What is Hemp Fiber?
Hemp is a plant from which bast fibers can be extracted from the stems of the plants. Hemp is the oldest cultivated textile grown throughout Europe until cotton became a major textile fiber. Now, China is the major producer of hemp, which comes from the cannabis plant and grows easily in many climates because it does not require fertilizers and it’s resistant to weeds and pests. Hemp is cut and left to rot, which allows the woody stems to break down and release their inner fibers. This is the retting process. Other processes remove any other woody parts in preparation for spinning (the use of enzymes speeds up this process). Hemp is a source of narcotic drugs and was banned, but most varieties have negligible narcotic content, so they can be grown more freely. Hemp has a high yield per acre, and it can be grown on fallow fields to stop soil erosion. Hemp has been spun into a wide range of yarns, from rough, sturdy stuffs for canvas, cordage, and ropes to fine, lustrous yarns for sheer, transparent cloths. Hemp fiber are used in clothing textiles, including work clothes; interior fabrics such as curtains, upholstery and bedspreads; vehicle insulation and animal bedding. Seeds produce oils and food.
Properties of Hemp Fiber:
- Strong and durable
- Good insulator
- Natural UV protector
- Stain-resistant
- Highly absorbent
- Hypoallergenic
- Poor draping
- Prone to wrinkle
- Renewable resource
- Environmentally friendly as requires no fertilizer or pest control.
Hemp Preparation and Spinning:
Conventionally there have been two principal types of hemp fiber – long line fibers and shorter tow fibers – produced during the extraction of the fibers from the stems and which can be spun into yarns. The long line fiber is usually spun to produce a relatively coarse yarn, while tow fiber hemp may be used to produce finer yarns and it is often blended with other fibers prior to spinning.
In the case of hemp the processing of long staple yarns differs from the processing of tow. Hemp reaches the mill in form of 400 to 1000 g sheafs, which feed the hackling machine. The short fibers are collected in boxes and delivered to the packing department as hackling tows.
The preparation process of long staple fibers allows to transform the sliver produced by the hackling machine into a 2 – 4 g/m roving through a series of drawing passages and a high number of doublings, which ensure the high blending rate necessary for heterogeneous fibers like hemp. The flow chart is similar to that used for flax processing and the machines employed are practically the same. At the delivery from last drawing passage, the sliver can be subjected to one of two alternative processes:
- Wet spinning, the typical process used for bast fibers, with bobbin drying and winding. As for flax, the roving can be degummed and bleached before spinning.
- Dry spinning directly from sliver through the same spinning frames used for flax tow spinning.
Tow spinning, as also dry spinning of long staple yarns, follows the same criteria as wool spinning on machines characterized by wider pitches and by more rigid and firm opening points, which can stand the high stresses caused by extremely hard and stiff fibers.
We point out that the card sliver has not the cleanness degree which is necessary to produce a regular yarn, therefore it requires a hackling operation on machines very similar to wool combers.
Tows can be dry or wet spun. For dry spinning, two kinds of spinning frames are used:
- With drafting cylinder systems which operate according to the typical criteria of the semi-worsted system, with settings suited to the high length of these fibres
- With gill-bars, i.e. with needle bars placed in the drafting fields assigned to the guide of the fibers, which are similar to those used for long fiber dry spinning.
Flow Chart of Hemp Spinning:
As already for flax, the prospects for a widening of hemp use are conditioned by the finishing operations. In fact the fiber can undergo some important changes, if the order and the crystalline lay-out of the fibrous cells are adequately varied ; moreover, if full advantage is taken of the inner channels (lumens) for fluid diffusion by preparing them for a more efficient migration of fluids capable of modifying the fiber’s physical properties, completely new handle and appearance effects, even adjustable by the finisher, can be obtained.
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
