Halogen-free Flame Retardant Research Articles

Influence of hydrophobic substance on enhancing washing durability of water soluble flame-retardant coating

Flame-retardant textiles are used in many consumer products. Among halogen-free flame retardant substances, inorganic flame retardants are mainly based on phosphorus, antimony, aluminum and boron-containing compounds. These coatings are soluble in water and therefore are not subjected to washing. In this study, washing durability of the inorganic flame retardant has been improved by incorporation of the hydrophobic substance to the coating. Composition of the coating which is the flame-retardant, monoammonium phosphate (MAP), and the hydrophobic substances, poly(methylhydrogen siloxane) (PMHS) and poly(dimethyl siloxane) (PDMS)), were varied to find the optimum coating solution. The results of SEM and TGA analysis, as well as the burning and washing tests, revealed that the coating solution consisting of MAP:PMHS:PDMS=5:2:1wt.% was the optimum condition. It showed the increased residue on the TGA profile compared to the uncoated sample, and self-extinguish after removal of the ignition source. The flame-retardant property can be maintained after washing, making it feasible for variety of applications.

Detection of the Intermediates in Preparation of Ammonium Polyphosphate by Temperature Raising Rate Factor

Detection of intermediates is the general way to investigate a reaction mechanism, because the intermediates connect the reactants and the products, the intermediates can reflect some internal relationships between the reactants and the products. By studying the the structures of intermediates, the reaction process and reaction mechanism can thus be understood. Ammonium polyphosphate (APP) is an effective material as halogen-free flame retardants, it has six crystalline forms.In preparation of APP, the factor of temperature raising rate is investigated, some intermediates are detected, the XRD spectra of these intermediates are discussed. The results are informative for controllable preparation of APP in industrial production.

Synthesis and Application of a Novel Polyamide Charring Agent for Halogen-Free Flame Retardant Polypropylene

A novel charring agent, poly(p-ethylene terephthalamide) (PETA), for halogen-free flame retardant polypropylene was synthesized by using p-phthaloyl chloride (TPC) and ethylenediamine through solution polycondensation at low temperature, and the effects of PETA on flame retardance of polypropylene (PP)/IFR systems were studied. The experimental results showed that PETA could considerably enhance the fire retardant performance as proved by evidence of the increase of limiting oxygen index (LOI) values, the results of UL-94 tests, and cone calorimeter tests (CCT). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) demonstrated that an appropriate amount of PETA could react with PP/IFR system to form cross-link network; a more compact char layer could be formed which was responsible for the improved thermal and flame retardant properties of PP/IFR systems. However, the superfluous amount of PETA would play the negative role.

ハロゲンフリー難燃性FPC接着剤用エポキシ樹脂／カルボキシル基含有・リン含有フェノキシ樹脂混合硬化物の特性

エポキシ樹脂／カルボキシル基含有・リン含有フェノキシ樹脂混合硬化物は，良好な電気絶縁信頼性を維持しつつ，硬化前接着剤のフロー性をエポキシ樹脂／リン含有フェノキシ樹脂混合系およびエポキシ樹脂／カルボキシル基含有フェノキシ樹脂混合系よりも低減改良できた。これは，リン源である 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)の剛直な分子構造とカルボキシル基の反応性の相乗効果と考えられる。しかし，ピール強度は，わずかな向上効果しか示さず，課題として認識した。

Gabriel-Chemie unveils new flame retardant, blowing agent and lubricant masterbatches

Austria's Gabriel-Chemie GmbH has introduced new halogen-free flame retardant masterbatches for both polyethylene (PE) and polypropylene (PP), alongside a blowing agent product for polylactic acid (PLA) applications and a lubricant masterbatch for PP-based wood-plastic composites. The products received their debut at the recent Fakuma trade fair in Friedrichshafen, where the company also revealed the latest edition of its colour trend guide.

Clariant opens new production unit for halogen-free flame retardants

In Germany, Clariant has opened a second production unit for its halogen-free Exolit® OP flame retardant at the Hürth-Knapsack plant near Cologne. The company has invested a double-digit million euro sum in the new facility, which doubles the company's baseline capacity for diethyl phosphinic acid aluminium salt (DEPAL)-based flame retardants. These additives are used primarily in the electronics and electrical engineering (E&EE) sector.

