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Microcapsule-Assisted Smart Coatings
Published in Munmaya K. Mishra, Applications of Encapsulation and Controlled Release, 2019
Mahendra S. Mahajan, Vikas V. Gite
Smart materials change their properties in response to external stimuli.[4] A smart self-healing coating works in a similar way; it responds to various external factors and is responsible for the healing of cracks without human intervention. The phenomenon is similar to the natural healing processes of wounds in living things. Nature provides self-defense against damage for the recovery of stable operation. Similarly, a self-healing material possesses the functionality to recover from damage or cuts resulting from mechanical or long-time use. These coatings can be classified into two types, as shown in Figure 14.1.
Shape Memory Polymers
Published in D I Arun, P Chakravarthy, R Arockiakumar, B Santhosh, Shape Memory Materials, 2018
D I Arun, P Chakravarthy, R Arockiakumar, B Santhosh
Any material capable of repairing mechanical damage by itself is defined as a self-healing material; this is one of the most promising fields of application for SMPs. The underlying principle is the activation of polymer chain networks via thermal stimulation, which causes the embedded linear polymer chains to diffuse and heal damaged areas.
Recent Developments in Waterborne Polyurethanes for Corrosion Protection
Published in Ram K. Gupta, Ajay Kumar Mishra, Eco-Friendly Waterborne Polyurethanes, 2022
Felipe M. de Souza, Muhammad Rizwan Sulaiman, Ram K. Gupta
Microencapsulation is an efficient method to attain self-healing characteristics. The microcapsules made up of polyurethane, phenol, or urea-formaldehyde, and silica capsules are promising to attain efficient self-healing coating. At the same time, the low viscosity epoxies, inorganic inhibitors, aliphatic diisocyanates, and vegetable oils can be employed as a healing agents. In one investigation, toluene diisocyanate and 1,4 butanediol were used as starting materials [63]. Isophorone diisocyanate, an aliphatic isocyanate, was used as a healing agent, which reacts with environmental moisture upon breakage, creates urea linkages, and offers UV resistivity. Self-healing properties are highly desirable in several areas as materials with such features can recover from physical and chemical damage, hence providing long-term protection. It can be handy for the case of oil pipelines or drilling platforms that can be difficult sites for maintenance. Self-healing materials can be extrinsic or intrinsic. The first consists of encapsulating a flaxseed oil, reactive monomer, or corrosion inhibitor in small hollow spheres that can be blended or interpenetrated into the coating [64]. Hence, when the coating is damaged these healing agents are released to repair the area. However, such composites are not able to perform multiple healing sessions nor be applied as extra thin coatings due to the required particle size to efficiency self-heal. On the other hand, intrinsic self-healing occurs through reversible chemical bonds, such as Dies–Alder bonds, siloxanes, metal coordination, and others [65,66]. Due to the reversibility of the chemical bonds, this type of self-healing material can perform several cycles of cracking and healing before it degrades. Hence, it is a viable tool for industrial applications. Yet, manufacturing of these materials can be challenging as they often require organic solvent and complex synthesis, which may increase the overall cost for large-scale processes. To find an alternative to these drawbacks, one possible way is using compounds that contain disulfide bonds (–S–S–), which do not impose challenging synthesis. Also, self-healing properties can be triggered by UV-light and thermal curing, among other ways [67]. Other paths to introduce these type of properties were studied by Shahabadi et al. [68], who manufactured lignin that was noncovalently bonded with graphene, named lignin modified graphene (LMG) composite. The LMG was blended with a WPU dispersion in the desired quantity. Different from the reversible bond mechanism for self-healing, the process with LMG occurs through viscoelastic recovery, which is the movement of two interfaces created after a cut toward each other to reestablish the surface. This process is effective since it can take place in around 150 s of exposure to infrared radiation. Aside from self-healing properties, the composite also presented UV resistance and conductibility of 0.276 S/m which prompted applications as an antistatic coating along with corrosion protection.
