Theme: digital textile

Theme: Chemistry of textile manufacturing.

Textile can be defined as “a flexible woven material consisting of a network of natural or artificial fibres often referred to as thread or yarn”. Textiles widely used for carpeting, furnishings, window shades, towels, coverings for tables, beds, flags, backpacks, tents, nets, handkerchiefs, balloons, kites, sails.

Textiles can be made from many materials. These materials come from four main sources: animal (wool, silk), plant (cotton, flax, jute), mineral (asbestos, glass fibre), and synthetic (nylon, polyester, acrylic). Textiles may contain residues of a large number of chemicals used in their manufacture. Some of these chemicals may have inherent properties that are hazardous to human health or the environment.

Imagine you're getting late for office, and you discover that your shirt hasn't been ironed. It makes you so angry, doesn't it?

Well, do you know there are fabrics that don't need ironing!

How do we feel when we come under the shadow of a big tree after walking for a few minutes in scorching heat?

Why do we start sweating too much if we are wearing synthetic clothes? But not cotton clothes!

Answers for all these are is depend on textile manufacturing, raw materials, chemicals treatment methods.

Fibres for fabrics come in three types

 1. Natural (cotton, silk, wool)

 2. Cellulosic (viscose, acetate, cupro)

 3. Synthetic (polyester, acrylic, and nylon)

Cellulosic fibres are regenerated from chemically treated cellulose, originally derived from wood pulp; while synthetics are derived from petrochemicals.

Man-made fibres have already begun to dominate the market. Within this category, it is polyester - poly(ethyleneterephthalate) or PET - that is powering demand. So the environmental impact of these fibres has become much more significant, and, for traditional synthetics, the picture is far from green. They are derived from petrochemicals, meaning their production depends on declining reserves of oil and gas and they are not renewable. Also, their production is energy-intensive, the fibres don’t biodegrade and they are not easy to recycle. Chemicals are used in the manufacture and treatment of textiles. Example: Process chemicals may be added at fiber manufacturing, bleaching, dyeing and printing of fabrics.

Chemicals may also be added to the finished product to obtain different functions. Example: Antibacterial treatment of sportswear, flame-retardant treatment of furnishing textiles, impregnation of outdoor clothing and anti-mould preparations for transport and storage.

Coatings in plastic on clothes may contain plasticizers such as phthalates.

Following steps shows the different stages of the textile manufacturing process where chemicals are applied

 1. Washing and scouring of fibers and yarn

 2. Bleaching of yarn and cloth

 3. Mercerizing of yarn and cloth

 4. Dyeing of yarn and cloth

 5. Printing of cloth and garment

 6. Finishing of cloth and garment

 7. Washing of treated yarn, cloth, and garment

Nowadays, it’s hard to imagine a world without textiles. This applies in particular to the clothing that each of us wear every day. Clothes provide comfort and protection, and for a large group of people it is also an extremely important way to express their style and personality. Textile industry is often called one of the longest and most complex industrial chains. It consists of a large number of sub-sectors that cover the entire production cycle, starting with the production of raw materials (e.g. synthetic fibers), through semi-finished products (e.g. yarns and fabrics), to ready-to-use products such as carpets, clothing and textiles for industrial use.

Textile fibers are made of a huge amount of materials. Most of them are characterized by polymeric construction. The main raw materials for fiber production are:

1. 
   natural fibers – these are animal fibers (also called: protein fibers – e.g. silk, wool, hair), vegetable (cellulose fibers – e.g. flax, hemp, cotton, nettle) or mineral fibers, found in many natural minerals,
   
2. 
   artificial fibers – man-made fibers. These can be cellulose-based fibers (e.g. cellulose acetate) or synthetic polymers, e.g. nylon, polyacrylonitrile (anilana), polyester (elana) and polyurethane (lycra) fibers,
   
3. 
   recycled materials (so-called rPET) – these are materials from renewable natural resources, e.g. PLA (Polylactide), which is produced mainly from maize and is biodegradable, or cupro fibers, created as a result of precipitation of cellulose fibers in a copper bath.
   

The first process to which natural and artificial fibers are subjected to is spinning. Initially, the loose fibers pass through a series of different mechanical operations (loosening, mixing and carding) and then undergo proper spinning. This process can be divided into two basic types:

1. 
   woolen – is used to obtain yarns from natural fibers (wool) and compound yarns, which contain wool and synthetic fibers, e.g. polyester, polyacrylonitrile or polyamide,
   
2. 
   cotton – used for the production of cotton and mixed yarns composed of cotton fibers and other material, e.g. polyester, viscose or polyamide fibers.
   

The spinning process uses hardly degradable chemicals that are applied to fibers in an amount of 2 to 5% of mass substances. This facilitates the course of subsequent stages of the yarn making process. Mineral and silicone oils as well as aromatic hydrocarbons are most often used at this stage and are completely removed from the yarn during the final treatment. Yarn is used to produce two basic assortments of flat textile products, i.e. fabrics and knits.

In the case of fabrics, the first operation is bonding of the warps. It involves the application of special chemicals on the yarn, which increases its mechanical strength. This process is called sizing. The textile sizing agents can be based on polysaccharides (e.g. carboxymethylcellulose) or synthetic polymers such as polyacrylates. This is not the case with the knitting process. The yarn for knit fabric is specially prepared by applying slip preparations. These substances are intended to reduce the stress in the knitting process that results from the friction between the yarn and the guiding elements of the machine.

One of the products that can be used at the stage of sizing is Rokrysol JW20, which is an effective, synthetic sizing agent. It gives the yarn properties in accordance with the requirements ensuring further correct processing of the yarn into the fabric. Rokrysol JW20 is soluble in water in any ratio, which provides even application and coating of the yarn. After applying Rokrysol JW20, further stages of fabric processing (desizing, bleaching, dyeing or printing) take place more effectively. In the case of electrification of the yarn during processing, it is recommended to add the specialized anti-electrostatic preparation Rostat A to the sizing. This product almost completely eliminates the occurrence of static electricity, and also gives the fibers good slip properties. The product works well in the processes of preparation of textile raw materials as an addition to sizing of warps, preparation of raw materials after dyeing and final finishing of fabrics and knitted fabrics.

The next stage of processing of the textile raw material is further pre-treatment. Loose fibers, yarn, fabric and knitwear are bleached, dyed and refined. The selection and the order of the unit operations depends on the type of raw material and the form of the product (yarn, fabric or knitwear).