Nylon 11/organoclay nanocomposites have been successfully prepared by melt-compounding.X-ray diffraction and transmission electron microscopy indicate the formation of the exfoliated nanocomposites at low clay concentrations (less than 4 wt%) and a mixture of exfoliated and intercalated nanocomposites at higher clay contents.Thermogravimetric and dynamic mechanical analyses as well as tensile tests show that the degree of dispersion of nanoclay within polymer matrix plays a vital role in property improvement.The thermal stability and mechanical properties of the exfoliated nylon 11/clay nanocomposites (containing lower clay concentrations) are superior to those of the intercalated ones (with higher clay contents),due to the finer dispersion of organoclay among the matrix.

The microstructure,morphology, thermal and mechanical properties of polyamide 6/layered-silicate nanocomposites (PLSN) have been studied using X-ray diffraction (XRD),tapping-mode atomic force microscopy (AFM),differential scanning calorimetry (DSC) and tensile tests.The XRD and AFM results indicate that the organically-modified layered silicates are intercalated in the polyamide 6 (PA6) matrix.Also,the crystallization and thermal behavior of PA6 are influenced by the addition of layered silicates into polymer matrix.A silicate-induced crystal transformation from the a-form to the g-form of PA6 is confirmed by XRD and DSC,i.e.,the formation of g crystal is enhanced by the presence of silicates.In comparison to PA6,the thermal property of PLSN has been investigated using DSC.The possible origins of a new silicate-induced endothermic peak are discussed.Tensile tests show that the tensile modulus and yield strength increase while the strain-at-yield decreases with increasing clay loading.

The multiple melting behacior and lamellar morphologies of isotactic polystyrene (iPS) isothermally crystallized from the glassy state have been investigated by differential scanning calorimetry (DSC) and transmission electron microscopy (TEM).The influences of different experiment variables (such as crystallization temperature and time,heating rate) on the melting behavior of iPS are studied.The combination of thermal analysis and morphological results indicates that:(1)the ‘annealing peak’ is not associated with the melting of subsidiary crystals formed by secondary crystallization as often suggested in the literature;(2)two lamellar population with different degrees of perfection within a single lamella are responsible for the so-called double melting behavior in iPS.The partial melting and repairing (via recrystallization) of iPS crystals are observed on lamellar level by TEM observations.From the obtained calorimetric and morphological results,the applicability of several crystallization and (subsequent) melting models is discussed.