The application of thermal analysis to the study of epoxy–clay nanocomposites

This is a copy of the author 's final draft version of an article published in the journal Journal of thermal analysis and calorimetry. The final publication is available at Springer via http://dx.doi.org/10.1007/s10973-016-5278-0The development of polymer layered silicate (PLS) nanocomposites goes back over 20 years now, and yet they still have not achieved their full potential. A principal reason for this is the difficulty of obtaining a truly exfoliated nanostructure. The fabrication procedure for such PLS nanocomposites based upon epoxy resin includes several stages, including dispersion of the clay in the resin, intercalation of the resin into the clay galleries, and finally curing of the nanocomposite system. Many attempts have been made to improve the degree of exfoliation in the final nanostructure by modifying the procedures involved in these fabrication stages, and the usual approach is to examine the nanostructure, by techniques such as small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM), as a function of the fabrication procedure. We show here, however, that thermal analytical techniques, and in particular differential scanning calorimetry, can complement the techniques of SAXS and TEM in the search for ways in which to achieve improved degrees of exfoliation in PLS nanocomposites based upon epoxy resin.Peer ReviewedPostprint (author's final draft

Globalisation, concentration and footloose firms: in search of the main cause of the declining labour share.

Over the last two decades the share of national income which accrues to labour has followed a marked downward trend across a host of industrialised countries. This paper attempts to assess the importance of several potential causes of this phenomenon. We investigate compositional effects, the effect of declining trade costs, changes in the market structure (concentration) and the effect of low-wage competition between countries. Overall, the findings suggest that lower trade costs and factors related to economic integration such as industry concentration, the market power of firms and increased international low-wage competition indeed affect the labour share. However, their effect has been quite limited when compared to changes in the sectoral composition, the effects of technological change, cyclical factors and changes in the prices of intermediary goods.

Non-isothermal cure and exfoliation of tri-functional epoxy-clay nanocomposites

The non-isothermal cure kinetics of polymer silicate layered nanocomposites based on a tri-functional epoxy resin has been investigated by differential scanning calorimetry. From an analysis of the kinetics as a function of the clay content, it can be concluded that the non-isothermal cure reaction can be considered to consist of four different processes: the reaction of epoxy groups with the diamine curing agent; an intra-gallery homopolymerisation reaction which occurs concurrently with the epoxy-amine reaction; and two extra-gallery homopolymerisation reactions, catalysed by the onium ion of the organically modified clay and by the tertiary amines resulting from the epoxy-amine reaction. The final nanostructure displays a similar quality of exfoliation as that observed for the isothermal cure of the same nanocomposite system. This implies that the intra-gallery reaction, which is responsible for the exfoliation, is not significantly inhibited by the extra-gallery epoxy-amine cross-linking reaction.Peer ReviewedPostprint (published version

Strategic consultation on the FE workforce and Initial Teacher Education workforce for the Education & Training Foundation

A research project undertaken on behalf of the Education and Training Foundation exploring barriers to attracting candidates with higher qualifications and skills to the FE sector and to explores if ITE predominantly attracts people from a humanities background. The report suggests that people move into FE teaching through opportunity. The issue if dual professionalism is an important element of identity. Those becoming teacher educators tend to drift into the role. Discussions were focused less on the background of people but on the space they have to deliver a curriculum which includes pedagogy theory and the extent to which ITE need to have subject specialisms to prepare teachers for effective classroom practice.Education and Training Foundatio

A novel comparative study of different layered silicate clay types on exfoliation process and final nanostructure of trifunctional epoxy nanocomposites

© 2016. This version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/The effect of three different organically modified layered silicate clays (Nanomer I.30E, Cloisite 30B and Nanofil SE 3000) on the exfoliation process and on the thermal properties and nanostructure of cured trifunctional epoxy resin based nanocomposites was studied. Optical microscopy showed that the best and poorest qualities of clay distribution in the epoxy matrix were obtained with Nanofil SE 3000 and Nanomer I.30E, respectively. However, the isothermal differential scanning calorimetry scans show that, of the three systems, it is only the Nanomer clay that promotes intra-gallery reaction due to homopolymerisation, appearing as an initial rapid peak prior to the cross-linking reaction. This rapid intra-gallery reaction is not present in the curing curve for the Cloisite and Nanofil systems. This fact implies that the fully cured nanostructure of the Cloisite and Nanofil system is poorly exfoliated, which is confirmed by small angle X-ray scattering which shows a scattering peak for these systems at around 2.53°, corresponding to about 3.5 nm d-spacing.Peer ReviewedPostprint (author's final draft

Lifetime Assessment for Thermal Barrier Coatings: Tests for Measuring Mixed Mode Delamination Toughness

Mechanisms leading to degradation of the adherence of thermal barrier coatings (TBC) used in aircraft and power generating turbines are numerous and complex. To date, robust methods for the lifetime assessment of coatings have not emerged based on predictions of the degradation processes due to their complexity. In the absence of mechanism-based predictive models, direct measurement of coating adherence as a function of thermal exposure must be a component of any practical approach toward lifetime assessment. This paper outlines an approach to lifetime assessment of TBC that has taken shape in the past few years. Most TBC delaminations occur under a mix of mode I and mode II cracking conditions, with mode II delamination being particularly relevant. Direct measurement of TBC delamination toughness has been challenging, but recent progress has made this feasible. This paper surveys a range of potentially promising tests for measuring the mode dependence of delamination toughness with particular emphasis on toughness under mode II conditions.Engineering and Applied Science

A study of the reactions of fluorocarbon iodides

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