Microcellular Foaming of Polymethylmethacrylate in a Batch Supercritical CO2 Process: Effect of Microstructure on Compression Behavior

Microcellular foaming of reinforced core/ shell Polymethylmethacrylate (PMMA) was carried out bymeans of supercritical CO2 in a single-step process. Samples were produced using a technique based on the saturation of the polymer under high pressure of CO2(300 bars,40 C), and cellular structure was controlled by varying the depressurization rate from 0.5 bar/s to 1.6 x10-2 bar/sleading to cell sizes from 1lm to 200l m, and densities from 0.8 to 1.0 g/cm3. It was found that the key parameter to control cell size was depressurization rate, and larger depressurization rates generated bigger cell sizes. On the other hand, variation of the density of the samples was not so considerable. Low rate compression tests were carried out, analyzing the dependence of mechanical parameters such as elastic modulus, yield stress and densification strain with cell size. Moreover, the calculation of the energy absorbed for each sample is presented, showing an optimum of energy absorption up to 50% of deformation in the micrometer cellular range (here at a cell size of about 5 µm). To conclude, a brief comparison between neat PMMA and the core/shell reinforced PMMA has been carried out, analyzing the effect of the core/shell particles in the foaming behavior and mechanical properties

Impact on soil degradation factors of changes in rain intensity patterns in southern Spain

In southern of Spain, the torrential nature of the rainfalls alters the soil water availability for vegetation and, consequently, its spatially and temporally pattern. This fact, combined with the current global warming, raises a modification of the eco-geomorphological processes dynamics in Mediterranean areas

Ontological Stakeholder View: An Innovative Proposition

This article describes a theoretical way of understanding business enterprise, for what it is used the stakeholder theory as a theory of the firm. Thus, the purpose of this article is to show an innovative perspective called ontological perspective of stakeholders that relies on a phenomenological model where the subjective perspective of agents is the key, from a purely monetarist model to an economic, social and emotional value creation model, and from a deductive model of stakeholder interests to an inductive model. The main contributions are: add a new perspective to the different classifications made of stakeholder theory, avoid monetarist reductionism under the concept of value in a way that the manager takes into account all interconnected interests of stakeholders, and finally prioritize interests map instead of roles map without accepting the assumption that the role involves joint and no conflicting interests