Synthesis and Properties of PET/Clay Nanocomposites

Abstract

Poly(ethylene terephthalate) (PET)/clay nanocomposites with various clays were synthesized by using in-situ polymerization. In order to prepare enhanced PET/clay nanocomposite (PCN), the pristine clay was newly modified for increasing compatibility with PET. The pristine clay was modified by two different methods which were organic modification by cationic exchange method and novel clay treatment from synthesizing ester oligomer under ethylene glycol (EG) swollen montmorillonite (MMT). The organic modification of the pristine MMT in this dissertation was based on N-methyl diethanol amine (MDEA). Four kinds of organifiers, MDEA I, MDEA II, MDEA III and MDEA IV were successfully prepared and then four types of organoclays, such as MDI-OC, MDII-OC, MDIII-OC and MDIV-OC were prepared with these organifiers by cationic exchange process. The organifiers were inserted to interlayers of the organoclays and the d-spacing values varied from 14 to 21 Å. MDII-OC had the largest d-spacing value among the organoclays but its thermal stability was not insufficient for preparing PCN. MDIII-OC and MDIV-OC had relatively small d-spacing values but their thermal stability and reactivity was estimated to good enough for preparing PCN from thermogravimetric analysis (TGA) and structure identification. Novel clay treatment for PCN was first proposed in this thesis. The novel clay treatment was based on synthesizing ester oligomer under MMT dispersed EG circumstance. The optimum condition for preparing MMT dispersed ester oligomer were investigated by controlling equivalent ratio between acidic reactants (1, 2, 4-Benzenetricarboxylic anhydride (TMA), isophthalic acid (IPA)) and EG. The optimum equivalent ratio of the ester oligomers was 1 acidic reactants / 1.5 EG from the wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS) and TGA analysis. The structure of the ester oligomer was confirmed by NMR spectrum. The dispersibility of the clay in the ester oligomer ma...