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In patients with established acute respiratory distress syndrome, open lung approach improved oxygenation and driving pressure, without detrimental effects on mortality, ventilator-free days, or barotrauma. This pilot study supports the need for a large, multicenter trial using recruitment maneuvers and a decremental positive end-expiratory pressure trial in persistent acute respiratory distress syndrome.

Smectite clays (e.g. montmorillonite), belonging to the structural family called 2:1 phyllosilicates, are the main choice for designing polymer nanocomposites due to their low cost and rich intercalation chemistry allowing them to be chemically modified (organoclays) and to improve the compatibility with the polymer matrix. These hybrid materials, normally called polymeric nanocomposites (PNC), represent a radical alternative to conventional polymer composites and have focused the attention of both academia and industry because of their unexpected properties, and their straightforward synthesis and processing. Such materials on the nanoscale level show significant improvements in mechanical properties, heat distortion temperatures, thermal stability, flame retardancy and enhanced barrier properties. The combination of enhanced properties, weight reduction, and low cost has led to interesting commercial applications such as automotive and packaging, among others. All this justifies the growing interest of both academia and industry in the development of these hybrid materials. In this paper we describe the most significant findings in the clay/polymer nanocomposites field considering three polymer families: elastomers, thermosets and polymers from natural resources or biopolymers.

A self-healing sulfur vulcanized natural rubber (NR) is here reported using the common ingredients in a traditional NR formulation. The dynamic character of the di- and polysulfide bonds naturally present in covalently cross-linked rubbers was found to be responsible for the healing ability and the full recovery of mechanical properties at moderate temperatures provided the material was employed in a nonfully cured starting state. Results show that a compromise between mechanical performance and healing capability can be reached by tailoring the amount of sulfur, the cross-linking density, and the disulfide/polysulfide ratio. The healing efficiency was found to depend on the postcuring storage time, the time between damage creation and re-establishment of mechanical contact, and the actual healing time. Furthermore, a dedicated electron spin resonance (ESR) test allowed establishing the underlying healing principle based on temperature-induced free sulfur radicals. The main observations presented here can serve as the basis for the design and preparation of other self-healing polymers with long-term durability based on di-/polysulfide bridges and other reversible moieties

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The local and global motions of polymer chains in non vulcanized and vulcanized natural rubber/layered silicate nanocomposites were studied by dielectric relaxation spectroscopy, with special consideration to the effect of clay type and loading on the time and length scale of the relaxation processes. Results reveal that the type and concentration of clay do not have an effect on the segmental mode of the NR matrix, while the vulcanization reaction shifts this relaxation to lower frequencies. In addition, a new slower mode attributable to restricted segmental dynamics is found in the nanocomposites where a highly intercalated structure is achieved, independently of having the rubber matrix vulcanized or not. The study of this new slower segmental relaxation contributes to a better understanding of the dynamics of rubber/layered silicate nanocomposites, with the intention of improving our knowledge on the reinforcement effects manifested in this kind of composites with low filler loadings.

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