires the highest limiting oxygen index value of 28.5% among the samples. The IFR-OMMT-metal oxide ternary system exerts a better synergistic effect on the generation of crosslinking and aromatic structures that supply the excellent charring effect and barrier effect for the EPs, and the synergistic efficiency of IFR-OMMT-metal oxide ternary system is varied with the types of metal oxides.     

Study on flame retardancy of APP/PEPA/MoO3 synergism in vinyl ester resins

A range of flame retardant vinyl ester resins (VERs) samples have been produced containing different contents of PEPA (1-oxo-4-hydroxymethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]octane), APP (ammonium polyphosphate), and MoO₃ (molybdenum trioxide). By investigating the flame retardancy of VER samples such as limiting oxygen index and UL-94, the synergistic flame retardance of APP, PEPA, and MoO3 has been revealed. The cone calorimeter is an instrument that measures the combustion data of samples. In the VER composites on fire, the synergistic smoke suppression effect of the APP, PEPA, and MoO₃ was detected. The gas and condensed phase of VER composites with APP, PEPA, and MoO₃ were tested by the thermogravimetric analysis (TGA)–Fourier transform infrared spectroscopy (FTIR) and FTIR. The char residues of samples have been studied at length by scanning electron microscopy and FTIR. The results show that the presence of MoO3 can promote the formation of P O and PO structures.     

Structure-property relationships of in-situ PMMA modified nano-sized antimony trioxide filled poly(vinyl chloride) nanocomposites

Nano-sized antimony trioxide (Sb₂O₃) particles were modified by in-situ methyl methacrylate (MMA)/Sb₂O₃ polymerization. Subsequently, these modified nanoparticles were compounded with poly(vinyl chloride) (PVC) to prepare PVC/Sb₂O₃ nanocomposites. In-situ MMA/Sb₂O₃ polymerization kinetics shows that nano-Sb₂O₃ particles do not inhibit polymerization of MMA. PMMA shell covered on the surface of nano-sized Sb₂O₃ particles have enhanced interactions with PVC matrix, breaking down nano-Sb₂O₃ particle agglomerates and improving their dispersion in the matrix (average particle size of 60-80 nm) and also increasing the particle-matrix interfacial adhesion. Thus, nano-Sb₂O₃ particles reinforce and toughen PVC. It was observed that at 2.5 wt% of nano-Sb₂O₃ particles modified by in-situ PMMA optimal properties were achieved in Young's modulus, tensile yield strength, elongation at break and Charpy notched impact strength. Detailed examinations of micro-failure mechanisms of tensile specimens showed that nano-Sb₂O₃ particles acted as stress concentrators leading to debonding/voiding and deformation of the matrix material around the nanoparticles. Under impact fracture, the nano-Sb₂O₃ particles prolonged crack initiation time, and increased energy absorptions for crack initiation and fracture propagation caused by strong interfacial interaction between nanoparticles and PVC matrix. These mechanisms lead to impact toughening of the nanocomposites.     

Preparation of expandable graphite and its flame retardant properties in HDPE composites

This study showed an efficient and novel way to prepare expandable graphite (EG) which is one kind of halogen‐free flame retardant using the O₃‐hydrothermal process. The results showed the expanded volume of EG using the O₃‐hydrothermal process was higher than those compared to convectional liquid phase synthesis, ultrasound irradiation and hydrothermal method. X‐ray diffraction pattern, Fourier transform infrared spectroscopy, and X‐ray photoelectron spectroscopy were used to analyze the structure and confirm that EG had been prepared. Scanning electron microscope was utilized to observe the morphology of EG and char from HDPE/O₃‐HEG composites. Cone calorimeter, limiting oxygen index, and UL‐94 were used to investigate the flame retardant property of the HDPE/O₃‐HEG composites and showed the HDPE/O₃‐HEG composite possesses excellent flame retardant property. POLYM. COMPOS., 38:2378–2386, 2017. © 2015 Society of Plastics Engineers     

MoO3 additives for PVC: A study of the molecular interactions

The detailed molecular interactions occurring during thermal degradation of PVC polymer formulations containing MoO₃ additives are investigated using laser microprobe techniques coupled with mass analysis of the volatile pyrolysis products. Comparison with Sb₂O₃–PVC compounds indicate that the additive effects exhibited by MoO₃ are fundamentally different from those observed for Sb₂O₃. Thermal decomposition of MoO₃–PVC is characterized by (1) catalyzed dehydrochlorination of PVC at a lower temperature and increased rate; (2) marked reduction in evolution of benzene, the major fuel species from PVC; and (3) decreased evolution of volatile hydrocarbon species from the polymer plasticizer component. Vapor-phase interactions involving volatile molybdenum species are found to be unimportant. The experimental data indicate that condensed-phase mechanisms and heterogeneous reactions involving MoO₃(s) control polymer decomposition processes. Molecular level details of these reactions are presented and their implications to polymer flame retardance and smoke suppression discussed.     

Vertical flame spread on charring materials at different ambient temperatures

A new flame spread apparatus for the measurement of flame spread rates at different ambient temperatures is presented. A 2‐m long sample is pre‐heated with air to the desired temperature and ignited from its lower end with a small propane burner. The flame spread is traced with thermocouples in contact with the sample surface. The features and function of the new apparatus are described, as well as series of vertical flame spread experiments on cylindrical birch rods and electrical cables made of polyvinylchloride (PVC) and flame retardant non‐corrosive (FRNC) materials. Vertical flame spread rates 6–62 mm/s (temperature range 22–271 °C) were determined for birch samples, 3–24 mm/s (22–190 °C) for PVC cable samples, and 0–4 mm/s (22–293 °C) for FRNC cable samples. Small‐scale experiments with thermogravimetric analysis and cone calorimeter were performed to characterize the sample materials in terms of their thermal and fire behaviour. Copyright © 2012 John Wiley & Sons, Ltd.     

