Modified Flame Retardant Research Articles

Synthesis and application of silicone modified flame retardant for polyester fabric

The flame-retardant treatment of polyester fabrics has been widely reported, but most of these treatments cause a significant decrease in the fabric’s handle, such as fluffiness and softness. This study designed and synthesised a new phosphorus-nitrogen-containing silicone oil (PNSO). Then, PNSO as a flame-retardant was treated on polyester fabric through a pad-dry-cure procedure. The limiting oxygen index (LOI), afterflame time and damaged length of the finished polyester fabric (PNSO-F) were enhanced from 20.5%, 73.1 s and 26.8 cm to 28.3%, 4.5 s and 12.3 cm, respectively. After 12 washes, PNSO-F retained its good flame-retardancy and anti-dripping properties. Furthermore, the flame-retardant mechanism of PNSO on fabric was investigated using different spectral methods, which revealed that nitrogen acting in the gas phase, and phosphorus and silicone in the condensed phase worked together to produce a synergistic flame-retardant effect. In addition, KES tests indicated that the fluffiness and softness of PNSO-F were significantly improved.

Preparation and characterization of low flammable asphalt for tunnel pavements

In this study, a silane modified flame retardant blend named FRB-SC was developed to combat combustion risks faced in tunnel asphalts. FRB-SC is a composite flame retardant principally made up of four components: Expandable Graphite (EG), Magnesium Hydroxide (MH), Calcium Hydroxide (CH) and Ammonium Polyphosphate (APP). The orthogonal design and the technique for order of preference by similarity to ideal solution were used to determine the optimal dosages of these four components. KH550 silane coupling agent was then added to modify the composite flame retardant and improve its functionality and stability in asphalt. Subsequently, the basic performance, rheological properties and flame retardancy of modified asphalts containing various dosages of FRB-SC (i.e., 2, 4, 6, 8, 10 and 12%) were evaluated, and thus the optimum dosage of FRB-SC was determined. The results showed that the asphalt's limiting oxygen index increased to 24.7% with the addition of 8% FRB-SC. Also, after the addition of FRB-SC, the asphalt's penetration and ductility decreased, its softening point increased, its high temperature stability increased, and its low temperature anti-cracking performance decreased. Meanwhile, based on the oil absorption and activation index of the FRB-SC, the optimal dosages of EG, MH, CH and APP were found to be 5%, 5%, 4%, and 9% by mass, respectively, and that of the silane coupling agent determined as 1.2%. Finally, the cone calorimeter test conducted on FRB-SC modified asphalt showed that carbon monoxide emissions were significantly reduced when combustion occurred, and the amount of heat and smoke released were also noticeably decreased, establishing the flame retardant efficacy of the FRB-SC. Now, although this study’s findings have not been applied in actual tunnel mixtures, this however provides an insight to the feasibility of its use for tunnel asphalt pavements, a move which could significantly reduce the hazards of tunnel fires and accidents.

A universal strategy toward flame retardant epoxy resin with ultra-tough and transparent properties

Flame-retardant epoxy composites have important application value in flexible optoelectronic devices, artificial intelligence and 5G fields. The flame retardancy of these composites, however, are often promoted at the expense of mechanical properties and transparency, particularly the toughness. In this work, we propose a simple strategy of introducing proper rigid-flexible groups into phosphorus-based flame retardant which realizes a dual performance improvement simultaneously in epoxy resin. The modified flame retardant epoxy resin has a limiting oxygen index (LOI) value of 32.3%, a high transmittance of approximately 92%, an excellent smoke and heat suppression properties. Remarkably, the addition of phosphorus-based flame retardant containing rigid-flexible groups (TOD) significantly enhances the mechanical properties of epoxy resin, especially the toughness. The impact strength is obviously increased from 6.8 kJ/m2 to 25.2 kJ/m2, with an increase of 271%, which mainly due to the flexible Si-O segment in TOD. This work provides a universal strategy for the design of flame retardant, ultra-tough and transparent epoxy resin, implying its enormous potential to promote the commercial application of epoxy resin.

Mechanical Properties of Polypropylene-Based Flame Retardant Composites by Surface Modification of Flame Retardants.

