Thickener in textile printing process:
Thickeners or thickening agents are compounds with high molecular weight. They can be mixed with water to form a paste in a thick adhesive. Thickener is an essential ingredient in printing paste. It keeps the colors in a specific place on the fabric according to the design of the printing so that the color does not spread unnecessarily. They also hold the dye in such a way that the dye is not destroyed by high heat or friction until it is permanently fixed in the fabric. The viscosity of the thickener needs to be such that the required amount of water, dyes, and other chemicals are not lost even after mixing with it and it works properly during printing. https://bdfabric.com/preparation-of-jute-and-silk-fabric-for-printing/
This viscosity of the printing paste is crucial for maintaining the design sharpness of the printing, the viscosity of the thickener largely depends on the method of application of the printing. Thickener’s viscosity is usually higher than that of printing paste. So that the required amount of dye is diluted with chemicals and water and forms the desired printing viscosity in the printing paste. Just as thicker solutions are used for the block or roller printing, so thinner for screen printing, and thinner for mechanical rotary screen printing, i.e. thinner viscosity. Thickeners can generally be classified as follows, e.g.
(A) Depending on the viscosity
(B) According to the preparation
(A) Thickener in textile printing process-Depending on viscosity:
Water-soluble thickeners or gums can be divided into 4 parts depending on their viscosity.
1. Newton flow
2. Dilatant flow
3. Thixotropic flow
4. Pseudo plastic flow
Before discussing different types of flow, one must have an idea about viscosity. Viscosity can usually be interpreted in two ways
# Viscosity is the ratio of the tensile stress and the fall rate.
# Viscosity can be measured by the obstruction encountered during the flow of fluid.
When a thin layer of liquid falls (flows), the fluid is transferred at different rates. The relative speed of this thin layer is the only factor that is the rate of fall. Another factor is the distance between the flat of the fall.
1. Newton flow:
In this case, the viscosity of the solution does not depend on the rate of fall. It depends on the concentration and temperature of the solution. In this method, the rate of fall is directly proportional to the applied fall stress.
2. Dilatant flow:
In this case, 50% of the solution remains tough, and with increasing viscosity, the fall rate also increases.
3. Thixotropic flow:
The value of viscosity decreases over time. The levels of carboxyl methylcellulose (CMC) and hydroxyl ethyl cellulose are usually calculated using this method.
4. Pseudo plastic flow:
The concentration of almost all polymer solutions is measurable in this process. In this case, the higher the rate of fall, the lower the level of viscosity. Ethyl Hydroxyl Ethyl Cellulose, CMC, Alginate, etc. can be measured in this method.
(B) Thickener in textile printing process-According to preparation:
The different types of thickeners used in textile printing can be divided into three main types based on the preparation method.
1. Natural Thickeners
2. Modified Thickeners
3. Synthetic Thickeners
- Natural Thickeners:
The process by which thickeners are prepared from natural sources is called natural thinner. There are 4 types of natural thickeners i.e.
# Cereals from food grains such as Maize Starch, Wheat Starch, etc.
# From plant exudates such as Gum Arabic, Gum Tragacanth, Gum Karaya, etc.
# Roots & Seeds such as Guar Gum, Locust bean Gum, etc.
# Sea Weeds such as Sodium Alginate etc.
2. Modified Thickener:
Modified thickeners are made by modifying the Thickeners obtained from natural sources. There are three types of modified thickeners i.e.
# Starch derivatives such as British gum, Carboxyl methyl starch, etc.
# Cellulose derivatives such as hydroxyl ethyl cellulose etc.
# Gum derivatives such as Meypro gum, Indica, etc.
3. Synthetic Thickener:
Such thickeners are artificially prepared in the laboratory. There are two types of synthetic thickeners. E.g.
# Acrylic such as Polyacrylic acid, Polyacrylic amide, etc.
# Vinyl such as Poly Vinyl Alcohol (PVA) etc.