29-01-2013, 02:48 PM
SELF HEALING MATERIALS AND APPLICATIONS
SELF HEALING MATERIALS AND APPL.ppt (Size: 2.49 MB / Downloads: 88)
Why Self healing?
Self-healing materials are designed to perform following functions
Provide continuous healing over lifetime
Integrate the material surface without any ridges
100 % recovery of mechanical strength
Provide early means of detection of damage
Self healing an be of two types:
Autonomic (without any intervention)
Non autonomic (needs human intervention/external triggering)
Release of healing agents:
Liquid active agents containing reservoirs embedded into the system
When crack occurs, reservoirs are ruptured, reactive agents react, solidify, heal the crack.
These can be of three types
- Capsule based:- The healing agent is stored in microcapsules
- Vascular:- Healing agent is stored in hollow channels until damage ruptures and releases the healing agent.
- Intrinsic:- This materials contain a latent functionality that triggers self healing via thermally reversible reactions, hydrogen bonding, molecular diffusion, entanglements etc.
Applications:-
Scratch proof paint:- Nissan Motor Co. Ltd has commercialized world’s first self healing clear coat.
Trade name is “Scratch Guard Coat”
It contains high elastic resins
It prevents scratches reaching the inner layers of a coated surface
Depending upon the depth of the scratch and surrounding temperature, the entire recovery occurs between 1-7 days.
Concluding Remarks and Future scope:
Micro cracking and hidden damages are the initiators for structural failures. High maintenance and repairing costs limit the acceptance of different materials in engineering disciplines. Repairing at remote positions is very difficult. Self healing materials thus help in increasing the longevity of structural materials.
Safety-critical structures such as aircraft or bridges cannot afford structural failure and so are candidates for using self-healing materials.
This field has some limitations in understanding crack healing kinetics and stability of healing functionality, thus the main challenge is autonomic detection of cracks and its subsequent healing.
SELF HEALING MATERIALS
Self healing materials.ppt (Size: 502.5 KB / Downloads: 43)
INTRODUCTION
What is self healing?
Ability of recovery
What are self healing materials?
1.A class of smart materials
2.have ability to recover them selves
process conducted through use of polymers as healing agents
process called as reverse self healing polymerization
Example Bullet Point slide
Two types of healing agents
1.Liquid based
injecting a liquid polymer to damaged area
2.solid state
introducing a catalyst into a damaged area
Inspired from biological routes
Three stages in healing
1.actuation(triggering)
2.transport
3.chemical repair
TYPES OF SELF HEALING MATERIALS
Broadly classified into three groups
1.capsule based self healing materials
2.vasculer based self healing materials
3.intrinsic self healing materials
Capsule based self healing materials
Sequester the healing agent in discrete capsules
When capsules ruptured by damage
Releases healing agent and reaction takes place
Developed for some of the most commonly used synthetic polymers and elastomers
Four main sequestration schemes
1.capsule-catalyst
2.multicapsule
3.latent functionality
4.phase seperation