| Summary: | 博士 === 中原大學 === 化學研究所 === 105 === Layered double hydroxides (LDHs) and clay are common inorganic layered hydroxides. In this study, three types of synthetic LDHs used and modified with sufanilic acid by ion exchange method. A natural montmorillonite (CL120) modified with Dimethyloctadecyl [3- (trimethoxysilyl) propyl] ammonium chloride (DTSACl) and Tetraethyl orthosilicate (TEOS) by sol gel method. These modified and pure inorganic layered materials (LDHs, Clay) were investigated by using X-ray Diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) to monitor the changes in the interlayer spacing, weight loss and functional groups of modified LDHs and CL120, respectively. The morphology and structures of LDH, and CL120 were observed by scanning electron microscope (SEM), while the amount of modifier intercalated into the LDH, and CL120 layers were calculated by TGA analysis.
In this report, we have been synthesized three kinds of polyethylene terephthalate / modified inorganic layered material nanocomposites. At first, polyethylene terephthalate / organomodified-layered double hydroxide (PET/organo-LDH) nanocomposites were successfully synthesized via a melt extrusion method. In an attempt to improve the compatibility with PET, and surface modified LiAl, MgAl and ZnAl LDHs. In PET nanocomposites containing SAS modified LDHs, the (00l) X-ray diffraction (XRD) peaks originating from organo-LDH were not observed, indicating that organomodified LDH layers were homogeneously dispersed within the PET matrix, which was also confirmed by TEM analysis. PET nanocomposites containing SAS modified LiAl, MgAl, and ZnAl LDH showed that organo-LDH was intercalated, flocculated and partially exfoliated morphologies, respectively. According to the TGA it was confirmed that the thermal stability of PET/organomodified-LDH nanocomposites significantly improved, depending on the type and loading content of organo-LDH compared to that of pure PET. PET nanocomposites substantial enhancement of the storage modulus and gas barrier properties were observed.
Secondly, PET/ZnAl LDH-SAS nanocomposites were prepared by intercalation, followed by in situ polymerization using Bis (2-hydroxyethyl) terephthalate (BHET) monomer. To enhance the compatibility between PET and the modified ZnAl LDH, the sodium salt of sulfanilic acid (SAS) had been previously intercalated in the LDH. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to detect the degree of dispersion of the filler and the type of the polymeric composites obtained. As identified by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), the crystallization rate and the thermal degradation temperature of the as-prepared PET nanocomposites sample were enhanced compared with the pure PET sample. The results indicated that the ZnAl LDH-SAS improves the interlayer compatibility between the PET and ZnAl LDH-SAS layers, thus making it easier for the oligomer to enter the gallery of ZnAl LDH-SAS layers. Hence, polymer chains can be intercalated between the LDH layers during the polymerization of the polymer matrix. The gas barriers and mechanical properties of these new types of PET nanocomposites were investigated.
Finally, PET/MgAl LDH-SAS or CL120-DT nanocomposites were successfully synthesized using Bis (2-hydroxyethyl) phthalate (BHEP) monomer by in situ polymerization method. Dispersion morphology of nanocomposites elevated by XRD and TEM, from these results it was confirmed that 1.0 wt% loaded PET/MgAl LDH-SAS and PET/CL120-DT nanocomposites were partially intercalated and aggregated morphology. From the DSC analysis, it is evidenced that regarding the effect of MgAl LDH-SAS and CL120-DT content on the melting temperatures (Tm) values of PET nanocomposites are virtually unchanged, regardless of MgAl LDH-SAS and CL120-DT loading. The extracted Moisture Vapor Transmission Rate (MVTR) value for pure PET was found to be 49 g·m−2·d-1. This value is in good accordance with the literature value for PET. For the nanocomposites PET/CL120-DT 0.5 wt% and PET/MgAl LDH-SAS 0.5 wt%, the MVTR values were 45 and 46 g·m−2·d−1, respectively. It is worth mentioning that in general, the transmission of the water vapor is strongly related to the nanofiller dispersion. The Oxygen Transmission Rate (OTR) was ranging from 128 to 88 cc/m2/day/atm whereas, the control recorded (90% RH) ranging from 109 to 86 cc/m2/day/atm. It was also observed that the maximum reduction in OTR over the control was 90% RH for the treatment 0.5 wt% clay loaded nanocomposites and there was no significant difference between the treatments 0.3 wt% loaded samples. The optical properties of PET composite films containing various amounts of inorganic nanoparticles are transparent. The transmittance was found in the hybrid film containing LDH or CL120 nanoparticles contents in the matrix, beyond which the transmittance was slightly decreased as compare to pure PET.
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