Abstract
Ethylene vinyl acetate (EVA) copolymer has been used extensively in many fields. However, EVA is flammable and releases CO gas during burning. In this work, a composite flame retardant with ammonium polyphosphate (APP), a charring–foaming agent (CFA), and a layered double hydroxide (LDH) containing rare-earth elements (REEs) was obtained and used to improve the flame retardancy, thermal stability, and smoke suppression for an EVA matrix. The thermal analysis showed that the maximum thermal degradation temperature of all composites increased by more than 37 °C compared with that of pure EVA. S-LaMgAl/APP/CFA/EVA, S-CeMgAl/APP/CFA/EVA, and S-NdMgAl/APP/CFA/EVA could achieve self-extinguishing behavior according to the UL-94 tests (V-0 rating). The peak heat release rate (pk-HRR) indicated that all LDHs containing REEs obviously reduced the fire strength in comparison with S-MgAl. In particular, pk-HRR of S-LaMgAl/APP/CFA/EVA, S-CeMgAl/APP/CFA/EVA and S-NdMgAl/APP/CFA/EVA were all decreased by more than 82% in comparison with pure EVA. Furthermore, the total heat release (THR), smoke production rate (SPR), and production rate of CO (COP) also decreased significantly. The average mass loss rate (AMLR) confirmed that the flame retardant exerted an effect in the condensed phase of the composites. Meanwhile, the combination of APP, CFA, and LDH containing REEs allowed the EVA matrix to maintain good mechanical properties.
Highlights
Ethylene vinyl acetate (EVA) copolymer is used extensively in many different fields, such as the wire, cable, and wrapper industries [1]
A 0.5 mol amount of intermediate II and a mixed solution containing 0.5 mol ethylenediamine and 1.0 mol sodium hydroxide in 500 mL water were added into a 2000 mL four-neck flask provided ethanolamine in acetone and a solution of sodium hydroxide were simultaneously added dropwise with a stirrer, a thermometer, and a reflux condenser, and the reacting solution was kept under reflux into the four-neck flask and the experimental temperature was kept at 0–5 ◦ C
Four LDHs revealed the typical layered double hydroxide structures with sharp and symmetrical characteristic diffraction peaks, namely (003), (006), (012), (015), (018), (110), and (113), which were indexed in a hexagonal lattice with an R3m rhombohedral space group symmetry
Summary
Ethylene vinyl acetate (EVA) copolymer is used extensively in many different fields, such as the wire, cable, and wrapper industries [1]. In recent years, layered double hydroxides (LDHs) and intumescent flame retardants (IFRs) have been used to increase the flame retardancy and smoke suppression of the EVA matrix [3,4]. The reported IFRs. Materials 2020, 13, 1251 consisted of ammonium polyphosphate (APP) and CFA; when the mass ratio of APP and CFA was equal to 3:1, the EVA matrix had the best flame retardancy [12]. REEs, LDHs, and IFRs on the flame retardancy of EVA has not been reported. The new flame-retardant system including APP, CFA, and LDH containing a transition element have been used to enhance the flame notretardancy only maintained of EVA their [13]. LDHs, and IFRs on the flame retardancy of EVA has not been reported. Sodium hydroxide (99%), sodium obtain a novel composite flame retardant of EVA.
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