Organoclay polybutylene terephthalate nanocomposites using dual surfactant modified montmorillonite prepared by the masterbatch method

This paper reports the application of dual-surfactant, thermally stable organoclays (OC) to the production of poly(butylene terephthalate) (PBT) nanocomposites by the masterbatch method. A common failing of single surfactant organoclays is their thermal instability at high polymer processing temperatures, such as that used for PBT (235°C). This can be overcome by first modifying the clay mineral with a thermally stable surfactant such as aminopropyl-POSS (AP-POSS). In this study, sodium montmorillonite (Na+Mt) was sequentially modified with AP-POSS and ditallowdimethylammonium chloride by ion-exchange reaction to give dual-surfactant organoclay (OC). This dual surfactant clay mineral was then used to prepare masterbatches comprising 40% clay mineral intercalated with CBT polymerized by ring-opening polymerization. The masterbatches were then processed with PBT by melt compounding to give PBT-clay nanocomposites whose morphology was studied by XRD and TEM and mechanical properties were assessed by tensile testing. Spectral examination showed that the dual surfactant clay mineral was readily intercalated by PBT, while electron microscopy revealed that an intercalated/exfoliated micromorphology was achieved. The elastic modulus and tensile strength of PBT were increased by inclusion of dual-surfactant clay, while the reduction in elongation typically associated with nanoclay inclusion was mitigated by the dual surfactant clay. The possible antagonism of the catalyst used in the ring-opening polymerization and the reinforcing effect of the dual surfactant clay is also discussed.