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Self Healing Materials

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Nathalie Moyano

on 19 November 2013

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Transcript of Self Healing Materials

Self Healing Materials
Structure & Properties
Nathalie Moyano
Ben Medina
Marie Williams
How are self healing materials made?
How do self healing materials work?
Structure of self healing materials
Properties of self healing materals
Performance and testing of existing self healing materials
The future of self healing materials

What Will be Covered
Alicia Reshard

Current Applications
Developing Applications
Future Applications
Self-healing porous asphalt
• Infrared heater driven over asphalt every few years to supply energy to the resin that binds the gravel together
• The resin cools and resets the loose gravel
• Structural integrity is regained

Self-healing Anticorrosion Coatings
Most commonly used are polymetrics (highly modifiable).
Mechanisms include:
passivation through oxidation
water repellant or absorbent properties
barrier formation
ruthenium Grubb's catalyst (RCG) reactions (unstable, toxic)
Micro or nano tubes in matrix (one time effect)
poly(HFBMA-co-ITEGMA) copolymer (zipper effect)
polyelectrolytes as pH stabiliers and mobile coatings
flourine based coatings and protective coating
Self Healing Scratches
When bonds are ruptured during a scratch, less reactive molecules do not reform bonds while more reactive molecules for linkage.
Nissan employs a scratch “healing” technology, Scratch Shield
Clearcoat on paint job is high strength, high density and highly elastic to deter scratches
Microvascular Substrate Networks
Biological Inspirations
Ultimate limitations on materials relies on the cohesion reactions between atoms
Current Testing on SHM
Pros & Cons of SHM's
Limitations of SHM's
Atomic bonding
Healing agent and concentration amount
Manufacturing & processing
Only low damage recoveries
Current Improvements
"Now, how curiously our ideas expand by watching those conditions of the attraction of cohesion! - how many new phenomena it gives us beyond those of the attraction of gravitation! See how it gives us great strength!" - Michal Faraday
SMH development and charaterization is inspired by the world around us
Current Testing Methods
Continuous Damage Mechanics Models
Continuous Damage Healing Mechanics Models (CDHM)
Fracture toughness Experiments
Tapered Double Cantilevered Beam
Initial Test
Rest period
Self Healing
Recorded recoveries of material properties
Manual Intervention
Voids with microcapsules
only low damage recoveries
Limited healing agents
Healing agent reactions
Faster more autonomic healing
Reduced stress concentrations
Fracture toughness recoveries
Manufacturing and processing techniques
Dicyclopentadiene (DCPD):
Liquid healing agent
Grubb's Catalyst:
Chemical trigger within epoxy material
Polymerization of Liquid Healing Agent

contacts with
Grubbs catalyst
, a ring opening
metathesis polymerization
starts, and a highly
polycyclopendiene is formed
that seals the crack.
The mean diameter of the microcapsules is 166 micrometers [4]
A 75 to 90% recovery of virgin fracture toughness is achieved [4]
Biological modeled system of isolated network region was filled with alternating components
Allows new healing chemistries to be explored, but ensures that neither healing agent is depleted [9]
1. Epoxy Resin
2. Catalyst
Bisphenol A based
Epikote 828
Hollow fibers or vascular networks embedded within polymer matrix
Bisphenol A based epoxy resin system
Matrix of epoxy and hardener within a polymer matrix releases the epoxy system when tubes are broken, causing polymerization to occur.
Bisphenol A
Bisphenol A cross-linked polymerization
Borosilicate glass fibers or microvascular networks
30 to 100 micrometers in diameter
Hollowness of 55%
Up to 97% of initial flexural strength [1]
Re-formation can be triggered by :
UV-based healing system based on cycloaddition of cinnamoyl groups (photochemical trigger)
A sample cut in half with a razor blade at room temperature healed the cut, with 97% efficiency, in just two hours
Sub-sea and Marine Applications
Epoxy with microcapsules used in protective sub-sea and marine applications
Use in oil and gas processes, both on-shore and off-shore, improved pipeline protection and reduced labor and maintenance costs due to lifetime extension [3]
• Healing rate competes with the rate of damaging forces
• Targeted self healing in aerospace and aircraft structures can simplify maintenance and allow for higher maximum stresses
• Healing rate increases under higher stresses and temperature
• It is proposed that acoustic energy can supply local stress and heat generation to defects
• A few studies support this idea but more research is needed to quantify the effects and analyze the mechanisms [8]
Polymer substrates, polymer composite
3-D networks deliver healing agents to cracks in coatings containing solid catalysts
Limited by concentration and availability of catalyst [6]
In addition to self-healing, thermal regulation, growth, and chemical detection are possible
Autonomic materials systems may lead to self-diagnosis and self-cooling
Use of biomaterials to promote tissue growth and fully regenerative materials [7]
Energy release rate
Independent of crack length by width taper
3 Types
Manual catalyzed, injected
Catalyst embedded, agent injected
Finite fracture-mechanics models
Prediction of formation of cracks
Strain energy
Single crack
Differentiated to find mechanical energy release rate
Fracture Test
4 point bending
Coating Tension
Crack detection
Acoustic emission sensor
The purpose of self-healing is considered as the recovery of mechanical strength through crack healing.

