A study of the structures and morphologies of PET/PEN blends.

摘要

Blends of Poly (ethylene terephthalate) (PET) and poly (ethylene naphthalate) (PEN) have been analyzed in terms of their crystal structures, crystal morphologies, and crystallization kinetics. Wide angle X-ray diffraction (WAXS), small angle X-ray diffraction (SAXS), small angle light scattering (SALS), optical microscopy (OM), and density measurements were performed on blend samples crystallized quiescently and on samples strain induced crystallized. For blends quiescently crystallized isothermally, the crystallite dimensions calculated from the WAXS diffraction patterns using the Scherrer equation, along with the results from the SAXS, led to the conclusion that the blends crystallized independently. This means the major component of the blend crystallized, while the minor component did not crystallize and was forced into the interlamellar amorphous region. WAXS studies on the strain induced crystallized samples showed a change in the lattice parameters with composition, leading to the conclusion of co-crystallization for these blends. SALS and OM results for the PET rich blend showed that as the percent PEN is increased, the spherulitic growth rates decrease. From the growth rate data, the lateral and fold surface free energies were calculated using the Hoffman and Lauritzen equation. With increasing PEN content, the lateral surface free energy was found to remain constant, while the fold surface free energy increased slightly. The nucleation densities for the PET rich blends were much higher than that of the pure PET, indicating that the presence of PEN causes a nucleation effect on the crystallizing PET component. When crystallizing the blends at various crystallization temperatures for long times, such that the percent crystallinity approaches its equilibrium value, density measurements show that the crystallizing component of the blend will achieve a lower percent crystallinity than that achieved by the pure component crystallized alone.