Intelligent textiles phase change materials shape memory materials

1. Intelligent Textiles
Using phase change & shape memory materials
SUBMITTED BY...............
BHARAT GUPTA
TEXTILE ENGINEERING
3RD
YEAR 2014-18
UPTTI KANPUR
Roll No.-1404463011

2. Introduction
Although intelligent textiles and smart clothing have only recently been
added to the textile vocabulary, we must admit that the industry has
already for several years focused on enhancing the functional
properties of textiles.
The current objective in intelligent textile development is to embed
electronics directly into textile substrates. A piece of clothing remains
visibly unchanged and at the end of the day the consumer can still wash
it in the washing machine without first removing all the electronics.
Intelligent systems
Intelligent systems are normally understood to consist of three parts: a
sensor, a processor and an actuator. For example, body temperature
monitored by the sensor is transferred to the processor, which on the
basis of the received information computes a solution and sends a
command to the actuator for temperature regulation. To achieve such
interactive reactions three separate parts may actually be
needed…………….. the processor, sensor and the actuators.
Phase change materials (PCM), shape memory materials (SMM),
chromic materials (colour change), conductive materials are examples
of intelligent textiles that are already commercially available.

3. Intelligent textile and garment research is very cross-scientific. Beside
textile knowhow many other skills, such as electronics,
telecommunications, biotechnology, medicine, etc., must be brought
into the projects. One research institute cannot carry out such projects
alone. Networking as well as considerable amounts of financing are
required. There are high hopes in the scientific community toward the
EU’s seventh framework programme for financing and for further
networking within the sector.
Physiology
The intelligent garment as research object
Design research
Fibre material technology
Context of use – application area: heavy industry
The intelligent garment as an object of interdisciplinary research from
the perspective of three research disciplines: design research, fibre
material technology, and physiology.

4. Intelligent Textiles
Intelligent textiles represent the next generation of fibres, fabrics and
articles produced from them . They can be described as textile
materials that think for themselves, for example through the
incorporation of electronic devices or smart materials. Many intelligent
textiles already feature in advanced types of clothing, principally for
protection and safety and for added fashion or convenience.
One of the main reasons for the rapid development of intelligent
textiles is the important investment made by the military industry. This
is because they are used in different projects such as extreme winter
condition jackets or uniforms that change colour so as to improve
camouflage effects. Nowadays, the military industry has become aware
of the advantage of sharing knowledge with the various industrial
sectors, because with joint collaboration far better results can be
obtained through teamwork.
Intelligent textiles provide ample evidence of the potential and
enormous wealth of opportunities still to be realised in the textile
industry in the fashion and clothing sector, as well as in the technical
textiles sector. Moreover, these developments will be the result of
active collaboration between people from a whole variety of
backgrounds and disciplines: engineering, science, design, process
development, and business and marketing. Our very day-to-day lives
will, within the next few years, be significantly regulated by intelligent
devices and many of these devices will be in textiles and clothing.

5. Definition and classification of smart textiles
Smart textiles are defined as textiles that can sense and react to
environmental conditions or stimuli from mechanical, thermal,
chemical, electrical or magnetic sources. According to functional
activity smart textiles can be classified in three categories :
Passive Smart Textiles: The first generations of smart textiles, which
can only sense the environmental conditions or stimulus, are called
Passive Smart Textiles.
Active Smart Textiles: The second generation has both actuators and
sensors. The actuators act upon the detected signal either directly or
from a central control unit. Active smart textiles are shape memory,
chameleonic, water-resistant and vapour permeable (hydrophilic/non
porous), heat storage, thermo regulated, vapour absorbing, heat
evolving fabric and electrically heated suits.
Ultra Smart Textiles: Very smart textiles are the third generation of
smart textiles, which can sense, react and adopt themselves to
environmental conditions or stimuli. A very smart or intelligent textile
essentially consists of a unit, which works like the brain, with cognition,
reasoning and activating capacities. The production of very smart
textiles is now a reality after a successful marriage of traditional textiles
and clothing technology with other branches of science like material
science, structural mechanics, sensor and actuator technology, advance
processing technology, communication, artificial intelligence, biology,
etc.

