Phase Change Materials (PCM) in the textile
In textiles, protection against extreme environmental conditions is a very important requirement. The clothes we out of water, cold, intense heat, flames, high voltage, protects powered bullets, toxic chemicals, radiation, biological toxins, etc. are just some of the images.

Such equipment is used as sportswear, wear the defense, to take account of firefighters to wear flak jackets and other professionals. TextilesProducts can be designed, useful if you change the properties of textile materials with all types of environments.

Currently, to satisfy the previous phase change materials requirement (PCM) is such an intelligent material. Absorbs, stores and releases heat in accordance with the various changes in temperature and is most often applied to the production of intelligent materials.

Phase change materials
"Phase Change" is the process whereby one state to another, for example,from solid to liquid. Any material that the process of phase change, the experience is designated as phase change materials (PCM).

Gather these materials, discharge or absorb heat in the range between the solid and liquid. The waste heat, as has been transformed into solid state and absorb as a return to a liquid state. There are three basic phases of solids, liquids and gases, but others, like the lens, are colloid, glassy, amorphous, and the phases of plasma as. There

This phenomenon of basic science was originally developed for the construction and suits for the astronauts of the space program of the United States are used. Fits the astronauts kept warm in the black void of space and the cold light of the solar system. Phase change materials are compounds that melt and solidify at certain temperatures and are therefore able to meet or maintain large amounts of energy.

The storage of thermal energy by changing the phase of a material at a constantThe temperature is called latent heat ", ie the transition from a liquid to solid state. PCM when changing experiences of a phase that requires an enormous amount of energy. The most important characteristic of the latent heat is that it is transferring the transfer of large amounts of energy as heat sensitive.

Quiet some of these stages PCM in a temperature range above and below the temperature of human skin. This property of certain substances used in manufacturingProtective clothing throughout the year, and suddenly changing environment. Fibers, fabrics and foams with PCM storage integrated body heat and leave behind the body as the body needs. As the phase change process is dynamic, the materials are in continuous transition from solid to liquid and back to the physical movement of the body and outside temperature. In addition, phase change materials used, but they never used to get up.

Are phase change materialsWax that the distinctive saturation and radiate heat, without the temperature. These waxes are eicosanoic, octadecane, Nonadecane, heptadecane and Hexadecane. All have different freezing and melting points, and when mixed in a micro heat and heat to release and maintain their temperature range of 30-34 ° C, which is very easy to accumulate in the body.

The amount of heat through a PCM at the present exchange rate with the absorbedQuantity of heat in a normal heating process can be absorbed by water are assessed as PCM. The melting of ice in water leads to the inclusion of latent heat of almost 335 J / g. When the water is further boiled, a sensible heat of only 4 J / g is absorbed, while the temperature has risen by one degree. Therefore, the absorption of latent heat in phase change from ice to water at 100 times more sensitive the absorption of heat.

How assimilate PCM in textiles?
Micro --Encapsulated PCM can be combined with non-woven or knitted fabric.

The capsules may be added to the tissue in various ways, such as:

Microcapsules: Microcapsules in different shapes - round, square, triangle fibers within the polymer phase. The PCM microcapsules are permanently in the structure of the fiber during the process of wet-spinning fiber production step. Microencapsulation is a softer hand, more distance, more breathability and air permeability ofMatter.

Embedded coating matrix in the process of finishing: The PCM microcapsules in a composition of coating, such as acrylic, polyurethane, etc, and applied to the tissue. There are methods of coating are available in many as the knife roll, knife-over-air, pad-dry-cure, gravure, Dip coating and transfer.

Dispersion Foam: microcapsules in a water-blown polyurethane foam blended mix and these foams, a substance used in a rolling process, where the water is removedthe system through the drying process.

Body and clothing systems
The thermal insulation of the necessary clothing system depends mainly on physical activity and environmental conditions such as temperature and relative humidity. The amount of heat generated by people, depends heavily on physical activity and can vary from 100W to about 1000W of rest during maximum exercise capacity.

Especially during the colder months (about 0 ° C), beat the heat insulationis defined to ensure that the body is sufficiently warm when resting. With vigorous activities, which are often a case with the winter sports, the body temperature increases with increased heat production. To keep the increase within a certain period of time, the body sweats to extract energy from the body through the evaporation of cold. If the thermal insulation of clothing is reduced during exercise, some of the heat generated can be removed by convection, rather than the body needsshould take as much sweat.

The quality of insulation in a garment in the form of heat and cold will be largely maintained by the thickness and density of the materials that compose it. High thickness and low density make a better insulation. It is, in many cases, the isolation provided by the air gap is observed between the layers garment.

