Self-Healing Technology for High-Performance Coatings

 

Gerald Wilson, Ph.D president and CEO of Autonomic Materials explains the concepts underlying the technology of self-healing high-performance coatings.

The Willamette Valley Chapter of the Construction Specifications Institute continues to produce well-attended “Lunch & Learn” continuing education opportunities. The latest edition featured a fascinating presentation on self-healing technology for coatings by Gerald Wilson, Ph.D, president and CEO of Autonomic Materials, Inc.. Self-healing materials are a class of smart materials that have the capability to repair themselves after damage.
 
Corrosion is a costly and ubiquitous problem. According to Gerald, the global cost of corrosion damage exceeds $2 trillion per year. Typical protective materials suffer a performance deficit after damage. Exposed substrates corrode, which leads to shorter lifecycles of metal assets, costly maintenance, downtime, and in the worst cases catastrophic failure. Moreover, the highest performing of the conventional protective coatings tend to be bad for the environment, generating 2 million tons of volatile organic compounds and 15 million tons of CO₂ equivalents per year in the U.S. alone. The new self-healing technologies eliminate the tradeoff between high performance and low-VOC properties.
 
In a nutshell, the concept of self-healing coatings draws inspiration from biological systems and mimics their ability to regenerate and heal. The concept is based on the ability of smart, self-healing compounds to react to physical damage by dynamically triggering the recovery of protective or aesthetic properties. Self-healing coatings are not reliant upon human intervention to activate their protection.
 
In a biological system, injury (damage) to organic tissues sets in motion a cascade of biochemical events to repair the damage. Platelets (thrombocytes) delivered through the vascular system aggregate at the injury site to form a fibrin clot. Self-healing coating technologies of the type pioneered by Autonomic Materials emulate this process. They maintain corrosion-resistance of metal assets through the delivery of microencapsulated liquid healing agents (dicyclopentadiene plus neat or wax-protected Grubb’s catalyst) carried in an epoxy resin matrix.
 
The tiny microcapsules (10 microns or less in diameter) rupture when damage occurs (such as caused by a scratch, abrasion, or weathering), releasing the healing agents to the damage site. The healing agents, which may be liquid or solid form, flow into the affected areas. They fill the voids and restore the coating’s integrity by polymerizing and healing the damage. This action occurs autonomously, without the need for external intervention. Self-healing coatings can repair multiple cycles of damage throughout their lifespan, enhancing their durability and providing sustained protection.
 
When the damage to the coated substrate is too large for the self-healing agent to completely repair, the agent will still reseal the edges of the damaged zone, preventing loss of adhesion and subsequent delamination of the coating. As a result, the coating will remain on the substrate for longer and the scope of damage needing a repair during a maintenance event will be smaller.

 

Autonomic Materials is at the forefront of the development of self-healing technology for high-performance coatings. Its potential application for the protection of metal assets is very broad. Among the markets the company is targeting for use of its products are the oil & gas, transportation, military, industrial, and infrastructure sectors. Of course, self-healing technology for high-performance coatings shows great potential for building construction applications. By incorporating self-healing coatings into construction materials, it is possible to enhance their durability, extend their service life, and reduce maintenance and repair costs.
 
Two obvious applications for the technology in building construction include the protection of concrete structures and in metal coatings.

• Corrosion of steel reinforcement can lead to structural damage and reduce a building’s lifespan. Self-healing coatings on the reinforcing steel can be formulated with corrosion inhibitors and encapsulated healing agents to neutralize the corrosive environment and prevent serious damage.
• Self-healing coatings (primarily employed in the form of primers) can provide improved resistance to UV radiation, moisture, chemicals, and physical abrasion on metal substrates used on various building surfaces, among them wall claddings, roofing, metal railings, and more.  

The implications of the widespread application of self-healing coatings are clear. Enhanced durability, and reduced maintenance and repair costs are key attributes of interest to building owners, but perhaps more importantly, self-healing coatings minimize material waste and environmental impact. With extended service life and reduced maintenance requirements, the demand for new construction materials decreases, resulting in resource conservation.

T-1000 (screen shot from Terminator 2: Judgment Day)

 
My immediate reaction as Gerald described self-healing technology is that science fiction is becoming fact. Perhaps it’s a product of my overactive imagination, but the remarkable properties of the self-healing chemistry brought to mind the T-1000, the shape shifting, menacing antagonist from the iconic movie Terminator 2: Judgment Day. Just as the T-1000 could reform itself after being shot, slashed, or torn apart, self-healing materials demonstrate an analogous level of resilience and adaptability. Their autonomous healing process mirrors the T-1000’s ability to autonomously regenerate and resume its mission.
 
Self-healing technology is a rapidly evolving field, with ongoing research and development efforts optimizing its effectiveness and rapidly expanding its range of applications. As companies like Autonomic Materials further develop new materials and methods, we can expect self-healing coatings to increasingly be relied upon to improve the durability, performance, and sustainability of construction materials.    
 

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Big thanks to the CSI Willamette Valley Chapter for producing yet another successful Lunch & Learn presentation. Thanks too to the Eugene Builders Exchange for hosting the event, and to Nick Forrest of Forrest Technical Coatings for bringing Gerald Wilson to Eugene. I’m glad I attended this session and learned about a technology I previously knew very little about. Be sure to look for the next Lunch & Learn opportunity!