El descanso del guerrero. Memoria visual del combatiente en Madrid, 1936-1939

Actas de las Quintas Jornadas Imagen, Cultura y Tecnología celebradas del 3 al 5 de julio de 2006 en la Universidad Carlos III de Madri

Effect of polymer architecture on the intrinsic self-healing character of polymers

Intrinsic and extrinsic self-healing strategies can be employed to mitigate the effects of local damage in order to (partially) restore a lost property or functionality and to avoid premature catastrophic failure of the whole system. It is well known that polymer architecture has a crucial influence on mechanical, physical and thermal properties. However, the effect of polymer architecture on the healing capabilities of self-healing polymers has not yet been studied in detail. This paper addresses the effect of polymer architecture on the intrinsic healing character of polymeric materials using different reversible chemistries and aims at highlighting the need for more studies on this particular topic.Aerospace Structures & MaterialsAerospace Engineerin

Simultaneous optical and electrochemical monitoring of the protective effect of functional surface healing agents

Encapsulation of reactive agents embedded within a matrix is the most studied concept to develop self-healing materials. The most common approaches employ either a single component with catalyst dispersed in the matrix or a single environment-reactive component for corrosion protection [1]. Recently an approach for corrosion protection based on a single reactive healing agent that combines wetting, reactivity with ambient humidity and the underlying metallic surface, hydrophobicity and densification in time was proposed [2]. Following this idea of using silyl esters, Huang et al. developed a similar system where 1H,1H,2H,2H-perfluorooctyltriethoxysilane (POTS) was used in place of a silyl ester [3]. Despite the good results offered by the octyldimethylsilyl ester and the POTS, there is room for improvement in the design of the healing agents employed for corrosion protection. The goal of this research is to better understand the wetting, barrier and densification properties of silane based healing agents to be able to develop efficient single reactive healing agents. Therefore a selection of silanes with different chemical backbone structure and surface-reactive end group is evaluated. The barrier properties and the hydrophobicity of the agents is investigated to gain insight into the relationship between chemical structure and final thin film properties. Moreover, in order to evaluate the time dependent corrosion protection performance of the different healing agents a novel optical-electrochemical analysis technique has been developed.Aerospace Structures & MaterialsAerospace Engineerin

A quantitative description of the surface healing of ionomers (abstract)

Aerospace Structures & MaterialsAerospace Engineerin

Understanding the molecular mechanisms involved in the interfacial self-healing of supramolecular rubbers

Supramolecular rubbers based on 2-aminoethylimidazolidone and fatty acids with epoxy crosslinks have been shown to self-heal via multiple hydrogen bonding sites. In this work, several tools are used to investigate the molecular mechanisms taking place at the interface to understand cohesive healing in these polymers. The quantification of self-healing was performed via a tapered double cantilever beam (TDCB) geometry. The TDCB geometry is especially amenable to studying multiple healing cycles due to the fracture toughness, and subsequently healing efficiencies being independent of crack length. Healing was carried out for multiple fracturehealing cycles and varying fracture testing experimental parameters to track the change in efficiency of interfacial healing. Strain rate and rate of crack closure are both shown to affect the self-healing efficiency.Aerospace Structures & MaterialsAerospace Engineerin

Use of compartmented sodium- alginate fibres as a healing agent delivery system for asphalt pavements

Structural EngineeringCivil Engineering and Geoscience

Electrochemical healing of MAX phase ceramics (abstract)

Aerospace Structures & MaterialsAerospace Engineerin

Self-healing anticorrosive organic coating based on the release of a reactive silyl ester: Use of local electrochemical techniques (poster abstract)

Delft University of Technolog

The role of clusters on the healing efficiency of a modified Zn based ionomer

Poly(ethylene-co-methacrylic acid) (EMAA) ionomers have shown healing capabilities in both ballistic and static tests. In previous studies it was shown that the degree of crosslinking (clusters) affects (positively or negatively) the healing under impact tests. Moreover, it has also been reported that the modification of the ionomers by additives leads to different healing behaviours under static puncture tests. Despite the preliminary tests the effect of the additives on the ionomers was not clarified. In this work we use scratch healing and WAXS to gain a major understanding of the effect of additives in ionomers. Several blends of a semi-crystalline ionomer partially neutralized with zinc (EMAA-Zn) with adipic acid were prepared. Temperature assisted healing (well below the melting temperature) of artificial scratches in the surface of modified and unmodified EMAA-Zn ionomers was performed. A confocal microscope was employed for the healing quantification and measurements of Young modulus. Wide Angle X Ray diffraction (WAXS) was employed to track the effect of the additive in the polymer structure. The results show a strong influence of the additive on the clusters leading to a clear increase of the healing efficiency when clusters disappear.Aerospace Structures & MaterialsAerospace Engineerin

On the healing mechanism of sol-gel derived hybrid materials containing dynamic di-sulfide bonds

Sol-gel technology is increasingly being used in coatings for corrosion protection and adhesion improvement. So far, the self-healing concept in sol-gel coatings has only been approached from extrinsic healing perspective (i.e. use of nano and micro carriers of corrosion inhibitors) [1]. Despite the benefits of this approach, the damaged area remains open to ambient environment. The implementation of intrinsic healing approaches in sol-gel coatings can thus very well complement current extrinsic ones in order to offer more extended corrosion protection. In the present work the intrinsic healing sol-gel hybrid systems containing dynamic disulfide bonds were developed. The ability of developed systems to restore their cohesion at three different temperatures was evaluated, revealing 70ºC as the optimum healing temperature. In order to get a better understanding of the healing mechanisms, dynamic mechanical thermal analysis (DMTA) was complemented by in-situ raman spectroscopy to follow the evolution of the di-sulfide bonds during the healing cycles. Mechanical properties and content of the broken dynamic bonds were found to be the key parameters in the healing performance of the developed systems. Faster healing kinetics at 70ºC disclosed the dominating role of the breaking/re-joining of the dynamic di-sulfide bonds in the healing mechanism.Aerospace Structures & MaterialsAerospace Engineerin