Jianzhong Lou

Biodegradable Poly(Lactic Acid)/Clay Nanocomposites by Melt Intercalation: A Study of Morphological, Thermal, and Mechanical Properties

Abstract Biodegradable polymer nanocomposites of poly(lactic acid) (PLA) and several organically modified montmorillonites (nanoclays), namely, Cloisite 30B, Cloisite Na+, Cloisite 25A, Cloisite 20A, Cloisite 93A, and Cloisite 15A were prepared by melt compounding using a Brabender twin-screw extruder. An exfoliated morphology was observed using both X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) for the combination of PLA and Cloisite 30B (the montmorillonite modified with a quaternary ammonium salt). The first XRD peaks for all the other nanocomposites were observed to shift to lower angles, indicating that intercalation occurred. The extent of intercalation depended on the type of organic modification on the Cloisite organoclay and was exhibited in the sequence of Cloisite Na+ > 25A > 20A > 93A > 15A. Further studies were carried out to compare the properties of the PLA-30B nanocomposites with those of the neat PLA at clay loading levels of 1%, 2%, 3%, 4%, and 5% (w/w). Thermal stability of the nanocomposites was studied using thermogravimetric analysis (TGA). An increase in thermal stability was observed with a high at a loading level of 3% (w/w). Glass transition data were collected and analyzed using differential scanning calorimeter (DSC). An optimum in the glass transition temperature (T g ) of the nanocomposites was observed at 3% (w/w). Improvement in the mechanical properties of the nanocomposites was also observed.

Graphene’s cousin: the present and future of graphane

The so-called graphane is a fully hydrogenated form of graphene. Because it is fully hydrogenated, graphane is expected to have a wide bandgap and is theoretically an electrical insulator. The transition from graphene to graphane is that of an electrical conductor, to a semiconductor, and ultimately to an electrical insulator. This unique characteristic of graphane has recently gained both academic and industrial interest. Towards the end of developing novel applications of this important class of nanoscale material, computational modeling work has been carried out by a number of theoreticians to predict the structures and electronic properties of graphane. At the same time, experimental evidence has emerged to support the proposed structure of graphane. This review article covers the important aspects of graphane including its theoretically predicted structures, properties, fabrication methods, as well as its potential applications.

Microencapsulation of capsaicin by solvent evaporation method and thermal stability study of microcapsules

With polylactic acid (PLA) as shell and capsaicin as core substances, microcapsules were prepared based on solvent evaporation method. The orthogonal test was used to analyze the effects of the process conditions such as polyvinyl alcohol and PLA concentrations, stirring rate, and oil/water ratio on the particle size of the microencapsulated capsaicin (MC) agents. The chemical composition, morphology and size distribution of the microcapsules prepared by the most satisfactory conditions were analyzed by Fourier transform infrared spectroscopy, laser light scattering, and scanning electron microscopy. The MC agents had a mean diameter of 3–5 μm. The thermal properties of the MC agents were measured by differential scanning calorimetry and thermogravimetric analysis, it was demonstrated that the thermal stability of the MC agents was changed or even improved by the encapsulated PLA over the surface, when compared with similar parameters of the uncovered capsaicin. The in vitro release profile suggested that the microcapsules could be a suitable material for controlled release of capsaicin.

Development of Nanofiller-Modulated Polymeric Oxygen Enrichment Membranes for Reduction of Nitrogen Oxides in Coal Combustion

North Carolina AT studied the influence of nano-fillers on the self diffusion, free volume, glass transition, oxygen diffusion and solubility, and perm-selectivity of oxygen in polymer membranes; developed molecular models of single-walled carbon nano-tube and nano-fumed silica PDMS membranes, and zeolites-modulated polyimide membranes. This project partially supported three graduate students (two finished degrees and one transferred to other institution). This project has resulted in two journal publications and additional publications will be prepared in the near future.

Characterization of the Thermo-Oxidative Stability of Filled Thermoplastic Polyetherimide

Selected fillers were incorporated to prepare polytherimide composite. The influence of fillers on the thermo-oxidative stability of the composite was studied by thermogravimetric analysis. The results showed that at optical filler loading and characteristics, the polymer composite became superior in its thermo-oxidative stability that is very promising in widening the window of service temperature of polyimides for extremely high temperature conditions where most polymeric composites fail. The findings should prove useful in developing high-temperature polymer composites for aerospace and electronics applications.Copyright