A flame retardant refers to a substance that can be added to a material having the property of being efficiently combusted to improve the material physically and chemically. It should not affect the physical properties required for the final product. Halogen-based compounds are representative flame retardants with excellent flame retardancy. However, their use is limited due to restrictions on the use of chemicals introduced due to human safety. Magnesium hydroxide, one alternative material of halogen flame retardants, is widely used as an eco-friendly flame retardant. However, the most significant disadvantage is high load. To find a solution to this problem, many studies have been conducted by mixing magnesium hydroxide with other additives to create a synergistic effect. In this study, flame retardancy and mechanical properties of polypropylene-based flame retardant composites as a function of mixing surface-modified magnesium hydroxide with phosphorus-based flame retardants were investigated. All materials including PP, additives, and flame retardants were mixed using an extrusion process. Specimens were prepared by an injection process of the compound made after mixing. As a result of the evaluation of the mechanical properties by the modified flame retardant, the relational expression of the mechanical performance degradation as a function of the amount of addition was obtained, and the tensile (CBATS) and bending strength (CBABS) were performed on the amount of flame retardant added. The relational expression obtained in this study is considered to be a formula for predicting the strength reduction according to the addition amount of the modified flame retardant and can be used in industry. In addition, it was found that the addition amount of the modified flame retardant had a greater effect on the lowering of the bending strength.

Synthetic novel, convenient and eco-friendly Si/P/N synergistic treatment agent to improve the flame retardancy and thermal stability of cotton fabrics

Modified flame retardant cotton fabrics were prepared by introducing a novel aminoethylpiperazine spirocyclic pentaerythritol bisphosphonate functional heptamethyltrisiloxane (ASPBH). The structure of the synthesized ASPBH was characterized using nuclear magnetic resonance (1H and 31P) and Fourier transform infrared spectra (FTIR). ASPBH successfully attached to the surface of cotton fibers, which was proved by the results of scanning electron microscope (SEM) combined with energy dispersive X-ray spectroscopy. The flame retardancy of ASPBH-treated cotton fabrics was further improved. The limiting oxygen index (LOI) value reached 30.4%, the residual char length was reduced to 7.5 cm, and there was no afterflame and afterglow. However, the LOI of untreated cotton fabric is only 18%, and the vertical burning test cannot be completed. Thermogravimetric analysis results showed that the modified cotton fabrics has excellent thermal stability, which can also be seen from SEM analysis of char residues. In addition, addition of ASPBH caused the peak heat release rate and total heat release decrease from 232.1 to 177.2 kW/m2 and from 6.5 to 5.0 MJ/m2, respectively. And the treated cotton fabrics released less smoke than untreated ones during the combustion, which would greatly reduce combustion harm. Based on analysis of condensed phase at different temperatures, the thermal degradation mechanism of ASPBH on cotton fabrics was presumed. A novel aminoethylpiperazine spiro pentaerythritol bisphosphonate functional heptamethyltrisiloxane (ASPBH) can be dissolved in a mixed solution of ethanol and water to prepare a flame retardant treating solution. The original cotton fabric was immersed for a certain period of time under certain conditions, then it was dried and solidified to complete finishing process. Treated cotton can form a stable SiO2 char layer at high temperature and release less smoke.

Mussel-Inspired General Interface Modification Method and Its Application in Polymer Reinforcement and as a Flame Retardant.

Inspired by the remarkable adhesion of mussels, the mimicking of natural adhesive molecules has been widely used for surface modification. In the present study, an economical and easily available biomimic material named as tannic acid–Fe3+ (TA–Fe3+) was first directly used as a surface modifier, carbonization agent, smoke inhibitor, and flame-retardant synergist. Compared with the flame-retardant magnesium hydroxide (Mg(OH)2), TA–Fe3+-modified Mg(OH)2 endowed polyamide 6 (PA 6) with improved mechanical performance and flame-retardant properties. The flame-retardant and smoke-suppressant properties were tested by the limiting oxygen index and cone calorimeter tests. The flame-retardation mechanism was investigated by thermogravimetric analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy. The tensile strength could increase up to 90%, and the modified flame retardant was found to have higher UL-94 grade with the same dosage of flame-retardant additives. The peak heat release rate, total heat release, peak of smoke production rate, and total smoke production were significantly reduced. The synergistic effect between TA–Fe3+ and Mg(OH)2 was also discussed. This study provides new insights into the direct utilization of a biomimicking adhesive molecule, TA–Fe3+, to realize simultaneous composite reinforcement and flame-retardant property enhancement. Meanwhile, because of the extensive synergies of flame-retardant metal oxide with iron element and the universal growth characteristics of TA–Fe3+, it has potential applications in the preparation of various flame-retardant polymers.

