Effect of Ni cations and microwave hydrothermal treatment on the related properties of layered double hydroxide–ethylene vinyl acetate copolymer composites

Abstract

The effect of Ni cations and synthetic methods on the crystallinity, morphology, thermal stability and hydrophobic properties of carbonate-containing layered double hydroxides (LDHs) was investigated. The conventional hydrothermal treatment (CHT) and microwave hydrothermal treatment (MHT) methods were used to synthesize LDHs. The microwave treatment LDHs (MgAl-MHT and NiMgAl-MHT) have higher crystallinity and smaller crystal sizes than the conventional hydrothermal treatment LDHs (MgAl-CHT and NiMgAl-CHT). IR results indicate that the interactions of both OH −– CO 3 2 - and CO 3 2 - – CO 3 2 - in NiMgAl-MHT are weaker. Furthermore, the thermal decomposition of OH − and CO 3 2 - in the NiMgAl-MHT sample occurred earlier and faster than that of other LDHs. The contact angle values indicate that NiMgAl-MHT has the highest hydrophobicity. The influences of the LDHs on the thermal degradation and flame retardance of ethylene vinyl acetate copolymer (EVA)–LDH composites have also been studied in detail. NiMgAl-MHT has the more homogeneous nano-dispersed layers in EVA matrix. All composites enhance the thermal stability compared with the pure EVA because of the release of H 2O and CO 2. Flame retardance of NiMgAl-MHT-EVA was obviously higher than that of the pure EVA and other composites.