An XPS study of the thermal degradation of polystyrene-clay nanocomposites

X-ray photoelectron spectroscopy, XPS, has been used to examine several polystyrene-clay nanocomposites. The accumulation of oxygen, from the almuniosilicate, on the surface of the polymer was observed, along with the loss of carbon. This confirms that the barrier properties of the clay provide a mechanism by which nanocomposite formation can enhance the fire retardancy of the polymers. No difference is detected depending upon the extent of exfoliation or intercalation of the nanocomposite. #2002 Elsevier Science Ltd. All rights reserved

An XPS Investigation of Thermal Degradation and Charring of PMMA Clay Nanocomposites

Poly(methyl methacrylate)–clay nanocomposites have been studied using X-ray photoelectron spectroscopy. It is clear that as the polymer undergoes thermal degradation, the clay accumulates at the surface and the barrier properties which result from this clay accumulation have been described as the reason for the decreased heat release rate for nanocomposites. The surface composition of the clay changes as the nanocomposite is heated and the changes are affected by the organic-modification that were applied to the clay in order to prepare the nanocomposite

Capital Structure of Public–Private Partnership Projects: A Sustainability Perspective

Capital is key to achieve the standardized operation of public–private partnership (PPP) projects. The capital structure of PPP projects stresses the structure of equity and debt funds, which are important for securing life-cycle ample funds and achieving the expected outcomes of projects. By incorporating sustainability into PPP projects, the capital structure not only secures current needs of funds, it also focuses on life-cycle stable operations and achieves economic, social, and environmental benefits. This study first set the equity–debt ratio and equity investment ratio of the private sector as the dependent variables and built a selection model of the capital structure of PPP projects from a sustainability perspective using the benefit, cost, and project conditions as core factors based on multi-objective programming and a discounted cash-flow model. Then, the qualitative analysis could be achieved according to the analysis of critical factors that had not been calculated. Afterwards, a selection process which combined the multi-objective programming model with qualitative analysis was proposed to achieve a comprehensive selection of the capital structure of PPP projects from the sustainability perspective. Finally, the process was applied to a real project to verify its rationality and usability. This study not only enriches the theoretical research of PPP projects and provides a new idea on which to build the capital structure selection model, it also proposes a selection process that can provide scientific references for the selection and optimization of the capital structure of PPP projects in practice