6. New fibre and textile materials, and miniaturised electronic
components make the preparation of smart textiles possible, in order
to create truly usable smart clothes. These intelligent clothes are worn
like ordinary clothing, providing help in various situations according to
the designed applications.
New/Smart materials and fibres used in smart textiles
'Smart' or 'Functional' materials usually form part of a 'Smart System'
that has the capability to sense its environment and the effects thereof
and, if truly smart, to respond to that external stimulus via an active
control mechanism. Smart materials and systems occupy a 'Technology
space', which also includes the areas of sensors and actuators.
Introduction to phase change materials
Generally speaking, phase change materials (PCM) are thermal storage
materials that are used to regulate temperature fluctuations. As
thermal barriers they use chemical bonds to store and release heat and
thus control the heat transfer, e.g., through buildings, appliances and
textile products.
In a cold environment the primary purpose of clothing is to protect the
wearer from cold and thus prevent the skin temperature from falling
too low. Conventional thermal insulation depends on the air trapped in
the clothing layers. When this layer of air gets thinner, e.g., due to

7. windy weather, thermal insulation will be reduced significantly. The
situation is the same when the garment becomes wet or perspiration
condenses in it. It is possible to increase the thermal comfort by
interactive insulation which means use of phase change materials,
because compression and water has no effect on the insulation
properties of PCM. Phase change technology in textiles means
incorporating microcapsules of PCM into textile structures. Thermal
performance of the textile is improved in consequence of the PCM
treatment. Phase change materials store energy when they change
from solid to liquid and dissipate it when they change back from liquid
to solid. It would be most ideal, if the excess heat a person produces
could be stored intermediately somewhere in the clothing system and
then, according to the requirement, activated again when it starts to
get chilly.
Heat balance and thermo-physiological comfort It is very important to
maintain a relatively even temperature to guarantee human vital
functions. The normal human body temperature, 37 ‒C, fluctuates a
little according to the time of the day, being at its lowest early in the
morning and its highest in the evening. Also temperatures in different
parts of the body fluctuate a little. For example, the temperature of the
internal organs in the core of the body is higher than the temperature
in other areas. In physical exercise the temperature of the muscles can
rise to 39–40 ‒C. The surface parts of the body and the extremities are
from time to time almost hemocryal according to the changes in the
ambient air temperature. Trying to reach thermal equilibrium, man
produces and dissipates different amounts of heat depending on the
ambient air temperature. Depending of the physical workload, the
human being produces a heat quantity of 100 W in the state of rest and

8. up to 600 W by physical effort. Heat production can temporarily be
even more, e.g., in skiing up to 1250 W. This resultant quantity of heat
has to be dissipated to prevent any marked increase in the rectal
temperature and to maintain thermal equilibrium. The human being is
in heat balance, when heat production is equal to heat loss. Factors
influencing heat balance are the produced heat quantity (physical
activity, work), ambient conditions (temperature, wind, humidity), the
clothing worn and the individual properties of humans. Clothing is
comfortable when humans feel physical, physiological, and mental
satisfaction as heat and moisture transfer efficiently from the body to
the environment through the clothing. Therefore, development of
intelligent fabrics, including thermal storage/release ones, which can
adjust and maintain comfort as circumstances change, is very important
and necessary.
Phase change technology
Phase change materials are latent thermal storage materials. They use
chemical bonds to store and release heat. The thermal energy transfer
occurs when a material changes from a solid to a liquid or from a liquid
to a solid. This is called a change in state, or phase.5 Every material
absorbs heat during a heating process while its temperature is rising
constantly. The temperature of a PCM rises until it reaches its melting
point. During the physical phase change the temperature remains
constant until the PCM has totally changed from solid to liquid.

