Improved Flame Retardant Properties Research Articles

Formulation of polyurea with improved flame retardant properties

This article addresses the flame retardancy of polyurea using three different sulfonate salts, sodium diphenylamine-4-sulfonate, 3-(1-pyridinio)-1-propane sulfonate, and ammonium sulfamate, and their combination with some conventional flame retardants. Cone calorimetry and thermogravimetry are used for the evaluation of the flame retardancy and thermal stability. Among the sulfonate salts, ammonium sulfamate shows the best flame retardancy both alone and in combination. The conventional additives that have been used include ammonium polyphosphate, expandable graphite, aluminum diethylphosphinate, melamine polyphosphate, and a chloroalkylphosphonate, as binary and ternary mixtures at 15 wt.% total loading. The nonsulfur-containing binary system exhibits higher ignition time and better flame and smoke resistance than do the ternary mixtures.

Study on Formula of New Type Flame Retardant Polyethylene

The Formula of flame retardant material for PE insulated cable was developed. It mainly included 42 phrs LDPE,18 phrs EVA,7phr Magnesium carbonate,32phr Aluminum hydroxide,6phr silica,6phr Zinc borate and 5phr Silicone. The mixture was extruded through mixing and samples were made. Relative experiment showed that silicone had good effect on improvement of flame retardant properties of insulating materials. Zinc borate had promoting effect of the flame retardant. Silica had barrier effect. When parts of PE was substituted by EVA, the mechanical and flame retardant properties of the materials increased.

A renewable approach to thermosetting resins

This is a review of recent developments of thermostable resins derived basically from vegetable oils. Natural vegetable oils have been transformed in polymers following three main routes. The first is the direct polymerization through the double bonds of the fatty acid chain. The cationic copolymerization of soybean oil with styrene, divinylbenzene and different amounts of styrenic monomers containing Si, B and P has been used to produce materials with improved flame retardant properties. The second route is the functionalization of the triglyceride double bonds to introduce readily polymerizable groups: The singlet oxygen photoperoxidation of the allylic positions of high oleic sunflower oil has been used to produce hydroperoxide-containing triglycerides that were dehydrated or reduced to produce respectively enone- and hydroxyl-containing triglycerides. The enone containing derivative has been chemically crosslinked with aromatic diamines through aza-Michael reactions leading to quinoline containing thermosets. The hydroxyl-containing triglycerides have been crosslinked radically prior the introduction of acrylate groups to produce conventional and flame retardant acrylate resins. The third route explored consists of using plant oil-derived chemicals like 10-undecenoic and oleic acids to produce tailor made monomers. Acyclic diene metathesis (ADMET) polymerization has been applied to prepare a set of thermosetting polyesters with flame retardant properties. Moreover thiol-ene “click” coupling has been used to prepare carboxylic monomers that have been explored to produce thermosetting polyanhydrides for fast drug delivery systems. A set of tailored polyols from the products of coordinative polymerization of the methyl epoxyoleate and the cationic ring opening polymerization of fatty acid-derived 2-oxazolines were also prepared. These polyols have been used to produce different thermosetting polyuretanes with a wide range of properties and characteristics.Finally, some recent research in producing benzoxazine thermosetting resins applying this renewable approach is presented. The benzoxazines based on diphenolic acid, a derivative of levulinic acid, are studied.

The non-halogen flame retardant epoxy resin based on a novel compound with phosphaphenanthrene and cyclotriphosphazene double functional groups

A novel flame retardant additive hexa-(phosphaphenanthrene -hydroxyl-methyl-phenoxyl)-cyclotriphosphazene (HAP–DOPO) with phosphazene and phosphaphenanthrene double functional groups has been synthesized from hexa-chloro-cyclotriphosphazene, 4-hydroxy-benzaldehyde and 9,10-dihydro-9-oxa-10- phosphaphenanthrene 10-oxide(DOPO). The structure of HAP–DOPO was characterized by Fourier transformed infrared (FT-IR) spectroscopy and 1H nuclear magnetic resonance ( 1H NMR) and 31P nuclear magnetic resonance ( 31P NMR). The additive HAP–DOPO was blended into diglycidyl ether of bisphenol-A (DGEBA) to prepare flame retardant epoxy resins. The flame retardant properties and thermal properties of the epoxy resins cured by 4, 4′-Diamino-diphenyl sulfone (DDS) were investigated from the differential scanning calorimeter (DSC), the thermogravimetric analysis (TGA), UL94 test, the limiting oxygen index (LOI) test and Cone calorimeter. Compared to traditional DOPO–DGEBA and ODOPB–DGEBA thermosets, the HAP–DOPO/DGEBA thermosets have higher T gs at the same UL94 V-0 flammability rating for their higher crosslinking density and have higher char yield and lower pk-HRR at same 1.2 wt.% phosphorus content which confirm that HAP–DOPO has higher flame retardant efficiency on thermosets. The scanning electron microscopy (SEM) results shows that HAP–DOPO in DGEBA/DDS system obviously accelerate formation of the sealing, stronger and phosphorus-rich char layer to improve flame retardant properties of matrix during combustion.