The high efficiency two stage intumescent-contractive flame retardant on ABS

One stage halogen-free flame retardant was prepared by poly(p-ethylene terephthalamide) (PETA) or poly(para-phenylene terephthanlamide) (PPTA) and ammonium polyphosphate (APP), the system had a good flame retardancy on acrylonitrile-butadiene-styrene (ABS) resin when loading was 30% or more, but once mass fraction decreased, the system did not maintain previous flame retardancy. To improve the efficiency of this kind of flame retardant, we mixed PETA with PPTA and introduced red phosphorus to play as the second acid source. This system had two charring process—swell and shrink. The flammability and thermal stability of IFR-ABS composites were investigated by limiting oxygen index (LOI), UL-94 vertical burning and thermo gravimetric analysis (TGA) test. Results showed that this IFR system had both good flame retardant and anti-dripping abilities for ABS, when the mass fractions of APP, PETA, PPTA and red phosphorus were only 12%, 4%, 1.33% and 2.66% respectively, the LOI of flame retardant ABS was 27 and UL-94 vertical burning test reached V-0. The TGA curves suggested that there was a distinct cooperation. Additionally, the structure and the mechanism of charring were studied by FTIR and SEM.

Conferring flame retardancy on cotton using novel halogen-free flame retardant bifunctional monomers: synthesis, characterizations and applications

Two novel halogen-free phosphorous–nitrogen flame retardant bifunctional monomers were synthesized and characterized using attenuated total reflectance/Fourier transform-infrared (ATR/FT-IR) and electrospray ionization mass spectrometry (+ESI-MS). The monomers were applied separately and graft polymerized on cotton in the presence of the thermal initiator K2S2O8. The performance of each monomer was evaluated using thermal gravimetric analysis (TGA), grafting efficiency, and vertical flame test. It was shown that the performance of N,N-dimethyl di(acryloyloxyethyl)phosphoramide (DMDAEP) (monomer 2) as flame retardant outperformed that of ethyl di(acryloyloxyethyl)phosphorodiamidate (EDAEP) (monomer 1). The superior performance of DMDAEP was attributed to the presence of more nitrogen atoms compared to EDAEP. The increased nitrogen content in DMDAEP increased the synergistic effect of the P–N system. Cotton treated using padding methods showed more promising results than cotton treated by exhaust methods.

Layered Double Hydroxides as Flame Retardant and Thermal Stabilizer for Polymers

Layered double hydroxides (LDH) has wide applications as non-toxic and halogen-free flame retardant for various resins and highly efficient thermal stabilizer for halogen-containing polymers. This review will discuss some public patents and relevant papers on the flame retardancy and the thermal stability of LDH/polymer composites when the LDHs with different chemical compositions are used as the additive in the polymer matrix. We have summarized these related LDHs in two tables: one for flame retardant and the other for thermal stabilizer.

Influence of polymeric flame retardants based on phosphorus‐containing polyesters on morphology and material characteristics of poly(butylene terephthalate)

AbstractFlame retarded poly(butylene terephthalate) (PBT) is required for electronic applications and is mostly achieved by low molar mass additives so far. Three phosphorus‐containing polyesters are suggested as halogen‐free and polymeric flame retardants for PBT. Flame retardancy was achieved according to cone calorimeter experiments showing that the peak heat release rate and total heat evolved were reduced because of flame inhibition and condensed‐phase activity. The presented polymers containing derivatives of 9,10‐dihydro‐9‐oxa‐10‐phosphaphenanthrene‐10‐oxide form immiscible blend systems with PBT. Shear‐rheology shows an increase in storage moduli at low frequencies. This is proposed as quantitative measure for the degree of phase interaction. The phase structure of the blends depends on the chemical structure of the phosphorus polyester and was quite different, depending also on the viscosity ratio between matrix and second phase. A lower viscosity ratio leads to two types of phases with spherical and additionally continuous droplets. Addition of the flame retardants showed no influence on the dielectric properties but on the mechanical behavior. The polymeric flame retardants significantly diminish the impact strength because of several reasons: (1) high brittleness of the phosphorus polyesters themselves, (2) thermodynamic immiscibility, and (3) weak phase adhesion. By adding a copolymer consisting of the two base polymers to the blend, an improvement of impact strength was obtained. The copolymer particularly acts as compatibilizer between the phases and therefore leads to a smaller phase size and to a stronger phase adhesion due to the formation of fibrils. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Preparation of halogen-free flame retardant hybrid paraffin composites as thermal energy storage materials by in-situ sol–gel process

