Spherulite Morphology and Thermal Behaviors of Short Carbon Fiber/Poly(Trimethylene Terephthalate) Composites

The spherulite morphology and thermal behavior of short carbon fiber/poly (trimethylene terephthalate) (SCF/PTT) composites were investigated by polarized optical microscopy (POM), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). The micrographs of the growing spherulites suggest the composites with more SCF content have faster nucleation rates; thus, their spherulite sizes are much smaller. Under the same cooling process, banded spherulites are detected in pure PTT as well as in SCF/PTT composites shown with decreasing band spacing with increasing radius. Melt-crystallization and melting behaviors in DSC indicate the SCF served as nucleating agents, increasing the crystallization rate of the PTT. When the samples were quenched from melt some microcrystals formed in SCF/PTT composites but not in pure PTT. When the SCF/PTT composites were heated to melt, they showed double melting peaks due to some less perfect crystals or thinner lamella formed during DSC scanning.