The correlation between structure, multifunctional properties and applications of PVD MAX phase coatings. Part II. Texture and high-temperature properties
Published in Surface Engineering, 2020
The multiple self-healing cyclic behaviour of Ti2AlC MAX phase bulk material as well as the two extreme cases, single cycle self-healing material and ideal self-healing healing material, are schematically shown in Figure 17. A single cycle self-healing material exhibits one healing action only. It repairs the damage almost completely and then fractures to failure if a new damage event occurs [254]. An ideal self-healing material is attractive because it can heal damage many times and in such a manner that the healed material has comparable mechanical properties to the base material. For such a material there is no accumulation of damage to such a level that catastrophic failure would occur and the material has an infinite lifetime under the encountered damage and healing conditions [254].
Reliability analysis for systems with self-healing mechanism under two different types of cumulative shocks
Published in Quality Technology & Quantitative Management, 2022
In the above literature, although some researches have considered the shock models and self-healing mechanism. However, either only the shock model is considered, or both the extreme shock model and the self-healing effect are considered. Moreover, for most practical systems, the shock damage of equipment or structure is cumulative. And the shock damage will have an evolutionary effect, (e.g., see reference Gao et al. (2020)), due to the self-healing mechanism. It is worth noting that this paper only considers the evolution of cumulative damage effect to good state until the system fails in a self-healing processes. In our model, two different types of cumulative shock models for systems with self-healing mechanism are considered in discrete time. Therefore, the study of cumulative shock model is very useful in practical engineering, especially in systems engineering with self-healing mechanism. For example, self-healing materials in the field of materials science produce self-healing effects when a self-healing material in a device or structure is stimulated by heat, light, electric field or moisture. Moreover, it can accurately identify the occurrence of equipment damage and repair the loss of the equipment itself. In the development of aerospace industry, this self-healing material has been widely used in the related products of polymer matrix composites. Aircraft with such self-healing material components may experience some external shocks, such as turbulence and so on, which can cause some damage to the fuselage. When the cumulative damage effect of the fuselage exceeds the required threshold, a component of the fuselage will fail, and which may even cause huge losses. However, if no shock occurs in a period of time, the damage to the fuselage will continue to heal itself until the next shock event interrupts the self-healing process. Based on the analysis above, this phenomenon can be described by the models to be developed in the paper.
Reliability assessment and lifetime prediction of degradation processes considering recoverable shock damages
Published in IISE Transactions, 2021
Tingting Huang, Yuepu Zhao, David W. Coit, Loon-Ching Tang
It is shown in the literature that recoverable shock damage exists for some types of products and materials, and these products and materials can recover fully or partially in a certain time after the occurrence of shock damage. Several examples of real-world problems in which a system can recover from shocks are:Materials such as rubber, fiber-reinforced plastics, and polyurethane can show an annealing (or lessening damage) phenomenon after damage (Takács, 1960; Nakagawa, 2007).In the material domain, a self-healing material can be developed by the integration of mono- bi- or tri-dimensional containers (layers, capsule, fibers or vascular network) loaded with active components into the matrix material or by the development of intrinsically self-healing materials, which can restore their chemical or physical bonds via thermo-reversible bonds under the influence of a non-disruptive external stimulus (Shen et al., 2018).A rotated mechanical device may be damaged by some small external shocks, and the damage does not result in a failure for the rotated device, i.e., the device can still run although it received some shocks. On the other hand, the health state of the device becomes worse for additional shocks. However, because of the lubrication oil, the health state of the device can be improved before the next shock arrives as the working process continues (Cui et al., 2018).Traffic accidents may have a great impact on the reliability and safety of traffic networks. For a traffic network, a traffic accident is a kind of damage that may cause traffic congestion, with the reliability and safety of the traffic network being decreased. Since traffic accidents need to be remedied by dispatching manpower and material resources, traffic accidents may not be dealt with immediately after an accident has occurred. The self-healing process of a traffic network can last for a period of time (Li et al., 2018).