Layer-by-layer assembly of silica-based flame retardant thin film on PET fabric

A novel method to improve flame retardant properties of textile fabric using multilayered thin films was evaluated. In this work, PET fabrics were coated with silica nanoparticles using layer-by-layer assembly. Five bilayers of positively and negatively charged colloidal silica (<10 nm average thickness) increased time to ignition and decreased heat release rate peak of PET fabric by 45% and 20%, respectively. In vertical burn test, this same nanocoating dramatically reduced burn time and eliminated melt dripping. This study demonstrates the ability to impart flame retardant behavior using a water-based, environmentally-friendly protective coating.

Flame retardant wool using zirconium oxychloride in various acidic media optimized by RSM

The flame retardant wool was prepared using zirconium oxychloride with various acids. The thermal degradation of wool treated with the flame retardant synergistic system, zirconium oxychloride, citric acid and hydrochloric acid, was studied by thermal analysis, mass loss, limiting oxygen index (LOI) and vertical flame test. The fabric surfaces were also observed by SEM. The wool treated with the flame-retardant shows an increase in the decomposition temperature, residual mass and LOI. Also the wool treated with hydrochloric acid showed improved flame retardant properties compared to the use of formic acid. The response surface methodology (RSM) was also used for the experimental plan with four variables on the results of flame retardancy. The statistical analysis confirms the optimum conditions obtained by the experimental results.

Synergistic effect between expandable graphite and ammonium polyphosphate on flame retarded polylactide

Synergistic effect was observed between expandable graphite (EG) and ammonium polyphosphate (APP) on flame retarded polylactide (PLA) in this paper using limiting oxygen index (LOI), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and X-ray spectroscopy (XPS) and cone calorimeter tests etc. In the experiments, PLA composites with 15 wt% of APP/EG(1:3) combinations showed a LOI value of 36.5 and V-0 rating in UL-94 tests, greatly improved flame retardant properties from composites with APP or EG alone. Results from TGA and cone calorimeter demonstrated that APP/EG combination could retard the degradation of polymeric materials above the temperature of 520 °C by promoting the formation of a compact char layer. This char layer protects the matrix effectively from heat penetrating inside and prevents its further degradation, resulting in lower weight loss rate and better flame retarded performance.

Improved flame retardant properties of epoxy resin by fluorinated MMT/MWCNT additives

Flame retardant additives of montmorillonite (MMT) and multi-walled carbon nanotube (MWCNT) were embedded in epoxy resin to improve the resin's flame retardant properties. MMT was fluorinated to exfoliate its layers and enhance its dispersion into the epoxy resin. The MWCNT was also fluorinated to create hydrophobic functional groups for improved dispersion into the epoxy resin. The MWCNT reduced the degradation rate of the epoxy resin and increased the char yield. Limiting oxygen index also increased showing first order against char yield. The exfoliated MMT acted as an energy storage medium to hinder thermal transfer within the epoxy resin. The activation energy increased almost two times by fluorinated MMT/MWCNT additives. The fluorination of the additives, MMT and MWCNT significantly improved the flame retardant properties of the epoxy resin.

