Preparation of poly (ethylent terephthalate)/montmorillonite nanocomposites by solution technique

Abstract

Poly (ethylene terephthalate) (PET)/montmorillonite (MMT) nanocomposites were prepared by solution technique using 50/50 phenol/ tetrachloroethane as a solvent, assisted with the ultrasonic power to promote the compatibility and dispersion of the montmorillonite in the PET solution. The PET concentrations were varied from 5, 7, and 9 %w/v. Two types of MMT: neat MMT and organoclay: MMT modified with dioctadecyl dimethyl ammonium (2C18-MMT) were used with various amount from 1, 3 and 5 phr to produce nano-scale composites. The effect of PET solution concentration, MMT types (organoclay and neat MMT), and MMT content on the physical, mechanical, and thermal properties of the PET/MMT nanocomposites were investigated. The homogeneous PET/MMT nanocomposites solution has been recieved by solution technique and ultrasonic power. The XRD results showed that the d001-spacing of organoclay (31.4 A: 20 = 2.8°) was higher than unmodified-MMT (12.5 A, 20 = 7.0° ). Besides, the XRD pattern of PET nanocomposites contained unmodified-MMT and 2C18-MMT indicated that the intercalation (15.9 A : 20 = 5.5° ) and exfoliation of clay occurs, respectively. For tensile properties, it was found that the maximum tensile strength and Young's modulus were obtained at low clay content (1 phr) and then decreased with further increase in the organoclay content due to the high interfacial properties and clay agglomeration, respectively. The optical transparency and water absorption properties of nanocomposite film were improved especially at low clay content (1 phr) resulting from the fine crystal structure formation. Thermal properties were measured by TGA and DSC. The onset of degradation temperature of nanocomposites was increased because of the good thermal barrier of clay itself. The degree of crystallinity of nanocomposites dramatically increased at 1 phr clay content due to the great dispersion and the nucleating effect of nanoclay.