However, the outside temperature also affects the effectiveness of isolation. The most extreme temperatures, either very high or very low, theless effective the insulation. To develop a suit for its ability to protect against heat and cold, and its producers as regards the aspect of climate in which the garment will be selected account.

Even if a dress made of thick fabric products will have more weight, and restrict the movement of the wearer. Of course, then a suit by an intelligent fabric designed by its nature can vary depending on the temperature, provide excellent protection.However, they have a garment comfortable for the wearer.

Effect of temperature change of PCM
PCM microcapsules can create small, the heating and cooling of a temporary effect in layers of clothing, the temperature reaches the level where the transition temperature PCM. The effect of phase change materials on the thermal comfort of protective clothing systems, is likely to be higher when the authors say is often caused by transient temperature (back and forth between a hot andcold) or touch from time to time, or handling cold objects. The temperature of the PCM layers of clothing must often vary for the buffering effect to continue.

The best known example is the transformation of water into ice at 0 ° and water vapor at 100 °. There are many products that the phase change near the body temperature and are incorporated into fibers and laminates or coating substrates, stage or close to body temperature and change in such a way that supports the body's equilibriumTemperature and keep it more stable. E 'for athletes in extreme conditions and people who have participated in extreme sports like mountaineering and trekking. Will be used in industrial applications where people are very mobile, for example inside and outside the cool room.

Effects on materials

If the PCM condensate is heated to the melting point, it takes energy to heat and a solid to liquid. This phase change produces a cooling effect in the short termclothing layers. The warmth of the body or may be from a hot environment. Once the PCM is completely melted the storage of heat stops

If the PCM garment is worn in a cold environment, where the temperature is below the freezing point of the PCM and the temperature of the material below the transition temperature, the micro-encapsulated liquid PCM will return to solid state, energy heating and heat a short-term effect. The developers claim that this is an exchange of heatBuffering effect in suits to minimize changes in skin temperature and continue with the thermal comfort of the wearer.

The layer of clothing (s), consisting of PCM needs to change through the phase transition temperature from the PCM and produce either go or absorb heat. Therefore, the carrier has to go to an overload on the temperature of the PCM-making tissue. PCM are temporary phenomena. They have no effect on steady-state thermal environment.

Microclimate active cooling systemsBatteries required, pump type, circulating fluid and plants for the production of body art cooling satisfactory, but their performance can be adjusted and made for a long time he continued. However, they are expensive and complicated. Currently, passive devices using micro-climate changes in the latent phase, both) through the liquid for evaporation of water gas (Hydroweave containing a solid phase shift through a liquid corn starch, water or gel in a paraffin plastic bubble.

The evaporation of a liquidClothing is cheaper to give, but only found minimal or short-term slowdown for the environment of high humidity in protective clothing. You also need to re-wet clothes for reuse revive. The water-cooling garment of starch gel is currently favored by the military, and can be used satisfactorily for an extended period and provide cooling in the vicinity of 32 degrees F () 0 degrees Celsius, but can also feel very cold on the skin and the need to practice a freezer very cold (5 ° F), in whole or rejuvenationGarment. If fully loaded, the gel-PCM are a bit 'rigid blocks, and the garment is limited breathability.

Paraffin PCM other garments are relatively less expensive, but their plastic bubbles can divide, so its content or the drop becomes a serious fire hazard. Moreover, it melts the paraffin-PCM of 65 ° C (18 ° C) and must be recharged at temperatures below 50 ° C (10 ° C) in refrigerator or ice chest. Their rate of cooling is also reduced with time, such as paraffinBlocks are thermal insulation and control of heat, which can be transferred within or outside of them. The use of plastic bubbles to the PCM, a severe limitation of airflow and breathability of the head, leading to their amenities included.

Uses PCM

Automotive textiles

The scientific theory of the temperature of the PCM is used in different ways for the production of textiles. In the summer may increase the temperature inside a carclear whether the car park outside. For the temperature inside the car while driving, many cars are equipped with air conditioning, although with a corresponding cooling capacity needed a lot of energy. Therefore, the application of technological change in the process of material in various applications for car interiors could increase the energy saving and thermal comfort in the interior.

Clothing plays an active role

Sportswear is expected to offer athermal equilibrium between the heat produced by the body, while a sport and the heat released into the environment. Not meet these requirements normal Active Wear forever. The heat from the body painstakingly created an often discharged into the sum required, so that in the circumstances of heat stress. On the other hand, in the pauses between activities that produce less heat generated by the human body. By virtue of the release of heat,Hypothermia can cause. The application of PCM in clothes seen under a thermal shock, thermal stress and thereby supporting and helping them to improve efficiency, work in conditions of high stress.

