How is bamboo fiber made?
Since the cultivation of bamboo takes less time and can be grown on any type of land, it is also known as a cash crop. Bamboo fiber production involves alkaline hydrolysis and multiphase-bleaching of bamboo stems and leaves for extraction of starchy pulp and then this pulp is treated in certain chemicals.
Manufacturing of regenerated bamboo fibers can be done by mechanical as well as chemical processing.
In mechanical processing, the bamboo is cut and crushed and then treated with natural enzymes that break the bamboo into a soft and mushy substance. After which the natural fibers are combed out mechanically to obtain individual fibers which are then spun into yarns. The yarns thus possess a soft texture and the fabric thus made is called bamboo linen and this process is considered to be eco-friendly because no harmful chemicals are involved. This method to produce bamboo does not involve the extraction of cellulose nor does it chemically alter the structure of cellulose.
The steps involved in chemical processing are as follows:
• Preparation: This step involves the extraction and crushing of bamboo leaves and soft inner pith from the hard bamboo trunk.
• Steeping: The cracked or crushed bamboo cellulose is kept in a sodium hydroxide solution to form alkali cellulose.
• Pressing: The bamboo alkali cellulose is pressed to get rid of any excess sodium hydroxide.
• Shredding: In this step, alkali cellulose is then shredded in a grinder to increase the surface area and make the cellulose easier to process.
• Ageing: Shredded alkali cellulose is left to dry for 24 hours to be in contact with the oxygen of the ambient air.
• Sulfurization: The next step involves the formation of cellulose sodium xanthogenate. In order to achieve this compound, the bamboo alkali cellulose is treated with carbon disulphide in order for its gel and then excess carbon disulfide is removed by evaporation due to decomposition (Xanthation).
• Dissolving: In this step dilute sodium hydroxide is added to cellulose sodium xanthogenate in order for it to dissolve and this results in the formation of a viscose solution. The viscous solution so formed comprises 5% NaOH and 7-5% bamboo fiber cellulose.
• Spinning: The viscose bamboo cellulose is then filtered and passed through a spinneret into a container consisting of dilute sulfuric acid solution which hardens the viscose bamboo cellulose sodium xanthate and finally converts it into cellulose bamboo fiber threads which are then spun to form yarns.