Environmental-friendly Flame Retardant Research Articles

Study on the thermal stability and combustion performance of polyurethane foams modified with manganese phytate

Abstract A new environmental friendly flame retardant manganese phytate (MnPa) was prepared by a direct precipitation method and the polyurethane foam (PUF) modified with MnPa was obtained by a one-step all-water foaming method. The thermal stability and combustion performance of the MnPa-modified PUF (MnPUF) were investigated by using thermogravimetric (TG), thermal decomposition kinetics, smoke density characterization, limiting oxygen index (LOI) and UL-94 horizontal combustion test. The results indicated that the addition of MnPa significantly improved the thermal stability and combustion performance of the modified PUF. On the basis of the thermogravimetric analysis, Flynn-Wall-Ozawa method, Kissinger method and Coats Redfern method, it could be concluded that PUF with 7.5 wt% MnPa (MnPUF3) had the highest activation energy and the best thermal stability. Smoke density analysis, LOI and horizontal combustion analysis also showed that the addition of MnPa was positively correlated with smoke suppression, LOI value and burning time. The current research results can provide a reference for the subsequent flame retardant modification of PUF.

Flame retardancy performance and mechanism of polyvinyl alcohol films grafted amino acid ionic liquids with high transparency and excellent flexibility

High transparency performance of polyvinyl alcohol (PVA) films with excellent flexibility plays an important role in wearable devices, solar cells displays and other fields. However, maintaining good transparency is a great challenge to prepare the flame retardancy PVA films. The PVA/L-Aspartic acid phosphate ionic liquid (AAILs) films (PL) with good transparency were firstly designed and prepared relying chemical-bands through sol-gel method. The flame retardancy and transparency performance of PL films were systematically characterized using various methods. The addition of AAILs did not affect the transparency of the PVA films, and the PL films had visible toughness and flexibility. Compared with the PVA films, the transparency and flame retardant performance of PL films were improved and the PL films with UL94 V0 rating and LOI of 30.1% were achieved when AAILs were added to 20.0 wt%. The homogeneous dispersion and high compatibility of AAILs in PVA films can be achieved relying chemical-bands using sol-gel method. The PL films had the high flame retardany performance and excellent flexiblility after the introduction of AAILs, while maintaining the transparency, biocompatibility and biodegradability. It provides a simple and low-cost method for the preparation of environmental-friendly flame retardant PL films.

Preparation of 4-formylphenylboronic modified chitosan and its effects on the flame retardancy of poly(lactic acid)

A boron-based biological flame retardant phenylboronic acid functionalized chitosan (B-CH) was prepared by reacting chitosan (CH) with 4-formylphenylboronic acids. The structure characterization was carried out by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. B-CH was added into polylactic acid (PLA) by the melt blending method to improve the fire performance of the composite. The results showed that the peak heat release rate (PHRR) of PLA-7% B-CH decreased to 432 kW·m−2 from 564 kW·m−2 of control PLA. The limiting oxygen index (LOI) was increased from 19.1% to 26.2%, and the vertical burning test (UL-94) could reach a V-0 rating. The B-CH participated in the char formation process, which could generate a continuous compact char layer during the combustion to effectively protect the PLA matrix. This work provided an effective strategy to develop environmental friendly flame retardant PLA composites.

Using recombinant adhesive proteins as durable and green flame-retardant coatings

Current fire retardants are known to be toxic to humans and our environment. As environmental-friendly flame retardants (FRs), protein-based flame retardants have been studied extensively recently, even though they are not durable. In this study, we designed, synthesized and tested a durable protein-based FR through the fusion of the adhesion domain from either mussel foot protein-5 (mfp-5) or cellulose-binding domain (CBD) with flame retardant protein (SR protein and alpha casein). We first verified the expression of the recombinant proteins in Escherichia coli using Western blot. Then, we coated the fusion protein (carrying cell lysates) to cotton fabrics and wood and verified with Infrared (IR) spectroscopy. Using a vertical burning test and wood flammability test, we confirmed the flame retardancy of the materials after the protein coating. In the vertical burning test, the SR protein and alpha casein flame retardant proteins with the CBD adhesion domain showed a 50.0% and 43.3% increase in flame retardancy. The data is also consistent in the wood flame retardancy test. Confocal imaging experiments also suggested these new fire retardants can be preserved on the materials well even after washing. Overall, our results showed that flame-retardant proteins with adhesion domains are high potential candidates of green alternative flame retardants.