The first demonstration in an engineered materials system: early 2001

1. Autonomic
-Without human intervention upon breaking
2. Nonautonomic
- External intervention required upon breaking
- Respond to specific external stimuli such as heat or UV radiation for healing.
Types of Self Healing Materials
Healing agent
Microcapsule shell
Chemical catalyst
Polymer matrix and fiber-reinforcement
How they're made:
How it works:
Capsules are embedded during the manufacturing process
Upon cracking, capsules release the catalyst
Chemical reaction seals the crack
Microcapsules were prepared by in situ polymerization in an oil-in-water emulsion
Microcapsule Fabrication
Testing Cont.
Diameter: Average microcapsule diameter = 10-100 um
Agitation rate increase = finer emulsion and the average microcapsule diameter decreases.
Testing of Capsules
Influence capsule rupture behavior and healing agent release in self-healing materials
UF Microcapsule size analysis was performed with an optical microscope
Surface morphology and capsule shell thickness were examined by scanning electron microscopy
Shell wall thickness consistently falls between 160–220nm
Elemental analysis was performed on microcapsules to determine their fill content.
Surface roughness is due to change in pH
Microvascualr Substrate Fabrication
Catalyst Recrystalization
Coating Application
Immediately following manufacturing and drying, microcapsules contain 83–92 wt% DCPD and 6–12wt% UF
After 30 days exposed to ambient laboratory conditions, the average fill content decreased by 2.3wt%
The surrounding matrix also limits further diffusion of DCPD through the microcapsule shell.
Direct-write assembly used to embed interconnected 3D microchannel networks in an epoxy matrix

3D scaffolds are fabricated and layered with a ink using a robotic deposition apparatus

60 wt% petroleum jelly (Vaseline, Chesebrough-Ponds) and 40 wt%
microcrystalline wax (Bard’s Tacky Wax, Bard)
Composed of an array of 200µm cylindrical rods

Separation distance of 2 mm between each rod in a given layer
Ink scaffold is filled with uncured EnviroTex Lite epoxy (ETI) and allowed to cure at room temperature for 48 h
Fugitive ink is removed by heating the substrate to 75 C and applying a light vacuum
Grubbs’ catalyst requires further processing to achieve better solubility in the DCPD.
The catalyst is recrystallized using methylene chloride and acetone
Catalyst crystals are composed of a rod-like morphology
Average length of 10µm and diameter of 0.75µm
Epoxy coating produced by degassing 12 p.p.h. of diethylenetriamine in EPON 828 resin
The mixture is poured into a mould, in which the microvascular substrate serves as the underlying substrate.
Substrate is filled with a fugitive wax -prevents the epoxy from entering the microchannels
Cures for 24hr at room temperature
Coating is polished using lapping oil to the desired thickness (approximately 700µm)
University of Illinois at Urbana-Champaign
E. N. Brown , University of Illinois at Urbana-Champaign
Dicyclopentadiene (DCPD) - Healing Agent
Urea-Formaldehyde (UF)
Ammonium Chloride
Ethylene maleic anhydride (EMA) - Copolymer
The shell wall thickness (of the smooth non-porous inner region) is largely independent of manufacturing
Enhances mechanical adhesion of the microcapsules when embedded in a polymer
Improves performance in self-healing applications
Self-healing reaction
Particles swarm
damaged area
Self-healing functionality
No agents
Damage triggered
Microcapsule Pro's & Con's
Remarkable mechanical performance
Large recoveries of material properties
Easy to manufacture
Limited repair
Size & concentration
Rate of polymerization
Microcapsule rigidity
Manufacturing & processing

Microvascular Pros & Cons
Biological architecture
Continuous delivery of healing agents
3D network structure
Manufacturing and processing
Catalyst concentration affects achievable healing cycles
Intrinsic Polymer Pros & Cons
High polymer concentration allows efficient reformation of bonds
Polymer properties
chemical stability
Long term durability
Complex nature
Degradation due to environmental conditions
Increased healing efficiency and repeatable healing functionality
Multiple thermal re-mending cycles
Contain chemical bonds that can re-form after having sustained damaged
Heat-initiated healing technologies include re-mendable polymers
Crack healing is based on Diels-Alder and retro-Diels-Alder reactions at temperatures between 90 and 120 degrees
Researcher Ibon Odriozola at CIDETEC Centre for Electrochemical Technologies

Comprised of a poly (urea-urethane) elastomeric matrix
a network of complex molecular interactions that will spontaneously cross-link to “heal” most any break
“spontaneous” meaning that the material needs no outside intervention
healing process is triggered by damage
What are the three types of self healing materials and what are their pros and cons/ limitation?
Describe how each type of self healing material works and what components they are made out of.
List and describe three applications of self healing materials and which type they use.
List and describe the current testing methods for self healing materials.
[1] Self-healing Materials: Fundamentals, Design Strategies, and
edited by Swapan Kumar Ghosh
[3] [3]
[7] Fundamentals of Composites Manufacturing: Materials, Methods
and Applications By A. Brent Strong
[8] Patrick, J.F., Sottos, N.R., White, S.R. Microvascular Based
Self-healing Polymeric Foam, Polymer, 53,4231-4240 (2012)
[12]Self-Healing Polymers: From Principles to Applications
edited by Wolfgang H. Binder
Thank You!
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