morden self healing polymer technology

Modern Self-Healing Polymer Technology
A REPORT
Submitted by:
VIVEK A. RANA (140520724008)
In partial fulfillment for award of degree
Of
MASTERS OF ENGINEERING
In
(PLASTIC ENGINEERING)
3rd
Semester
Central Institute of Plastic Engineering and Technology,
Department Of Chemicals & Petrochemicals Ministry of Chemicals & Fertilizers
Govt. Of India
Plot No.630, Phase IV,G.I.D.C.,
Vatva Ahmedabad – 382445
Gujarat Technological University, Ahmedabad
2015

CENTRAL INSTITUTE OF PLASTIC ENGINEERING AND TECHNOLOGY
AHMEDABAD
PLASTIC ENGINEERING
2015
CERTIFICATE
Date:
This is to certify that the report entitled “Modern Self-Healing
Polymer Technology” has been carried out by Vivek A. Rana
(140520724008) Under my guidance in partial fulfillment of the
degree of Masters of Engineering Degree in Plastic Engineering
(3rd
Semester) of Gujarat Technological University, Ahmedabad,
during the academic year 2015.
Dr. Rajeev Vaghmare Dr. S K Jain
Principal Chief Manager (Technical)
HLC/CIPET- Ahmedabad HLC/CIPET- Ahmedabad
Dr. Radheshyam Giri Mrs. Hetal shah
Lecturer Lecturer
HLC/CIPET- Ahmedabad HLC/CIPET- Ahmedabad
Central Institute of Plastic Engineering and Technology,
Phase - 4, Plot No.630, Vatva G.I.D.C., Ahmedabad-382445

ACKNOWLADGEMENT
This report shall be incomplete if we do not heartfelt gratitude to those people from whom we
have got considerable support and encouragement during this semester, many people have
helped, provided direction, technical information and advice at all stages of semester and it’s our
pleasure to say thanks to all of them.
We would also deeply acknowledge Dr. Rajeev Vaghmare, Principal, HLC/CIPET-
Ahmedabad who gave us opportunity to make the report.
We are also deeply indebted to the lecturers of Plastic Engineering Department for their
motivational support and continuous flow of encouragement while working in the direction of
preparation of the seminar.
We are thankful to Dr. S K Jain, Dr. Radheshyam Giri and Mrs. Hetal shah for helping us
and providing more technical information about Modern Self-Healing Polymer Technology
and also encouraged us during the preparation of this report.
Lastly, our warm thanks to our professor staff and all our supportive well-wishers for all that we
will always be indebted to.
We are thankful to our friends for helping us out in difficult situations during our report
preparations and also our parents for supporting us throughout the semester. Above all we like to
thank Almighty for giving us strength to do the work on seminar and report.
VIVEK A. RANA (140520724008)
M.E. 3rd Semester
Plastic Engineering
CIPET Ahmedabad

Abstract
This abstract frames the complexity of the Self-healing Materials for polymer
research with a purpose & significance that any reader can understand. Polymers and
polymer composites are used in a variety of applications, which include transport
vehicles, sporting goods, civil engineering, electronics etc.., However, these materials are
susceptible to damage induced by mechanical, chemical, thermal, UV radiation, or a
combination of these factors. This could lead to the formation of microcracks deep within
the structure where detection and external intervention are difficult or impossible. The
presence of microcracks in the polymer matrix can affect properties of a polymer such as
tensile strength, fatigue life, compressive strength, impact strength etc.., Several
techniques have been developed and adopted by industries for repairing visible or
detectable damages on the polymeric structures. However these conventional repairing
methods are not effective for healing invisible microcracks within the structure during its
service life. In response, the concept of self-healing polymeric materials was proposed as
a means of healing invisible microcracks for extending the working life and safety of the
polymeric components. The development and characterization of self-healing synthetic
polymeric materials have been inspired by biological systems in which the damage
triggers an autonomic healing response. Polymeric materials may be broadly classified as
Thermoplastics, Thermosets and Elastomers. An attempt is made to draw together much
of work published in the literature and to understand the progress and prospects of
Modern Self-healing Polymeric Material.