Mechanisms Summary and Potential Analysis of EPS as a Flame Retardant

High value-added extracellular polymer substance (EPS) extracted from excess sludge can effectively promote resource recovery from wastewater. EPS can replace traditional alginate in the food, medicine, textile, printing and dyeing, papermaking, and household chemicals industries. Moreover, its unique performance as a flame retardant has shown attractive potential for aircraft including space shuttles. This is due to the complicated chemical structure and composition of EPS, the excellent compatibility, adhesion, and other advantages of which could yield environmental-friendly flame-retardants. Therefore, a systematic analysis and summary on the mechanisms of EPS as flame retardants is of significance for future application. On the basis of the advantages and disadvantages of other fire-resistant materials on the market, the characteristics and application potential of EPS are analyzed and summarized. Second, the possible fire-resistant mechanisms of phosphorus and alginate-like substance (ALE) in EPS are revealed, and the synergistic flame-retardant effects of extracellular-proteins are also elucidated. Based on this, the flame-retardant characteristics of EPS are comprehensively evaluated and compared with other fire-resistant materials. To further improving the performance of EPS as a flame-retardant material, some modification strategies are proposed, such as increasing their phosphorus content, purifying and enhancing the content of ALE in EPS, and optimizing the modification methods of EPS on their substrates.

Stabilizing effects of novel phosphorus flame retardant on PET for high-temperature applications

Promising effects of DOPO-PEPA (DP), an environmental-friendly flame retardant, on the processing of polyethylene terephthalate (PET) are studied via rheological experiments. DP reveals profound melt stabilization and lubrication effects even at low concentrations (~1 wt%). Mechanical characterization of PET films confirms that the direct addition of DP powder to PET during extrusion has no adverse effects even if the films are exposed to elevated temperatures for prolonged periods. This property is particularly interesting for high-temperature applications, for instance flexible power electronics, where mechanical flexibility should not be compromised by using a melt process stabilizer.

FORMALDEHYDE-FREE AND HALOGEN-FREE FLAME RETARDANT FINISHING ON COTTON FABRIC

This study focuses on the application of environmental-friendly flame retardant (FR) finishing which does not include formaldehyde or halogen based chemicals on cotton fabrics since it has been announced that these kinds of materials have environmental and toxicological hazards. Three different types of FR agents were used in the finishing bath and applied on raw, pre-treated and dyed cotton fabrics, respectively. One of them was the mixture of inorganic and organic salts while the other type was chosen as phosphate structured which have a commercial use in textile industry widely in order to compare the flame retardant effects on cotton. The third type was calcium carbonate based chemical produced in Balıkesir Turkey named Firetex. After finishing treatment of all types of FRs, performance tests as burning tests and color spectrums were carried out beside the characterization tests as SEM and FTIR-ATR analysis. In order to determine the washing durability of the cotton fabrics, each performance test was performed after 5 repeated washing cycle. According to the results, it was observed that both three types of flame retardant agents improved the flame retardant effect of cotton fabrics however the char length of cotton fabric which treated with Firetex was lower than the rest and it was indicated in the study that using natural structured FR could be a new area in green chemistry as a FR textile chemical.

Environmentally friendly polychlorinated naphthalenes (PCNs) derivatives designed using 3D-QSAR and screened using molecular docking, density functional theory and health-based risk assessment

