Flame Retardant Properties Of Epoxy Resin Research Articles

Thermal and flame-retardant properties of intrinsic flame-retardant epoxy resin containing biphenyl structures and phosphorus

An intrinsic flame-retardant epoxy resin was synthesized by introducing biphenyl structures and phosphorous into epoxy resin. The biphenyl structures could increase the glass transition temperature by more than 10 °C, as well thermal stability as indicated by the elevation in char yield. They could also enhance mechanical properties as reflected by the increments of 86.4% and 176.5% in tensile strength and breaking elongation, respectively, and offset the negative effects of phosphorus-containing structures. The introduction of elemental phosphorus could improve the flame-retardant properties of epoxy resin. The resulting epoxy resin presented a high limiting oxygen index of 32.4% and a V-0 rating in the UL-94 test. Moreover, it exhibited better flame-retardant parameters than pure epoxy resin in the cone calorimeter test. It could be decomposed to generate PO∙ and PO2∙ radicals to quench active free radicals, reduce toxic and smoke gas generation, and form a dense and stable char layer. It could simultaneously achieve gas and condensed phase flame retardancy. The presence of the biphenyl structure and phosphorus element in the epoxy resin system improved the thermal, mechanical, and flame-retardant properties of epoxy resin simultaneously. This work offered a facile method for preparing intrinsic phosphorus-containing flame-retardant epoxy resin without sacrificing thermal and mechanical properties.

Synthesis of multielement phosphazene derivative and the study on flame-retardant properties of epoxy resin

Herein, we have successfully synthesized phosphorus/nitrogen/silicon tri-elements compound phosphazene derivative hexa-[4-( N-(3-(triethoxysilyl)propyl)acetamide)phenoxy]cyclotriphosphazene (HNTPC) from hexachlorotriphosphazenitrile, methyl 4-hydroxybenzoate, and 3-triethoxysilylpropylamine, and it was used as an additive flame retardant in epoxy resin (EP). Then, the thermal stability and flame retardancy of the composite (HNTPC/EP) were tested. Thermogravimetric analysis showed that the presence of HNTPC made EP matrix decompose at a relatively low temperature, thus promoted the formation of a stable coke layer and protected the matrix from fire. Therefore, the amount of carbon residue was markedly increased at 800°C, indicating an outstanding condensed phase flame-retardant effect. Furthermore, various combustion test data manifested that the addition of HNTPC could significantly improve the flame-retardant performance of EP. In addition, the sample could pass the vertical burning tests (UL-94) V-1 grade when the addition amount was 10% and the limiting oxygen index value was 32.6%, the peak heat release rate and total heat release rate decreased by 40.0% and 21.5%, respectively. Besides, the results of scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy also showed that HNTPC can promote the formation of carbon layer and improved the flame-retardant property of EP. Finally, the condensed phase and gas phase synergistic flame-retardant mechanism of HNTPC was proposed.

Thermal Stability and Flame Retardancy Properties of Epoxy Resin Modified with Functionalized Graphene Oxide Containing Phosphorus and Silicon Elements.

Phosphorus- and silicon-modified graphene oxide was prepared to improve the thermal stability and flame retardancy properties of epoxy resin. 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and vinyltriethoxysilane (VTES) were successfully grafted onto the surface of graphene oxide (GO) through solvothermal synthesis and hydrolysis–condensation reaction, respectively. Subsequently, the functionalized graphene oxide grafted by DOPO and VTES (DOPO–VTES–GO) was incorporated into the epoxy resin by the solution blending method. The effect of DOPO–VTES–GO on the thermal stability and flame-retardant properties of epoxy resin was systematically studied. Thermogravimetric analysis showed that the thermal stability and char residue yield of DOPO–VTES–GO/epoxy were increased obviously compared with those of pure epoxy resin and DOPO–GO/epoxy. Cone calorimeter test results showed that DOPO–VTES–GO/epoxy had better flame retardancy than pure epoxy resin and DOPO–GO/epoxy on reducing the peak of heat release rate, total heat release, and total smoke production. Furthermore, the char residue after the cone calorimeter tests was investigated by scanning electron microscopy–energy-dispersive X-ray spectrometry, Raman spectroscopy, and Fourier transform infrared measurements. These results demonstrated that the DOPO–VTES–GO can enhance the graphitization degree of char residues and promote the formation of the thermally stable char. In addition, the mechanism of flame retardancy was proposed, and DOPO–VTES–GO exerts the synergistic effect mainly by means of catalytic charring in the condensed phase and capturing hydroxyl or hydrogen radicals from thermal decomposition of epoxy resin in the gas phase. This work provides novel insights into the preparation of phosphorus–silicon–graphene oxide ternary synergistic flame retardants for thermosetting polymer materials.