List of Figures
Figure no Figure description Page no
1
Schematic diagram of repair concept for polymer matrix composites
using pre-embedded hollow tube
6
2
Schematic diagram of repair concept using pre-embedded hollow tubes 6
3
Self-healing concept using hollow fibers or tubes 7
4
Schematic drawing of the principle of self-healing epoxy based
laminates with epoxy loaded microcapsules and latent hardener
10
4a
Schematic drawing of the principle of self-healing epoxy based
microcapsules
11
4b
Self-healing effect by microencapsulation method in Thermoset 12
5
Car painted with “Scratch Guard Coat” 15

INDEX
Acknowledgement……………………………………………………………………………………………..…………………….I
Abstract…………………………………………………………………………………………………………………….….………….II
List of figure……………………………………………………………………………………………………………..………….… III
Index…………………………………………………………………………………………………………………………….…..…… IV
Chapter No Description Page No.
1. Introduction 1
1.1 Types of self-healing materials and the healing mechanisms 1
1.1.1 Plastics/polymers 2
1.1.2 Paint 2
1.1.3 Metals 2
1.1.4 Ceramics/concrete 3
2. Classification of Self-healing Polymers 4
2.1 Intrinsic self-healing 4
2.1.1 Self-healing based on physical interactions 4
2.1.2 Self-healing based on chemical interactions 4
2.2 Extrinsic self-healing 5
2.2.1 Self-healing in terms of healant loaded pipelines 5
2.2.1.1. Hollow glass tubes and glass fibers 5
2.2.1.2 Three-dimensional microvascular networks 8
2.2.2 Self-healing in terms of healant loaded microcapsules 9
3. Applications 14
3.1 Low cost sensitive applications 14
3.1.1 Medical dental/ artificial body replacements 14
3.1.2 Aero/Space 14
3.1.3Military 15
3.2 High cost sensitive applications 15
3.2.1Car painting 15

3.2.2 Civil construction 16
4. Benefits, Problems and Challenges 17
4.1 Benefits 17
4.2 Problems and Challenging 17
Conclusion 18
References 19

CENTRAL INSTITUTE OF PLASTIC ENGINEERING AND TECHNOLOGY Page 1
Chapter 1: Introduction
Self-healing materials, where does it come from? Indeed, this is what everyone
saw at least several times. Wounds or skin cuts heal after some time. So, it has been
natural to try to create materials possessing such a wonderful property. One can list
thousands of possible applications for such materials in variety of different fields.
Increased reliability and lifetime can be critical in medicine, space missions, traffic,
military, construction, and so on. In principle, it is possible to “heal” (recover) different
properties. For now self-healing means mostly recovery of mechanical properties. Recent
news from Nissan about successful commercial release of “self-healing” car painting has
heated public interest in such type of materials. Common names for these materials are
self–healing, self– repairing, autonomic–healing, autonomic-repairing materials. Because
all these names mean the same thing in nature, we will use just one, self-healing. As
usual, these names are used for quite a broad variety of materials with very different
healing/repair mechanisms. Here we briefly overview this variety of materials and the
mechanisms of healing, possible applications, general technical challenges.
1.1 Types of self-healing materials and the healing mechanisms
Although all types of these materials have their own self-healing mechanism, we
start from describing some common features. Virtually all materials with long
degradation time deteriorate through development of microcracks (fatigue). A sharp apex
of each crack works as a knife cutting the materials with ease. This results in larger
cracks, and consequently, mechanical degradation. Example of such material would be
plastics used for construction, artificial bones, dental cement, etc. To heal such materials,
one needs to seal those microcracks before their further growing. The other type of
degradation and the healing mechanism is important for materials that can degrade
sufficiently fast. Example of such materials can be various coatings, armor, all surfaces
that can suffer sudden impact or collision with a projectile. In such a case, not only
cracks, but even holes should be sealed and healed. Definitely there are materials of dual
purposes, which would degrade through both of the above mechanisms.