9. Energy is absorbed by the material and is used to break down the
bonding responsible for the solid structure. A large amount of heatis
absorbed during the phase change (latent heat). If the material is
warmed up further its temperature will begin to rise again. The latent
heat will be released to the surroundings when the material cools
down. The temperature remains constant again until the phase change
from a liquid to a solid is complete, when the crystallization
temperature of the PCM is reached. PCMs absorb and emit heat while
maintaining a nearly constant temperature. In order to compare the
amount of heat absorbed by a PCM during the actual phase change
with the amount of heat absorbed in an ordinary heating process,
water is used for comparison. If ice melts into water it absorbs
approximately a latent heat of 335 J/g. If water is further heated, a
sensible heat of only 4 J/g is absorbed while the temperature rises by
one degree. Therefore the latent heat absorption during the phase
change from ice to water is nearly 100 times higher than the sensible
heat absorption during the heating process of water outside the phase
range.6 In addition to water, more than 500 natural and synthetic PCMs
are known. These materials differ from one another in their phase
change temperature ranges and their heat-storage capacities. Solid-
solid PCMs absorb and release heat in the same manner as solidliquid
PCMs. These materials do not change into a liquid state under normal
conditions; they merely soften or harden. Relatively few of the solid-
solid PCMs that have been identified are suitable for thermal storage
applications. Liquid-gas PCMs are not yet practical for use as thermal
storage. Although they have a high heat of transformation, the increase
in volume during the phase change from liquid to gas makes their use
impractical.

10. PCMs in textiles
The most widespread PCMs in textiles are paraffin-waxes with various
phase change temperatures (melting and crystallization) depending on
their carbon numbers. The characteristics of some of these PCMs are
summarized in Table . These phase change materials are enclosed in
microcapsules, which are 1–30 mm in diameter. Compared to our hair
the size of the capsule is usually about half the diameter of human hair
or it can be 1/20th of it. Phase change materials can be incorporated in
textiles only enclosed in thesecapsules in order to prevent the
paraffin’s dissolution while in the liquid state. The shell material of the
capsule has to be abrasion and pressure resistant, heatproof and
resistant to most types of chemicals. Outlast®, Comfortemp® and
Thermasorb® are commercially available PCM products based on
paraffin-waxes and microcapsule technology. Hydrated inorganic salts
have also been used in clothes for cooling applications. PCM elements
containing Glauber’s salt (sodium sulphate) have been packed in the
pockets of cooling vests.

11. Textile treatment with PCM microcapsules
Usually PCM microcapsules are coated on the textile surface.
Microcapsules are embedded in a coating compound such as acrylic,
polyurethane and rubber latex, and applied to a fabric or foam.
Capsules can also be mixed into a polyurethane foam matrix, from
which moisture is removed, and then the foam is laminated on a fabric.
you can see PCM microcapsules (Outlast) in fabric and how it works.
PCMs-containing microcapsules can be incorporated also into acrylic
fibre in a wet spinning process.
In this case the PCM is locked permanently within the fibre. The fibre
can then normally be processed into yarns and fabrics.
a ‘cooling’ effect, by absorbing surplus body heat „ an insulation effect,
caused by heat emission of the PCM into the textile structure; the PCM
heat emission creates a thermal barrier which reduces the heat flux
from the body to the environment and avoids undesired body heat loss
„ a thermo regulating effect, resulting from either heat absorption or
heat emission of the PCM in response to any temperature change in the
microclimate; the thermo-regulating effect keeps the microclimate
temperature nearly constant.