Graft copolymerization of nitrogen‐ and phosphorus‐containing monomers onto cellulosics for flame‐retardant finishing of cotton textiles

Phosphoramide containing an active vinyl group (P‐III) was prepared. Its structure was confirmed by elemental analysis and Fourier transform infrared, nuclear magnetic resonance, and mass spectroscopy. P‐III was evaluated as a fire‐retardant finishing agent for cotton fabrics. It was applied to cotton fabrics using a graft process with an Fe²⁺/H₂O₂ redox system. The major factors affecting the reaction were studied. The finished cotton fabrics were examined for flammability, and the effect of washing on treated fabrics was also examined. The results showed that P‐III can be successfully used as a flame retardant for cotton fabrics. Durably flame‐retardant cotton fabrics were obtained at add‐on levels higher than 38%. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2573–2578, 2003     

Performance of Room Temperature Vulcanized (RTV) Silicone Rubber-Based Composites: DBDPO/RTV and DBDPE/Sb2O3/RTV

Composites with high flame-retardant behavior based on room temperature vulcanizing silicone rubber (RTV), decabromodiphenyloxide (DBDPO) and decabromodiphenylethane (DBDPE)/Sb₂O₃ as fire retardant were fabricated employing reactive solution mixing process and the method of three-roller milling. The influences of DBDPO and DBDPE/Sb₂O₃ on the morphologies, mechanical properties, flame-retardant properties, OI, insulating properties, hot properties of RTV were systematically investigated. It has been discovered that both kinds of doping agents can significantly improve the property characteristics of RTV matrix composites. Also, DBDPE/Sb₂O₃/RTV were of better comprehensive performances than DBDPO/RTV. We report final performances as follows: tear strength was 13.68 kN/m; elongation at break was 233.4%; tensile strength was 2.18 Mpa; the level of flame-retardant property was FV-0; OI was 46; Volume electric resistivity was 6.9 × 10¹⁴Ω · m; the range of decomposition temperature was 300°C to 690°C and the ending percentage of remain weight was 30.6%. The above properties were acquired on the condition of mass percent of DBDPE/Sb₂O₃ as 15 wt% for DBDPE/Sb₂O₃/RTV.     

Characterization of PVC cable insulation materials and products obtained after removal of additives

Organic solvents cyclohexane, dichloromethane, hexane, and tetrahydrofuran were tested to separate the dioctylphthalate (DOP) as plasticizer from the poly(vinyl chloride) (PVC)‐based materials. It was found that the efficiency of ultrasound‐enhanced hexane extraction of the DOP from PVC is 70% and the efficiency of the separation of the DOP and other compounds from the PVC by dissolution in THF followed by subsequent precipitation was 98–99%. Differential scanning calorimetry (DSC) and thermogravimetry (TG) were used to characterize the thermal behavior of PVC materials before and after extraction of plasticizers. It was found that during heating in the range 20–800°C the total mass loss measured for the nontreated, extracted, and precipitated PVC samples was 71.6, 66.6, and 97%, respectively. In the temperature range 200–340°C, the release of DOP, HCl, and CO₂ was observed by simultaneous thermogravimetry (TG)/FTIR. The effect of plasticizers on thermal behavior of PVC‐based insulation material was characterized by DSC in the range ?40–140°C. It was found that, concerning the PVC cable insulation material before treatment, the value of the glass transition temperature (T_g) was 1.4°C, whereas for the PVC sample extracted by hexane, the value of T_g was 39.5°C and for the PVC dissolved in THF and subsequently precipitated, the value of T_g was 80.4°C. Moreover, the PVC samples after extraction of plasticizers, fillers, and other agents were tested to characterize their thermal degradation. The TG and FTIR results of chemically nontreated, extracted, and precipitated samples were compared. The release of DOP, HCl, CO₂, and benzene was studied during thermal degradation of the samples by FTIR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 788–795, 2006     

Effect of curprous oxide in combination with molybdenum trioxide on smoke suppression in rigid poly(vinyl chloride)

Further investigation of the synergistic effect of smoke suppression between cuprous oxide and molybdenum trioxide in rigid poly(vinyl chloride) (PVC) was carried out by using a cone calorimeter (cone) at a high incident heat flux of 50 kW m^?2. Experimental data derived from the cone calorimeter indicated that binary mixtures of Cu₂O and MoO₃ clearly showed the synergistic effect in reducing smoke by decreasing total smoke production (TSP), average specific extinction area (av‐SEA), and smoke production rate (SPR). This result is in good agreement with that obtained from the NBS smoke chamber. However, the combustion process of rigid PVC could clearly be seen from the heat release rate (HRR), curve, SPR, and fire degradation obtained from the cone test, which could not be determined from the NBS smoke chamber. It was also found that the binary mixture showed the synergistic effect by increasing was also found that the binary mixture showed the synergistic effect by increasing char residue and reducing the fire degradation of the PVC backbone at a high incident heat flux of 50 kW.m^?2. All experimental data well supported the early cross‐linking mechanism of the PVC backbone mentioned in the literature and were consistent with the fire degradation behavior obtained from the cone calorimeter.