To classify self-healing materials, one can consider four different classes:
1. Plastics/polymers,
2. Paints/coatings,
3. Metals, and
4. Ceramics/concrete.
1.1.1 Plastics/polymers
Polymers/plastics are attractive from mechanical and chemical points of view. Many
plastic materials are strong and resistant to breaking. However, once fractured, the material
deteriorates irreversibly. Even under normal wearing, plastics used to develop small cracks
that also grow irreversibly. This leads to degradation of their mechanical properties and
decreasing life time of such materials. This is where self-healing is needed the most.
It is worth noting that thermoplastic materials demonstrate interesting natural healing
property. Being heated, they can recover their mechanical integrity and properties. This can
be used to fix some impact damage even autonomically. For example, after collision with
such a plastic, there can be a dent/hole/scratch. However, as a part of the collision energy
transfers into heat. So the area of the damage can be melted and heal itself.
1.1.2 Paint
Apart from cosmetic reason, paint is typically serves to protect surfaces. Self-
healing protection coating for cars from Nissan is one of such examples. However, main
cause of wearing of paint coating is due to scratches, abrasion, and mechanical damage. It
implies a specific restriction to a possible healing mechanism. Specifically, recover of
mechanical recovery is not as important as recovery of protective property. This means,
for example, that the healing agent can seal or inhibit corrosion of the surface underneath
the crack rather than seal the crack itself. To fix scratches cosmetically, and up to some
extend protect coated surface, a rather viscous polymer can be used instead of glue.
1.1.3 Metals
Metals being superior materials in many respects, suffer from cracks, dents and
corrosion. Presently, the issue of corrosion is addressed by various coating. Self-healing

of metals is not as developed as that for plastics. So far this activity was mainly
computational, and focused on modeling of a possible design of such metals.
Electro conductivity of metals can be used in self-healing of both metals and ceramics.
1.1.4 Ceramics/concrete
There are at least three different directions in autonomic healing of structural materials.
The first one is the “classical” use of healing capsules. The second one is inhibiting
corrosion of inner reinforcement frame (like the frame in concrete). Combination of both
showed promises. An encapsulated healing compound was added to concrete. Both
corrosion mitigation (using a time-release corrosion inhibitor) and crack sealing studies
have demonstrated these materials to have the potential for increasing the life of
reinforced concrete Structures.

Chapter 2: Classification of Self-healing Polymers
According to the ways of healing, self-healing polymers and polymer composites
can be classified into two categories:
(i) Intrinsic ones that are able to heal cracks by the polymers themselves, and
(ii) Extrinsic in which healing agent has to be pre embedded.
2.1 Intrinsic self-healing
The so-called intrinsic self-healing polymers and polymer composites are based
on specific performance of the polymers and polymeric matrices that enables crack
healing under certain stimulation (mostly heating). Autonomic healing without external
intervention is not available in these materials for the time being. As viewed from the
predominant molecular mechanisms involved in the healing processes, the reported
achievements consist of two modes:
(i) Physical interactions, and
(ii) Chemical interactions.
2.1.1 Self-healing based on physical interactions
Compared to the case of thermosetting polymers, crack healing in thermoplastic
polymers received more attention at an earlier time. Wool and coworkers systematically
studied the theory involved. They pointed out that the healing process goes through five
phases:
(i) Surface rearrangement, which affects initial diffusion function and topological
feature;
(ii) Surface approach, related to healing patterns;
(iii) Wetting,
(iv) Diffusion, the main factor that controls recovery of mechanical properties, and
(v) Randomization, ensuring disappearance of cracking interface.
2.1.2 Self-healing based on chemical interactions
In fact, cracks and strength decay might be caused by structural changes of atoms
or molecules, like chain scission. Therefore, inverse reaction, i.e. recombination of the
broken molecules, should be one of the repairing strategies. Such method does
not focus on cracks healing but on ‘nanoscopic’ deterioration.