12. Intelligent textileswith PCM
Basic information on phase change materials Phase change is a process
of going from one physical state to another. The three fundamental
phases of matter, solid, liquid and gas, are known but others are
considered to exist, including crystalline, colloid, glassy, amorphous and
plasma phases. Substances that undergo the process of phase change
are known as phase change materials (PCMs). By definition PCMs are
materials that can absorb, store and release large amounts of energy, in
the form of latent heat, over a narrowly defined temperature range,
also known as the phase change range, while that material changes
phase or state (from solid to liquid or liquid to solid). The phase change
from the solid to the liquid state occurs when the melting temperature
in a heating process is reached. During this melting process the PCM
absorbs and stores large amounts of a latent heat. The temperature of
the PCM remains nearly constant during the entire process (Fig. 4.1).
During the cooling process of the PCM the stored heat is released into
the environment within a certain temperature range and a reverse
phase change from the liquid to the solid state takes place. During this
solidifying process the temperature of the PCM also remains constant.
Thus the PCM can be used as an absorber to protect an object from
additional heat, as a quantity of thermal energy will be absorbed by the
PCM before its temperature can rise. The PCM may also be preheated
and used as a barrier to cold, as a larger quantity of heat must be
removed from the PCM before its temperature begins to drop. The
phase change process results in a density and volume change of the
PCM that has to be taken in consideration into its application. The best-
known PCM is water, which at 0 ‒C becomes ice or evaporates at 100

13. oC. In addition to water, the number of natural and synthetic phase
change materials known today exceeds 500. These materials differ from
one another in their phase change temperature range and their heat
storage capacities. In order to obtain textiles and clothing with thermal
storage and release properties the most frequently used PCMs are
solid–liquid change materials. Research on solid–liquid phase change
materials has concentrated on the following materials…. linear
crystalline alkyl hydrocarbons „ fatty acids and esters „ polyethylene
glycols (PEG) „ quaternary ammonium clathrates and semi-clathrates „
hydrated inorganic salts (e.g.lithium nitrite trihydrate, calcium chloride
hexahydrate, sodium sulphate decahydrate, zinc nitrate hexahydrate) „
eutectic alloys, containing bismuth, cadmium, indium, lead.
The keyparametersof microencapsulated PCMare:„ particle size anditsuniformity„core-to-shell
ratio,withPCMcontentas highas possible „thermal andchemical stability„stabilitytomechanical
action.

14. Applications of textiles containing PCMs
Fabrics containing microPCMs have been used in a variety of
applications including apparel, home textiles and technical textiles.
Some exemplary applications are presented below……
Apparel
Major end-use areas include: „ life style apparel – smart jackets, vests,
men’s and women’s hats, gloves and rainwear „ outdoor activewear
apparel – jackets and jacket lining, boots, golf shoes, trekking shoes,
socks, ski and snowboard gloves „ protective garments.
In protective garments PCMs functions are as specified:
„ absorption of body heat surplus „ insulation effect caused by heat
emission of the PCM into the fibrous structure „ thermo-regulating
effect, which maintains the microclimate temperature nearly constant.
 Smart Apparel
 Medical Textiles
 Textile Sensors
 Space Wears
 Extreme Climate Wears
 Active Sports Wear
 Automative Textiles
 Domestic Textiles

15. The use of phase change materials in outdoor clothing

16. Introduction to shape memory material
Overview
Shape memory materials(SMMs) are a set of materialsthat,
due to external stimulus, can change their shape from some
temporary deformed shape to a previously‘programmed’
shape. The shape change is activatedmost often by changing
the surrounding temperature, but with certain materials also
stress, magnetic field, electric field, pH-value, UV light and even
water can be the triggering stimulus . When sensing this
material specific stimulus, SMMs can exhibit dramatic
deformationsin a stress free recovery. On the other hand, if the
SMM is prevented from recovering this initialstrain, a recovery
stress (tensile stress) is induced, and the SMM actuator can
perform work. Thissituationwhere SMA deforms under load is
called restrained recovery.
TYPES
Shape memory alloys
Shape memory ceramics
Magnetic shape memory materials
Shape memory polymers and gel
Here shape memory polymers are described for textile
purpose....