Novel halogen-free flame retardant hybrid phase change composites were prepared by an in-situ sol–gel process, using paraffin as the thermal energy storage material and tri-(triethoxysilylpropyl) phosphamide as the sol–gel precursor. The structure of paraffin composites was characterized by Fourier transform infrared spectrum (FT-IR) and X-ray diffraction (XRD). The behaviors of thermal stability and thermal energy storage properties were investigated through thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The char residue of composites was characterized by FT-IR, XRD and scanning electron microscope (SEM). The flame retardancy property of paraffin composites was investigated by pyrolysis combustion flow calorimetry (PCFC). Results showed that the paraffin composites had good thermal energy storage property as well as enhanced thermal stability and flame retardancy properties.

Effects of poly(dimethylsiloxane) and inorganic fillers in halogen free flame retardant poly(ethylene-co-vinyl acetate) compound: A chemometric approach

A quaternary system based on poly(ethylene-co-vinyl acetate) has been studied by Mixture Design in order to analyse the effect of additives on flame retardant properties. The FR components of the system are magnesium hydroxide (MDH), a silicon additive (Sil) based on poly(dimethylsiloxane) and a calcium borate additive (CaB). Many parameters from different flame retardant tests (LOI, UL94-V, DIN 4102 B2 and Cone Calorimeter) are selected as experimental responses and mathematical models with good quality are obtained for most of them. Principal Components Analysis (PCA) on flame retardant parameters points out no particular strong correlations among the three FR tests. The Experimental Design (DoE) approach allows minimization of the number of experiments and analysis of the influence of each component and of the interactions among them. Sil additive shows positive effects on LOI results and in the heat release rate and the fillers, mostly MDH, have positive influence on Cone Calorimeter and vertical burning test performance. Two optimal formulations have been obtained with improved stability of the residue together with LOI value in one case and Cone Calorimeter performance in the other case.

Synthesis of ammonium polyphosphate with crystalline form V (APP-V) from melamine polyphosphate (MPP)

Ammonium polyphosphate (APP) is a well known component of halogen-free flame retardants. Ammonium polyphosphate with crystalline form V (APP-V) was prepared by diammonium phosphate and melamine polyphosphate (MPP). The prepared APP-V was characterized by FTIR and XRD, its water solubility and thermal stability were tested and compared with those of APP-I, APP-II and MPP, its flame retardancy was measured by limiting oxygen index (LOI) and compared with APP-II. Finally, the synthesis mechanism of APP-V from MPP was discussed.

Are novel aryl phosphates competitors for bisphenol A bis(diphenyl phosphate) in halogen-free flame-retarded polycarbonate/acrylonitrile–butadiene–styrene blends?

