Caustic soda, otherwise known as sodium hydroxide or lye, is a chemical that was first prepared and used by soap makers. Today, it is widely used in the textile industry for processes such as scouring, mercerization, and dyeing, integral parts of the textile manufacturing process.
Uses of caustic soda:
- Scouring, is a chemical washing process used to remove unwanted materials from the cotton fabric. In this process, the fabric is boiled in an alkaline solution made up of caustic soda. The caustic soda forms a soap with the free fatty acids through a process called saponification to remove natural wax, oil and other impurities such as the remaining seed fragments in the fabric. This process is usually a prerequisite to most finishing processes within the textile industry.
- Caustic soda is also used in mercerizing, a process used to increase the strength, luster and dye affinity of the fabric. In this process, caustic soda is added to the fabric to cause swelling of the fibres which in turn enhances the properties of the fabric. The fabric is usually mercerized under tension to reduce shrinkage, a common occurrence during the mercerizing process.
- Lastly, caustic soda is used in textile dyeing as most dyeing processes require a controlled pH level. Hence, caustic soda is added into the solution to maintain the pH levels during dyeing processes.
Some other uses of caustic soda include water treatment by increasing the pH of the water supply and as a cleaning agent for drain and pipe cleaning. It is also used in petroleum processing of crude oil. Fun fact, sodium hydroxide was used as a detector for carbon monoxide poisoning in the past as well! Visit our textile industry website to find out more about caustic soda and other chemicals used in the textile industry.