A complete design and screening system for environmental-friendly polychlorinated naphthalene (PCN) derivatives was established through three-dimensional quantitative structure-activity relationship (3D-QSAR), molecular docking, density functional theory (DFT) methods and health-based risk assessment based on dynamic multimedia fugacity model. Two types of 3D-QSAR models were established for PCNs using the experimental biological toxicity (logEC50) of 14 PCNs to carry out a modification to lower the logEC50 of CN-70. Consequently, 67 new monosubstituted and disubstituted derivatives with a lower biological toxicity than CN-70 were designed. Furthermore, 21 new CN-70 derivatives were selected through the evaluation of their persistent organic pollutant properties (biological toxicity, bio-concentration, long-range transport potential, biodegradability) and practicability (stability, insulativity, flame retardancy) using 3D-QSAR, molecular docking and DFT methods. Finally, the non-carcinogenic and carcinogenic risks of 19 new CN-70 derivatives in different exposure pathways were reduced, and 5 derivatives with a significant decrease both in biological toxicity (amplitude reduction: 12.73%-32.51%) and risk (amplitude reduction: 32.18%-59.19%) were selected as environmental-friendly PCN derivatives, which had been screened using the health-based risk assessment system associated with dynamic multimedia fugacity model. This study provides a theoretical basis for the design of environmental-friendly flame retardants and insulating materials.

Waterborne polyurethanes: A three step synthetic approach towards environmental friendly flame retardant coatings

Flame retardant waterborne polyurethanes (WBPU) were synthesized by reacting a phosphorous based polyester polyol with isophorone diisocyanate (IPDI) in different mole ratios of NCO:OH in three steps. In first step, the polyester polyol was synthesized by reacting tris(bisphenol-A)mono phosphate (TBAMP), sebacic acid, polyethylene glycol which was characterised by measuring acid value and hydroxyl value. Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and gel-permeation chromatographic techniques were used for the characterization of polyester polyol. In second step, the polyurethanes were synthesized by reacting polyester polyol with diisocyanate in different proportions. In third step, the polyurethane was neutralised using tertiaryamine. A calculated amount of water was then added at this stage followed by addition of a chain extender at controlled pH. This resulted into waterborne polyurethanes. By varying the proportion of NCO/OH, four WBPUs have been prepared. These WBPUs were subjected for coating and casting purposes. Physico-chemical properties such as particle size, dispersion stability, viscosity were measured. The flame retardency of casted films were studied by LOI (limiting oxygen index) and UL-94 test methods. Thermal properties were determined using thermogravimatric analysis (TGA) technique of casted film. Chemical resistance and Mechanical properties of the coated samples have been found out.

Synthesis of microencapsulated zinc stannate and its application in flame‐retardant poly(vinyl chloride) membrane material

SummaryThe novel core‐shell magnesium dihydroxide (MDH)/zinc stannate (ZS) and melamine‐formaldehyde (MF) resin/MDH/ZS microcapsules were prepared. Their structures were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and X‐ray photoelectron spectroscopy analysis techniques, then its flame‐retardant application in poly(vinyl chloride) (PVC) composites. The PVC composites were investigated by the limited oxygen index, smoke density, vertical burning test (UL‐94), cone calorimeter test, scanning electron microscopy, and thermogravimetric analysis. When directly exposed to flame, PVC generated a high‐density char layer, giving PVC a self‐extinguishing property. Furthermore, when the mass ratio of MDH/ZS and MF/MDH/ZS microcapsules were 2/8 and 10/2/8 with 16 wt% loading, the results showed that the limited oxygen index value reached 29% and 33%, and the smoke density value reached 51% and 41%. Thus, the microencapsulated ZS could greatly suppress the generation of the flame and smoke during combustion, showing potential applications as multifunctional advanced composites.Two aspects of this manuscript will make it interesting to general readers of Fire and Materials. The magnesium dihydroxide (MDH)/zinc stannate (ZS) microcapsule was firstly prepared via chemical deposition method, and then melamine‐formaldehyde (MF) resin/MDH/ZS microcapsule was secondly prepared. The smoke density of poly(vinyl chloride) (PVC)/MDH/ZS microcapsule and PVC/MF/MDH/ZS microcapsule composites were less than half of the neat PVC. With the addition of the 16 wt% of MDH/ZS or MF/MDH/ZS microcapsules into PVC, the limited oxygen index value of PVC composites achieved a significantly high limited oxygen index value at 29%, 33%, and the smoke density value of PVC reached 51%, 41%, respectively. They are V‐0 rating in UL‐94 test. The results indicated that MDH/ZS and MF/MDH/ZS microcapsules behaved as an environmental friendly flame retardant and smoke suppressant. Thus, this study demonstrated the great potentials of the intrinsically flame‐retardant MDH/ZS and MF/MDH/ZS microcapsules in the application of high performance matrix resin and composite material.

