Electrospun fibers of poly(ethylene terephthalate) blended with poly(lactic acid)

Fibrous blends of polyethylene terephthalate (PET) and polylactic acid (PLA) were fabricated by electrospinning (ES) from a common solvent, at concentrations of PET/PLA = 100/0, 70/30, 50/50, 30/70, and 0/100. Oriented fiber mats were studied either as-spun, or after a cold-crystallization treatment. Scanning electron microscopy of as-spun amorphous fibers showed that addition of PLA into the ES solution prevents occurrence of beads. In some compositions, two glass transitions were observed by temperature-modulated differential scanning calorimetry indicating that the two components in the ES fibers were phase separated. Thermogravimetric analysis was used to study thermal degradation at high temperatures. PLA degrades at a temperature about 100 °C lower than that of PET, and holding or cycling the blends to high temperature can result in the degradation of PLA. Degree of crystallinity was determined using DSC for as-spun and cold-crystallized ES blend fibers. The degree of crystallinity of each blend component is reduced by the presence of the other blend component, and the overall crystallinity of the blend fibers is less than that of the homopolymer fibers. Wide-angle X-ray scattering results show that oriented crystals were formed in the blended electrospun fibers collected on a rotating collector. The cold-crystallization process leads to both PET and PLA crystallizations. Oriented crystallites form even when the fiber is crystallized with its ends free to shrink.