The scientific name for the strain of cannabis plant used to produce textiles is known as cannabis sativa, which is more commonly known as hemp. Processing fibers from cannabis plants produce a material with a similar texture to cotton but significantly stronger, which is why humans have used the plant for thousands of years to make textiles from hemp fiber. However, processing these lengthy yet sturdy fibers requires special machinery to handle the tough fibers in hemp. Processing equipment must also be sufficiently robust to transform hemp fibers into hemp fabric and other textiles.
Hemp Processing: From Fiber in the Field to Textiles
The reason hemp fell out of fashion with the textile industry stems not only from the decades when it was banned due to the psychoactive substance found within its flowers, known in Mexican slang as marijuana. With the natural strength of hemp fiber, processing cannabis into textiles was a particularly labor-intensive activity, while the introduction of the cotton gin in the 19th century made producing cotton textiles for fabrics much cheaper. However, modern hemp processing equipment has developed to the point where hemp textiles are economically viable once more.
Hemp fiber processing begins with harvesting the cannabis plant when in early bloom and before overly seeded. While flowers and seeds aren’t necessarily undesirable when harvesting the plant for hemp fiber, processing occurs at this time due to the plants being less woody and their fibers more flexible. While conventional methods involved manually separating the woody core of the plant – known as the hurd – from the hemp fiber, processing today often involves sophisticated systems for turning raw cannabis into textiles.
Hemp fiber processing results in fabrics that are:
- Very soft
- Up to triple the strength of cotton fabrics
- Softer with subsequent washings
- Resistant to molds, mildew, and other destructive microbes
- Not inclined to shrink
- Lightweight
- Highly durable
- Exceptionally breathable
- Easily dyed
Hemp clothing also allows moisture from perspiration to permeate through the fabric, cooling the wearer as it evaporates. Additionally, hemp fiber processing into textiles is more sustainable than cotton, making it ideal for making clothing.
Stages of Hemp Fiber Processing
After harvest, the first stage of hemp fiber processing entails separating the hurd from the hemp fiber. Processing involves two initial processes – retting and decortication – for removing the fibers from the plants’ stalks. Conventional retting entails simply leaving the harvested hemp in the field, where bacteria and fungi break down the stem, which separates out the hemp fiber. Processing these stalks mechanically to remove fiber is called decortication, which for modern hemp processing entails the use of machinery to enable what’s referred to as decortication.
Retting
Proper retting is necessary in the initial stage of hemp fiber processing, as the stalks must be dried until moisture makes up only about 10 to 15 percent of their weight. Proper retting of stalks ensures quality textiles can be manufactured from the hemp fiber. Processing through retting – a word related to “rotting” – involves removing both the long outer fibers used for textiles as well as shorter inner fibers that are suitable for hemp paper or certain industrial applications. Normally, it takes about ten to twenty days for cannabis plants to ret properly.
There are two types of retting. Water retting is a simulated process that entails submersing the stalks into tanks, streams or ponds for about ten days. This should be warmer water, ideally containing plenty of bacteria. Dew retting is a natural process that involves bacteria and fungi breaking down the pectin within the plant as it lies in the field after harvest, which weakens the bonds more slowly between the stem and hemp fiber. Processing moves on to the decortication stage once the fiber separates easily from its woody core, indicated by the fiber bundles turning white.
Softening & Combing
After decortication, rollers are used to soften the hemp fiber, with processing at this point seeking to increase flexibility. This also involves milling equipment, especially if cannabidiol (CBD) extraction is a secondary product from hemp fiber processing. In modern hemp processing facilities, specialized lump breakers are often used at this point to break down the longer lengths of fiber, which can reach 10 feet (about 3 m) in length. Combing processes reduce them to more manageable lengths of just over 2 feet (about 650 mm). Essentially this involves shortening and untangling the hemp fiber, processing these into smooth strands that run in parallel lengths. This stage also removes wood particles to prepare the hemp fiber for spinning.
Spinning
After softening and combing the hemp fiber, processing involves spinning these fibers into yarn on a spindle. Just as with yarn made from other materials, hemp fiber processing can be done as a wet or dry process. Simply put, wet spinning involves a medium that coagulates with the yarn, whereas dry spinning entails using a solvent that evaporates after a heating process. Dry spinning tends to produce coarser fibers for ropes and twine, while wet spinning produces finer textiles for fabrics and clothing.
Hemp Processing Equipment
An array of different machines can be used in the making of textiles from hemp. Processing equipment for fiber will differ dramatically from that used to produce oil or seeds from the flowers, for example. For fiber manufacturers looking to produce secondary products, destemming mechanisms should cut flowers smoothly from the stems to preserve them and enable their later processing for hemp oil or seed. Industrial hemp fiber processing efficiency should also allow throughputs of multiple tons per hour.
Additionally, the reactor through which stalks pass must remove the stalks efficiently from the pulp so as to process multiple tons per hour. Many modern decorticator systems incorporate hammer mills at this stage to separate out the hemp fiber from the plants’ flowers. Next comes hemp carding machines, which use rollers to clean, separate, cut to size, and align the hemp fiber. Processing next proceeds to compacting and baling the fiber, like how hay is baled.
Hemp Fiber Processing Applications
While hemp processing for fiber can produce textiles of various quality and strength, the cannabis plant’s applications go well beyond textiles.
Primary and ancillary products from hemp fiber processing can include:
- Animal bedding and feed
- Biofuels
- Bioplastics and composites for packaging and other purposes
- Canvas for heavy-duty tarps, sacks, sails for sailboats, and other applications
- Carpeting, rugs, and other interior design applications
- CBD-based medicines, edibles, and other pharmaceuticals
- Construction materials like hempcrete and paperboard, including for acoustic and thermal insulation
- Cordage, rop,e and twine
- Cosmetics and other personal care products
- Detergents, solvents, and other cleaning agents
- Hats, pants, shirts, and other personal attire
- Hemp seed oil, gluten-free flour, and other ingredients for food or beverages
- Mulch
- Paint, paper, and printing inks
For manufacturers, the applications for hemp processing equipment go well beyond textile manufacturing.
Hemp Processing Equipment from Prater
Prater Industries makes cutting-edge machinery that can support hemp processing operations of any size. Our engineering team also has ample experience integrating hemp processing equipment into systems for producing hemp fiber and processing other plant parts. Above all, Prater’s commitment to quality and century-long
Prater equipment for hemp processing includes:
- Lump breakers: Used to reduce compacted hemp fiber agglomeration that may occur during storage, shipping or production.
- Air classifying mills: Used for grinding down more difficult parts of the plant or for hemp processing applications that require narrow particle size distributions.
To learn more about our equipment for hemp fiber processing, contact the material handling experts at Prater today.
