Coating and lamination are among the production methods of textile products that come to the forefront with their technical performance and functional properties rather than the appearance and aesthetic features they provide. Coating or laminated fabrics have many uses, from agricultural textiles to medical textiles, from home textiles to protective clothing. The performance and functional properties of the fabrics produced by these methods vary according to the coating material used, the technique applied, and the structure and properties of the textile surface.
In order to be protected from external factors such as bad weather conditions, the first step was taken to coating fabric technology by transferring substances such as oil and wax onto the fabric, obtaining a fabric with limited permeability properties. With the discovery of rubber and polymer materials and the developments in the chemical sector, products with different properties and different usage areas have begun to be obtained.
Technical textiles are an expensive product group with high added value, resistant to chemicals, weather conditions, microorganisms, having superior performance and functional properties. Lamination and coating are techniques applied to add functional properties to fabrics used in technical textile production and to increase their usage areas. Coated and laminated fabrics produced for protection from external factors have many uses, from agricultural textiles to medical textiles, from construction areas to protective clothing.. The functional properties of these fabrics may vary according to the coating material used, the production technique applied, and the structure and properties of the textile surface.
Coating fabrics; It is obtained by coating one or both surfaces of the fabric produced as woven, knitted or non-woven surface with a chemical substance.
Coating and lamination is applied in order to improve and change the physical and aesthetic properties of fabrics, and to expand the usage area by combining the advantages of fabrics, polymers, foams and films.
Textile products obtained as a result of coating and lamination processes constitute an important part of the textile industry today. The increase in the demand for technical textiles has also increased the demand for coated fabrics, especially in recent years.
As a result of the coating or lamination process, it is possible to produce fabrics for daily wear such as windbreakers, coats, trousers, as well as technical textiles for different uses, from agricultural textiles to medical textiles, from home textiles to protective clothing. Basically, these usage areas are apparel products, non-clothing products (artificial leather, textile products used in the construction field, airbag applications, carpet backing, applications for automobile interior upholstery), high-tech products (protective or camouflage clothing, etc.). conductive polymer coated fabrics). The properties of the product to be obtained as a result of the coating or lamination process are determined by choosing a suitable floor fabric, suitable coating material, appropriate coating or lamination technique.
Materials Used in Coating:
The possible variations of coating techniques and coating material (liquid, paste, foam) open up an almost limitless field with possible modifications of textiles for the various application purposes listed below.
Coating is a process applied for special effects that cannot be given to the fabric by normal finishing processes. According to the desired effect, chemicals in liquid, paste or powder form are transferred to the fabric in the form of powder, paste or foam, and a film layer is formed on the fabric.
The fabrics used on the floor are in the final product; while providing properties such as rupture, tearing and elongation, the coating material; It provides porosity, protection of the fabric from chemical and environmental effects and in some cases, appearance improvement. Some properties such as waterproofing, heat insulation, aesthetic appearance expected from textile material can be achieved by coating the fabrics with polymer.
The coating materials are all thermoplastic polymers, which are long chain linear molecules. The durability and performance of the final product directly affect the properties of these materials. During the coating and lamination process, the fabric and the polymer material are exposed to heat treatment and therefore it is necessary to know beforehand how the fabric and polymer material will change.
The selection criteria of the coating material are chemical, environmental, mechanical requirements, price and processing properties, depending on the desired property. General information and usage areas of the most commonly used polymer materials in coating are given above.
Floor Fabrics Used in Covering:
The fabric to be coated can be woven or knitted fabric, as well as nonwoven fabrics produced directly from fibers, and also coating can be applied in the form of yarn.
In order to make a good coating process, some basic properties are expected from the selected fabric. These are the ground fabric,
Clean, smooth, smooth surface and dense structure
to be durable
Having dimensional stability
Resistant to acids and chemicals
It is adhesion and low cost.
The most preferred fibers in ground fabric and the advantages and disadvantages of fabrics made from these fibers in terms of coating processes are given below.
In addition to the selection of the floor fabric and coating material, the method to be applied for the coating process determines the performance characteristics of the final product.
Although the coating can be made with different techniques, the technique planned to be used depends on the type of material to be coated and the desired feature to be achieved. The coating material should be in a viscosity that will allow it to spread on the yarn and fiber surfaces, and the fabric surface should be flat and smooth after coating. In each technique, before coating, the fabric should be opened to the full width, tension controlled feeding should be done, the coated fabric should be treated in a dryer before being cooled and rolled so that the solvents in the fabric can be removed by evaporation after coating.
The basis of classical coating techniques; The impregnation creates a fixed width drying in a dry hot air environment and mostly in the stenter immediately after. In addition to classical coating techniques, plasma and sol-gel technologies, which have been increasingly used in recent years, are also accepted as new methods in coating. It is possible to examine the coating methods in three sections: methods in which the coating material is liquid, methods in which it is solid, and also modern coating methods with plasma and sol-gel technology.