Fire Retardancy of Aluminum Hydroxide Reinforced Flame Retardant Modified Epoxy Resin Composite

A novel phosphorous containing flame retardant epoxy resin is synthesized by modifying the epoxy resin initially with phosphoric acid and further with aluminum hydroxide (ATH) to enhance the fire retardancy of the modified epoxy resin. The several phosphorous modified epoxy resin to ATH mass ratios were used to study the effect of ATH addition on epoxy. Thermal and mechanical properties. The structure of the modified flame retardant epoxy resin was characterized using Fourier-transform infrared spectroscopy (FTIR) while thermal degradation behavior and flame retardant properties were examined using thermo-gravimetric analysis (TGA) and UL-94 testing. Furthermore, ultimate tensile strength and young modulus were analyzed to study the effect of ATH addition on mechanical properties. The findings indicated that fire retardancy of ATH reinforced modified ep oxy resin is higher than virgin and phosphorous modified epoxy resin and depicted eminent flame retardant properties with suitable mechanical properties.

Functionalized MWCNTs modified flame retardant PLA nanocomposites and cold rolling process for improving mechanical properties

10-hydroxy-9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-OH) has been successfully covalently grafted onto the surfaces of multi-walled carbon nanotubes (MWCNTs) to obtain DOPO-functionalized MWCNTs (MWCNT-DOPO-OH) by a three-step process. The resultant core-shell nanostructured MWCNT-DOPO-OH was introduced into aluminum hypophosphite/poly(lactic acid) (AHP/PLA) flame retardant systems via melt blending to improve both flame retardancy and mechanical properties. AHP/PLA/MWCNT-DOPO-OH nanocomposites with synergistic effect of 1 wt.% MWCNT-DOPO-OH and 14 wt.% AHP were shown to be effective in improving flame retardancy with UL 94 V-0 rating and limiting oxygen index (LOI) value of 28.6. And these flame-retardant nanocomposites show a usable Tg higher than 57.8 °C and much higher char yield for preventing the anti-dropping. Moreover, a cold rolling process was performed for AHP/PLA/MWCNT-DOPO-OH nanocomposites to further improve the mechanical properties for secondary processing. For 1 wt.% MWCNT-DOPO-OH loading PLA nanocomposites, the tensile strength increased from 69.5 MPa to 77.9 MPa and 82.0 MPa, and the fracture strain increased from 17.9% to 27.5% and 120%, at rolling ratios of 30% and 50%, respectively, indicating that MWCNT-DOPO-OH modified PLA was homogenized plastic deformation during the rolling process.

Poorly-/well-dispersed graphene: Abnormal influence on flammability and fire behavior of intumescent flame retardant

Surface feature of ammonium polyphosphate is modified by cation exchange reaction with piperazine, and then reduced graphene oxide nanosheets are attached to the surface of modified flame retardant via hydrogen bonding interactions. Good dispersion of graphene in the polypropylene matrix is observed. The dispersion state of graphene has an abnormal effect on the flammability results under small flame and fire behavior under forced flaming condition of intumescent flame retardant (IFR) composites. The well-dispersed graphene results in significantly deteriorated limiting oxygen index and UL-94 rating. The graphene with good dispersion is adverse to flammability results, which is in contrary to the widely-acknowledged flame retardant mechanisms. Low content of well-dispersed graphene exhibits higher reduction effect on heat release than that of poorly-dispersed counterpart. Novel flame retardant mechanism and model are proposed and new understanding of the role of graphene in the combustion of IFR is provided.

