Abstract
The effects of transition metals on the hydrophobicity of nano–structured layered double hydroxides (LDHs) and the compatibility of LDHs/ethylene vinyl acetate (EVA) composites have seldom been reported. NiMgAl–LDHs slightly surface–modified with stearate and doped with transition metal cations (Mn2+, Co2+, Cu2+, Zn2+) are investigated. Compared to the pure EVA, not only were the maximal degradation–rate temperatures (Tmax) of the ethylene–based chains enhanced, but also the smoke production rate (SPR) and the production rate of CO (COP) were sharply decreased for all the composites. Most importantly, a new flame retardant mechanism was found, namely the peak heat release rate (pk-HRR) time, which directly depends on the peak production rate of CO2 (pk-CO2) time for EVA and all composites by cone calorimeter test. Moreover, the Mn–doped LDH S–NiMgAl–Mn shows more uniform dispersion and better interfacial compatibility in the EVA matrix. The cone calorimetric residue of S–NiMgAl–Mn/EVA has the intumescent char layer and the compact metal oxide layer. Therefore, S–NiMgAl–Mn/EVA shows the lowest pk-HRR and the longest pk-HRR time among all the composites.
Highlights
The ethylene vinyl acetate (EVA) copolymer is an important thermoplastic elastomer used in many fields, such as wires, cables, wrappers, encapsulations, adhesive and the drug industries [1,2,3,4,5,6].EVA is flammable and its subsequent combustion emits toxic smoke CO which limits its application in numerous fields
We explored NiMgAl–layered double hydroxides (LDHs) with rare earth ions to improve the hydrophobicity of LDHs
This study mainly focuses on the effects of the transition metal ions on the crystallinity, morphology, thermal property and hydrophobicity of the LDHs
Summary
The ethylene vinyl acetate (EVA) copolymer is an important thermoplastic elastomer used in many fields, such as wires, cables, wrappers, encapsulations, adhesive and the drug industries [1,2,3,4,5,6]. Layered double hydroxides (LDHs) are a kind of layered materials that consist of positively charged layers and the interlayer anions. Their general formula can be represented as [M2+ 1 ́x M3+ x (OH)2 ]x+ [An ]x /nmH2 O, where M2+ and M3+. Sci. 2016, 6, 131 treatment can enhance the hydrophobicity of LDHs, the use of large amounts of organic modifiers is detrimental to the flame retardancy of LDHs/polymer composites due to the existence of large amounts of carbon, but is not environment–friendly. This study mainly focuses on the effects of the transition metal ions on the crystallinity, morphology, thermal property and hydrophobicity of the LDHs. the influences of the transition metals on the thermal properties and flame retardancy of LDHs/EVA composites are investigated
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