The reactivity of the flame retardant and its decomposition temperature control the condensed-phase action in bisphenol A polycarbonate/acrylonitrile–butadiene–styrene/polytetrafluoroethylene (PC/ABSPTFE) blends. Thus, to increase charring in the condensed phase of PC/ABSPTFE+aryl phosphate, two halogen-free flame retardants were synthesized: 3,3,5-trimethylcyclohexylbisphenol bis(diphenyl phosphate) (TMC-BDP) and bisphenol A bis(diethyl phosphate) (BEP). Their performance is compared to bisphenol A bis(diphenyl phosphate) (BDP) in PC/ABSPTFE blend. The comprehensive study was carried out using thermogravimetry (TG); TG coupled with Fourier transform infrared spectrometer (TG-FTIR); the Underwriters Laboratory burning chamber (UL 94); limiting oxygen index (LOI); cone calorimeter at different irradiations; tensile, bending and heat distortion temperature tests; as well as rheological studies and differential scanning calorimeter (DSC). With respect to pyrolysis, TMC-BDP works as well as BDP in the PC/ABSPTFE blend by enhancing the cross-linking of PC, whereas BEP shows worse performance because it prefers cross-linking with itself rather than with PC. As to its fire behavior, PC/ABSPTFE+TMC-BDP presents results very similar to PC/ABSPTFE+BDP; the blend PC/ABSPTFE+BEP shows lower flame inhibition and higher total heat evolved (THE). The UL 94 for the materials with TMC-BDP and BDP improved from HB to V0 for specimens of 3.2mm thickness compared to PC/ABSPTFE and PC/ABSPTFE+BEP; the LOI increased from around 24% up to around 28%, respectively. BEP works as the strongest plasticizer in PC/ABSPTFE, whereas the blends with TMC-BDP and BDP present the same rheological properties. PC/ABSPTFE+TMC-BDP exhibits the best mechanical properties among all flame-retarded blends.

Red phosphorus acts as second acid source to form a novel intumescent-contractive flame-retardant system on ABS

A novel halogen-free flame retardant prepared by poly(p-ethylene terephthalamide) and ammonium polyphosphate (APP) on acrylonitrile–butadiene–styrene (ABS) resin has a good flame retardancy when loading is 30 %; but, once the mass fraction is <30 %, the system does not maintain outstanding flame retardancy. To improve the efficiency of this kind of flame retardant and LOI values, higher thermal stability acid source-red phosphorus is introduced. It is found that a little quantity of red phosphorus will improve the flame retardancy of ABS remarkably and will change the process of charring; when the mass fractions of APP, PPTA, and red phosphorus are only 15, 5, and 2 %, respectively, though the LOI of flame-retardant ABS is 27, UL-94 vertical burning test still reach V-0. Thermogravimetric analysis data show that red phosphorus changes the thermal degradation behavior of IFR-ABS system, shrink digital photo display system, and yield more stable residue at higher temperature; Fourier transform infrared results and scanning electron microscopic micrographs show that red phosphorus can catalyze the charring and form much denser char to improve the flame-retardant performance of the materials.

Modulation of human α4β2 nicotinic acetylcholine receptors by brominated and halogen-free flame retardants as a measure for in vitro neurotoxicity

Brominated flame retardants (BFRs) are abundant persistent organic pollutants with well-studied toxicity. The toxicological and ecological concern associated with BFRs argues for replacement by safer alternatives. However, the (neuro)toxic potential of alternative halogen-free flame retardants (HFFRs) is unknown. Previous research identified the nervous system as a sensitive target organ for BFRs, with modulation of excitatory nicotinic acetylcholine (nACh) receptors as one of the modes of action. Since it is essential to assess the (neuro)toxic potential of HFFRs before large scale use, we measured the effects of three BFRs and 13 HFFRs on the function of human α4β2 nACh receptors, expressed in Xenopus oocytes, using the two-electrode voltage-clamp technique. The results demonstrate that some BFRs (TBBPA and to a lesser extent BDE-209) and HFFRs (TPP, Alpi, APP, MMT and to a lesser extent ATH, ATO, MHO, MPP, RDP and ZHS) act as nACh receptor antagonists. Contrary, BPS, BDP, DOPO and ZS were unable to modulate nACh receptors. Despite the lack of toxicological data on HFFRs and the need for additional studies to perform a full (neuro)toxic risk assessment, the current data on antagonistic effects on nACh receptors could be an important step in prioritizing viable HFFRs for substitution of BFRs.

