| Summary: | 碩士 === 國立清華大學 === 化學工程學系 === 104 === Ethylene vinyl alcohol (EVOH) is a random copolymer of ethylene and vinyl alcohol, which has been widely used for food package due to its excellent barrier property against oxygen, moisture and organic solvents. With the objective of further enhancing the barrier, mechanical and thermal properties of EVOH, here we investigate the nanocomposite of EVOH with surfactant-modified montmorillonite nanoclay.
A fraction of the EVOH chains were found to be intercalated between the clay galleries, leading to a swelling of the interlamellar distance of clay platelets from 1.9 nm to 3.4 nm. This is the best degree of intercalation having been achieved in this type of nanocomposite with EVOH. The EVOH-intercalated platelets stacked coherently over a limited length (ca. 10 nm), forming the dislike clusters which further aggregated to construct a fractal superstructure with the mass fractal dimension of ca. 2.8. Consequently, the morphology of the nanocomposite was characterized by a hierarchical structure with three distinct levels, i.e., the EVOH-intercalated clay platelets (level one) stacked to form disklike clusters (level two) which further constructed a fractal network.
The addition of a small amount of clay ( ~ 1 wt%) accelerated the crystallization of EVOH slightly, showing the effect of nucleating agent. However, EVOH crystallization was slowed down drastically upon the addition of 5 wt% of clay. The thermal stability of EVOH was significantly enhanced by forming the composite with clay.
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