Clothing Lifestyle - stylish fleece jackets, men and ladies' hats, gloves and waterproof clothing.

Outdoor sports - Jackets Clothing and coatings jacket, boots, golf shoes, sports shoes, socks and gloves to ski and snowboard.

Real benefit in space suits and gloves, phaseChange materials are also used in consumer products.

Aerospace Textile

Phase change materials used in consumer products were made primarily for use in space suits and gloves to protect astronauts from temperature fluctuations higher, while vehicular activities in space.

The benefits of insulation comes from micro-encapsulated phase change material (PCM micro), set up primarily to make the room warm gloves of astronauts walking.The materials have been accepted as an ideal liner glove, extreme temperatures, while the support of the space environment.

Medical Textiles

Tissues with phase change materials (PCM), already may soon find use in the medical field. To increase the comfort thermo-physical surgical clothing as coats, hats and gloves. In bed, as mattress covers, tents and blankets. A product that the burden on the patient, warm enough to remain in service, helping insulateadapted to the temperature of the body.

Other uses of PCM

Phase change materials are currently used in textiles, the extremities: including gloves, boots, hats, etc. can be selected PCM different for different applications. For example, the skin temperature near the fuselage is about 33 ° C (91 ° F). Even if the skin temperature of almost 30 feet -31 ° C. PCM materials can be useful at 16 ° C, sufficient for the comfort of a man wearing a ski boot to ensure the snow.Are increasingly applied in the protection of basic body, and in areas of displacement blankets, sleeping bags, mattresses and mattress pads.

PCM Types

Standard phase change materials are generally a polymer / carrier with a thermally conductive filler, which changes from a solid into a highly viscous liquid (or semi-solid) was filled to a certain transition temperature. These materials are also uneven surfaces and possess wetting properties such as thermal grease, thegreatly reduce the contact resistance at the distinctiveness of the interfaces. Because of this composite structure, phase change materials in order to survive the mechanical forces during the shock and vibration of the situation, provide, or component to mechanical damage. Even the semi-solid state of these materials at high temperatures leads to the issue of the "out" under the curve of thermo-mechanical pump.

Significantly when heated to a temperature of transition focused materialsoftened fluids near as physical condition, in which the thermally conductive material expands a bit 'volume. This volume growth is more thermally conductive material in the river and replace the microscopic air gaps exist between the heat sink and electronic components. With the air gaps between the surface temperature, a high degree of wetting of surfaces filled reduces the contact resistance.

In general, there are two types of material phase transitions:

.Thermally conductive and electrically insulating.
. Electrically conductive.

The main difference between the thermally and electrically conductive material, the film or the carrier that covers the phase-change with the polymer. With electrically insulating material that can least voltage insulation properties are achieved.

Analysis of the thermal barrier function of phase change materials in textiles

Producers can now access with PCM thermal comfort in a vastRange of clothing. But knowing how much and what type of PCM for application and modification of textiles to make a fit for their purpose, it is important to quantify the effect of the provision of these active thermal barrier materials.

The total capacity of the heat of PCM in many products depends on the specific heat and its quantity. The amount requested, taking into account the expected operating conditions, the desired effect and its thermalduration and the thermal capacity of the specific PCM. The structure of the carrier system and the end-use product also affects the thermal efficiency of the PCM, which has to be measured with respect to the material selection and the product design.

Prospect of PCM

The main challenge in developing textile PCM structure is the method of their use. Encapsulation of PCMs in a polymeric shell is an evident selection, but it adds stiff weight to the active material. Efficient encapsulation, core-to-wall ratio, out put of encapsulation, stability during application and incorporation of capsules onto fabric structure are some of the technological aspects being measured.
Though PCMs are being promoted in various types of apparel and connected products, the applications in which they can really work are limited. As superior test methods are developed for PCMs, makers of PCM materials and garments will have to further cautiously target the markets in which their products do work well.

Conclusion

Since a huge amount has been invested in research and development in these areas in the developed counties, it is expected that very soon all-season outfits will be mass-produced. For example, in Britain, scientists have designed an acrylic fibre by integrating microcapsules covering Phase Change Materials. These fibres have been used for producing lightweight all-season blankets.

Many garment making companies in USA are now producing many of such garments, like thermal underwear and socks for inner layer, knit shirt or coated fleece for insulating layer; and a jacket with PCM interlines for outer layer, beside helmets, other head gears and gloves. Such clothing can maintain warm and comfortable temperatures in the extreme of both weathers. There is no doubt that textile which integrate PCMs will find their way into several uses in the near future.

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