Structure and properties of nanocomposites based on poly(butylene succinate) and supercritical carbon dioxide-processed montmorillonite

Abstract

Montmorillonite is intercalated with different amounts of tetradecyltrihexylphosphonium chloride in supercritical carbon dioxide and poly(butylene succinate)-based nanocomposites are prepared with the organically modified or commercial organoclay via melt-mixing. The effect of amount of tetradecyltrihexylphosphonium chloride on the structure of organically modified montmorillonite tactoids, organically modified montmorillonite dispersion and finally on properties of nanocomposites is systematically investigated. Different from the compact spherical structure for pristine montmorillonite tactoids, flexible expanded structure with large cavities on the surface can be obtained for organically modified montmorillonites, and their structure show slight difference with the tetradecyltrihexylphosphonium chloride amount. It is interesting to find that, despite almost no polymer molecule being intercalated into the interlayer, significant dispersion can be achieved for the scCO2-processed organically modified montmorillonite in polymer matrix, due to the easily broken tactoid structure. It is noteworthy, montmorillonite-tetradecyltrihexylphosphonium chloride 08, which is modified with 0.8 CEC tetradecyltrihexylphosphonium chloride, less than in most of the literature, shows almost the same degree of dispersion in poly(butylene succinate) matrix as commercial montmorillonite, which has a stronger interaction with the polymer. Differential scanning calorimetry and dynamic modulus analysis results demonstrate that the crystallization temperature and storage modulus of poly(butylene succinate)-based nanocomposites increase with the amount of tetradecyltrihexylphosphonium chloride, and montmorillonite-tetradecyltrihexylphosphonium chloride08/poly(butylene succinate) shows even higher crystallization temperature and low-temperature storage modulus compared to commercial montmorillonite/poly(butylene succinate).