Science & Tech

Why Do Some Clothes Shrink When Washed? 

It is a sad experience when a beloved garment shrinks in size when washed. Cleaning all clothes by following the care and washing instructions on their labels is a task that requires a lot of time and attention. Having an idea about the chemical structure of textile products and how they interact with water can help us keep them in the size we want.

Fabric fibers can be examined in 3 basic categories: synthetic, plant-based and animal-based. Most clothes are produced by using these fiber types purely or by mixing them, which can react differently to cleaning methods due to their chemical structures. Synthetic fibers are polymer chains consisting of small units called monomers, usually obtained from petroleum. These fibers, which we often encounter with examples such as polyester and nylon, are hydrophobic, meaning they repel water molecules. For this reason, fabrics made from synthetic fibers generally do not interact negatively with water molecules when washed and maintain their size.

Plant-based fabrics such as cotton and linen contain cellulose polymer, which is formed by joining glucose monomers end to end. The cellulose fibers in the structure of these fabrics are hydrophilic, meaning they attract water molecules. Thanks to this feature, cotton fabrics absorb water when washed in the washing machine and then release it when dried. In this way, the fabrics are cleaned without any permanent effects. However, high-temperature washing and drying processes can change the structure of these fibers and reduce the size of the fabric. Most manufacturers try to prevent this problem by shrinking plant fibers with appropriate methods during the production stages.

The fibers from which animal protein-based fabrics such as wool and silk are produced have sections that interact with water differently. These fibers contain tube-shaped structures with a hydrophilic inner section and a hydrophobic outer section. The outer surface of the fibers can repel water in situations with low water interaction, such as light rain, and keep the fabric dry. However, when the fabric is washed with plenty of water, water molecules can enter the hydrophilic inner section of the fiber and get trapped there. This is the reason why woolen clothes dry for a long time after washing. The entry of a large number of water molecules into the inner section causes the fiber to swell. The outer section of the fiber starts to shrink in length to compensate for the volume change in the inner section. When the garment dries as a result of evaporation, the fibers maintain their shortened shape, in other words, the fabric shrinks.

To clean garments at risk of shrinkage, the manufacturer's recommended instructions can be applied, or the dry cleaning method, which uses special chemical cleaners with solvents other than water, can be preferred.

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Personalized Smart Clothing Production

Electronic textile products (also called e-textiles) are produced by applying wearable technologies to fabrics. These products have begun to play an important role in health monitoring systems thanks to their comfortable and unobtrusive use.

By equipping textile products with various sensors, critical health information can be monitored in real time and mobile. These technological textile materials are used in military, sports and various fields as well as healthcare services.

So far, a wide variety of methods and materials have been used in the production of e-textile materials. These include methods such as dip coating, electrochemical deposition, chemical and physical vapor deposition and various printing techniques. By applying these techniques, conductive materials can be integrated onto textile materials. However, in most of these techniques, it becomes quite difficult to apply complex and personalized sensor designs to different fabric types due to the needs such as heat, vacuum, precursors, plasma systems and evaporation. In general, a series of conductors such as nanoparticles, nanowires, nanotubes, graphite, polymers or composites are used in the production of e-textile materials.

Among all these materials, the conductive polymer polypyrrole (PPy) stands out for its use in e-textile production due to its properties such as mechanical softness, high electrical conductivity, ease of synthesis, compatibility with human skin and resistance to corrosion and oxidation. However, the high precision and accuracy of coating conductive polymers such as polypyrrole on different types of fabrics is quite difficult due to the nature of the wet polymerization process. Because when the polymerization reaction takes place, undesirable events such as agglomeration and clustering can occur, making it impossible to print at high resolution.

Reactive spray printing was developed to overcome this problem. This method provides polymerization on the ground, that is, by allowing long-chain molecules to react on the fabric surface. Thus, problems such as agglomeration and clogging at the spray tip are eliminated. However, due to the lack of sufficient development of efficient and fast chemical mixing mechanisms, large-scale printing still faces problems. In a study conducted jointly by Purdue University and Hanyang University and published in the journal ACS Nano, researchers announced that they have succeeded in presenting an innovative method that enables programmable printing of sensor arrays onto consumer textiles using a two-stage spraying system. This new development aimed at solving the problem in question has achieved high-efficiency textile printing. For this purpose, an advanced spray technology that facilitates printing through high-efficiency chemical mixing and high-speed spraying has been introduced.

Unlike traditional spraying techniques, this approach obtains conductive polymers through a reaction carried out on the fabric. With this method, which can be described as in-situ printing, printing processes can be carried out at very high resolution even on very large fabrics. In addition, since the polymerization reaction takes place on the fabric, the problems of nozzle (the tip that allows the material to be applied to the fabric) clogging, which are commonly encountered in such processes, are eliminated. With all these positive developments, the performance of sensors integrated into fabrics is increasing, while at the same time user-friendly e-textile products with comfortable, easy-to-wear and clean features can be obtained.

E-textiles produced with flexible fabrics can better adapt to the body and provide a wide range of monitoring opportunities from subtle movements to larger body movements. Beyond such very basic sensing applications, e-textiles, which have the potential for real-time environmental and biometric monitoring, dynamic user interaction and virtual reality experiences, are expected to be of great importance in various markets such as interactive fashion, sports, security equipment and entertainment, and this technology, which can be designed specifically for the individual, is expected to become even more integrated into daily life in the near future.