Environment-friendly, flame retardant thermoplastic elastomer–magnesium hydroxide composites

Halogen-free and environment-friendly magnesium hydroxide (Mg(OH)2) was synthesized to enhance the flame retardant properties of thermoplastic elastomer (TPE). When the Mg(OH)2content was optimized to 35[Formula: see text]wt.%, the TPE–Mg(OH)2composites exhibited the best flame retardant properties. The results showed that there was a delay of ignition time of the samples containing Mg(OH)2; compared with the samples without Mg(OH)2, the heat release rate and total heat release decrease by 31.4% and 35.6%, while total smoke production and mass loss rate reduce by 56% and 34.2%, respectively. This work opens a door to manufacture fire-resistant polymer-based composites with environmental-friendly flame retardant additives by controllable crystallization and chemical strategies.

A recycled environmental friendly flame retardant by modifying para-aramid fiber with phosphorus acid for thermoplastic polyurethane elastomer

The application of fibers is more and more extensive, and the pollution caused by abandoned fibers is getting more serious, which has aroused wide attention. So it is necessary to find a way to solve the problem. In this paper, the para-aramid fiber (AF) was recycled and modified by phosphoric acid, and then was applied as environmental friendly flame retardant for thermoplastic polyurethane elastomer (TPU). The flame retardant properties of TPU were tested using cone calorimeter test (CCT) and thermogravimetric/Fourier transform infrared spectroscopy (TG-IR). The CCT test showed that AF-P had better flame retardant effect on TPU than pure AF. Remarkably, the pHRR value for the sample with 1.00wt% content of AF-P was decreased by 48.1%; AF-P had improved the char forming progress and the residual mass was 30.6%, which was much more than pure TPU. TG test showed that AF-P could improve the thermal stability of TPU at high temperature. The TG-IR test revealed that AF-P had reduced the release of CO2 at the beginning. Based on the above results, it will make a great influence on the study of reuse of fibers and environmental friendly flame retardant of polymer.

Effect of Fumed Silica and Zinc Borate on the Thermal Property of ABS/Magnesium Hydroxide Flame Retardant Composites

Magnesium hydroxide (MH) has been used with polymers to make composites having flame retardancy as an environmental-friendly flame retardant. An attempt has been made in this direction, in order to enhance its flame retardant effectiveness. The synergistic effect of fumed silica (SiO2) and zinc borate (ZB) with MH in ABS based flame retardant composites was investigated with DSC. The endothermic effect of MH had little influence on the heat release reaction of ABS. The addition of ZB could not improve the thermal property of flame retarded ABS with MH. SiO2 or SiO2/ZB could significantly enhance the thermal property of the flame retarded ABS with MH based on the cooling effect of MH and the restraining effect of SiO2 or SiO2/ZB on the heat release reaction of SAN copolymer in ABS.

Research Progress of Magnesium Hydroxide Flame Retardant from Concentrated Seawater and Brine

Magnesium hydroxide is an environmental friendly flame retardant with high flame retardancy and low smoke non-toxic characteristics. In this paper, the flame retardant effects of magnesium hydroxide was introduced, the production application and technology experiment of magnesium hydroxide flame retardant was studied. Meanwhile, the development trend of magnesium hydroxide flame retardant prepared from concentrated seawater or brine in China was analyzed.

Mechanism and Preparation Methods of Inorganic Fire-Retardant

The flame-retardant mechanisms of aluminium hydroxide (ATH) and magnesium hydroxide (MH) that used as typical inorganic fire-retardant were illustrated. The preparation methods of the fire-retardants are reviewed. And the modification approaches and future development direction of the fire-retardants were also discussed. Although the ATH and MH are environmental friendly flame retardants, they still have drawbacks and further research is needed to improve their flame retardant properties.

