Characterization of polylactic acid green composites and its biodegradation in a bacterial environment

The growing interest in the preservation of our environment is pushing for solutions to develop less impacting materials. Thus, the development of biocomposites and is recyclable and compostable end-of-life resources seem an interesting alternative. In this study, the characterization of Polylactic acid (PLA) reinforced with treated and untreated Olive husk flour (OHF) were investigated. More then, their biodegradation with a Bacillus sp. has been evaluated. The main results show that the bacteria degraded both the PLA and the composite. This degradation was confirmed by the release of reducing sugars as well as increasing weight loss of PLA matrix and composites.     

Localised Evolved Gas Analysis by Micro-thermal Analysis

Micro-thermal analysis employs a scanning probe microscope fitted with a miniature resistive heater/thermometer to obtain images of the surface of materials and then perform localised thermo analytical measurements. We have demonstrated that it is possible to use the same configuration to pyrolyse selected areas of the specimen by rapidly heating the probe to 600–800°C. This generates a plume of evolved gases which can be trapped using a sampling tube containing a suitable sorbent placed close to the heated tip. Thermal desorption-gas chromatogaphy/mass spectrometry can then be used to separate and identify the evolved gases. This capability extends the normal visualisation and characterisation by micro-thermal analysis to include the possibility of localised chemical analysis of the sample (or a domain, feature or contaminant). The isolation and identification of natural products from a plant leaf are given as an example to illustrate this approach. Preliminary results from direct sampling of pyrolysis products by mass spectrometry are also presented. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ursane‐Type Triterpene Saponins from Zygophyllum geslini

Four new ursane‐based triterpene glycosides, compounds 1 – 4 , as well as the known glycosides zygophylosides E, G, and H, and 3‐O‐(β‐D ‐quinovopyranosyl)quinovic acid 28‐(O‐β‐D ‐glucopyranosyl) ester, were isolated from the BuOH‐soluble fraction of the MeOH/H₂O 7 : 3 extracts of Zygophyllum geslini (roots or aerial parts). Their structures were established mainly by 1D‐ and 2D‐NMR techniques, in combination with HR‐MS analysis and acid hydrolysis.     

Micro‐thermal analysis of polymers: current capabilities and future prospects

The current state of development of micro‐thermal analysis (micro‐TA) and related techniques are briefly reviewed. Results for a PET/epoxy resin composite and a bilayer polymer film are given as illustrations. Details are given of a new interface that enables the micro‐TA unit to be placed inside a conventional FTIR spectrometer to carry out photothermal IR microscopy. New results are presented for a micro‐pyrolysis‐mass spectroscopy technique. The limitations of the current instrumentation are discussed in terms of the overriding problem being one of spatial resolution. Images obtained using pulsed force mode AFM with a high‐resolution heated tip indicate the scope for future development of this technique. The possibility of even higher spatial resolution with other forms of probe are discussed along with the potential for imaging micro‐pyrolysis time of flight mass spectroscopy and even tomography. It is concluded that these methods offer excellent prospects for characterising a wide range of polymer systems.     

New Adventures in Thermal Analysis

This paper describes recent advances in thermal analysis instrumentation which combine the high resolution imaging capabilities of the atomic force microscope with physical characterisation by thermal analysis. Images of the surface may be obtained according to the specimen's thermal conductivity and thermal expansivity differences in addition to the usual topographic relief. Localised equivalents of modulated temperature differential scanning calorimetry, thermomechanical and dynamic mechanical analysis have been developed with a spatial resolution of a few micrometres. A form of localised thermogravimetry-evolved gas analysis has also been demonstrated. The same instrument configuration can be adapted to allow IR microspectrometry at a resolution better than the optical diffraction limit. This revised version was published online in August 2006 with corrections to the Cover Date.     

Modulated Differential Scanning Calorimetry Analysis of Interphases in Multi-Component Polymer Materials

A modulated-temperature differential scanning calorimetry (M-TDSC) method for the analysis of interphases in multi-component polymer materials has been developed further. As examples, interphases in a polybutadiene-natural rubber (50:50 by mass) blend, a poly(methyl methacrylate)-poly(vinyl acetate) (50:50 by mass) structured latex film, a polyepichlorohydrinpoly(vinyl acetate) bilayer film, and polystyrene-polyurethane (40:60 by mass) and poly(ethyl methacrylate)-polyurethane (60:40 by mass) interpenetrating polymer networks were investigated. The mass fraction of interphase and its composition can be calculated quantitatively. These interphases do not exhibit clear separate glass transition temperatures, but occur continually between the glass transition temperatures of the constituent polymers. This revised version was published online in August 2006 with corrections to the Cover Date.     

Modulated differential scanning calorimetry

Modulated-temperature differential scanning calorimetry was used to measure the glass transition temperature,T _g, the heat capacity relaxation in the glassy state and the increment of heat capacity, C_p, in the glass transition region for several polymers. The differential of heat capacity with respect to temperature was used to analyseT _g and C_p simply and accurately. These measurements are not affected by complex thermal histories.