Self Healing Coatings
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Final Presentation for CHEM466 Polymers Course at Texas A&M University
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Self Healing Coatings
- 1. Self-Healing Coatings A Case Study: Poly(DCPD) Mohammed AlShammasi April 11th 2012
- 2. Presentation Layout • Introduction – Self-healing coatings – Structural schemes • Synthesis • Characterization – Chemical properties – Mechanical properties • Applications • Conclusion
- 3. Introduction> Self-healing Coatings Smart Materials (stimuli: mechanical, electrical, thermal, …) Coatings (antifouling, antimicrobial, Poly(dicyclopentadiene)/Gru conductive, ….) bbs’ catalyst system Self-healing Coating Systems
- 4. Introduction> Self-healing Coatings • are characterized by: 1. Responsiveness
- 5. Introduction> Self-healing Coatings • are characterized by: 2. External stimuli
- 6. Introduction> Self-healing Coatings • are characterized by: 3. Programmed structure
- 7. Introduction> Structural Schemes Capsule-based Microvascular Intrinsic
- 8. Synthesis> ROMP of DCPD
- 9. Synthesis> ROMP of DCPD
- 10. Characterization> Chemical Properties 1. NMR
- 13. Characterization> Mechanical Properties Material Structure Loading Conditions Maximum healing scheme efficiency (%) Epoxy Microvascular Mode I four-point 38-70 bend Expoy/E-glass FRC Capsule-based Mode I DCB 60 Epoxy Capsule-based Mode I TDCB 75-93 Epoxy/embedded SMA Capsule-based Mode I TDCB 77 wires Epoxy vinyl ester Capsule-based Mode I TDCB 30 Epoxy/carbon FRC Capsule-based Mode I WTDCB 80
- 14. Characterization> Mechanical Properties • SEM Images
- 15. Applications> Benefits • Benefits of using self-healing coatings: Enhances product safety Protects structural bodies Reduces inspection costs
- 17. Conclusion • Types of structural schemes for healable coatings: 1. Capsule-based 2. Microvascular 3. Intrinsic • In poly(DCPD)/Grubbs’ coating system – Polymerization via ROMP – Chemical characterization through NMR and UAS – Mechanical testing to examine healing efficiency – Benefits are product safety, costs, and protection – Has applications in military, auto, construction, ...
- 18. THANK YOU!
Editor's Notes
- So as you can in this chart, smart materials include a wide variety of materials which are able to response to different external stimuli. They can be divided according to their stimuli into many groups such as or their functionalities... A specific functional group of smart materials so-called smart coatings contains many subgroups such as antifouling, antimicrobial, conductive, and others. In this presentation, we will focus on one of these groups, that is self-healing coating systems.
- So three things make self-healing coatings different from other types of coatings: one is responsiveness. As you can see in this chart, self-healing coatings behave similar to biological healing systems in our bodies except that their response is usually much faster. The healing mechanism is often very similar too to the biological one. As soon as a damage occurs, an actuator triggers the healing mechanism in which some healing materials is moved to replace the damaged part of the coatings and to finally restore the matrix.
- 2. The types of external stimuli for self-healing coatings are very specific. They include certain types of mechanical damages to the materials such as microcracking and scratch.
- 3. self-healing coatings have programmed structures which can be described by what we call structural schemes. One of the common structural schemes is capsule-based structure which is usually used for our case study: poly(DCPD)/Grubbs’ catalyst systems. In this system, healing agents are stored in microcapsules which are distributed in an epoxy that contains a catalyst.
- Speaking of structural schemes for self-healing coatings, there are three main types of structural schemes: capsule-based, microvascular, and intrinsic. Capsule-based coating systems are the most common type and they are based on embedding liquid healing agents in discrete particles in the resin.When damage occurs, the capsules release their contents which undergo a polymerization reaction as soon as they come into contact with the monomers that are embodied in the epoxy.
- As a highly-branched cross-linked polymer, poly(DCPD) is well-known for its high impact and high chemical corrosion resistance. For the poly(DCPD)/Grubbs’ catalyst coating system, the polymerization is based on the ring-opening metathesis polymerization (ROMP) of DCPD monomer via Grubbs’ catalyst as shown in this slide.
- ROMP is a well-known method of polymerization that allows synthesizing long chains of polymers with C=C double bonds. Grubbs’ catalyst, through the formation of transition-metal/alkylidene complex, serves as an initiator. The transition-metal/alkylidene complex is formed via a 2+2 cycloaddition of an alkylidene to C=C double bond which result in a metallocyclobutane intermediate followed by cycloreversion.
- Using solution 1H or 13C NMR, the ROMP of DCPD in polyester resin systems were studied and analyzed by several research groups.
- Ultrasound attenuation spectroscopyIn a groundbreaking work by Constable et al. in 2003, ROMP of DCPD with ruthenium-based Grubbs’ catalyst was monitored by ultrasonic spectroscopy in a reaction injection modeling cell. Reaction kinetics’ parameters were computed from real-time measurements of density, sound velocity, acoustic modulus, and attenuation. Constable, G.S.; Lesser, A.J.; Coughlin, E.B. J. Polym. Sci.Part B: Poly Phys.2003, 41, 1323–1333.
- In order to quantify the healing performance in self-healing coating systems, a quantity called healing efficiency, 𝜂, is defined as followswhere 𝑓 is a specific mechanical property, usually fracture toughness, measured before the material is cracked (virgin state) and after it is repaired (healed state).Many factors, including structural scheme, temperature, crack size, loading conditions, and cracking rate, may affect the mechanical properties of the self-healing system after recovery In order to quantify the healing performance in self-healing coating systems, a quantity called healing efficiency, 𝜂, is defined as followswhere 𝑓 is a specific mechanical property, usually fracture toughness, measured before the material is cracked (virgin state) and after it is repaired (healed state).Many factors, including structural scheme, temperature, crack size, loading conditions, and cracking rate, may affect the mechanical properties of the self-healing system after recovery
- FRC = Fiber-reinforced compositesHere are some of the results of mechanical tests on poly(DCPD)/Grubbs’ system as conducted by White et al. in University of Michiganbased on fracture toughness. As you can see, a healing of efficiency above 90% was achieved in some cases.
- Scanning electron microscopy (SEM) is commonly used to validate the healing mechanism and the check surface before and after healing.
- Structural durabilityIn applications where a mechanical failure could lead to a catastrophic disaster, such as in aerospace parts and military equipment, material’s ability to repair its structural damage is of great interest. For other applications, where the crack detection is either difficult or costly, the use of self-healing coating systems prolongs the material’s lifespan and enhances its structural durability.Reducing inspection costs – crack detection is often a hard and costly process so using self-healing coating systems would help reducing these inspection-and-replacement-related costs.
- In summary, we talked about three structural schemes for self-healing coatings: capsule-based, microvascular networks, and intrinsic.We discussed the how poly(DCPD) is synthesized through ROMP in these systems, and how chemical and mechanical characterization is performed through NMR, ultrasonic spectroscopy, and mechanical testing. Finally we presented some of the benefits of using such systems in military and other areas as they enhance product safety, protect material’s structure, and reduce inspection costs. Thank you for listening. Any questions!!