Cover page describe the Typical fracture surface of nuclear graphite blocks after irradiation (cracks occur during reactor operation). This picture Summarize the Fractographic studies of GR-280 nuclear graphite after irradiation up to neutron fluence above the turnaround dose (with a decrease in of the mechanical properties to the values close to the initial one after primary radiation-induced increase) showed along with the presence of transcrystalline fracture, appearance of intercrystalline fracture regions along the “filler-binder” type boundaries.
Polycaprolactone/organoclay biodegradable nanocomposites: dissimilar tendencies of different clay modifiers
Romina P. Ollier, Matias R. Lanfranconi, Vera A. Alvarez, Leandro N. Ludueña*
Materiales Compuestos Termoplásticos (CoMP), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), CONICET - Universidad Nacional de Mar del Plata (UNMdP). Av. Colón 10890, Mar del Plata, 7600, Argentina.
Adv. Mater. Lett., 2018, 9 (11), pp 796-804
Publication Date (Web): Jul 25, 2018
Copyright © 2018 VBRI Press
In this work, biodegradable nanocomposites based on polycaprolactone (PCL) reinforced with 2.5, 5.0 and 7.5 wt.% of two different clays, a commercial organo-clay (Cloisite 20A, C20A) and a laboratory modified bentonite with tributylhexadecyl phosphonium bromide (bTBHP), were prepared by melt intercalation followed by compression molding. The study contemplates the analysis of chemical (Infrared Spectrometry, FTIR), morphological (X-Ray Diffractometry, XRD, Scanning Electron Microscopy, SEM, and Transmission Electron Microscopy, TEM), rheological, thermal (Differential Scanning Calorimetry, DSC, and Thermogravimetrical Analysis, TGA) and mechanical properties (tensile tests), which are important properties for packaging applications.In previous works, we concluded that higher clay dispersion degree inside the PCL matrix is expected when clays with large interlayer distance, strong hydrophobicityand strong processing stability are used. In the present work the opposite result was obtained. Although the phosphonium treated clay (bTBHP) showed the largest interlayer distance (d001), strongest hydrophobicity and the best processing stability, the clay dispersion degree inside PCL was worse than in the case of the alkylammonium treated clay (C20A). PCL/bTBHP nanocomposites showed weaker mechanical properties in comparison with PCL/C20A ones, which is in accordance with the morphological analysis. On the other hand, the thermal properties of the matrix were not substantially affected by clay incorporation in both nanocomposites.
Nanocomposites, compatibility, biodegradable polymer, bentonite, montmorrillonite