A study on electrical and thermal conductivities of ethylene–octene copolymer/expandable graphite composites

AbstractA series of ethylene–octene copolymer (EOC) composites have been prepared by melt‐mixing with different weight ratios of expandable graphite filler (0–50% by weight). Electrical conductivity [both alternating current (AC) and direct current (DC)] and thermal conductivity studies were carried out. Effect of filler loading and frequency on electrical conductivity was studied. DC conductivity has increased from 1.51 × 10−13 S cm−1 to 1.17 × 10−1 S cm−1. Percolation threshold by DC and also AC methods was observed at about 16 vol% of the filler. Real part of permittivity was found to be decreasing with increase in frequency while conductivity was increasing. Thermal conductivity was also found to be increasing gradually from 0.196 to 0.676 Wm−1 K−1 which is about 245% increase. Graphite not only increases the electrical and thermal conductivities but at and above 40 wt%, also acts as a halogen‐free, environmental friendly flame retardant. Shore‐A hardness of EOC/graphite composites shows that even with high graphite loading, the hardness is increased from about 50–68 only so that the rubbery nature of the composite is not affected very much. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers

Structure of Tetrakis(melaminium) Bis(dihydrogenphosphate) Monohydrogenphosphate Trihydrate from X-ray Powder Diffraction and Solid-State NMR Spectroscopy

The crystal structure of the melamine phosphate salt tetrakis(melaminium) bis(dihydrogenphosphate) monohydrogenphosphate trihydrate with as much as ten independent moieties in the unit cell was determined by a direct-space global optimization technique from X-ray powder diffraction data using additional geometry constraints obtained by 31P double-quantum solid-state NMR spectroscopy. The structure analysis of the compound and its comparison with other melamine phosphates reveals the packing and bonding characteristics that are important for melamine-phosphate salts with a melamine-to-phosphor ratio larger than one, which are promising environmental-friendly flame retardants.

Organo-modified magnesium hydroxide nano-needle and its polystyrene nanocomposite

Acrylic acid modified magnesium hydroxide nano-needles (AA–Mg(OH)2) had been synthesized by alkaline injected into magnesium chloride solution at about 0°C in the presence of acrylic acid (AA). Then the polystyrene/magnesium hydroxide nano-needles composite (PS/Mg(OH)2) had been prepared by the radical copolymerization with styrene in toluene system using AA–Mg(OH)2 as a macro-monomer. The elemental analysis (EA) and Fourier transform infrared (FTIR) analyses show that the polystyrene had been grafted onto the surfaces of the nano-needles (AA–Mg(OH)2). The nano-needles (AA–Mg(OH)2) had better dispersibility in polystyrene matrix as observed by transmission electron microscope (TEM) analysis. The thermal behavior analysis results from the differential scanning calorimetry (DSC) indicated that the magnesium hydroxide nano-needles had lower thermal decomposition temperature than that of the polymer matrix and it is expected that the nano-needles prepared by the proposed method could be used as an environmental-friendly flame retardant.

Structure of Melaminium Dihydrogenpyrophosphate and Its Formation from Melaminium Dihydrogenphosphate Studied with Powder Diffraction Data, Solid-State NMR, and Theoretical Calculations

Melaminium dihydrogenpyrophosphate (bis(2,4,6-triamino-1,3,5-triazinium dihydrogenpyrophosphate, MPy), obtained as a crystalline powder by thermal treatment of melaminium dihydrogenphosphate (MP), is the first intermediate in the synthesis of polymerized melamine phosphates that are used as environmental-friendly flame retardants. The crystal structure of MPy was determined by X-ray powder diffraction and the proposed hydrogen-bonding model was corroborated by solid-state NMR and periodic DFT calculations. A mechanism is proposed for the endothermic dehydration process that takes place in the reaction from MP to MPy, in accordance with energy calculations based on the optimized crystal structures of MPy and MP. A packing analysis of MPy and other melamine-containing compounds revealed some typical melamine packing motifs.

New Types of Ecologically Safe Flame Retardant Systems for Polymethylmethacrylate

Abstract The addition of silica gels is explored to develop an environmental friendly flame retardant polymethylmethacrylate system.