Polymer nanocomposites using zinc aluminum and magnesium aluminum oleate layered double hydroxides: Effects of LDH divalent metals on dispersion, thermal, mechanical and fire performance in various polymers

Abstract

Abstract:Oleate-containing layered double hydroxides of zinc aluminum (ZnAl) and magnesium aluminum (MgAl) were used to prepare nanocomposites of polyethylene, poly(ethylene-co-butyl acrylate) and poly(methyl methacrylate). The additives and/or their polymer composites were characterized by X-ray diffraction, FTIR, elemental analysis, thermogravimetric analysis, mechanical testing, and cone calorimetry. The unusual packing of the monounsaturated oleate anions in the gallery of these LDHs facilitates the dispersion of these nanomaterials. The inorganic LDH protects the polymer from thermal oxidation, shown by enhancement of the thermal and fire properties of the corresponding polymer nanocomposites. There is a qualitative difference in the morphology of the two LDHs in PE and PMMA. ZnAl is better dispersed in PE while MgAl is better dispersed in PMMA. The zinc-containing material led to a large reduction in the peak heat release rate in polyethylene, while the magnesium-containing material led to enhancement of the fire properties of the more polar poly(methyl methacrylate). These fire properties are consistent with the morphological differences. Neither of these LDHs shows efficacy with poly(ethylene-co-butyl acrylate), which indicates a selective interaction between the LDH and the various polymers.

The effect of boron-containing layered hydroxy salt (LHS) on the thermal stability and degradation kinetics of poly (methyl methacrylate)

“…8 respectively. The plots show that pure PMMA (commercial; MW 120,000) degradation under the heating profiles used here is a two step process regardless of the atmosphere being used which is in agreement with results obtained by other workers [26]. The two steps in the degradation of PMMA have been attributed to scission at the vinyl terminated end and to random scission of the PMMA back bone respectively [27].…”

“…14 and the summary of results presented in Table 4 is the significant lowering of the peak heat release rate by up to 48% for PMMA/ZHTMDBB-10. The reduction of PHRR obtained here is comparable to values obtained for LDH systems [14], [26] and [33] and this shows that the LHS system studied here is equally effective in reducing PHRR of PMMA as LDH systems. The lowering of the PHRR or increase in the limiting oxygen index has been shown to correspond with the increase in the production of char for condensed phase FR [1] and [9].…”

Thermal and flammability study of polystyrene composites containing magnesium–aluminum layered double hydroxide (MgAl–C16 LDH), and an organophosphate

“…However, there were little increases in the composites which had the LDH additive, with the composite having 5 mass% loading of the LDH having a higher increase than the one with 10 mass% loading. The decrease in thermal stability at higher clay loading observed here has been reported elsewhere and has been attributed to the large content of organic anions which destabilize char formation process during pyrolytic degradation [36,37]. The increased thermal stability for a loading of 10 mass% of DPP may be due to the radical trapping effect of DPP that increases the thermal stability and also enhances charring.…”

Nanocompósitos poliméricos de polietileno de alta densidade contendo hidróxidos duplos lamelares intercalados com anions derivados de corantes azo

“…Essa observação vai à direção oposta do que é geralmente observado para HDLs utilizados como cargas em polietileno [23][24][25] , quando maiores cargas, de modo geral, preconizam um aumento da estabilidade térmica do polímero. Esse fenômeno da diminuição da estabilidade do PEAD observado nos picos de DTA e nos onsets das Para avaliar a estrutura do nanocompósito obtido, efetuou-se a análise dos corpos de prova por difração de raios X (Figura 11).…”