Yarn coating is a vital part of textile processing to improve the performance and utility of the yarns be it textured thread or trilobal polyester thread. It entails covering the yarn with a very thin layer of a particular substance. These coatings can greatly change the properties of the yarn for its use in various applications.
Although in most related researches and commercially promoted products, the coating process is applied on synthetic yarns like polyester, nylon and acrylic, the coating process can be done on natural yarns such as cotton, wool and silk. The type of material to be used in the coating as well as the process for achieving the coating are defined by the characteristics {that should be) possessed by the final yarn.
Several approaches exist on how coating can be applied to yarns and each process also has its pros and cons. Such methods include solution coating, emulsion coating, dispersion coating and plasma coating. The choice of the proper process of layering includes some factors which are yarn type, required characteristics, and quantity.
If the key coating processes and their uses are taken into consideration, willingness to think beyond the conventional yarn making processes and develop new forms of yarn that can meet the versatile demands of the textile industry increases enormously.
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The Categories of Yarn Coating Explained
Yarn coating refers to a process of depositing a material layer on the yarn surface from a polymer, metal or a chemical compound. This coating further improves the properties of this yarn for several applications.
The primary purposes of yarn coating include:
- Improved Performance: Another advantage of coatings is that it can increase the yarn count, as well as the strength and durability of the yarns, as well as their ability to withstand regular wear and tear.
- Enhanced Aesthetics: Some of the benefits of getting a coating is that it can change the color of the yarn, enhance shine and also change the feel of the yarn.
- Functional Properties: Thus, coatings can give desired specific functional traits to yarn such as; water resistance, fire resistance, resistivity to static electricity, and protection against UV radiation.
- Protection: Some of the benefits of coatings include protection of the yarn from such conditions as humidity, UV and chemical treatment.
This way, vendors can identify the right kind of coating process and materials in order to gain the right properties needed in the use areas of yarn coating.
Types of Coating Processes
- Solution Coating
Solution coating entails treatment of yarns with a polymer solution and then subjecting them to drying to acquire an inconsequential depth film. This method is widely used on softening, lubricating and flame proofing finishes.
Key steps in solution coating:
- Preparation: The yarn is processed by first of all scouring and bleaching to wash out contamination and enhance the capacity of fibers to receive new dyes.
- Coating: The yarn is taken through a coating bath in which there is a polymer solution.
- Drying: Coating is prepared by using solvent which is allowed to evaporate and leave solid film behind on the yarn.
2. Emulsion Coating
In the emulsion coating process, a polymer emulsion is used and coated on the yarn. The emulgent is the polymer microscopic droplet dispersed in water. This method is ideal for adding finishes such as; water repellent, antistats, and UV protectors.
Key steps in emulsion coating:
- Preparation: The yarn is treated like that of solution coating.
- Coating: Subsequently, the yarn goes through an emulsion bath.
- Drying: The coated yarn is allowed to get dry to minimize formation of water which is used to form the polymer film.
3. Melt Coating
With melt coating, the polymer is applied in the molten state to the yarn. This method is used in cases where the number of layers to be applied is many and where the thickness of one layer is large like flame resistant coating and weather proof coatings.
Key steps in melt coating:
- Preparation: The yarn is prepared as in solution coating.
- Coating: The yarn is directed through a melt composed of polymer.
- Cooling: The coated yarn is cooled to materials in which the polymer has solidified.
4. Plasma Coating
Plasma coating means that the yarn is treated with plasma gas which is a gas containing partially ionized, namely a mixture of ions and electrons and neutral atom. It also has the capability to depositing thin and uniform films made from a range of materials of carbon steel, ceramics, polymers, and metals.
Key steps in plasma coating:
- Preparation: The yarn is formatted as by solution coating.
- Plasma Treatment: A plasma gas is subjected to the yarn to activate the surface thereby improving its bonding capacity.
- Coating: This yarn is then treated by what is referred to as activation, and then coated with the material that one requires.
5. Chemical Vapor Deposition (CVD)
CVD is employed as a thin film forming technique that coats materials onto the surface of the yarn. It is the process of treating yarns with gaseous chemicals and allows chemical reactions that deposit a soli coat on yarns. This method is most commonly used for the purposes of depositing a protective layer, for example a layer that will offer protection against corrosion or against wear.
Key steps in CVD:
- Preparation: The yarn is prepared as in the solution coating process.
- CVD Process: In one embodiment, the yarn is immersed into a reaction chamber where it is exposed to reactive gases.
- Coating Formation: Some chemical reactions take place on the yarns where a thin layer of the material fuses on the surface of the others.
Factors Affecting Coating Process Selection
The selection of a suitable coating process for yarn depends on several factors, including:
- Desired Properties: That is, the specific end-use properties needed in the yarn, for example, water repellent, fire retardant or anti-static, will determine the choice of coating process.
- Yarn Type: Based on the natural or synthetic nature of the yarn type, then the best coating method is as indicated above.
- Production Volume: Depending on the required production volume the proper coating process will be selected. It is seen that, where the volume of production is high, the continuous process is likely to prevail while where the extent of production is low, the batch process is more likely to prevail.
- Cost Considerations: The cost of the coating process should include the cost of the chemicals used in the process, cost of the equipment and the cost of man power used in the process.
- Environmental Impact: The coating process consumes chemicals and also energy; the effects of these materials on the environment are a factor of consideration.
Conclusion
In conclusion it has been seen how process of yarn coating are important in improving the performance and looks of clothing textiles. Manufacturers are able to apply certain characteristics, such as water proofing, fire resistance, anti-static and UV protection, among others, through using different coatings on yarns. Such coatings can be introduced by padding, spraying or dipping and some of them can be used in their pure form while others need a binder for application.
Decisions on the type of coating process are therefore influenced by the following factors; Properties of the coated yarn, Type of yarn, Production quantity. Through proper choice of the right coating process, its possible to develop textiles with desired performance characteristics to suit the individual buyer or user.
There has been an emergence of new coating techniques depending on the current trends in technology. These advancements have further capacity to develop sustainable as well as more functional textural products. For instance, low-emitting coatings that have little or no influence on the environment are now extending their market. The analysis of the various categories in coating processes and their uses will thus equip the textile producers with adequate knowledge on the various trends in the market so that they develop the right high quality and modern textiles for the market.