The lamination process is based on the principle of combining layers of fabric, or fabric and material, to form a composite material. Polymer materials that cannot be formed into coating paste are firstly filmed and then laminated to the fabric. As it can be done in coating, in lamination, the chemical substance can be transferred to the fabric in the form of foam as a solution or aqueous dispersion. At the end of the lamination process, a structure consisting of 2 or more layers, including the ground fabric, is obtained.
There are a wide variety of techniques used in lamination, and adhesives of different structures. In order to create the bonding force between the fabric and the film, it is necessary to use an adhesive material suitable for both. Adhesives used in lamination are generally water-based, solvent-based substances or substances in the form of solid or gel and hot melt. These substances, which are in hot melt form, are produced in the form of films, granules, powders or gels. These materials can be polyolefin, polyurethane, polyester, polyamide or a combination of different polymers or copolymers.
Similar to the coating technique, the method and machine to be used are determined by the method and machine to be used in lamination, the desired performance properties of the laminated fabric and the physical properties of the ground fabric. The aim in lamination is to produce a flexible laminated fabric with the desired attitude, aesthetic properties and strength by preserving the properties of the ground fabric as it is.
Lamination technique manufacture of waterproof and breathable fabrics, automobile seat upholstery and footwear can be used in many fields such as Lamination is also used in the apparel industry as a substitute for sewing on the collar, cuff or hem of garments or to support the stitching, as well as in the automotive industry and sail production.
Factors to be considered in lamination:
- Chemical structure of the materials to be used
- Surface properties of fabric
- fabric construction
- Fabric stability (stretch or shrink)
- Fabric finishing processes or oily substances on the fabric and any factor that may affect adhesion
- heat resistance
- UV and light resistance
- The durability of the bond between the fabric and the polymer substance (resistance to water, high humidity)
- Bond strength
Flame lamination is used in the production of automobile seat upholstery fabrics. The surface fabric, polyurethane foam and sub-base fabric are fed into the laminating machine, and the three materials are combined as a result. The flame that passes the surface by licking melts the foam on the surface. During the process, the foam covers the fabric surface and acts as an adhesive. Using slightly more than the required amount of foam balances the amount of foam burned.
With this method, flexible laminated fabric is produced. It is one of the most important requirements to be able to perform the bending and curling movements without cracking, especially in automobile interior upholstery fabrics.
B-Hot Melt Lamination
In hot melt lamination, two materials are joined together as a hot melt adhesive film, mesh or powder. These materials, which are then brought into the form of sandwiches, are fed into cylinders that heat the materials and melt the adhesive to form the laminate. The rollers are heated electrically and the materials take the heat from the machine but at the same time the heat is dissipated to the environment. One of the most important problems encountered in hot melt lamination is the rapid cooling of the adhesive material before contact with the second material and losing its adhesiveness.
In coated or laminated fabrics, as in other fabrics, basic structural features such as density, thickness, square meter weight of the floor fabric are important. In addition, expected performance properties are tested in order to determine the effect of coating or lamination.
A- Adhesion Test
The adhesion test is based on testing the bond strength performance of the fabric between the base fabric and its coating. This test is important because if the bond strength (adhesion) of the coating layer to the ground fabric is insufficient, separation between the layers may occur. For coated or laminated fabrics, the tensile force is measured enough to separate the film layer from the base fabric. For this, 5 fabric samples of 2,5 or 5 cm width are prepared in the weft and warp direction. In order for the coating or film layer and the fabric to be attached to the jaws separately, the coating layer is pulled from the fabric by hand and the amount of force sufficient to separate the two layers from each other is measured in the sample placed on the jaws. Adhesion testing is commonly performed according to BS 3424 or ASTM D 751-98 standards. The force required for coating adhesion is 50N/5cm. This test is applied to wet fabrics, although lower values are obtained, the acceptable adhesion force is 35 N/5 cm.
B-Wear Resistance Test
In coated fabric, testing the abrasion resistance of the coating layer is of great importance, especially since it affects the waterproofing of the fabric. The abrasion resistance of the coated fabric is determined by abrading the coated surface of the fabric with the help of an abrasive. Commonly tested, Made with a Martindale abrasion resistance meter. The amount of weight loss in the fabric after abrasion gives an idea about the abrasion resistance of the coating. In addition to its abrasion resistance, the coated fabric sample according to the usage area is expected to have a waterproof feature after 5000 cycles of rubbing.
C-Dimensional Stabilization Test
The dimensional stability test is based on calculating the percentage shrinkage that occurs in the fabric after the coated fabric has been thoroughly soaked in cold water or heated in the oven at different temperatures. Effectively adjusting the temperature settings during the finishing processes of the fabric significantly reduces the possibility of shrinkage of the fabric. If the fabric is exposed to high tension during the coating process, shrinkage may occur in the fabric during rest.