2.2 Extrinsic self-healing
In the case of extrinsic self-healing, the matrix resin itself is not a healable one.
Healing agent has to be encapsulated and embedded into the materials in advance. As
soon as the cracks destroy the fragile capsules, the healing agent would be released into
the crack planes due to capillary effect and heals the cracks.
In accordance with types of the containers, there are two modes of the repair
activity:
(i) Self-healing in terms of healant loaded pipelines, and
(ii) Self-healing in terms of healant loaded microcapsules.
Taking the advantages of crack triggered delivery of healing agent, manual intervention
(e.g. heating that used to be applied for intrinsic self-healing) might be no longer
necessary.
2.2.1 Self-healing in terms of healant loaded pipelines
2.2.1.1. Hollow glass tubes and glass fibers
The core issue of this technique lies in filling the brittle-walled vessels with
polymerizable medium, which should be fluid at least at the healing temperature.
Subsequent polymerization of the chemicals flowing to the damage area plays the role of
crack elimination. Dry first identified the potential applicability of hollow glass tubes.
Similar approach was adopted by Motuku et al. and Zhao et al. Because the hollow glass
capillaries have diameters (on millimeter scale) much larger than those of the reinforcing
fibers in composites, they have to act as initiation for composites failure. Instead, Bleay
et al. employed hollow glass fiber (with an external diameter of 15 μm and an internal
diameter of 5 μm) to minimize the detrimental effect associated with large diameter
fibers. Complete filling of healing agent into the tiny tubes was achieved by vacuum
assisted capillary action filling technique.
Accordingly, three types of healing system were developed (Figure 1)

Figure1. Schematic diagram of repair concept for polymer matrix composites using
pre-embedded hollow tubes
Figure 2. Schematic diagram of repair concept using pre-embedded hollow tubes

Figure. 3 Self-healing concept using hollow fibers or tubes
(i) Single-part adhesive All hollow pipettes contained only one kind of resin like epoxy particles
(that can be flowable upon heating and then cured by the residual hardener) or cyanoacrylate
(that can be consolidated under the induction of air).
(ii) Two-part adhesive. In general, epoxy and its curing agent were used in this case. They were
filled into neighboring hollow tubes, respectively.
(iii) Two-part adhesive. One component was incorporated into hollow tubes and the other in
microcapsules.
With the aid of the pre-embedded healing system in hollow pipettes, Motuku and
co-workers studied the healing ability of glass fiber/unsaturated polyester composites
subjected to low velocity impact. The species of healing agent, characteristic parameters
of the hollow pipes (amount, type of tubing materials and spatial distribution),
composites panel thickness, and impact energy level were found to be critical to the

healing efficiency. Meanwhile, Bleay et al. proved that the epoxy based composites
reinforced by hollow glass fibers containing solvent diluted two-part epoxy became
repairable as assessed by compression after impact test.
Recently, Trask et al. considered the placement of self-healing hollow glass fibers
layers within both glass fibre/epoxy and carbon fibre/ epoxy composite laminates to
mitigate damage and restore mechanical strength. The hollow fibers were be spoken with
diameters between 30 and 100 μm and a hollowness of approximately 50%. The study
revealed that after the laminates were subjected to quasi-static impact damage, a
significant fraction of flexural strength can be restored by the self repairing effect of a
healing resin stored within hollow fibers. For example, Pang et al. added UV fluorescent
dye to the healing resin within the hollow fibers so that bleeding of the repair substance
in the composites can be visualized.
2.2.1.2 Three-dimensional microvascular networks
In conventional extrinsic self-healing composites it is hard to perform repeated
healing, because rupture of the embedded healant-loaded containers would lead to
depletion of the healing agent after the first damage. To overcome this difficulty, Toohey
et al. proposed a self-healing system consisting of a three-dimensional microvascular
network capable of autonomously repairing repeated damage events. Their work
mimicked architecture of human skin. When a cut in the skin triggers blood flow from the
capillary network in the dermal layer to the wound site, a clot would rapidly form, which
serves as a matrix through which cells and growth factors migrate as healing ensues. Owing to
the vascular nature of this supply system, minor damage to the same area can be healed
repeatedly. The 3D microvascular networks were fabricated by deposition of fugitive ink (a
mixture of Vaseline/microcrystalline wax (60/40 by weight)) in terms of direct-write assembly
through a cylindrical nozzle. Then, the yielded multilayer scaffold was infiltrated with epoxy
resin. When the resin was consolidated, structural matrix was obtained. With the help of heating
and light vacuum, the fugitive ink was removed and 3D microvascular networks were created. By
inserting a syringe tip into an open channel at one end of the microvascular networks, fluidic
polymerizable healing agent was injected into the networks.
The healing chemistry of this method used ring opening metathesis
polymerization of dicyclopentadiene (DCPD) monomer by Grubbs’ catalyst,

