Project description:We report a flame retardant epoxy nanocomposite reinforced with 9,10-dihydro-9-oxa-10-phosphaphenantrene-10-oxide (DOPO)-tethered SiO2 (DOPO-t-SiO2) hybrid nanoparticles (NPs). The DOPO-t-SiO2 NPs were successfully synthesized through surface treatment of SiO2 NPs with (3-glycidyloxypropyl)trimethoxysilane (GPTMS), followed by a click reaction between GPTMS on SiO2 and DOPO. The epoxy nanocomposites with DOPO-t-SiO2 NPs as multifunctional additive exhibited not only high flexural strength and fracture toughness but also excellent flame retardant properties and thermal stability, compared to those of pristine epoxy and epoxy nanocomposites with a single additive of SiO2 or DOPO, respectively. Our approach allows a facile, yet effective strategy to synthesize a functional hybrid additive for developing flame retardant nanocomposites.
Project description:In this study, to develop an organic/inorganic synergistic flame retardant and to reduce the dosage and cost of flame retardants, organic/inorganic synergistic flame retardants, hexakis(4-boronic acid-phenoxy)-cyclophosphazene (CP-6B), and magnesium hydroxide (MH) were chosen. The flame retardant properties of CP-6B/MH in epoxy resin (EP) were discussed. EP/CP-6B/MH had better flame retardancy and heat resistance compared with EP/CP-6B and EP/MH. A limiting oxygen index of EP/3.0%CP-6B/0.5%MH of 31.9% was achieved, and vertical burning V-0 rating was achieved. Compared with EP, the cone calorimeter dates of EP/CP-6B/MH decreased. CP-6B/MH inhibited combustion and did little to damage mechanical properties. Besides, the flame retardant mechanism was studied by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and pyrolysis-gas chromatography-mass spectrometry. CP-6B/MH exerted good synergistic effects.
Project description:A facile route of 'copolymerization/blending' was proposed to fabricate silicon/nitrogen synergistically reinforced flame-retardant PA6 nanocomposites with simultaneously improved anti-dripping and mechanical properties. Firstly, a persistently inherent flame-retardant PA6 (FR-PA6), with 1,3-bis(3-aminopropyl)tetramethyl disiloxane (MSDS), was synthesized via controllable amidation and a polycondensation reaction. Melamine cyanurate (MCA) nanoparticles as a 'gas phase' synergistic agent were then added into FR-PA6 to further improve its flame retardancy. The primarily obtained FR-PA6 could be extinguished after a few melt droplets dropped as ignited, and passed the V-2 rating with enhanced mechanical properties, while PA6 had no rating (NR). The prepared FR-PA6/MCA nanocomposites could attain a limiting oxygen index (LOI) value of 32.7%, and passed the V-0 level with only 1 melting droplet with similar mechanical properties to PA6. Accordingly, the special 'condensed-gas phase' synergistic flame-retardant mechanism of FR-PA6/MCA nanocomposites was proposed through studying the residues and pyrolysis volatiles. This work provided a facile route as a model for developing functional PA6 for diverse engineering applications.
Project description:In this study, a nitrogen-phosphorus intumescent flame-retardant 3-(N-diphenyl phosphate) amino propyl triethoxy silane (DPES), the ionic liquid (IL) of 1-butyl-3-methyl-imidazole phosphate, and a phosphorous-containing ionic liquid-modified expandable graphite (IL-EG), were synthesized, and their molecular structures were characterized. The flame-retardant rigid polyurethane foams (RPUFs) were compounded with synergistic flame-retardant IL-EG/DPES to study the effects of the combination IL-EG and DPES on the pore structure, mechanical properties, thermal decomposition behavior and thermal decomposition mechanism of RPUF. The results showed that IL-EG/DPES had good thermal stability, and an excellent expansibility and char yield. The flame-retardant RPUF, modified with IL-EG and DPES at the ratio of 1:1, had a relatively uniform pore size, the highest compressive strength, and an excellent flame-retardant performance due to the form interwoven hydrogen bonds between IL-EG and DPES, as well as the new synergistic flame-retardant coating on the RPUF surface to restrict the transfer of gas or heat into the PU matrix.
Project description:Cellulose nanofibers (CNFs) have excellent properties, such as high strength, high specific surface areas (SSA), and low coefficients of thermal expansion (CTE), making them a promising candidate for bio-based reinforcing fillers of polymers. A challenge in the field of CNF-reinforced composite research is to produce strong and transparent CNF/polymer composites that are sufficiently thick for use as load-bearing structural materials. In this study, we successfully prepared millimeter-thick, transparent CNF/polymer composites using CNF xerogels, with high porosity (~70%) and high SSA (~350 m2 g-1), as a template for monomer impregnation. A methacrylate was used as the monomer and was cured by UV irradiation after impregnation into the CNF xerogels. The CNF xerogels effectively reinforced the methacrylate polymer matrix, resulting in an improvement in the flexural modulus (up to 546%) and a reduction in the CTE value (up to 78%) while maintaining the optical transparency of the matrix polymer. Interestingly, the composites exhibited flame retardancy at high CNF loading. These unique features highlight the applicability of CNF xerogels as a reinforcing template for producing multifunctional and load-bearing polymer composites.
