Industrial hemp originates from the botanical class of the plant species Cannabis sativa. Its utilization has gained popularity due to the plant’s versatile uses. Hemp fiber is now used in place of wood due to its cheaper cost and insulation properties. It is also a source of oilseed and can be employed to make shoes, cords and paper.
Today, the annual growth of this plant is more than 30% annually, and the numbers will heighten as people strive to make its products eco-friendly. Since its future is promising, producers are working towards finding out the most profitable manufacturing processes. However, because it is a newcomer crop in most states, farmers need to meet federal rules and regulations, including a Dry Weight Potency (USDA) not exceeding 0.3%
Since it has been in existence for thousands of years, most of the manufacturing methods used were passed down from previous generations. Among these processes is retting, a crucial step in the extraction of the strand.
The practice of obtaining fiber from hemp stems from other naturally occurring materials, including flax. Soaking aids the transformation of natural products into functional textiles used for beddings, furnishing and clothing. The information below gives you more insight into the plant’s thread extraction procedure.
Cultivation
Hemp plants for industrial use are particularly grown for tendril production. The plants produce two types of fiber – long outer threads for textiles and short inner strands suitable for paper fabrication.
Harvest
A conventional combine harvester machine is used to cut out greenery, which is left on the ground for approximately 10 to 20 days to ret.
Retting
Retting is a process that employs natural material, including moisture and bacterial, to decompose cellular tissues that surround bast filament in stalks. It is a crucial process in strand extraction since it facilitates the separation of roughage from the stem.
The basic drenching methods include water and field or dew retting. Choosing which process to use needs the consideration of different factors, including your location and budget. While both approaches are viable options, most farmers use field retting due to its cost-effective nature.
Although water sopping produces higher-quality fibers, it requires extensive infrastructure, labor and water, making it a less desirable option. In addition, the value of fibers from water retting may not exceed the financial expenses of its production.
Types of retting
· Field retting
For this approach, harvested stalks are left out on the ground for 2-3 weeks after reaping. The straws are evenly spread on the field, where the combined action of bacteria, air, dew and sunlight causes fermentation. The stem material surrounding the roughage dissolves, allowing for strand separation.
Decomposition time is subject to a region’s climatic conditions. Dew or field retting is common in humid locations with high dew points and limited water resources. Such regions have the right environmental conditions which accelerate the growth of bacteria. The obtained fiber has a darker color and is of poor quality compared to thread from water sopping.
· Water retting
Water retting involves submerging bundles of stalks in water, initiating the breakdown of cellular materials surrounding the fiber. Through osmosis, water penetrates the inner stem and causes the cells to swell. Increased moisture absorption occurs when the cells’ outermost layer bursts.
The process can be done in ponds or holding tanks where producers can monitor the soaking time. Precision is crucial as falling short or surpassing needed time affects thread quality. Some producers employ double drenching where stalks are extracted from the water before time, dried, and drenched again.
Decortication
For this step, stems are passed through fluted rollers to break down. The hemp fibers are then passed through rotary blades or a beech stick to separate them from the hard materials.
Hackling
The fibril lengths are trimmed down to 650 mm from 3m using a special cutting machine. Fibers that are tangled are then combed, while long strands are refined using a hackling machine. The machine removes any woody particle and aligns the threads into a continuous sliver ready for spinning.
Spinning
The process transforms the strands into a continuous yarn which can then be sold to textile manufacturers. It can be done using the dry method, which produces coarser yarns or the wet method, which results in finer ply.
Most of the choices in the manufacturing process determine the quality of your end product. Understanding what the extraction method entails will help you obtain better quality fibers for industrial use.