benzylidenebis (tricyclohexylphosphine) dichlororuthenium, which was used successfully
in microencapsulated composites. In the crack plane, the healing agent interacted with the
catalyst particles in the composites to initiate polymerization, re bonding the crack faces
autonomously. After a sufficient time period, the cracks were healed and the structural
integrity of the coating was restored. As cracks reopened under subsequent loading, the
healing cycle was repeated.
By means of four-point bending configuration monitored with an acoustic-
emission sensor, the above approach proved to be feasible. The authors imagined
extending this approach further to integrate pumps, valves and internal reservoirs, as well
as to introduce new functionalities, including self diagnosis or self-cooling, through the
circulation of molecular signals, coolants or other species. To provide theoretical
understanding how to vascularize a self-healing composite material so that healing fluid
reaches all the crack sites that may occur randomly through the material, Bejana et al.
studied the network configuration that is capable of delivering fluid to all the cracks the
fastest.
2.2.2 Self-healing in terms of healant loadedmicrocapsules
The principle of this approach resembles the aforesaid pipelines but the containers
for storing healing agent are replaced by fragile microcapsules. Because the technique of
microencapsulation has been rapidly developed since its emergency in 1950s and mass
production of microcapsules can be easily industrialized, self-healing composites might
be thus used in practice accordingly. Jung et al. prepared self-healing polyester composite
with pre-embedded polyoxymethylene urea (PMU) microspheres. The crack repair agent
is mostly composed of styrene monomers and high molecular weight polystyrene. The
latter helps to lower the rate of diffusion of styrene or diethenyl benzene into polyester
matrix. The system of 23% polystyrene (Mn = 2.5·105), 76.99% styrene and a trace
amount of inhibitor proved to offer the optimum healing efficiency. Jung et al. also tried
to utilize epoxide monomer loaded PMU microcapsules for rebinding the cracked faces in
polyester matrix. Solidification of the epoxy resin (i.e. the repair action) was triggered by
the naturally occurring functional sites or embedded amine in the composites.
The features of this healing system lie in the following.
(i) When the healing agent is applied to epoxy based composites, the miscibility between

the crack adhesive and matrix is guaranteed because of identity of their species.
(ii) The latent hardener possesses long-term stability and is hardly affected by the
surrounding environment. Moreover, it can be well pre-dissolved in uncured composites’
matrix, leading to homogenous distribution of the reagent on the molecular scale. Thus
the epoxy released from the ruptured microcapsules might meet the latent hardener
everywhere (Figure 4 ). The two-component healant is able to take effect in the woven
glass fabric/epoxy composite laminates.
Figure 4. Schematic drawing of the principle of self-healing epoxy based laminates
with epoxy loaded microcapsules and latent hardener

Figure 4 a. Schematic drawing of the principle of self-healing epoxy based
microcapsules

Figure 4 b

Self-healing performance reached maximum levels only when sufficient healing
agent was available to entirely fill the crack. Based on these relationships, the size and
weight fraction of microcapsules can be rationally chosen to give optimal healing of a
predetermined crack size. By using this strategy, self-healing was demonstrated with
smaller microcapsules and with lower weight fractions of microcapsules.
It is believed that the nanocapsules will make selfhealing materials responsive to
damage initiated at a scale that is not currently possible and compatible with composites
where the reinforcement spacing requires smaller capsules for applications such as self-
healing thin films, coatings, and adhesives.
If the inclusion has higher modulus than the matrix, the approaching crack tends
to pass by the microcapsules; conversely, the crack could penetrate the microcapsules
when the matrix is stiffer. On the other hand, simulation experiments manifest that the
difference in fracture toughness of the microcapsules and matrix should be less than 0.11
MPa·m1/2. Otherwise, cracks would not pass through the microcapsules.
 The other critical factors include
(i) Good adhesion between microencapsulated healing agent and the matrix,
(ii) Size and concentration of microencapsulated healing agent,
(iii) Rate and degree of polymerization of the released healing agent, and
(iv) Shell thickness and core content of the microencapsulated healing agent.
 This system possesses some advantages, including
(i) The healing chemistry remains stable in humid or wet environments,
(ii) The chemistry is stable to an elevated temperature (>100°C), enabling healing in
higher-temperature thermoset systems,
(iii) The components are widely available and comparatively low in cost, and
(iv) The concept of phase separation of the healing agent simplifies processing, as the
healing agent can now be simply mixed into the polymer matrix.

