Fabric finishing is a technique employed for treating fabrics. It imparts color effects and alters their tactile qualities, such as making them smooth or velvety. By doing so, fabric finishing enhances the visual appeal and tactile comfort of fabrics. Additionally, it improves their performance or endows them with special features through chemical or physical means. It is indeed a processing procedure that serves as an “icing on the cake” for textiles.
Fabric finishing techniques can be broadly categorized into two main types: physical/mechanical finishing and chemical finishing. Based on the objective of the finishing process and the diverse effects it generates, fabric finishing can be further classified into basic finishing, appearance finishing, and functional finishing.
The basic fabric finishing methods encompass: finishing techniques aimed at stabilizing the size and enhancing the appearance, those focused on improving the hand feel and optimizing performance, methods that render fabrics multifunctional and increase their value-added nature, finishing approaches that elevate fabrics to a more advanced level, and techniques that meet specific requirements.
Purpose of Fabric Finishing
Improve the Appearance of Textiles:
This involves improving the luster and whiteness of textiles, as well as either enhancing or reducing the fluff on the textile surface. Examples include whitening, calendering, electro-optical treatment, embossing (Yawen), sanding, shearing, and shrinking.
Improve the Tactile Quality of Textiles:
Chemical and mechanical methods are utilized to endow textiles with various textures. These textures can range from soft, smooth, plump, stiff, light, to thick. For instance, softening, stiffening, and weight gain treatments fall under this category.
Improve the Durability of Textiles:
Chemical methods play a crucial role in safeguarding fibers from damage caused by sunlight, air, or microorganisms. They effectively extend the lifespan of textiles. Moth-proof and mildew-proof finishing are typical examples.
Grant Special Properties to Textiles:
This includes conferring certain protective properties or other unique functions to textiles. Such properties may involve flame retardancy, antibacterial capabilities, water repellency, oil repellency, UV protection, and antistatic properties.
Common Fabric Finishing Processes
Preshrinkage
Preshrinkage is a method designed to minimize the degree of shrinkage that fabrics experience after getting wet. It employs physical techniques to reduce the shrinkage rate. Mechanical preshrinkage consists of the following steps: initially, moisten the fabric with steam or a spray. Subsequently, apply warp mechanical extrusion to increase the buckling wave height. Finally, dry the fabric in a relaxed state.
Stretching
Stenting is a process that capitalizes on the plasticity of fibers like cellulose, silk, and wool under wet conditions. It gradually widens the fabric to a specified dimension and dries it to stabilize the fabric’s shape. This process is also known as fixed-width finishing.
Sizing
Sizing refers to the finishing procedure in which the fabric is immersed in sizing liquid and then dried to achieve a thick and stiff tactile sensation.
Heat Setting
Heat setting serves to stabilize the shape of thermoplastic fibers and their blended or interwoven fabrics. It is primarily applied to the processing of synthetic fibers such as nylon or polyester and their blends, which are prone to shrinkage and deformation upon heating. Fabrics that have undergone heat setting exhibit improved dimensional stability and a relatively stiff feel.
Whitening
Whitening makes textiles appear whiter by utilizing complementary colors of light. There are two common whitening methods: blueing and fluorescent whitening.
Calendaring, Electro-optical, and Embossing
Calendaring is a process that takes advantage of the flexibility of fibers in hot and wet conditions. It helps to flatten the fabric’s surface and creates fine twills to enhance the fabric’s luster. Flat calendering involves a hard calendering point composed of a hard roller and a soft roller.
After calendering, the yarns in the fabric are flattened, the surface becomes smooth, the luster is enhanced, and the hand feel is rather stiff. Soft calendering, on the other hand, features a soft calendering point made up of two soft rollers. After the fabric is calendered, the yarns are slightly flattened, the luster is soft, and the hand feel is soft.
Electro-calendering involves using electrically heated rollers to calender the fabric.
Embossing utilizes a calendering point consisting of a steel roller with a positive pattern and a soft roller. Under hot rolling conditions, the fabric can obtain a glossy pattern.
Grinding, Sanding
The process of creating a short and dense layer of fluff on the fabric surface using a sanding roller (or belt) is called sanding, also known as sanding. Sanding finishing can cause both the warp and weft yarns to produce fluff simultaneously, and the fluff is short and dense.
Raising
Raising is the process of using dense needles or thorns to lift the fibers on the fabric’s surface, resulting in the formation of a fluffy layer, which is referred to as napping finishing. Raising is mainly applied to woolen fabrics, acrylic fabrics, and cotton fabrics. The fluffy layer can improve the fabric’s thermal insulation properties, enhance its appearance, and make it soft.
Shearing
Shearing is the process of using a shearing machine to cut off the unnecessary fluff on the fabric surface. Its aim is to make the fabric texture distinct and the surface smooth, or to make the fluff or velvet of raised and piled fabrics neat. Generally, wool, velvet, artificial fur, carpets, and other products require shearing.
Softening
There are two approaches to soft finishing: mechanical finishing and chemical finishing. Mechanical soft finishing is accomplished by repeatedly rubbing and bending the fabric, but the softening effect achieved is often not ideal. Chemical soft finishing involves adding a softener to the fabric. This reduces the friction between fibers and yarns, imparting a soft and smooth tactile sensation, and the finishing effect is quite noticeable.
The fabric finishing technology is constantly evolving, with a focus on functionalization, differentiation, and high-end processing. The overarching goal is to enhance the wearing performance and increase the product value. In recent times, new technologies have emerged, such as low-temperature plasma treatment, bioengineering, ultrasonic technology, and electron beam radiation, which have deepened the processing depth and improved the quality.
Other techniques like inkjet printing, microcapsule technology, and nanotechnology are also being increasingly utilized. With growing concerns about environmental pollution and degradation, people are placing greater emphasis on health and supporting a “low-carbon” economy. As a result, finishing technology calls for environmentally friendly “green” processing, which contributes to the production of “clean” and “low-carbon” textile products.