Crystallization and properties of poly(ethylene terephthalate)/layered double hydroxide nanocomposites

Poly(ethylene terephthalate) (PET) generally suffers from low crystallization rate and long molding duration, which as a result limit its application as engineering plastics. To overcome these drawbacks, series of PET/layered double hydroxide (LDH) nanocomposites were prepared by a solution blending process. The effect of metal composition (MgAl and CaAl) and organo-modification (stearic acid intercalated) for LDH fillers on the crystallization behavior of the nanocomposites was investigated. It was revealed that, compared with PET/CaAl-LDH, the PET/MgAl-LDH nanocomposite exhibits a higher crystallization temperature and faster crystallization rate, which is associated with the superior nucleation ability of MgAl-LDH. The nucleation mechanism of PET induced by LDHs was explored by means of Avrami equation and theory of Hoffman-Lauritzen, pointing out that the incorporation of LDHs reduce the free energy of nucleation and the fold surface free energy of PET. In order to improve the compatibility between LDH and PET, stearic acid (SA) intercalated MgAl-LDH was prepared and filled into PET matrix. The resultant PET/MgAl-LDH-SA shows a further enhanced crystallization temperature and accelerated crystallization rate, in comparison with PET/MgAl-LDH nanocomposites. In addition, the thermal stability, gas barrier and mechanical properties of PET/LDH composites were improved upon incorporation of LDH fillers.