Project description:Waterborne polyurethanes (WPUs) have attracted great interest owing to their environmentally friendly properties, and are wildly applied in production and daily life. However, waterborne polyurethanes are flammable. Up to now, the challenge remains to prepare WPUs with excellent flame resistance, high emulsion stability, and outstanding mechanical properties. Herein, a novel flame-retardant additive, 2-hydroxyethan-1-aminium (2-(1H-benzo[d]imidazol-2-yl)ethyl)(phenyl)phosphinate (BIEP-ETA) has been synthesized and applied to improve the flame resistance of WPUs, which has both phosphorus nitrogen synergistic effect and the ability to form hydrogen bonds with WPUs. The WPU blends (WPU/FRs) exhibited a positive fire-retardant effect in both the vapor and condensed phases, with significantly improved self-extinguishing performance and reduced heat release value. Interestingly, thanks to the good compatibility between BIEP-ETA and WPUs, WPU/FRs not only have higher emulsion stability, but also have better mechanical properties with synchronously improved tensile strength and toughness. Moreover, WPU/FRs also exhibit excellent potential as a corrosion-resistant coating.
Project description:Deoxyribonucleic Acid (DNA) has been recently found to be an efficient renewable and environmentally-friendly flame retardant. In this work, for the first time, we have used waste DNA from fishing industry to modify clay structure in order to increase the clay interactions with epoxy resin and take benefit of its additional thermal property effect on thermo-physical properties of epoxy-clay nanocomposites. Intercalation of DNA within the clay layers was accomplished in a one-step approach confirmed by FT-IR, XPS, TGA, and XRD analyses, indicating that d-space of clay layers was expanded from ~1.2 nm for pristine clay to ~1.9 nm for clay modified with DNA (d-clay). Compared to epoxy nanocomposite containing 2.5%wt of Nanomer I.28E organoclay (m-clay), it was found that at 2.5%wt d-clay loading, significant enhancements of ~14%, ~6% and ~26% in tensile strength, tensile modulus, and fracture toughness of epoxy nanocomposite can be achieved, respectively. Effect of DNA as clay modifier on thermal performance of epoxy nanocomposite containing 2.5%wt d-clay was evaluated using TGA and cone calorimetry analysis, revealing significant decreases of ~4000 kJ/m2 and ~78 kW/m2 in total heat release and peak of heat release rate, respectively, in comparison to that containing 2.5%wt of m-clay.
Project description:A novel intumescent flame retardant (IFR) agent designated as Dohor-6000A has been used to prepare halogen-free flame retardant polypropylene (PP) fibers via melting spinning. Before being blended with PP resin, a surface modification of Dohor-6000A was carried out to improve its compatibility with the PP matrix. The rheological behavior of flame retardant Dohor-6000A/PP resin, the structure, morphology, mechanical properties, flammability of the Dohor-6000A/PP fibers were studied in detail, as well as the action mode of flame retardant. X-ray diffraction (XRD) showed that the addition of Dohor-6000A did not damage the crystal as well as the orientation structure of PP matrix, which was helpful to the maintenance of mechanical properties. The presence of the IFR significantly improved the flame retardant performance and thermal stability of PP fibers. When the content of Dohor-6000A reached 25%, the fibers displayed a limiting oxygen index (LOI) value of 29.1% and good melt-drop resistance. Moreover, the peak heat release rate (PHRR) and total heat release (THR) from microscale combustion colorimetry (MCC) tests were decreased by 26.0% and 16.0% in comparison with the same conditions for pure PP fibers. In the condensed phase, the IFR promoted a carbonization process and promoted the formation of a glassy or stable foam protective layer on the surface of the polymer matrix. In addition, the IFR decomposed endothermically to release of non-combustible gases such as NH3 and CO2 which dilutes the combustible gases in the combustion zone.
Project description:Ceramifiable flame-retardant ethylene-vinyl acetate (EVA) copolymer composites for wire and cable sheathing materials were prepared through melt compounding with ammonium polyphosphate (APP), aluminum hydroxide (ATH) and fluorophlogopite mica as the addition agents. The effects of ammonium polyphosphate, alumina trihydrate, and APP/ATH hybrid on the flame retardant, as well as on the thermal and ceramifiable properties of EVA composites, were investigated. The results demonstrated that the composites with the ratio of APP:ATH = 1:1 displayed the best flame retardancy and the greatest char residues among the various EVA composites. The tensile strength of the composites was 6.8 MPa, and the residue strength sintered at 1000 °C reached 5.2 MPa. The effect of sintering temperature on the ceramifiable properties, microstructures, and crystalline phases of the sintered specimen was subsequently investigated through X-ray diffraction, Fourier transform infrared, and scanning electron microscopy. The XRD and FTIR results demonstrated that the crystal structure of mica was disintegrated, while magnesium orthophosphate (Mg₃(PO₄)₂) was simultaneously produced at an elevated temperature, indicating that the ceramization of EVA composites had occurred. The SEM results demonstrated that a more continuous and compact microstructure was produced with the rise in the sintering temperature. This contributed to the flexural strength improvement of the ceramics.
Project description:Various inorganic fillers are proved to be desirable synergists to improve the fire resistance of fire-retardant coatings. Herein, a functional filler (ANE) with flame retardant property was prepared by intercalating aluminum diethylphosphinate into microwave expanded vermiculite and grafting sodium stearate on its surface. The structure of ANE was fully characterized by FTIR, XRD, XPS and SEM analyses. Then ANE was applied to melamine modified urea-formaldehyde resin to produce fire-retardant coatings. The fire resistance test, TGA and cone calorimeter test demonstrate that ANE imparts great heat insulation, thermal stability, and flame retardancy to the coatings. Moreover, the introduction of ANE exhibits an excellent synergistic effect on reducing the heat release and smoke emission of the coatings. Specifically, with the addition of 3 wt% ANE, the heat release rate and smoke density grade of the coatings are decreased by 25.24% and 60.32%, respectively, compared to that without ANE. The excellent flame retardancy and smoke suppression performances of the coatings are mainly attributed to the formation of more cross-linking structures in the carbon layers, resulting in a more stable and compact char structure. In addition, the good hydrophobicity of ANE coatings can ensure the durability of flame retardancy.