Four organically modified montmorillonite (OMMT) clays were prepared by exchanging Na⁺ ions in silicate layers with organic modifiers: 1-aminododecane, n-octadecylamine, trimethylstearyl ammonium chloride and tributylhexadecyle phosphonium bromide. OMMT clays were mixed with biodegradable polymers, polylactic acid (PLA) and polybutyrene succinate (PBS), by melt intercalation. In order to characterize the composites, the average number of regularly stacked silicate layers (N) and average interparticle distance (ξ) of OMMT were determined by transmission electron microscopy and X-ray diffraction, respectively. Dynamic viscoelastic measurements and differential scanning calorimetory were also carried out. The chemical interaction between polar groups of the organic modifier and matrix polymer played an important role in the intercalation process, and residual Na⁺ ion hindered delamination of the silicate layers. Modulus of the composites increased significantly when ξ was smaller than 80nm. OMMT behaved as a nucleating agent and enhanced the crystallization rate in PLA based nanocomposites.

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Side-by-side bicomponent fibers consisting of poly (ethylene terephthalate) (PET) with different molecular weights, i. e. high molecular weight virgin PET and low molecular weight PET recycled from post consumer bottles were prepared by melt spinning, continuous drawing, and postdrawing heat treatment processes. The effects of process conditions on the higher-order structure and crimp formation of resultant fibers were investigated. The structure of each component in the bicomponent fibers was evaluated through an analysis of birefringence and Lorentz density, which are based on refractive index measurements using an interference microscope. Distinct crimp formation was observed for the high-speed spun fibers prepared at take-up velocities higher than 5km/min. In comparison with the respective single component fibers, the birefringence of the high molecular weight component increased and that of the low molecular weight component decreased. Accordingly, there was a significant birefringence difference between the two components in the high-speed spun bicomponent fibers with severe crimp formation. Intensive crimp formation was also observed for fibers prepared by drawing the melt spun fibers at relatively low take-up velocities to a draw ratio close to their respective limits. In these drawn fibers, the birefringences of both components were high and the birefringence difference between the two components was small in comparison with the high-speed spun fibers. For fibers drawn at various drawing temperatures, a smaller radius of curvature in the crimps was observed for fibers with a larger birefringence difference between the two components. When a combination of polymers with smaller molecular weight difference was used, a similar degree of crimp was observed for bicomponent fibers with the smaller birefringence difference. In other words, there is no universal relationship between the birefringence difference between the two components and the radius of curvature, and the relation varies depending on the combination of polymers used for the preparation of fibers. High temperature heat treatment of fibers drawn at low drawing temperatures was found to be a most effective method for the preparation of crimped fibers with small radii of curvature. In these fibers, surprisingly, the radius of curvature decreased with decreasing birefringence difference between the two components.

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