Preparation, thermal stability and flame-retardant properties of halogen-free polypropylene composites

A flame retardant containing phosphorus and nitrogen was prepared. This halogen-free flame retardant was blended with polypropylene (PP) by hot melting to improve the flame-retardant capability and thermal stability of the composites. Fourier transform infrared spectroscopy, energy dispersive X-ray measurements, thermogravimetric analysis, limiting oxygen index (LOI) measurements, and UL-94 measurements were applied to characterize the structure and thermal and flame-retardant properties of the composites. When the flame-retardant concentration was 40 wt%, the LOI value of the composite was 40, passing the V-0 rating of the UL-94 test. The LOI and UL-94 data showed the composites have an excellent flame-retardant property. For a kinetic study of thermal degradation, Ozawa’s method was applied to calculate the activation energies of pure PP and the composites. Analytical results indicate that the composites had higher values, meaning they have better thermal stability.

Effect of Rare Earth Ions on the Properties of Composites Composed of Ethylene Vinyl Acetate Copolymer and Layered Double Hydroxides

BackgroundThe study on the rare earth (RE)-doped layered double hydroxides (LDHs) has received considerable attention due to their potential applications in catalysts. However, the use of RE-doped LDHs as polymer halogen-free flame retardants was seldom investigated. Furthermore, the effect of rare earth elements on the hydrophobicity of LDHs materials and the compatibility of LDHs/polymer composite has seldom been reported.Methodology/Principal FindingsThe stearate sodium surface modified Ni-containing LDHs and RE-doped Ni-containing LDHs were rapidly synthesized by a coprecipitation method coupled with the microwave hydrothermal treatment. The influences of trace amounts of rare earth ions La, Ce and Nd on the amount of water molecules, the crystallinity, the morphology, the hydrophobicity of modified Ni-containing LDHs and the adsorption of modifier in the surface of LDHs were investigated by TGA, XRD, TEM, contact angle and IR, respectively. Moreover, the effects of the rare earth ions on the interfacial compatibility, the flame retardancy and the mechanical properties of ethylene vinyl acetate copolymer (EVA)/LDHs composites were also explored in detail.Conclusions/SignificanceS-Ni0.1MgAl-La displayed more uniform dispersion and better interfacial compatibility in EVA matrix compared with other LDHs. Furthermore, the S-Ni0.1MgAl-La/EVA composite showed the best fire retardancy and mechanical properties in all composites.

Thermal and flame properties of calcium borate and intumescent ammonium polyphosphate in epoxy/glass fiber composites

The thermal and flammability properties of halogen-free flame retardants, calcium borate and intumescent ammonium polyphosphate, were evaluated on epoxy/glass fiber composites. The evolved volatile products under thermal stresses were analyzed accordingly, and the thermal decomposition of the composites was studied. It was determined that ammonium polyphosphate and calcium borate releases water vapor and carbon dioxide during their thermal decomposition, as a method to overcome the fire. Ammonium polyphosphate that achieved the V-0 rating at 5 vol% loading had showed better fire resistance than calcium borate that failed to achieve any rating even at high loading of 20 vol%. However, the calcium borate had recorded higher residual content. The combination of 1 vol% calcium borate and 4 vol% ammonium polyphosphate exhibited a synergistic performance by mass producing more char as a protection for the composites. Nevertheless, this synergism was not observed with the other combination, which comprised a 50:50 ratio of ammonium polyphosphate–calcium borate.

Preparation of halogen free flame retardant polymer materials by reactive extrusion

The reactive processing of polymers which combines the polymer processing and chemical reaction together, using polymer processing equipment to conduct the chemical reaction during the processing, so as to form new structure and new materials, and enhance polymer performances. This paper reviewed our research works on preparation of halogen-free flame retardant polymers materials by reactive extrusion in recent years. Taking advantages of the strong shear force, controllable temperature, and high efficiency in heat and mass transfer during twin-extruder extrusion, two halogen free flame retardants with high viscosity during synthesis, melamine salt of pentaerythritol phosphate (MPP) and melamine cyanurate (MCA), as well as the flame retardant polypropylene/MPP and polyamide 6/MCA with good comprehensive properties were successfully prepared. The involved chemical and physical processes were investigated. These results showed that reactive extrusion is an efficient, economic, environment-friendly and easily commercialized novel technology to prepare halogen free flame retardant polymer materials.