Chapter 3: Applications
Applications of self-healing materials are expected to be very broad. In the future
it will have a massive impact on virtually all industries, from the automotive industry to
the energy sector. It will be able to extend product lifetimes, to increase safety, to reduce
maintenance cost. The major applications being developed today are in automobile,
building/construction, and aerospace industries. Because nowadays the self-healing
materials are in their baby stage of development, research interest and funding focus
mostly on the development of the materials rather than their applications. Below we
overview the existing and probable applications in which the self-healing is expected to
be the most valuable. It makes sense to divide all applications on low and high cost
sensitivity.
3.1 Low cost sensitive applications
In average, these applications will be developed first because self-healing can be
attainedthrough a fast development cycle, using rather cost consuming mechanisms and
materials.
3.1.1 Medical dental/ artificial body replacements
Nowadays an artificial bone replacement can last up to 10 -- 15 years.
Development of good biocompatible self-healing composite materials may extend this
time. Another application will be in dentistry. In making artificial teeth and tooth filling
materials, self-healing would benefit their functional lifetime. All such material would be
in big demand virtually independent of price.
3.1.2 Aero/Space
Extending lifetime of a satellite in orbit around Earth, say twice, would
approximately decrease the cost of the mission two times. Furthermore the increase of a
spacecraft lifetime will result in longer time missions to the destinations far away in the
Solar System, and maybe beyond. Having satellites made of lighter self-healing polymer
materials instead of metal, which is relatively heavy, is a very cost-effective solution. A

single space carrier will be able to deliver multiple satellites. And finally, safety of air-
and space crafts can be improved by using self-healing components.
3.1.3Military
Having armor, body protection that could heal itself even during the battle will be
beneficial for the Army. Air force and Navy can additionally benefit from fast self
disappearing holes in the skin of a jet or ship. A prototype of such material already exists.
Dupont’s Surlyn® show good properties to heal after ballistic damage.
3.2High cost sensitive applications
3.2.1Car painting
Cost here is one of the main issues. Self-healing should definitely be cheaper than
just repainting. One of the first commercial self-healing materials, “Scratch Guard Coat”
was released by Nisan in December of 2005. According to the press release, Scratch
Guard Coat contains a newly developed high elastic resin that helps prevent scratches
from affecting the inner layers of a car’s painted surface. With Scratch Guard Coat a car’s
scratched surface will return to its original state anywhere from one day to a week,
depending on temperature and the depth of the scratch. Moreover, the paint is
hydrophobic. While the composition and healing principle has not been resealed, the
New scratches One week later
Figure 5. Car painted with “Scratch Guard Coat”

healing mechanism is clearly within the mechanisms described above. Presumably it was
possible to create a similar paint a while ago. The real state-of-the-art of the Nissan paint
is its fairly low cost and long lifetime.
3.2.2 Civil construction
Tones of these materials are required. Self-healing capsules might solve some
problems. However, this action is unlikely to be within the range of reasonable cost. So
far a reasonable solution was using the chalk. Calcium for self-healing concrete is cheap.
Self-healing coatings on structural steel components in, for example, bridges can be very
popular. Again, here the healing mechanism is not in recovery mechanics of the coating
but rather in protection against rust. This helps sustaining mechanical integrity of the
coated steel constructions. The working mechanism of the self-healing coating is the
release of healing/inhibiting corrosion compounds when microcapsules containing these
compounds are abraded.

