Synthesis of polylactide/clay nanocomposites by in situ intercalative polymerization in supercritical carbon dioxide

in European Polymer Journal (2009), 45(3), 643-648

Polylactide (PLA)/clay nanocomposites have been prepared by in situ ring-opening polymerization in supercritical carbon dioxide. Depending on the type of organoclay used, polylactide chains can be grafted ... [more ▼]

Polylactide (PLA)/clay nanocomposites have been prepared by in situ ring-opening polymerization in supercritical carbon dioxide. Depending on the type of organoclay used, polylactide chains can be grafted onto the clay surface, leading to an exfoliated morphology. Nanocomposites with high clay contents (30–50 wt.%), called masterbatches, have also been successfully prepared and were recovered as fine powders thanks to the unique properties of the supercritical fluid. Dilution of these masterbatches into commercial l-polylactide by melt blending has led to essentially exfoliated nanocomposites containing 3 wt.% of clay. The mechanical properties of these materials have been assessed by flexion and impact tests. Significant improvements of stiffness and toughness have been observed for the PLA/clay nanocomposites compared to the pure matrix, together with improved impact resistance. [less ▲]

Patenting activity in manufacturing organoclays for nanocomposite applications

in Recent Patents on Materials Science (2009), 2(1), 43-49

For the last two decades, intensive research has been focused on developing reinforced polymers with incorporation of nanometric fillers. Amongst the different types of nanofillers, those based on layered ... [more ▼]

For the last two decades, intensive research has been focused on developing reinforced polymers with incorporation of nanometric fillers. Amongst the different types of nanofillers, those based on layered silicates (commonly known as clays), have been most widely investigated. Dispersing clay sheets on a nanoscopic scale (so-called exfoliation) indeed allows materials with enhanced thermal, mechanical, rheological, flame retardancy and barrier properties to be produced. However, the nanocomposite performances are strongly dependent upon the extent of clay exfoliation. In order to enhance the compatibility between the pristine clay, hydrophilic, and the polymer, hydrophobic, and to achieve a good delamination of the nanolayers, an organo-modification of the clay is most usually necessary. This mini-review will provide an outline of patenting activity in the field of manufacturing organoclays through ionic exchange. The variety of organic modifiers and the diverse processing techniques will be detailed, aiming to extract the most relevant organoclays for successful nanocomposite formation at industrial scale. [less ▲]

A new method to prepare poly(styrene-co-acrylonitrile)/clay nanocomposites with significantly improved properties

Poster (2008, November 28)

Supercritical carbon dioxide as an efficient process to obtain specialty organoclays : from lab preparation to pre-industrial production

Conference (2008, October 07)

About the use of PCL/clay nanohybrid masterbatches

Poster (2008, September 09)

Thermal behaviour of well-dispersed poly(styrene-co-acrylonitrile)/clay nanocomposites prepared by using supercritical technology

Poster (2008, September 08)

Poly(caprolactone)/clay masterbatches prepared in supercritical CO2 as efficient clay delamination promoters in poly(styrene-co-acrylonitrile)

in Journal of Materials Chemistry (2008), 18(39), 4623-4630

Poly(styrene-co-acrylonitrile) (SAN)/clay nanocomposites with a high degree of clay exfoliation were prepared upon melt blending of pre-exfoliated poly(-caprolactone) (PCL)/organoclay masterbatches in a ... [more ▼]

Poly(styrene-co-acrylonitrile) (SAN)/clay nanocomposites with a high degree of clay exfoliation were prepared upon melt blending of pre-exfoliated poly(-caprolactone) (PCL)/organoclay masterbatches in a Brabender-type internal mixer. These highly filled masterbatches were synthesized by a one-pot process using supercritical carbon dioxide as a polymerization medium. During their dispersion into SAN, PCL is expected to act as a compatibilizer at the polymer–clay interface as it is miscible with the host matrix under these conditions. Reference nanocomposites based on direct melt mixing of the commercial organoclay were also prepared for the sake of comparison. The superiority of the masterbatch route in term of clay delamination efficiency has been evidenced by XRD analysis, visual and TEM observations. The effect of the nanocomposite morphology on the polymer properties was then investigated. A substantial improvement of the fire behaviour and a decrease in gas permeability have been observed for the nanocomposite containing the highest level of clay exfoliation, accompanied with a higher brittleness as evidenced by traction and impact tests. [less ▲]