17. Shape memory polymers and gels
General properties of shape memory polymers Shape
memory polymers (SMPs) were first introducedin 1984 in
Japan.Shape memory behaviourcan be observed for
several polymers that may differ significantlyin their
chemical composition. In SMPs, the shape memory effect
is not related to a specific material property of single
polymers; it rather results from a combinationof the
polymer structure and the polymer morphology together
with the appliedprocessing and programming technology .
Just like SMAs, the most common stimulus in SMP
applicationsis heat. However, there is much ongoing
research on systems, which may respond also to other
stimuli, such as UV light, water, pH, electric or magnetic
field. Some success has been reported on light and water
induced SMPs [3, 5]. A thermally inducedpolymer
undergoes a shape change from its actual, deformed
temporary shape to its programmed permanent shape
after being heated above a certain activationtemperature
Ttrans [2]. SMPs are characterised by two main features,
triggering segments having the thermal transition Ttrans
within desired temperature range, and cross-links
determining the permanent shape.

18. Depending on the kind of cross-links, SMPs can be
thermoplastic elastomers or thermosets . Segmented
polyurethanethermoplastic SMPs have two separated
molecularphases, a hard segment and a soft segment,
with different glass transition temperatures, Tg,hard being
higher than Tg,soft. The polymer can be processed using
conventionaltechniques(injection,extrusion, blow
moulding) to desired shapes. During the processing stage,
the material is at or above the melting temperature,
Tmelt, and all of the polymer chainshave high degrees of
mobility.Once the material cools down to Tg,hard, the
configurationof the hard segments is ‘stored’ by physical
cross-links. However, at temperatures between Tg,soft
and Tg,hard, the soft segments still allow the material to
deform to a temporary shape while the physical cross-links
of the hard segments store strain energy. Below Tg,soft,
the material is completely glassy, and will hold a deformed
shape without external constraint. When the material is
heated back above Tg,soft, the soft segments are too
mobile to resist the strain energy stored in the bonds of
the hard segments, and an unconstrainedrecovery from
the temporary deformed shape to the original‘stored’
shape occurs. At temperatures higher than Tg,hard, the
physical cross-links of the hard segments are released,
thus erasing the ‘memory’ of the polymer.

19. As the polymer is a three-dimensionalnetwork, a SMP can
fully recover near 100% strain in all three dimensions .
Before starting the cycle the SMP is first heated to Tg,soft..
The first step of the cycle describes the high-strain
deformation of the SMP to the desired temporary shape.
During step 2 the material is cooled under constraint to
hold the deformation. The stress required to hold this
earlier deformed shape diminishes graduallyto zero as
temperature decreases. The temporary shape is now
‘locked’ and the constraint can be removed. In the final
step of the cycle, the SMP is subjected to a prescribed
constraint level and then heated again towards Tg,soft. ,
the two limiting cases of constraint are shown, namely a
constrained recovery and an unconstrainedrecovery.
Constrained recovery implies the fixing of the
predeformation strain and the generation of a gradually
increasing recovery stress. Unconstrained recovery implies
the absence of external stresses and the free recovery of
the induced strain. With the increase of temperature, the
strain is graduallyrecovered. After the shape recovery
step, the remaining strain is calledresidual strain.
Recovered strain is defined as the pre-deformation strain
minus the residual strain . further illustratesthe material’s
behaviourduring an unconstrainedshape recovery.

20. The benefits of SMPs over SMAs : „ much lower density „
very high shape recoverability (maximum strain recovery
more than 400%) the shape recovery temperature can be
engineered to occur over a wide range „ the recovery
temperature can be customised by adjustingthe fraction
of the hard and soft phases „ less complicated(and more
economical) processing using conventionaltechnologies„
fast programming process „ some polymer networks are
also biocompatibleand biodegradable.
Drawbacks of SMPs: „ low recovery time „ low recovery
force; SMP’s abilityto generate a ‘recovery’ stress under
strain constraint is limitedby their relatively lower
stiffness, the shaperecovery property is lost when rather a
small amount of stress (<4 MPa) is appliedto the
polyurethanecomponents[1]. However, the stiffness and
recovery stress of shape memory polymers can be
substantiallyincreased, at the expense of recoverable
strain, by the inclusionof hard ceramic reinforcements . „
Polyurethane SMP may lose its shape fixing capabilityafter
being exposed to airat room temperature (about 20 ‒C)
for several days. It can, however, fully regain its original
properties after being heated up to its melting
temperature .

