0000000000354677
AUTHOR
Daniel López
Reversible stress softening of collagen based networks from the jumbo squid mantle (Dosidicus gigas).
Dosidicus gigas is the largest and one of the most abundant jumbo squids in the eastern Pacific Ocean. In this paper we have studied the muscle of the mantle of D. gigas (DGM). Morphological, thermal and rheological properties were assessed by means of atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, differential scanning calorimetry, thermogravimetry and oscillatory rheometry. This study allowed us to assess the morphological and rheological properties of a collagen based network occurring in nature. The results showed that the DGM network displays a nonlinear effect called reversible stress softening (RSS) that has been previously described for …
Viscoelastic behavior of epoxy prepolymer/organophilic montmorillonite dispersions
Dispersions of a bisphenol A-based epoxy resin with an organophilic montmorillonite (Nanofil 919) were studied by X-ray diffraction and oscillatory shear rheometry. X-ray studies reveal that the clay is intercalated by the epoxy and forms stable dispersions. The viscoelastic behavior of the nanodispersions was measured as a function of the Nanofil concentration and temperature. An increase in both G′ and G″ moduli was detected as the concentration increases. Furthermore, a transition from a liquid-like behavior, at low temperatures, to a solid-like behavior, at higher temperatures, was observed for all the samples. This transition is accounted for the formation of a percolated structure of …
Revista complutense de educación
The incorporation of the European Credit Transfer System (ECTS) will pay off soon with the release of the first labor market new-plan graduates. In this study an initial assessment of the results is done by analyzing whether the curriculum (new-plan degree or old-plan degree) and the use of new teaching methodologies have led to significant differences in academic performance or if, on the contrary, they did not. These results suggest that this performance is higher for old-plan graduates, and also for those who have benefited from a new pedagogical tool (students from both the old and new plan). Data used corresponds to that from two different classes, one of them from an old-plan double d…
An overview of nanoparticles role in the improvement of barrier properties of bioplastics for food packaging applications
Abstract Plastics are the most demanding materials for the food packaging industry due to economical and practical reasons such as their low cost, lightness, easy to handle in integrated production lines, and their higher resistance than other materials. Besides containment and information, the packaging should protect foodstuffs from not only contamination but also the loss of food quality. Despite the many advantages, their inherent permeability is perhaps the foremost drawback that could lead to the loss of some food components and, also, to the transference of gases or moisture from the surrounding to the food. Thus, the barrier properties and the wettability are of fundamental importan…
Rheological study of gel phenomena during epoxide network formation in the presence of sepiolite
The dynamic behaviour during the crosslinking of an epoxy polymer near the gel point was monitored using rheological multiple frequency experiments. The influence of a needle-shaped inorganic nanofiller, sepiolite, either non-modified or organically surface modified during the cure process in the presence of an aliphatic and an aromatic hardener was investigated. The validity of various criteria for determining the gel point was examined for the crosslinking of these filled thermosets. The Winter–Chambon criterion at the gel point is obeyed by the unfilled and by the non-modified sepiolite-filled epoxy matrix with either of the two hardeners. However, physical gels are formed in the presenc…
Reversible stress softening and stress recovery of cellulose networks
The mechanical properties of the plant cell wall play an important role in communication, differentiation and growth of plant cells. In particular, the expansive growth of plant cells is only possible because the material that forms the plant cell wall yields at a specific stress level, allowing for an increase in cell wall area. This process can be defined in mechanical terms as the relaxation of the wall stress. The current understanding of plant cell growth suggests that such relaxation behaviour occurs due to the presence of wall loosening agents rather than to the properties of the cellulose network itself. It is believed that certain nonenzymatic proteins, acting as wall loosening age…