Effect of 3-Aminopropyltrimethoxysilane-g-Rice Husk Silica on Flame Retardant of ABS/Organomontmorillonite Nanocomposites

This work focused on an improvement of flame retardant properties of acrylonitrile-butadiene-styrene (ABS) by varying amount of silica and organomontmorillonite (OMT). The silica was extracted from agricultural waste such as rice husk by chemical treatment. The obtained silica was characterized by SEM-EDX, XRF, FTIR, laser particle size analysis, and surface area analysis. After that, the rice husk silica (RHS) was surface-modified with 3-aminopropyltrimethoxysilane (AMMO) before blending with ABS and OMT at various ratios by melt blending technique using twin-screw extruder. The effect of silane coupling agent on flammability properties of ABS nanocomposites was studied. The prepared nanocomposites were characterized by TEM to examine the dispersibility of OMT and AMMO-g-RHS in ABS matrix. The flammability properties were evaluated by measuring the limiting oxygen index (LOI) values and UL-94 classes. The TEM results revealed that the ABS/OMT/AMMO-g-RHS nanocomposites were a kind of exfoliated structure. The modified silica particles and OMT were found to disperse and reside in the SAN phase of the matrix. Furthermore, OMT and modified silica could enhance flame retardant properties of ABS polymer matrix because of a synergistic effect between OMT and modified silica during the combustion of ABS nanocomposites.

Ethylene vinyl acetate/layered silicate nanocomposites prepared by a surfactant-free method: Enhanced flame retardant and mechanical properties

Exfoliated EVA/layered silicate nanocomposites were prepared by a masterbatch process using polymer-modified layered silicate instead of small molecule surfactant-modified clays. The nanocomposites exhibited improved mechanical properties and flame retardancy. Microscale flammability test showed that the heat release capacity (HRC) and total heat release (THR) were reduced by 21–24% and 16%, respectively. Radiant gasification studies revealed that the exfoliated EVA nanocomposites exhibited better improvements in flame retardant properties of EVA than did the corresponding intercalated nanocomposites. The peak mass loss rate of the exfoliated EVA nanocomposite containing about 5 wt% clay was reduced by 80% and the mass loss rate plot was spread over a much longer period of time. The mechanical and flammability tests revealed that the observed improvements in all the desirable properties were due to the presence of both the incorporated polymeric surfactant and the nanoclay.

Preparation and properties of halogen-free flame retardant epoxy resins with phosphorus-containing siloxanes

Novel epoxy resin modifiers, DOPO–TMDS and DOPO–DMDP were synthesized by addition reaction of divinylsiloxane with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Halogen-free flame retardant epoxy resins were obtained through modification of o-cresol novolac epoxy resin cured by phenol novolac resin using DOPO–TMDS and DOPO–DMDP which were characterized by 1H NMR, 13C NMR, 31P NMR and FT-IR measurements. Effects of the phosphorus-containing siloxanes on thermal stabilities, mechanical properties and flame retardant properties of the epoxy resins were investigated. The cured epoxy resins exhibited better mechanical properties and greatly improved flame retardant properties due to the presence of phosphorus-containing siloxanes. The cured epoxy resins with phosphorus loading of 2.0 wt% showed LOI values of 32–33 and achieved UL94V-0 ratings.

Studies on the effect of 4A zeolite on the properties of intumescent flame-retardant agent filled natural rubber composites

This investigation focused on the research of 4A zeolite on the properties of intumescent flame retardant (IFR) agent filled natural rubber (NR) systems. The first part focused on the evaluation of such characteristics as cure characteristics, tensile property, abrasion loss, and cross-linking density of NR composites. Experimental results demonstrated that the addition of 4A zeolite could increase the cross-linking density of the NR systems. The incorporation of 0.3 phr of 4A zeolite with 50 phr of IF Ragent could improve the elongation value from 480 to 610%, probably 27% increase. Also, the abrasion loss was decreased from 0.95 to 0.70 cm3, nearly 26%. The second part focused on the study of flame-retardant (FR) properties of 4A zeolite filled NR systems. The properties and structure of these composites were characterized by limited oxygen index (LOI), thermogravimetric analysis (TGA), and cone calorimeter. It was proved that the addition of 0.3 phr of 4A zeolite into the IFR filled NR systems could lead to an increase of LOI value and thermal stability, together with a decrease of mass loss ration, rate of heat release (RHR), carbon monoxide (CO) evolution and carbon dioxide (CO2) evolution, and so on, in a word, an improvement of FR properties.

