Preparation Of EVA/LDH Composites And Study On Their Structure And Properties

Layered double hydrotalcides (LDHs) as the host to prepare polymer/inorganic layered nanocomposites have unique characteristic of sandwich structure. The layerd structure and the exchangeability of anion in the layer space are necessary to prepare nanocomposites. Polymer/LDH composites attract much attention because of their prospective applications in absorption, ion exchange, catalyzing, light, electricity and magnetic fields.In this paper, two kinds of modified LDH, surface modified LDH by titanate coupling agent (S-LDH) and interlayer modified LDH by sodium sodecyl sulfate (I-LDH), were used to prepare EVA/LDH composites. The structure of modified LDH and their composites were analyzed by X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The effects of the composites structure on thermal stability, charring, crystallinity and mechanical properties were also discussed by thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and other means.Following results can be obtained in the paper. (1) The modified LDH had different structure. Compared with pristine LDH, S-LDH showed well dispersed structure with unchanged layer space while I-LDH showed increased layer space distance by successful intercalation of SDS. (2) The structure of modified LDH played important role in the structure of composites. EVA/S-LDH was microcomposites with the same interlayer space with pristine LDH while EVA/I-LDH was nanocomposites with exfoliated and intercalated structure at 5% and 30% loading of LDH, respectively. (3) Thermal stability of composites decreased thanks to the lower decomposition temperature of LDH. But the thermal stability of main chains increased owing to the charring effect of LDH. The charring effects of LDH depended on the structure and the loading levels of crystallizing process of EVA was not affected by LDH, but the increasing LDH. EVA/I-LDH with 30% LDH showed better charring effect. (4) The crystallizing process of EVA was not affected by LDH, but the increasing crystallinity of EVA thanks to S-LDH and I-LDH as heterogeneous nucleation. Such effect was enhanced by the formation of nano-structure of LDH. (5) For the composites with the same amout of LDH, EVA/I-LDH had greater maximum stess than the other two composites due to the nano-sturcture while EVA/S-LDH had greater maximum stress than EVA/LDH due to the improved compatibility. The systems with modified LDH showed better elongation than that with LDH.