Micro/nanocapsules for anticorrosion coatings

In the last decade, the interest in the self-healing and slow release coatings applied against corrosion increased dramatically as it helps to expand duration of coating and, at the same time, to increase the structural materials’ life. In these types of paints are micro and nanoncapsules that enable the reparation of the coating upon exposure to external stimuli like mechanical degradation, changes in the pH and/or temperature. In spite of the extensive laboratory research work, there are many unsolved problems in understanding the function of smart coatings. To summarize the knowledge accumulated up-to-now in this topic will help both academic and industrial specialists to keep in center of interest for further research to solve problems that will result in development of more effective micro- and nanocontainers for different paints. Coatings with micro- and nano-containers/capsules improve the basic coating characteristics like anticorrosion efficiency.The chapter first discusses the importance of self-healing and slow release phenomena, and then it focuses on the basic knowledge of micro- and nano-capsule preparation techniques as well as on the importance of “filled” capsules. Advances on preparation of different types of the containers (organic, inorganic, and multilayer) are reviewed. Then the shell and wall materials, the wall thickness and its mechanical properties is discussed as one of the most important questions. One must keep in mind that the capsules must remain intact for years during storage, coating formulation and application and, additionally, in the dry coating. Experimental techniques used for characterization of micro/nanocapsules (size, size distribution, mechanical stability etc.) are discussed

A comparison of contact angle measurement results obtained on bare, treated, and coated alloy samples by both dynamic sessile drop and Wilhelmy method

The goal of this work was to compare the performance of our home-built dynamic sessile drop contact angle (CA) goniometer with our NIMA Dynamic Surface Tensiometer. Water CA measurements on different alloy samples (aluminium brass, copper-nickel 70/30, stainless steel 304) have been carried out by 1) sessile drop and 2) Wilhelmy plate method. Different sets of substrates were i) cleaned; ii) cleaned and pre-treated; iii) cleaned, pre-treated and coated with atactic polystyrene. During these experiments, the main features of the two setups in connection with our sample properties were understood. We therefore found it desirable and justified to sum up our findings

Thermotropic and structural effects of poly(malic acid) on fully hydrated multilamellar DPPC–water systems

The thermotropic and structural effects of low molecular weight poly(malic acid) (PMLA) on fully hydrated multilamellar dipalmitoylphosphatidylcholine (DPPC)-water systems were investigated using differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS), and freeze-fracture transmission electron microscopy (FFTEM). Systems of 20 wt% DPPC concentration and 1 and 5 wt% PMLA to lipid ratios were studied. The PMLA derivatives changed the thermal behavior of DPPC significantly and caused a drastic loss in correlation between lamellae in the three characteristic thermotropic states (i.e., in the gel, rippled gel and liquid crystalline phases). In the presence of PBS or NaCl, the perturbation was more moderate. The structural behavior on the atomic level was revealed by FTIR spectroscopy. The molecular interactions between DPPC and PMLA were simulated via modeling its measured infrared spectra, and their peculiar spectral features were interpreted. Through this interpretation, the poly(malic acid) is inferred to attach to the headgroups of the phospholipids through hydrogen bonds between the free hydroxil groups of PMLA and the phosphodiester groups of DPPC