| Summary: | 博士 === 中原大學 === 化學研究所 === 101 === Poly-ethylene terephthalate (PET)/ MgAl or LiAl layered double hydroxides (LDH) nanocomposites were successfully prepared by polycondensation of bis(2-hydroxyethyl) terephthalate (BHET) mixing sulfanilic acid sodium salt hydrate (SAS) modified - LDH or dimethyl 5-sulfoisophthalate (DMSI) - modified LDH. Effects of MgAl or LiAl LDH contents on the crystallization, mechanical properties, thermal stability and barrier properties of the PET/LDH nanocomposites were discussed.
The MgAl LDH and LiAl LDH were synthesized by hydrothermal reaction with the different of aspect ratio and AEC (anionic exchange capacity). The modified LDH, synthesized by hydrothermal reaction, can promote the compatibility both of LDH and PET matrix. The d-spacing of modified- LDH by XRD (X-ray diffraction) measurement and corroboration by JCPDS (Joint Committee on Powder Diffraction Standars). Function groups of modified agents intercalated into LDH galleries, were provide by FT-IR (Fouier Transform Infrared) spectrum. Not only interlayer anion of modified LDH, but also contents of modified agents were calculated and analyzed by TGA (Thermogravimetry Analyzer).
Both XRD data and TEM (Transmission Electron Microscopy) micrographs of PET/MgAl LDH-SAS nanocomposites indicate the co-existence of island type exfoliated and intercalated morphologies. TEM images provide the island type intercalated morphologies of PET/MgAl LDH-DMSI whereas sea type intercalated and exforliated morphologies of PET/LiAl LDH nanocomposites.
The crystallization behaviors and kinetics of PET and PET/LDH nanocomposites were investigated by using DSC (Differential Scanning Calorimetry). Two stages heating/cooling and non-isothermal melt-crystallization results show that the addition LDH into PET induced nucleation in the crystallization that significantly increases crystallization rate. Decreasing of the crystallization rate is PET/LiAl LDH-DMSI > PET/MgAl LDH-SAS > PET/LiAl LDH-SAS > PET/MgAl LDH-SAS.
Mechanical properties of PET and PET/LDH nanocomposites were investigated by using DMA (Dynamic Mechanical Analyzer). The result indicate that the best of storage modulus is increased from 1790 Mpa for pristine PET to 3271 Mpa for PET/MgAl LDH-SAS-1.0 wt% nanocomposites.
Thermal properties of PET and PET/LDH nanocomposites were investigated using TGA (Thermal Gravimetry Analyzer). The result indicate the best of decomposed temperature is increased from 383 ℃ for pristine PET to 405 ℃ for PET/LiAl LDH-SAS-1.0 wt% and PET/ LiAl LDH-DMSI 1.0 wt% nanocomposites.
The UV-visible barrier properties of PET and PET/LDH nanocomposites were measured by UV-visible spectrophotometer. It indicates that the UV light transmittance is decreased from 79.3 % for pristine PET to 39.3 % for PET/LiAl LDH-SAS-1.0 wt% nanocomposites at the wavelength 375 nm.
The gas barrier property of PET and PET/LDH nanocomposites were measured by GPA (gas permeability analyzer). The result indicate the best of BIF (Barrier Improvement Factor) is 4.5 (O2), 5.3 (N2) and 8.6 (CO2) for PET/MgAl LDH-SAS-1.0 wt% nanocomposites.
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