Crystalline structure and mechanical property of poly(lactic acid) nanocomposite probed by near-infrared (NIR) hyperspectral imaging

The crystalline structure of a poly(lactic acid) (PLA) nanocomposite is probed by near-infrared (NIR) hyperspectral imaging to derive penetrating insight into its improved mechanical properties by inclusion of organoclay particles. A set of PLA nanocomposite samples are prepared under varying levels of clay content. The variation of the crystalline structure of PLA and corresponding mechanical strength are examined by NIR hyperspectral imaging and thermomechanical analysis (TMA), respectively. By carrying out the detailed analysis of the NIR hyperspectral image, it effectively provided a more detailed picture of the nanocomposite system. Namely, the addition of the clay substantially increases the frequency of the spontaneous nucleation of the PLA crystals. Corresponding decrease of the amorphous portion, in turn, restricts mechanical deformation of the samples under a certain level of load. Consequently, by carrying out detailed band position shift analysis of the NIR image spectra, the chemically meaningful information concerning the nanocomposite system can be effectively extracted.