Morphology, Structure, and Properties of Poly(lactic acid) Microporous Films Containing Poly(butylene terephthalate) Fine Fibers Fabricated by Biaxial Stretching

The effects of size and shape, i.e., sphere and fiber, of dispersed poly(butylene terephthalate) (PBT) in poly(lactic acid) (PLA) matrix on the morphology and porous structure of the biaxially stretched films are comparatively investigated. Scanning electron microscope results confirm that the PBT fine fibers can be produced by melt-stretching following by fast quenching. Rheological characterization reveals the random network structure of PBT fibers. Further, the stretched films composed of spherical PBT particles show the ellipsoidal microvoids due to the interfacial debonding, and the void size relates to the particle size of PBT. However, size of PBT droplets does not influence the void content of the stretched films. The void content considerably increases for equibiaxial deformation as compared with planar deformation, particularly at high draw ratio. Additionally, the stretched films containing fibrous dispersion exhibit the nonaffine behavior and the highest void content of 8%, which is probably due to the localized deformation between fibers. (C) 2014 Wiley Periodicals, Inc.