Synergistic Flame Retardant Effect of Fumed Silica and Zinc Borate with Magnesium Hydroxide in ABS Based Flame Retardant Composites

For achieving sufficient flame retardancy, high magnesim hydroxide (MH) content is needed in MH flame retardant Acrylonitrile-butadiene-styrene copolymer (ABS) composite (ABS/MH), which will cause difficulty in processing and poor mechanical property. We prepared modified flame retardant MH, fumed silica (SiO2) and zinc borate (ZB) via TX-10 phosphate/polyacrylate latex as well as MH flame retardant ABS with the modified flame retardant of 60.0wt% and studied the synergistic flame retardant effect of SiO2 and ZB with MH in ABS/MH. The incorporation of ZB, SiO2 or SiO2/ZB could prolong the time to ignition, reduce the average and peak heat release rate of ABS/MH in cone calorimeter test.

Effect of Fumed Silica and Zinc Borate on the Thermogravimetric Analysis Curves of ABS/Magnesium Hydroxide Composite

For achieving sufficient flame retardancy, high magnesim hydroxide (MH) content is needed in MH flame retardant Acrylonitrile-butadiene-styrene copolymer (ABS) composites (ABS/MH), which will cause a great decrease in mechanical property and difficulty in preparing samples for measurement. We prepared ABS/MH filled high 60.0% flame retardant by compounding ABS and modified flame retardant MH, fumed silica (SiO2) and zinc borate (ZB) via TX-10 phosphate/polyacrylate latex and studied the effect of a small amount of SiO2 and ZB with MH in ABS for improving the thermal decomposition of ABS/MH. The thermal stability of the modified flame retardant could meet the processing temperature of ABS. The incorporation of ZB, SiO2 or SiO2/ZB could improve the thermal stability of ABS/MH.

Rigid bio-foam plastics with intrinsic flame retardancy derived from soybean oil

Acrylated epoxidized soybean oil was chemically grafted with difunctional flame retardants carrying phosphorus, double bonds or biphenyl groups, and then copolymerized with styrene to produce bio-foams with high mechanical properties and intrinsic flame resistance. Owing to the introduction of rigid comonomer, phosphorus, additional double bonds or biphenyl side groups, the bio-foams showed compressive strength similar to that of conventional unsaturated polyester foam, antiflaming capability and biodegradability as well. More importantly, the modified flame retardant partially took the role of styrene, leading to a lower fraction of petroleum based substance in the bio-foams without the expense of foam strength, and improved biodegradability. The comparison between the bio-foams with intrinsic flame retardancy on a molecular level and those containing inflaming retardant fillers revealed that the latter have acquired rather poor mechanical properties and hence are obviously inferior to the former in practical applications where a load-bearing capability is required.

Preparation and Application of Microencapsulated Flame Retardant Containing Phosphorus-Silicon

The silica sol containing epoxy groups was prepared with tetraethoxysilane and silane coupling agent GPTMS as precursors by sol-gel technique and was used to encapsulate the microencapsulated flame retardant to enhance its flame retarding efficiency and water fastness for textile material. The prepared silica sol and gel were characterized by nano particle size analyzer, FT-IR spectrum analysis, energy spectrum analysis and SEM. The experimental results were proved that silica gel containing epoxy group was assuredly deposited on the surface of microencapsulated flame retardant. The cotton fabric was finished by the modified flame retardant and the test results (including the test of flame spread properties of textiles in vertical direction and the fastness to washing) showed that it had better flame retarding efficiency and water fastness.

Ionizing radiation graft polymerized and modified flame retardant cotton fabric

Halogen free flame retardant cotton (FR cotton) fabric was prepared by grafting 2,3-epoxypropyl methacrylate (GMA) on ordinary or untreated cotton (UT cotton) fabric by γ-rays from 60Co source. Epoxy groups present in GMA grafted cotton (GMA-g-cotton) fabric was reacted with ethylene diamine and subsequently modified with orthophosphoric acid solution to convert in to FR cotton fabric. Effects of imparted dose, concentration of monomer on grafting percentage were studied. The changes in thermal properties after treatment were investigated by using Thermo gravimetric analyser. Limiting oxygen index, char length, time after glow and time after flame were also studied as per ASTM D2863 and IS11871, respectively, for both FR cotton and UT cotton fabrics. The FR cotton fabric was found to pass all the above tests. Washing durability of the FR cotton fabric in different cleaning agents was also studied and a washing solution containing organic solvent mixture is suggested.