Crystallization behavior of poly(L‐lactic acid)/montmorillonite nanocomposites

Abstract

In this study, we modified montmorillonite (MMT) with dilauryl dimethyl ammonium bromide (DDAB) and then exfoliated the structures in a poly(L-lactic acid) (PLLA) matrix. We used polar optical microscopy and X-ray diffraction (XRD) to examine the morphologies of the resulting composites, differential scanning calorimetry to study the melting and crystallization behavior, and Fourier transform infrared (FTIR) and Raman spectroscopy to measure the influence of the intermolecular interactions between PLLA and MMT on the isothermal crystallization temperature. We found that the DDAB-modified MMT was distributed uniformly in the PLLA matrix. At temperatures ranging from 130 to 140 C, the crystalline morphology resembled smaller Maltese cross-patterned crystallites; at temperatures from 150 to 170 C, however, the number of crystallites decreased, their sizes increased, and they possessed ringed spherulite structures. In the XRD spectra, the intensity of the diffraction peaks of the 200/110 and 203 facets of the PLLA/MMT nanocomposites decreased as the crystallization temperature increased. In the FTIR spectra, the absorption peak of the C¼ ¼O groups split into two signals at 1748 and 1755 cm À1 when the isothermal crystallization temperature was higher than 140 C.

Electrospun nylon fibers for the improvement of mechanical properties and for the control of degradation behavior of poly(lactide)-based composites

“…42,43 Fibers have the same effect on the crystallization behavior of PLA, as noted for kenaf fibers and rice straw, 44 and for CNTs. 45 DSC was used to assess the nucleating ability of electrospun fibers.…”

“…On the other hand, as previously observed for other nanofillers, for example CNTs or electrospun fibers, increasing the filler content, and therefore its surface area, some hindering effects on the free motion of macromolecular chains appear, leading to difficulties in attaining thick lamellae, as observed also in this work. 10,13,34,35,41,42 In Table II, it can be seen that the crystallinities assessed by SAXS had larger values relative to those estimated by WAXD. This divergence can be explained considering the difference between the two techniques.…”

Thermal Properties, Crystallinity, and Oxygen Permeability of Na-montmorillonite Reinforced Plasticized Poly(lactic acid) Film

“…Na-MMT distribution into plasticized PLA can be seen from the chromatogram pattern of XRD analysis results [17]. The distribution pattern can be classified as three structure types: dispersion, intercalation, and exfoliation.…”

Thermal Properties, Crystallinity, and Oxygen Permeability of Na-montmorillonite Reinforced Plasticized Poly(lactic acid) Film

“…Other researchers measured the main peak of MMT at 2θ 7-8° and basal spacing 11.7 A [21]; the main peak was at 2θ 4° and basal spacing 22 A [17]. From this research, the main peak plasticized PLA was absent at 2θ 2-10 o ; however, plasticized PLA/Na-MMT composites show the main peak close to 2θ 5°.…”

“…Generally, Na-MMT was dispersed into plasticized matrix film, although a tiny intercalated structure occurred for Na-MMT addition about 3% and 5% that shows a shift diffraction angle at about 0.25° and 0.18°. Other researchers reported a shift angle diffraction when added MMT of 5% into a pure PLA matrix from 2θ 16.6° to 16.4° [17].…”