Investigating the properties of cotton product surface modified with corona by nano silicone softeners

Dissertation to receive a master degree ‹‹ M.S.c ››

Treatment: Textile Chemistry and Fiber Science

Abstract:

One of the important processes in the completion of textile goods is the underhand improvement in textiles. Finishing the softener provides a desirable softness to the fabric and improves its properties, and the main goals of the softener are to reduce static electricity, more softness, wear resistance and smoothness. The classification of softeners is based on their ionic structure, which can be called anionic, cationic, non-ionic and silicone softeners. In terms of molecular size, silicone softeners are divided into macro, micro and nano particles. In this research, the aim is to compare silicone and nano silicone softener on cotton fabric surface modified with corona and corona. For this purpose, cotton fabrics are coated with concentrations of 1%, 2%, 3% and 4% of silicon and nano-silicon softeners. Bending strength, friction coefficient, water absorption and wrinkle recovery were measured. Bending strength, friction coefficient and water absorption decreased with increasing concentration of softener, and recovery from wrinkles of samples increased with increasing concentration of softener. Regarding the spectrophotometric properties of reflection, an increase in whiteness and a decrease in yellowness are observed in the samples that are surface modified and coated with nanosilicone softener. Using the SEM microscope, nano particles and modification of the fabric surface by corona can be seen. Samples coated with nano-silicone and corona softeners show better properties and more suitable results compared to silicone softener without corona.

Key words: softener, corona, cotton, nano-silicon, bending length, water absorption

1-1 cotton:

1-1-1 cotton fiber structure:

pure cotton It is the most cellulose found in nature. Cotton cellulose molecules consist of linear polymers that contain at least 5000 indroglucose units. Usually, these molecules are in the form of flat plates in the solid state, and in the presence of water, these plates stick together regularly, but sometimes they do not follow this flat state, and some cellulosic fiber chain folds are observed. Cotton cellulose molecules are completely spread and parallel to the axis of the fibrils. Studies using the absorption of infrared light show that most of the hydroxyl groups in the cellulose chain form hydrogen bonds with each other, but the exact way in which these hydrogen bonds are formed has not yet been determined [1]. The thickness of the surface can be formed when more hydrogen bonds are formed between the hydroxyl groups of the oxygen atoms in the adjacent chains. Bonding between molecular sheets is probably achieved by van der Waals forces. It should be added that straight linear chains capable of forming cellulose fibers are not obtained from the bonding of alpha glucose molecules, but other cellulose materials such as starch are obtained. The primary wall consists of a shell with a thickness of 0.1 under a specific angle to the fiber axis. The secondary wall is composed of several layers, which is denser than the primary wall, and its fibril bundles change the angle of their fibrils with respect to the fiber axis during the length of the fiber, in order to arrange them, and this change causes the cotton fiber to bend. These fibrils form a bundle of fibrils with a thickness of 200 nm, which can be observed by an optical microscope. These bundles of fibrils are connected to each other with a very thick force, which are easily separated. In an X-ray study, it has been shown that 58 to 60% of the hydroxyl groups of cotton have regular hydrogen bonds and the other 40% are irregular [1].

1-1-2 Characteristics of cotton:

One of the important characteristics of these fibers is high strength in the fabric, having strength and flexibility against any spinning and weaving operations, and the tendency to absorb different colors] [2]

1-1-3 Materials Constituents of cellulose fibers (cotton): Regardless of cellulose, which makes up approximately 88-94% of the weight of cotton fibers, there are other substances such as pectin, wax, and protein in this fiber. Water molecules are able to penetrate the cellulose network of cotton and are placed in the spaces between the fibrils.. By creating hydrogen bonds with groups in cellulose, some water is also absorbed. In any case, the absorbed water molecules create pressure between the fibers and cause a decrease in the hardness of the cellulose fiber structure [2]. In fact, the water absorbed in the cotton performs a simple softening action, the fibrils of the cellulose molecules become more mobile, as a result, due to the application of external force, the shape and displacement of the cellulose chains increases. The quality of water absorption in cotton fabric which leads to the swelling of fibers and thread causes the fabric to shrink [2].

1-1-4 Moisture absorption:

The amount of recycled cotton moisture in relative humidity of 65% is equal to 7% and the water retention capacity of this fiber is 50%. The density of cotton fibers is 1.35 [3].

1-1-5 Chemical properties:

The solvents of cotton in aqueous environment are cuprammonium hydroxide, cupraethylenediamine, ethylenediamine, cadmium. Cotton fibers are decomposed and destroyed in amides and strong oxidizing substances, while organic solvents do not have a special effect on these fibers [3]. 1-1-6 Physical properties: The cross-section of cotton fiber is bean-shaped and the core of the fiber can be seen as a line. The average length of natural cotton fibers is about 14-36 mm and its diameter is 15-20 microns. The strength of the leaf is about 3-6 grams per denier and its elongation is 5-7% until it breaks. Cellulose molecules can establish hydrogen bonds with water molecules due to having three hydroxyl groups. Cotton fiber is a suitable water absorbent because theoretically each unit of cellulose can absorb three molecules of water [1]. 1-2 Introduction to surface modification methods: Surface modification of textiles has always been considered and surface modification is used to change the composition or structure of fiber properties. The purpose of modification can be the following:

Obtaining new properties

Influencing some desirable properties

Eliminating negative properties, such as reducing NEP and increasing the capacity to absorb dyes, chemicals and water.

The basic problem is that there is no ideal modification that eliminates all negative properties and replaces positive properties. That is why there are different surface modification methods. Despite the multitude of surface modification methods, a specific classification has not yet been determined for them. Some researchers have divided them into two groups, one group are those that change the chemical composition of fibers (chemical modification) and the other ones that change the structure of fibers and are known as (physical modification) [8]. In 1923, Long Muir and Tonx, two American physicists, announced that plasma is a gas in which most of its atoms or molecules are ionized. Basically, plasma is a state of matter with a temperature of 1000 and above, and this is the same state of matter that most celestial bodies such as the sun are made of. Plasma is the most abundant form of matter in the world, and the heavenly bodies that are the source of heat are called dense masses of plasma. The upper layer of the atmosphere is also composed of plasma, that is why it is called the ionosphere [9]. In scientific definitions, plasma is an ionized gas in which many parts of its atoms have lost one or more electrons and become positive ions. The plasma environment includes free electrons, radicals, ions, ultraviolet, infrared radiation and many different excited components [10].

Plasma is a special state of matter because it has uniform and unique properties. Ionization or the word (Ionized) refers to the presence of one or more free electrons that do not bond with atoms and molecules. This is why we consider plasma electrically conductive. Plasma is created by heating or ionizing a gas by removing electrons from neutral atoms. In normal gas, each atom contains an equal number of positive and negative charges. Positive charges in the nucleus are surrounded by negatively charged electrons and each atom is electrically neutral. A gas becomes a plasma when some of its atoms release some or all of their electrons by applying additional heat or other energies. To separate electrons from neutral atoms and form plasma, energy is required, which can be from different sources such as thermal, electrical, optical (ultraviolet, visible light or laser). Plasma is accelerated and controlled by magnetic and electric fields [11].