Morphology, thermal, and crystallization analysis of polylactic acid in the presence of carbon nanotube fibers with tunable fiber loadings through polymer infiltration

Abstract

The effects of high loading of carbon nanotube (CNT) fibers on the morphological, thermal, and crystallization properties of polylactic acid (PLA) in PLA-CNT fiber composites are investigated. The fabrication methods ensure full impregnation of the fiber by PLA and formation of a large fiber/polymer interface, resulting in an oriented transcrystalline (TC) layer of PLA on the fiber surface. The presence of TC layer in the composite leads to increased PLA thermal stability, higher crystallinity, and faster nucleation. However, the crystal growth rate of TC and bulk spherulite is independent of the type of nucleation. In addition, real-time variable-temperature synchrotron wide-angle X-ray scattering and fiber 2D-wide-angle X-ray diffraction analyses reveal that crystals from either pure PLA or PLA on the fiber surface develop a thermodynamically stable ¿ phase of PLA when isothermally crystallized at 110 °C. Furthermore, PLA crystals and long spacing lamellae are preferentially orientated and packed parallel to the fiber axis.