Structure, surface morphology, thermal and flammability characterizations of polyamide6/organic-modified Fe-montmorillonite nanocomposite fibers functionalized by sputter coating of silicon

In the present work, Fe-montmorillonite was synthesized by hydrothermal method, and then was modified by cetyltrimethyl ammonium bromide (CTAB). The polyamide6 (PA6) nanofibers and PA6/organic-modified Fe-montmorillonite (Fe-OMT) nanocomposite fibers were firstly prepared by a facile compounding process with electrospinning, and then coated by silicon nanoparticles (Si) using magnetron sputter technique. The High-resolution transmission electron microscopy (HRTEM) image indicated that the silicate clay layers were well dispersed within the nanocomposite fibers and aligned almost along the axis of the nanofibers. The influences of the Si sputter coating on structures, surface morphology, thermal and flammability properties of PA6 nanocomposite fibers were characterized by Scanning electron microscope (SEM), Energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Atomic force microscope (AFM), Thermogravimetric analyses (TGA) and Micro Combustion Calorimeter (MCC), respectively. The SEM images showed that the diameters of nanocomposite fibers were decreased with the loadings of the Fe-OMT, and the Si thin film with nanoparticles were well coated on the surface of homogeneous and cylindrical nanofibers. The EDX analyses confirmed the presences of the Fe-OMT and Si nanoparticles on the nanofibers. The XPS spectra reflected the chemical features of the deposited nanostructures. The AFM observations revealed a remarkable difference in the surface morphology of nanocomposite fibers after sputter coating. The TGA analyses indicated the barrier effects of silicate clay layers, catalysis effect of Fe 3+ and synergistic effects between the Fe-OMT and Si improved thermal stability properties of the coated nanocomposite fibers. It was found from the MCC tests that the peak of heat release rate (PHRR) of the coated nanocomposite fibers decreased significantly, contributing to the improved flame retardant properties.

Flame Retardancy of Thermoplastic Polyurethane and Polyvinyl Chloride by Organoclays

Thermooxidative stability and peak of heat release rates of thermoplastic polyurethane nanocomposites are improved by organoclays; but time to ignition of these composites is reduced. A cable with a thermoplastic polyurethane nanocomposite jacket does not pass a simple flame spread test by a Bunsen burner, indicating that the reduction of the peak of heat release rate does not prevent the flame spread. Polyvinyl chloride (PVC) with organoclays shows a fast HCl release by an accelerated chain-stripping reaction of the polymer catalyzed by the quaternary ammonium compound within the organoclays resulting in strong discolorations. Synthesis routes based on ethylene-vinyl acetate copolymer (EVA) or thermoplastic polyurethane (TPU) masterbatches of organoclays strongly diminish the darkening of the PVC compounds. Cone calorimeter experiments do not show remarkably improved flame retardancy properties of PVC filled with organoclays.

Characterization of organosilicon films synthesized by N 2-PACVD. Application to fire retardant properties of coated polymers

Organosilicon thin films, obtained from the polymerization of 1,1,3,3-tetramethyldisiloxane monomer pre-mixed with oxygen using a cold remote nitrogen plasma process, are used to improve flame retardant properties of polyamide-6 (PA-6) and polyamide-6 clay nanocomposite (PA-6 nano) substrates. A comparison between virgin PA-6 and coated PA-6 nano shows that the clay addition combined with the coating leads to an efficient fire retardant effect. The limiting oxygen index increases by 130% while, at the same time, the rate of heat release and the total heat evolved decrease by 41% and 33%, respectively. The nanocomposite structure leads to the formation of a silicon and carbonaceous protective layer during the combustion. This layer acts as a barrier limiting heat and mass transfers between the polymer and the flame, and this effect is reinforced by the coating.

Fire retardant mechanism in intumescent ethylene vinyl acetate compositions

The thermal and combustion behaviour of an intumescent fire retardant system based on Polyamide 6 (PA6) and Ammonium Polyphosphate (APP), used to improve flame retardant properties of poly(ethylene-co-vinyl acetate) (EVA), loaded with Mg(OH) 2 (MH) was examined. The study of the interactions between the additives introduced in EVA was focused in particular on the MH-APP interaction. The evolution of water from MH takes place at about 400 °C, with a fair overlap with ammonia and water evolution from APP degradation. Ammonia evolution from APP is facilitated by the presence of MH, in their mixture heated alone or in the polymer matrix. UL94 test shows that the interaction between MH and APP modifies the combustion behaviour of the intumescent mixture.

Developing flame retarded plastics: New guidance wanted

AbstractThe development of plastics with improved flame retardant properties is going through a phase of stagnation. Fire test concepts are following a new direction and the serial tests currently used do not adequately tie up with the development objective of reducing fire risks. In the short term no improvement in this situation is expected.