Effect of filler content and size on transport properties of water vapour in PLA/calcium sulfate composites

in Biomacromolecules (2008), 9

Starting from calcium sulfate (gypsum) as fermentation byproduct of lactic acid production process, high performance composites have been produced by melt-blending polylactide (PLA) and -anhydrite II (AII ... [more ▼]

Starting from calcium sulfate (gypsum) as fermentation byproduct of lactic acid production process, high performance composites have been produced by melt-blending polylactide (PLA) and -anhydrite II (AII) filler, i.e., calcium sulfate hemihydrate previously dried at 500 °C. Characterized by attractive properties due to good filler dispersion throughout the polyester matrix and favorable interactions between components, these composites are interesting for potential use as biodegradable rigid packaging. The effect of filler content and mean particle diameter on the barrier properties such as sorption and diffusion to water vapor has been examined and compared to unfilled PLA. Even without additional treatments, the presence of the filler introduced constraints on molecular mobility in the permeable phase of amorphous PLA and the amount of solvent absorbed appears lower in the highly filled composites. Surprisingly, for PLA-30% AII compositions, by addition of filler characterized by high mean particle diameter (e.g., 43 μm) the thermodynamic diffusion parameter, D0, decreased up to 2 orders of magnitude. The dimension of filler particles and their percentage in the continuous polymeric phase seem to be the most important parameters that determine the barrier properties of the PLA-AII composites to water vapor. [less ▲]

Microscopic morphology of chlorinated polyethylene nanocomposites synthesized from poly(e-caprolactone)/clay masterbatches

in Langmuir (2008), 24

Chlorinated polyethylene (CPE) nanocomposites were synthesized by melt blending clay-rich/poly( -caprolactone) (PCL) masterbatches to CPE matrices. The masterbatches were prepared following two synthetic ... [more ▼]

Chlorinated polyethylene (CPE) nanocomposites were synthesized by melt blending clay-rich/poly( -caprolactone) (PCL) masterbatches to CPE matrices. The masterbatches were prepared following two synthetic routes: either PCL is melt-blended to the clay or it is grafted to the clay platelets by in situ polymerization. The microscopic morphology of the nanocomposites was characterized by X-ray diffraction, atomic force microscopy, transmission electron microscopy, and modulated temperature differential scanning calorimetry. When using free PCL, intercalated composites are formed, with clay aggregates that can have micrometric dimensions and a morphology similar to that of the talc particles used as fillers in commercial CPE. PCL crystallizes as long lamellae dispersed in the polymer matrix. When using grafted PCL, the nanocomposite is intercalated/exfoliated, and the clay stacks are small and homogeneously dispersed. PCL crystallizes as lamellae and smaller crystals, which are localized along the clay layers. Thanks to the grafting of PCL to the clay platelets, these crystalline domains are thought to form a network with the clay sheets, which is responsible for the large improvement of the mechanical properties of these materials. [less ▲]

Poly(ethylene-co-vinyl acetate)/clay nanocomposites: Effect of clay nature and organic modifiers on morphology, mechanical and thermal properties

in Polymer Degradation & Stability (2005), 90(2), 288-294

Nanocomposites based on an ethylene vinyl acetate copolymer (27 wt% vinyl acetate) and various (organo-modified) clays have been prepared by melt blending and their morphology, tensile and thermal ... [more ▼]

Nanocomposites based on an ethylene vinyl acetate copolymer (27 wt% vinyl acetate) and various (organo-modified) clays have been prepared by melt blending and their morphology, tensile and thermal degradation properties have been evaluated. Special attention has been paid to the influence of the clay nature and origin (montmorillonite or fluoromica) as well as on the nature of the ammonium cation organic modifier. It has been shown that nanostructure and tensile properties mainly depend on the nature of the organic modifier while the delay in thermal volatilisation of EVA during thermo-oxidation is mainly driven by the nature of the clay (mainly its aspect ratio), with no significant influence of the nanostructure of the nature of the organic modifier. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]