Abstract
The effects of a magnesium-based layered composite on the flammability of a phenolic epoxy resin (EP) are studied. In order to produce the required composite material, first, magnesium hydroxide, aluminum salt and deionized water are mixed into a reactor according to a certain proportion to induce a hydrothermal reaction; then, the feed liquid is filtered out using a solid-liquid separation procedure; finally, the material is dried and crushed. In order to evaluate its effects on the flammability of the EP, first, m-phenylenediamine is added to EP and vacuum defoamation is performed; then, EP is poured into a polytetrafluoroethylene mold, cooled to room temperature and demoulded; finally, the magnesium-based layered composite is added to EP, and its flame retardance is characterized by thermogravimetric analysis, limiting oxygen index and cone calorimetry. The X-ray diffraction patterns show that the baseline of magnesium-based layered composite is stable and the front shape is sharp and symmetrical when the molar ratio of magnesium to aluminium is 3.2:1; with the addition of magnesium-based layered composite, the initial pyrolysis temperature of EP of 10%, 15% and 30% magnesium-based layered composite decreases to 318.2°C, 317.9°C and 357.1°C, respectively. After the reaction, the amount of residual carbon increases to 0.1%, 3.45% and 8.3%, and the limiting oxygen index increases by 28.3%, 29.1% and 29.6%, respectively. The maximum heat release rate of cone calorimeter decreases gradually. The optimum molar ratio of Mg:Al for green synthesis is 3.2:1, and the NO3- intercalated magnesium-based layered composite has the best flame retardance properties.
Highlights
Layered double hydroxides (LDHs) are layered materials composed of positively charged main lamina, negatively charged interlayer anions and interlayer water molecules, known as hydrotalcite or hydrotalcite-like compounds [1]
The more the amount is, the better the smoke suppression performance is; the experimental results of thermal energy analysis based on MgAl-LDHs intercalated with different anions show that during the heating process, the LDHs intercalated with three different anions can promote the carbon formation efficiency of epoxy resin (EP), so as to improve the flame retardancy of EP; the results of limiting oxygen index (LOI) analysis of MgAl-LDHs intercalated with different anions show that MgAlNO3-30%, MgAl-Cl-30% and MgAl-SO4-30% have certain flame retardancy in EP matrix; the cone calorimetric analysis results of MgAl-LDHs based on different anion intercalations show that among the three MgAl-LDHs, MgAl-NO3-LDHs has the best flame retardant performance in EP matrix
Magnesium-based LDHs are green synthesized by a new method and added to the EP matrix
Summary
Layered double hydroxides (LDHs) are layered materials composed of positively charged main lamina, negatively charged interlayer anions and interlayer water molecules, known as hydrotalcite or hydrotalcite-like compounds [1]. Based on the two aspects of green synthesis MgAl-LDHs addition and anion intercalation, three characterization methods including thermogravimetric analysis, limiting oxygen index (LOI) and cone calorimetry are adopted to evaluate the effect of MgAl-LDHs on the flame retardance of EP [8]. To deal with the characteristics of easy combustion of EP, green synthetic magnesium-based layered composite is introduced to EP for flame retardant. The green synthesis of magnesium-based layered composite is carried out by introducing the characteristics of magnesium-based layered composite and the evaluation method of their flame retardant properties. On this basis, thermogravimetric analysis, LOI and cone calorimetry are adopted to study the flame retardant properties of magnesium-based layered composite. The magnesium-based layered composite is added to EP, and its flame retardance is evaluated, which has a certain reference value for the flame retardance application of this kind of product
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