Applications of Smart Polymers in Textiles

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In the past few decades, revolutionary advancements in the clothing and textile industry have occurred at an unprecedented rate. Smart materials and structures brought tremendous advances in the field of smart textiles. They are divided into passive smart, active smart, and very active materials. Smart materials are actually those materials that sense and react to stimuli and surrounding environment sources like from, electrical, magnetic, and thermal sources etc. Current demand in the textile industry is of the materials with high functionality and material smartness.

For high performance of garments, shape memory polymers are used in film, foam, and fiber form. One aspect of smart clothing is that the clothing should be compatible with the skin temperature (30.4 – 36.4 °C) and any sort of environment either hot or cold. For the last 30 years, new research is done to manufacture and get suitable and desired properties for thermo-regulated and heat storage clothing. This includes various Phase Change Materials also known as latent heat storage materials.

The important functional properties of smart polymers used in textiles include volume expansion or contraction, moisture permeability, and refractive index. These properties are ­­highly dependent upon the glass transition temperature/melting temperature (Tg/Tm).

Ultraviolet, near IR, far IR rays absorbing clothing have been manufactured that provides heating or cooling effects. Smart nano-textile is also developed having some special features like self-cleaning and it also has the ability to sense and to actuate. Different conductive polymers, composites (of carbon nanotubes (CNTs) and polymers) are coated on the fiber used in the textiles. This helps to improve the mechanical and thermal properties of the textiles as well as their production. Prominent methodologies used for textile-coating include continuous wet spin coating, continuous knife over roll coater, vapor and spray methods of polymerization.

The functional properties of smart polymers play an important role in textile applications. The important functional properties include volume expansion or contraction, moisture permeability, and refractive index. These properties are ­­significantly prominent above and below the glass transition temperature/melting temperature (Tg/Tm). This is because the kinetic properties of polymer chains are very different above and below the Tg and Tm of the respective polymer. Several characterization techniques were used to test the coating’s adhesion and resistivity and other functionalities.

The objective of developing smart textiles is that they can recognize external stimuli, process the information obtained, and finally respond in a specific time and manner. Inherently conductive polymers (ICPs) show these specific properties.

The new class of textiles which is coated with conductive polymers brought tremendous changes in the field of ordinary clothing and textile. The objective is to develop textiles that can recognize external stimuli, process the information obtained, and finally respond in a specific time and manner (which is the core property of a smart material). Inherently conductive polymers (ICPs) show these specific properties and are so considered smart materials. The most commonly used ICPs in their undoped state are either insulator or semiconductor and, upon doping, their electrical conductivity increases. These include Polyacethylene, Polypyrrole (PPy), Polyaniline (PAni), and Polythiophene (PTh).

Applications of Smart Polymers

Smart polymeric textiles have wide applications in different fields of life; they are used in healthcare, sports, life jackets, and entertainment and military applications. Smart shape memory (SM) fibers are compatible with body fluids. They are mostly used to fill small or difficult wounds where access is limited.

Figure 1: Smart vent structure in smart fabrics [1]

The other potential applications are cardiac valve repair, heart stunt, bones holding screws due to their temperature adaptive change features. SMs coated surgical protective garments are used due to their thermo-physiological properties and comfort, duvet products.

Multilayer Garments

Layers of SMs are incorporated in multilayer garments, used as protective coatings and high quality leisure garments. Wide range temperature variation property with adaptable features makes SMs most promising garments. United States Army Soldiers Systems Center produces wet or dry suits for their marine force to keep them warm in marine environment and provide thermal insulation. SMs are light, so they are mostly used for such purposes. Other applications are head caps, shirt neck bands, fishing yarns [2].

Figure 2: Stimuli responsive polymer woven fabrics with time recovery (a) 0 sec (b) 30 sec (c) 60 sec [1].
Seat belts & Photochrome fabrics

Damping SM fabrics have good impact/damping strength at glass transition temperature (switching temperature). For example, block co-polymer polyethylene terephthalate and poly caprolactone SM fibers are used in seat belts and other safety fabrics. They absorb the impact force or kinetic force by utilizing the damping properties and expand as cushions for safety of passenger [3]. Polymeric hydrogels such as N-isopropylacrylamide are used as deodorant fabrics on the textile surface. They release the deodorant agents at specific temperature. These fabrics are not widely used because of handling and stability issue [3].

Photochromic fabrics have been widely used in textile as color change material. They absorb the light, change their color depending upon the wavelength of the light absorbed. Mostly used photochromes include azeobenzenes, viologens and spiropyrans. These SM materials are widely used in Jacquard fabrics, embroideries and printed garments for sake of decoration and soft display [4].

Smart Surfaces

The SM fabrics are used as smart surfaces with reversible switching between hydrophobicity, hydrophilicity and wettability. These materials are used in industrial applications for self-cleaning surfaces and tuneable optical fibers. The dual nature help the components adjust properties in both cases when the temperature is above or below the Lower Critical Solution Temperature (LCST).

Foams

Shape memory polymers have been widely used in aerospace industry as weight reducing agent e.g., as foam in pillows [3]. The pillow filled with SM foams remember the neck and shoulder shape of the user and change their shape at body temperature to provide a body comfort. SM-foams are also used in shoe insoles which effectively enhance the shoe fitting.

Figure 3: Shape memory foams applications [2].
Other applications of smart polymers

In recent decades, smart polymer coatings have been heavily investigated. This is because of their high potential in soft robotics, smart surfaces, strain sensors, wearable displays, bio-motion detectors and anti-corrosive coatings for steel. In the future, smart textiles will be used in the transportation and other industries.

Challenges

At present, the growth of this sector is slow because of the high production cost. In addition to the production cost, improvements are required in the adhesive and mechanical properties of smart polymeric textiles [5].

References

[1] J. Hu, H. Meng, G. Li, S.I. Ibekwe, A review of stimuli-responsive polymers for smart textile applications, Smart Mater. Struct. 21 (2012) 053001. doi:10.1088/0964-1726/21/5/053001.

[2] M.O. Gök, M.Z. Bilir, B.H. Gürcüm, Shape-Memory Applications in Textile Design, Procedia – Soc. Behav. Sci. 195 (2015) 2160–2169. doi:10.1016/j.sbspro.2015.06.283.

[3] S. Thakur, Shape Memory Polymers for Smart Textile Applications, in: Text. Adv. Appl., InTech, 2017.doi:10.5772/intechopen.69742.

[4] O.M. Wani, H. Zeng, A. Priimagi, A light-driven artificial flytrap, Nat. Commun. 8 (2017) 1–7. doi:10.1038/ncomms15546.

[5] M.S. Sarif Ullah Patwary, Smart Textiles and Nano-Technology: A General Overview, J. Text. Sci. Eng. 05 (2015). doi:10.4172/2165-8064.1000181.

[6] S. Park, S. Jayaraman, Smart textiles: Wearable electronic systems, MRS Bull. 28 (2003) 585–591. doi:10.1557/mrs2003.170.


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