What is coating?
Before we talk about fabric coating and its various methods, we must first examine the general concept of coating. In general, coating means creating a coating layer on various objects. Coatings are used in various industries to create new properties in materials or to increase its durability and strength. In the textile industry, it is also used for various purposes, such as preventing the shifting of the fabric and maintaining its durability, waterproofing the fabric, resistance to the sun, shining the surface of the fabric (specifically for banner fabric) and… Fabric coating operation is used. Different methods are used for fabric coating in the world, and we will explain these types of methods below.
Why do we need fabric coating?
For different fabrics with different applications, naturally, there can be different reasons for coating, which we mention here. For example, for the banner fabric, the coating operation is done to waterproof the fabric as well as the ability to print with high quality on the fabric. Actually, the banner fabric is a simple fabric with a thin white PVC coating on it. This PVC layer increases the durability of the fabric so that it is not so-called loose when installing the banner in different places and can maintain its appearance. Another advantage of banner fabric coating is that, in addition to making the fabric waterproof, it has the ability to print different designs with a high variety of colors easily and with very good quality without spreading the color.
As another example, to increase the resistance and sun protection of tarpaulin fabric, it is also coated.
In the case of bag and luggage fabrics (fabrics that are used in the production of bags and luggage), fabric coating is done to prevent the weft of the fabric from shifting. If the bag and luggage fabrics are not coated, the product produced with them will be soft and loose, and the fabric will not have the necessary endurance to maintain its shape.
In special cases, polyurethane can be used instead of PVC material, which is one of the types of adhesives. The use of polyurethane makes the fabric waterproof completely and with a high quality level, so that it does not disappear after washing, getting moisture, wrinkling, etc. It should be noted that the fabric waterproofed by polyurethane does not change much in terms of thickness. In fact, these materials penetrate into the fabric and are not clearly recognizable like other coatings.
Types of fabric coating methods:
CALENDERING method:
In this method, first a thin film of PVC material is made by calender machine and it is rolled into a roll exactly like a cloth roll. After the PVC film is produced, it is time for the laminating machine. In such a way that the fabric roll on which the coating operation is to be performed is placed on one side and the PVC film roll produced by the calender machine on the other side is placed in the laminating machine. This device has two pressure rollers, one of which is metal and the other is rubber. The roll of fabric and the roll of PVC film enter these pressure rollers and due to the pressure and heat applied to them, they stick to each other or are ironed. If the PVC film does not have the required heat to stick properly on the fabric, before this step it is passed over several thermal cylinders to reach the desired temperature. Finally, the PVC film completely adheres to the surface of the fabric through the appropriate heat and pressure, and the coating operation is performed.
In another method, PVC powder is poured on the fabric and heated until it becomes molten or paste-like. Then, like the previous method, the cloth and PVC powder that is poured on it and becomes a paste, passes under the pressure rollers. In this way, the PVC powder sticks evenly and flat on the fabric through the heat and pressure applied to it, and the coating operation is performed.
Paste coating method:
first step: Production of PVC paste
In this method, PVC paste is first produced with a special formulation. To put it simply, PVC powder is purchased and mixed with other materials such as auxiliary oil, DOP oil, carbonate, etc. based on the formula and percentage. After that, these materials are mixed with a good mixer so that the materials are uniformly combined in the whole dough, and PVC dough, which can be said to be similar to cream in appearance, is produced.
The formulation of materials for fabric coating can be different according to the application of the fabric or the customer’s order. For example, to produce waterproof tarpaulin fabric, anti-UV materials are added to the coating formulation. Or to make the banner fabric shiny, titanium is added to the formulation. In general, the fabric’s softness or dryness, sun protection, shine, shape or sponginess, etc. can be managed by changing the fabric coating formulation. Apart from the mentioned items, the desired color can be added to the PVC paste to color the fabric coating.
Golshan Resalat Factories Group, with several decades of experience in the production of industrial and resistant fabrics and using modern knowledge, formulates fabric coating in various types with the utmost precision and quality using the paste coating method.Paste Coating) and even in summer and winter due to the change in the ambient temperature, in order to manage the softness and dryness of the fabric, fabric coating is done with different formulas. This has caused the final product produced by this company to be of the highest quality, according to market participants and consumers.
This coating method is also known as Roll and Knife method. The reason for this name is that the fabric coating machine consists of a wide and large roller (Roll) and a blade (Knife) that is located on this roller. The distance between the blade and the roller can be changed and it is usually adjusted from one tenth to half a millimeter based on the thickness of the coating material on the fabric.
second step: Impregnation (coating) fabric with PVC paste
The process of fabric coating in this method is that the PVC paste produced in the previous step is poured behind this blade and the fabric is fully attached and fixed on the surface of the roller. As long as the roller is rotating, the fabric is passing under the blade, and the PVC material or PVC paste sticks to the fabric as thick as the distance between the blade and the surface of the fabric. In this way, a layer of PVC paste is uniformly placed on the surface of the fabric.
third step: Cooking ingredients
At this stage, the cloth impregnated with the material is heated and the PVC paste is completely cooked and sticks better on the cloth through the heat given to it. In other words, after the fabric is coated with PVC paste, both sides of the fabric are fixed and heated using a Stenter device. In this way, the PVC paste is completely cooked and sticks to the surface of the fabric.
Fourth step: Perfect adhesion
At the end, for full adhesion and fixation of the material on the fabric while the fabric is still hot and cooling, it is put into the pressure rollers. The pressure applied to the PVC paste at this stage makes the material stick completely and uniformly on the surface of the fabric.
You may have seen that some coated fabrics have a special pattern or design. This role is hacked at the stage of pressure rollers on the fabric. As mentioned earlier, the upper roller is made of metal and the lower roller is made of rubber. If the metal roller that is on top of the fabric and is in contact with the coated part, has a pattern or design, its design is engraved on the coated part of the fabric.
The fifth step: cooling
After this stage and in the final stage, the fabric coated with the coated material is placed on the cold water rollers to cool down. In fact, the role of these rollers is only to lower the temperature and cool the fabric. After this stage, the coating operation is completed and the fabric is rolled and ready to be sold in the market.
Golshan Factory Group carries out the mission of fabric coating operations with advanced formulations and based on the uses and applications of the fabric, as well as according to the customer’s order, with the highest quality. To order fabric coating, contact the factory’s sales experts.
