Quantitative electron tomography of PLA/clay nanocomposites to understand the effect of the clays in the thermal stability

Abstract

Poly(lactic acid) (PLA) is one of the most promising bio-based and biodegradable polymers. However, its processability and range of applications are limited by its low thermal stability. The novelty of this work is studying the thermal stability of two PLA/clay nanocomposites (PLA/Cloisite 20A and PLA/Cloisite 30B) as a function of the composition and the microstructure, which is exhaustively studied by performing quantitative electron tomography (ET). Quantitative ET involves image acquisition, reconstruction of the volume and a subsequent segmentation of the objects under study. In this work, an objective segmentation is applied to compare the two PLA/clay microstructures. Then, relevant descriptors of the 3D microstructure (dimensions of the reconstructed objects, their specific surface area and orientation) are measured and used to quantitatively explain the effect of the clay particles on the thermal stability of the nanocomposites. The tortuous path has been calculated-based on the descriptors of the microsturecture-and proved to be larger for PLA/Cloisite 30B nanocomposite compared to that of PLA/Cloisite 20A. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44691.

Nanocomposite PLA/C20A Nanoclay by Ultrasound-Assisted Melt Extrusion for Adsorption of Uremic Toxins and Methylene Blue Dye

“…These authors observed the changes that nanocomposites presented when modifying extrusion, and injection molding processing parameters [15]. Several studies have been carried out on the preparation of nanocomposites based on PLA with cloisite for application as a water vapor barrier, antimicrobial properties [16], thermal properties [17] and mechanical properties [18][19][20].…”

Quantitative electron tomography of polylactic acid/clay nanocomposites for better comprehension of processing–microstructure–elastic modulus

“…A Leica (SGiker, University of the Basque Country) Ultracut UCT cryo-ultramicrotome stage was used to cut 130-nm-thick slices from the middle and inner area of the A-type injection-molded samples (Figure 2) of each nanocomposite. 25…”

“…A threshold-based segmentation was carried out following the methodology previously reported in the literature. 25 The quantified microstructural parameters are described in Table 1 and Figure 3 and were calculated using Fiji free software. 31…”

“…A Leica (SGiker, University of the Basque Country) Ultracut UCT cryo-ultramicrotome stage was used to cut 130-nm-thick slices from the middle and inner area of the A-type injection-molded samples (Figure 2) of each nanocomposite. 25 The experimental tilt series was acquired in BF-TEM mode using a Zeiss (SGiker, University of the Basque Country) EM 912 Omega microscope operated at 120 kV. BF-TEM images were acquired at every 2 in the angular range of +70 .…”

“…Actually manual segmentation still remains as the prevalent method of choice. In this regard, a simple efficient and objective methodology to perform the segmentation that was previously reported 24,25 will be applied herein. An objective procedure is of great importance when the aim of the 3D quantification is to compare microstructures of different materials.…”