Structure evolution of α′‐phase poly(lactic acid)

Abstract

Poly(lactic acid) films consisting of a 0 -forms were prepared and uniaxially drawn. The effects of the draw rate at temperatures above the glass transition temperature on chain conformation, degree of crystallinity, and crystalline phase transformation were investigated by a combination of vibrational spectroscopy (infrared and Raman), differential scanning calorimetry, and wide-angle X-ray diffraction (WAXD). It was established that the a 0 -crystal's phase of poly(lactic acid) films does not transform into either an a or b crystals on uniaxial drawing at a fixed draw ratio of 4. However, the degree of crystallinity was significantly increased on deformation. The structural change as a function of deformation also promotes an increase in the strain-induced enthalpic relaxation endothermic peak appearing near the glass transition region. While the overall changes in physical properties can be attributed to the changes in the degree of crystallinity as a function of strain rate, polarized Raman spectra, and WAXD clearly illustrated changes and the differences in the amorphous and crystalline orientation as a function of processing conditions.

Thermal transitions and stability of melt mixed TiO2/Poly(L‐lactic acid) nanocomposites

“…In the graphs corresponding to pure PLLA and TiO 2 /PLLA composites (Fig. a–d), the peaks obtained at 2 θ = 16.6°, as well as those at 2 θ 19.1 and 35.6°, might be due to the (110/200), (010) and (203) reflections of the α crystal form of PLLA with significant disorder, which is in agreement with some relevant literature reports . The XRD pattern of pure PLLA shows a broad area (2 θ = 10–25°), corresponding to the less ordered structure of the semicrystalline PLLA, with an intense narrow reflection peak located at 2 θ = 16.6° .…”

Morphological structure, thermal and mechanical properties of tough poly(lactic acid) upon stereocomplexes

“…According to our previous study [42], it is easy to see that T m1 corresponds to a 0 -crystals phase and T m2 corresponds to stereocomplex PLA. The stereocomplex phase has higher melt temperature than neat PLA.…”

Polylactic acid (PLA)/Silver-NP/VitaminE bionanocomposite electrospun nanofibers with antibacterial and antioxidant activity

“…The peak at 2h = 38.1°corresponds to the three d-spacing (111) (He et al 2002). The peak at 35.4°can be attributed to the strain-induced crystallization of PLA (Chen et al 2011). Also, the crystalline phase of PLA nanofibers is responsible for appearance of the peaks at 16.7° (Tábi et al 2010) and 27.8° (Srithep et al 2013), respectively.…”