Last updated on September 18th, 2023 at 11:01 am
Definition of Functional Finishing
The word “textile finishing” defines a series of processing operations applied to grey fabrics to enhance their appearance and hand, properties and possible applications. The term “finishing” includes all the treatments applied to grey fabrics such as scouring, bleaching, dyeing or printing while we will use the term ‘functional finishing’ with reference to all the mechanical or chemical finishing operations carried out on fabrics already bleached, dyed or printed to further enhance their properties and possibly add some new ones.
The term ‘finishing’ and ‘functional finishing’ are therefore similar and both play a fundamental role for the commercial excellence of the results of textile, strictly depending on market requirements that are becoming increasingly stringent and unpredictable and permit very short response times.
Depending upon the type of textile substrate to be treated (staple, yarn or fabric) functional finishing processes are carried out using different means:
Involving the application of physical principles such as friction, temperature, pressure, tension and many others.
Involving the application of synthesis or natural chemical products, which bind to the fibres more or less permanently.
Combined Mechanical and Chemical Mean
Involving the application of both chemical and mechanical processes.
The main purposes of functional finishing processes are the following –
- Develop the “product finishing” in all its fundamental elements such as hand and appearance.
- Give the finished fabric some properties that grant an optimum behavior during the making up and all through the life of the textile.
The parameters influencing the choice of the most suitable finishing process are the following –
- Fibre nature or fabric to be subjected to functional finishing treatments.
- Final application of the fabric to be subjected to functional finishing treatments.
Mechanical Finishing Treatments
Mechanical finishing process can be referred to as those processes generally carried out on open width dry fabrics, with or without heat application, which give the fabric good dimensional stability (shrink proof and shape retention) and modify the ‘hand’ of the textile product by altering its structure (at least its surface structure).
A lustrous, dense and compact appearance can be obtained by means of friction, pressure, and heat.
This is a particular type of calendering process allows engraving a simple pattern on the fabric.
Thanks to this process, the fabric has a much softer hand and an improved insulating effect thanks to the fibre end pulled out of the fabric surface. This process is carried out by means of a roller coated with abrasive material.
The fibre end pulled out to the fabric surface imparts an insulating effect. This process is carried out by means of hook-needles running in different directions on the fabric.
The fibre ends on the fabric surface are cut by using special cutting tools.
The fibre ends pulled out to the fabric surface are burnt by means of a flame.
This process is quite similar to the dry one. The only difference is the use of steam.
The structure, bulk and shrinkage of wool are modified by applying heat combined with friction and compression.
The fabric is given an optimum dimensional stability by applying mechanic forces and water vapor.
The lustrous appearance of the textile material is eliminated, the surface is smoothed and the fabric is given an optimum dimensional stability thanks to the action of dry or overheated saturated vapor.
Chemical Finishing Treatments
By applying chemicals of different origins, a fabric can receive properties otherwise impossible to obtain with mechanical means. Chemical finishing treatments –
- Allow the stabilization of fabrics already subjected to mechanical finishing processes, such as calendaring.
- Give fabrics some properties (e.g. flame retardancy and water repellency), which would be otherwise absent.
Padding is by far the most common among the various finishing technique. This is certainly the most popular process for both conventional and innovative finishing treatments. The machine used for this process can be referred to various definitions such as padding unit, squeezing unit, etc. After ensuring that the textile substrate can be padded by evaluating its mechanical and structural properties, this technique can be applied to carry out all wet finishing operations, except for some cases.
The application of finishing substances by spraying is used for carrying out gentle finishing processes which leave on the textile material a small concentration of products, and is particularly indicated for applying softening, anti-static and anti-mildew agents. For a good and homogeneous penetration and diffusion of the finish in the textile material, it is better to let the sprayed and wound fabric rest for some hours before drying. In the last few years, a very important field has been developed in the textile sector, i.e. the production of webs made synthetic fibres. For this particular type of product, the resin coating process is carried out only by spraying the finish directly on the fibrous substrate and by generally applying synthetic resins in aqueous emulsion.
The treatment of yarns or fabrics in exhaustion liquor is recommended above all when stable chemical products are applied on the textile substrate. The manufacturing process undergone by the material is useful to precisely evaluate the best method for applying the finish, for example on hosiery or tubular knitted goods. From a chemical point of view, the most suitable products for the exhaust process are those with cation-active properties. In particular cation-active softening agents are often applied with this process, as well as paraffin and wax-based emulsions, and more recently, cation-active polymer emulsions.
At present, after the launch and diffusion of synthetic resins, so called “coating and bonding” applications have been experiencing an extraordinary growth, above all in Italy. Coated and bonded fabrics are now simply classified, according to their end use, i.e. for garments, upholstery, draperies and tapestries, footwear, leather goods and technical articles. Generally the process starts from a fabric or from a non-woven fabric as a backing. All fibres can be used. As regards the resins used for the coating layer, manufacturers once employed only natural substances, but are now using almost exclusively synthetic polymers of high molecular weight.
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