Chapter 4: Benefits, Problems and Challenges
4.1 Benefits
– Improving product safety and reliability and to extend product lifetimes.
– Improved toughness
– Reduced waste disposal
– Building sustainable society
4.2 Problems and Challenging
Apart from problems and challenges related to high-cost, there are many
technological problems. It would be far beyond the scope of the present overview to
discuss these problems in detail. We will outline just main issues that are common.
Virtually any self-healing mechanism has the following steps. The healing agent has to be
delivered to the damaged region, after that the healing should be initiated, and finally, the
result of healing should be compatible with the surrounding materials.
Therefore, technical challenges can be ordered as follows:
1. Storage of healing agent inside the material for a long period of time. This is
especially difficult inside of polymeric materials, which intrinsically permeable on
molecular level.
2. Initiation of healing. The healing agent should start react either with the
surrounding material or with a special initiator. Such an initiator can be impregnated in
the surrounding material or should be mixed with the healing agent. All these create
additional problems of storage of the initiator, and mixing the initiator and the healing
agent.
3. Finally, the healing agent should be strongly bound to the material, and be
stable with respect to the surrounding environment. This indeed is typically the simplest
problem, which is however, restrictive to the type of the healing agent.
The main challenge of course is to find the solution of the above problems in the way that
can be scaled up to the mass production.

Conclusion
Achievements in the field of self-healing polymers and polymer composites are
far from satisfactory, but the new opportunities that were found during research and
development have demonstrated it is a challenging job to either invent new polymers
with inherent crack repair capability or integrate existing materials with novel healing
system.
Methods of incorporating self-healing capabilities in polymeric materials can now
effectively address numerous damage mechanisms at molecular and structural levels.
Activities in the field not only focus on mechanical and chemical approaches to
improving the durability of materials but also involves new damage detection technique
incorporated in-situ the material, although none of these are commercially viable at
present.
Besides the approaches described in the above text, ongoing attempts are
continuously presenting new concepts.
From a long-term point of view, synthesis of brand new polymers accompanied
by intrinsic self-healing function through molecular design would be a reasonable
solution. Working out the solutions would certainly push polymer sciences and
engineering forward.

References
 D. Y. Wu et al./ Prog. Polym. Sci. 33 (2008) 479 – 522 (review paper).
 Jung D. Performance and properties of embedded microspheres for self-repairing
applications. Master thesis, univ of Illinois at Urbana-Champaign, Urbana, USA,
1997.
 Kessler MR. Characterization and performance of self-healing composite material.
PhD, univ of Illinois at Urbana-Champaign, Urbana, USA, 2002.
 Brown EN, Kessler MR, Sottos NR, White SR. In-situ poly(Urea-formaldehyde)
microencapsulation of DCPD. J Microencapsule 2003: 20: 719-30.
 Self healing in polymers and polymer composites. Concepts, realization and outlook:
A review Y. C. Yuan1, T. Yin1, M. Z. Rong2, M. Q. Zhang2* 10 February 2008
 Modern Self-Healing Materials Igor Sokolov, Department of Physics, Department of
Chemistry, Center for Advanced Material Processing, Clarkson University, Potsdam,
NY 13699, USA
 Department of Materials Science and Engineering, Iowa State University, 2220
Hoover Hall, Ames, IA 50011-2300, USA.
 Nissan Motor Co., L. Nissan develops world's first clear paint that repairs scratches
on car surfaces. 2005 [Available from: http://www.nissanglobal.
com/EN/NEWS/2005/_STORY/051202-01-e.html.
 Beyer, M. and U. Keil, From abrasion resistant to self healing. Kunststoffe-Plast
Europe, 2003. 93(6): p. 88-+.
 Dry, C., Two views on self-healing polymers. Chemical & Engineering News, 2001.
79(11): p. 8-8.
 Fab, R., K.H. Kochem, and K. Muller-Nagel, New BOPP capacitor film
formetallisation with improved, performance at higher temperatures. Electronics
Information & Planning, 2000. 28(3): p. 103-109.
 Gobin, P.F., et al., Smart materials group at the national institute of applied
sciencerecent data and trends. Materials Transactions, 2004. 45(2): p. 166-172.
 EXPRESS Polymer Letters Vol.2, No.4 (2008) 238–250 Available online at
www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2008.29

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