Stress reduction mechanisms during photopolymerization of functionally graded polymer nanocomposite coatings

From the experimental analysis of the photocuring process in terms of reaction kinetics as well as modulus and shrinkage build-up, the residual stresses arising during the photopolymerization of functionally graded composite coatings based on an acrylate matrix and Fe3O4@SiO2 core@shell nanoparticles are evaluated through a Finite Element Modeling approach. Owing to the monotonous variation of volume fraction of the constituent phases that influences the local conversion of the polymeric matrix, these coatings are able to decrease the residual stresseS at the coating/substrate interface by as much as approximate to 25% compared to those encountered in composites with homogeneous compositions, and by as much as approximate to 40% compared to those arising in the pure polymer. The influence of substrate stiffness, nanoparticle stiffness and conversion degree of the polymer matrix was also analyzed, providing further information for the optimization of the stress reduction mechanism in graded nanocomposite coatings. (C) 2015 Elsevier B.V. All rights reserved

Optimized pcm-based heat exchanger for infant incubator

The invention relates to a PCM-based heat exchanger (1) exploiting the characteristics of a phase change material (PCM), comprising a base (100); a metallic heat exchanger (101) adapted to be included into the base (100) and having a plurality of hollow volumes (104) defined by a network of metallic walls (105); a PCM (103) adapted to be included into the metallic heat exchanger (101) so to fill the plurality of hollow volumes (104); and at least one metallic tubular element 102 having an inlet, an outlet and a hollow body adapted to allow a fluid flow, operatively connected with the metallic heat exchanger 102 wherein each point of the PCM (103) is at maximum 5 mm far from a wall of the network of metallic walls (105), the metallic heat exchanger (101) or from the metallic tubular element (102). The heat exchanger (1) is particularly adapted to be implemented into an infant incubator; accordingly, the invention also features an infant incubator comprising the heat exchanger (1), which is especially suitable for use in developing countries