Study On The EVOH/MMT Nanocomposite

In the thesis, the montmorillonite (MMT) was treated by polyvinyl pyrrolidone and hexadecyl quaternary ammonium salt respectively to get two kinds of montmorillonite with good intercalation written as PVP-MMT and HD-MMT, and then the ethylene-vinyl alcohol copolymer (EVOH)/PVP-MMT nano-composites were prepared by dynamic melt blending. The phase morphology as well as the crystallization behavior of the nano-composites were characterized by using X-ray diffraction (XRD), atomic force microscope (AFM) and differential scanning calorimetry (DSC).XRD indicate that EVOH intercalate into the galleries of montmorillonite, the less content of PVP-MMT, the larger of interlamellar spacing will be. When the content of PVP-MMT is 8%, the exfoliated nano-composites are produced, and the intercalated nano-composites could be prepared as the content is 15%. Additionally, the interlamellar spacing has no clear changes after PVP-MMT content exceeds 15%. AFM indicate that the nanocomposites with 8% PVP-MMT have a more uniform distribution and smooth surface than nanocomposites containing 20% PVP-MMT. The interaction between polymer matrix and MMT observed in nanoscale is obtained, from which the analogical crystallization was found in these micrographs, and the nanocomposites expose ordering structure due to the ordered segment of EVOH. The result of DSC shows that the heterogeneous nucleation acting of montmorillonite lamella treated by quaternary ammonium salt in the crystallization process is not distinct. In same condition, the rate of crystallization of EVOH/PVP-MMT is higher than that of EVOH. The Tc of the nanocomposites decreases from 159.7℃(EVOH) to 153.1℃, and the T_m decreases from 180.7℃to 175.2℃due to the mixing of MMT. However, the T_g of EVOH/PVP-MMT increases about 2.6℃comparing with that of EVOH. The water resisting property of the nanocomposites with 5%, 10% PVP-MMT increase 3.3% comparing to that of neat EVOH, which is good for barrier property as the EVOH/PVP-MMT nanocomposites using as packing materials. What is over, the relative adsorption quantity of water have a little change when the PVP-MMT content reach 20% in nanocomposites. The extrusive material is smooth and its performance is good, when the temperature is set at above 200℃and the shear rate at about 20rpm; The melt of EVOH/PVP-MMT composite is a type pseudoplastic fluid, and the viscosity decreases with the increase of the shear rate, which is a shear-thinning phenomenon; The flowing property decreases and the viscosity increases, when the amount of montmorillonite increases; The viscosity of EVOH/PVP-MMT composite decrease with the increase of the temperature, and the change is puny, so the material can be machininged in wide temperature.