Effect of a novel P/N/S-containing reactive flame retardant on curing behavior, thermal and flame-retardant properties of epoxy resin

A novel P/N/S-containing flame retardant DHBAZ was synthesized with 9, 10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, p-hydroxybenzaldehyde and 2-aminothiazole, and used as a co-curing agent for epoxy resin (EP). With the aid of DHBAZ, EP/7.5% DHBAZ passed UL-94 V-0 rating, and owned a LOI value of 31.4%. Besides, DHBAZ also played a positive role in inhibiting the release of heat and the production of smoke. Through non-isothermal DSC tests it revealed that in the presence of DHBAZ, epoxy resin was cured at a lower temperature and showed lower curing-reaction activity energy. DMA analyses indicated that EP/7.5% DHBAZ showed an increased storage modulus, and it had a close glass transition temperature with EP. While, DHBAZ presented a decreased effect on the thermal stability of epoxy resin acquired from TG analyses. Finally, the flame-retardant mechanism studied by TG-FTIR and py-GC/MS deduced that DHBAZ worked in the gaseous phase by producing P, PO and incombustible gases.

Improving thermal and flame-retardant properties of epoxy resins by a novel reactive phosphorous-containing curing agent

In an attempt to improve thermal and flame-retardant properties of epoxy resins efficiently, a new reactive phosphorus-containing curing agent called 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl-(phenylimino)-(4-hydroxyphenyl)me-thane (DOPO-PHM) was synthesized and was combined with 4,4′-diaminodiphenyl methane (DDM) to co-cure epoxy resins (E51), which covalently incorporated halogen-free DOPO organ groups into the epoxy networks. The chemical structure of this curing agent was confirmed by FTIR, 1D, and 2D NMR spectra. A reaction mechanism during the preparation was proposed, and the electron effect on the stabilization of the carbocation was discussed. Various DDM/DOPO-PHM molar ratios were used to get the materials with different phosphorus contents. Their dynamic mechanical, thermal, and flame-retardant properties were evaluated by dynamic mechanical thermal analysis, thermogravimetric analysis, and limiting oxygen index (LOI) respectively. All samples had a single Tg, showing that these epoxy resins were homogeneous phase for long-term use in spite of adding DOPO-PHM. Both char yields (under nitrogen and air atmospheres) increased with the increasing of phosphorus content and the LOI values increased from 24.5 for standard resin to 33.5 for phosphorus-containing resins, indicating the significant enhancement of thermal stability and flame retardancy. POLYM. ENG. SCI., 54:1192–1200, 2014. © 2013 Society of Plastics Engineers

Synthesis, characterization and flame-retardant properties of epoxy resins and AACHH composites

Flame retardant epoxy resins were prepared by a simple mixed method using ammonium aluminum carbonate hydroxy hydrate (AACHH) as a halogen-free flame retardant. The prepared samples were characterized by X-ray diffraction, thermogravimetric and differential scanning calorimetry, scanning electron microscope and limiting oxygen index(LOI) experiments. Effects of AACHH content on LOI of epoxy resins/AACHH composite and flame retardant mechanism were investigated and discussed. Results show that AACHH exhibites excellent flame-retardant properties in epoxy resin(EP). When the content of AACHH was 47.4%, the LOI of EP reached 32.2%. Moreover, the initial and terminal decomposition temperature of EP increased by 48°C and 40 °C, respectively. The flame retarded mechanism of AACHH is due to the synergic flame retardant effects of diluting, cooling, decomposition resisting and obstructing.