23. Principle of temperature sensitive shape memory
polymer
Shape-memory materialsare stimuli-responsive materials. They
have the capabilityof changing their shape uponapplicationof
an external stimulus. Shape memory may be triggered by heat,
light, electric field, magnetic field, chemical, moisture, pH and
other external stimuli [5–6]. Change in shape caused by a
change in temperature is called a thermally induced
shapememory effect. These are materials which are stable at
two or more temperature states. While in these different
temperature states, they have the potentialto be different
shapes once their ‘transformation temperatures’ (Tx) have
been reached. Shape memory alloys(SMAs) and Shape
Memory Polymers (SMPs) are materials with very different
shape changing characteristics. While exposed to their Tx,
devices made from SMAs have the potentialto provide force

24. such as in the case of actuators. Devices made from SMPs in
contrast, while exposed to theirTx, provide mechanical
property loss as in the case with releasable fasteners. The
shape memory polymers described in this chapter are all
thermosensitive shape memory polymers. Temperature
sensitive shape memory polymers are a special class of
adaptivematerialswhich can convert thermal energy directly
into mechanicalwork. This phenomenon,known as the shape-
memory effect (SME) occurs when one of these special
polymers is mechanicallystretched at low temperatures, then
heated above a critical transition temperature, which results in
the restoration of the originalshorter ‘memory’ shape of the
specimen [14]. The proposed theory expresses well the
thermomechanicalproperties of thermoplastic polymer, such
as shape fixity, shape recovery, and recovery stress [1]. The
mechanism of shape memory behaviorwith temperature
stimuli can be shown as outlinedin Fig. 7.3. These materials
have two phase structures, namely, the fixing phase which
remembers the initialshape and the reversible phase which
shows a reversible soft and rigid transition with temperature.
At temperatures above the glass transition temperature (Tg),
the polymer achieves a rubbery elastic state (Fig. 7.4) where it
can be easily deformed without stress relaxationby applying
external forces over a time frame t < t, where t is a
characteristic relaxationtime. When the material is cooled

25. below its Tg, the deformation is fixed and the deformed shape
remains stable. The pre-deformation shape can be easily
recovered by reheating the material to a temperature higher
than the Tg [15]. Therefore, admirableshape memory behavior
requires a sharp transition from glassy state to rubbery state, a
long relaxationtime, and a high ratio of glassy modulusto
rubbery modulus. The micromorphologyof SMPs strongly
affects its mechanical properties. There are many factors that
can influencethese SMPs: chemical structure, composition,and
sequence-length distributionof the hard and soft segment in
segmented polymer, overall molecularweight and its
distribution.An elastomer will exhibit a shape-memory
functionalityif the material can be stabilized in the deformed
state in a temperature range that is relevant for the particular
application.The shape is deformed under stress at a
temperature near or above Tg or the segment crystal melting
temperature, Tms. The deformed shape is fixed by cooling
below Tg or Tms. The deformed form reverts to the original
shape by heating the sample above Tg or Tms.

27. APPLICATIONS
Medicaltextiles
Smart fibre
Surgical protective garments
Outdoorclothing
Casual clothing
Sportswear
Breathable fabrics
Protective Clothing
References……
1..Intelligent textiles and clothing
Edited by H. R. Mattila
CRC Press Boca Raton Boston New York Washington, DC
WOODHEAD PUBLISHING LIMITED Cambridge, England
2..http://www.indiantextilejournal.com/articles/FAdetails.asp?i
d=852