Most people are familiar with bamboo planks; however, the plant’s versatility is not limited to solid boards. Bamboo fibers are incredibly versatile and are essential to several industries. Whether you’re a home decor enthusiast, work with bamboo textiles, or are curious about the world, you’ll be interested to know how bamboo fiber is made.
Bamboo fibers are extracted from bamboo plants through various methods, depending on the desired end product. Extraction methods are mechanical, chemical, or a combination and include mulching/pulping, grinding, and treating with chemicals to produce a usable product.
While harvesting bamboo is not complicated, extracting the fibers from the plant is longer and more involved. But what are some of the end products of bamboo fibers? And how do the end products influence the extraction and processing methods?
Bamboo Fiber And How It’s Made
The term “bamboo fiber,” relates to several products derived from processing bamboo into a less recognizable form and then reconstructed into a useful item.
We can divide bamboo fibers into three categories based on their end products.
- Fibers that are used in the textile industry (including linen and clothing).
- Fibers that are used as biocomposites (for example, strand woven bamboo).
- Fibers used in cooking (bamboo powder).
No matter the end product, there are three methods of extracting bamboo fibers, which are:
- Mechanical – bamboo parts are crushed, ground, stripped, cut, pressed, and other similar activities to produce fibers (smaller pieces).
- Chemical – Instead of force, bamboo fibers are extracted by mixing the plant parts with a type of chemical. These chemicals break down the cellulose into a more usable form.
- Mechanical and chemical – combining the processes speeds up the chemical reactions. Combination methods also produce finer/pulpier products for further manufacturing. This combination technique produces the best quality fibers.
Different Bamboo Fibers Types And Their Purpose Influence Production
Bamboo is a wonderfully versatile product. Although most of the plant is useful (leaves, branches, roots, etc.), the culms (stems) are the primary resource, either in their whole state or broken down into fibers.
First, Bamboo Is Harvested
Before bamboo becomes fiber, it must be harvested. Harvesters select appropriate bamboo plants for the end product (mature plants for composites and textiles, while shoots are preferred for cooking).
The culms (stems) of mature bamboo are the ideal thickness and strength for turning into fiber. Although it varies between species, plants aged between 3 and 5 years usually provide the best material.
Harvesting is mostly through mechanical means, and depending on the outcome, the harvesting techniques vary.
Some methods include:
- Mature plants are cut with a blade at the 1st or 2nd node.
- Shoots (for cooking) are cut off the rhizome or dug out of the ground.
- Leaves are stripped and crushed along with the soft pith inside the culms.
After harvesting, bamboo culms move to the industry that requires them, where they undergo the relevant procedures.
The most useful fibers are adequate length (not too short), undamaged, and good quality.
Bamboo Fibers In Bio-Composites
Although it has a complicated name, bio-composites are mixtures of organic/natural products (like bamboo fibers) with synthetic (human-made) items to create stronger, renewable items.
A fantastic example of bamboo fiber composites is strand-woven bamboo. Manufacturers produce an incredibly strong composite (mixture), a popular floor material, by mixing bamboo fibers with resin.
There has been considerable research into using bamboo fibers as reinforcement for concrete beams (in place of steel). I.e., bamboo fibers are mixed with concrete instead of resin.
While some significant issues relate to how the fibers absorb water through the cement, tests show they have similar structural integrity to mild steel.
A means to overcome the water issue is by using pre-resin-mixed bamboo fibers.
These would be cheaper to produce and more readily available for developing countries than steel.
To make useful bamboo strands/fibers, manufacturers remove/alter the bamboo skins to make them more absorbent (the bamboo is shredded, punctured, and softened to better absorb the resin).
Some methods include:
- Rectangular milling (especially for laminated bamboo).
- Flattened bamboo sheets – full or half culms are treated with steam and bleached with hydrogen peroxide. They are then flattened. Alternatively, bamboo is “carbonized,” where it is “cooked” under extreme temperature and pressure.
- Scrimming – the most efficient method- produces deep grooves in the fibers.
The process of “shredding” bamboo leads to severe cracks and splits in the wood, which heat and resin need to repair in the next step.
There are several different resins used, including:
- Emulsion polymer isocyanate
- Hybrid polymer adhesive
- Melamine-urea-formaldehyde
- Phenolic resin
- Polyurethane
- Polyvinyl acetate
- Urea
These resins are applied as a liquid, powder, or dry film and pressed. The mixture is usually exposed to heat ranging from 1940F to 4460F.
Once cured, the composite is cut to size with saws.
Bamboo Fibers As Textiles
Bamboo “fabric” is not a new concept. Part of the process was patented in 1864 in the US. However, extracting usable fibers to create fabric has improved/changed dramatically.
Bamboo textiles are in complete juxtaposition to bio-composites. They are produced from the leaves and soft cellulose in the plant’s “pith.”
The pith is a spongy material inside the bamboo stems, which assists in its growth and development (particularly in younger plants). When the plant matures, these structures dry up and leave the familiar hollow cavity.
Bamboo fibers are extracted mechanically or chemically.
The Mechanical Process
- Once harvested, the culm is split (often using a rasping tool) to expose the fibers.
- The fibers soak in a water and natural enzyme mixture. These enzymes detach the softer fibers from the culm.
- After soaking, the fibers are “combed out” to produce long filaments, which are spun into yarn.
- Once the fibers are a “yarn,” they may be woven into textiles.
Aside from not posing a health risk to manufacturers or the environment, the “chemicals” are reusable, saving production costs.
Bamboo Viscose/Rayon Through Chemical Extraction
Bamboo viscose is the most commonly produced fabric but requires strong chemicals, which pose a health risk to manufacturers and the environment.
- After the wood is crushed into pulp/smaller fragments, strong chemicals (usually sodium hydroxide) are added to break down the cellulose.
- Once disassociated, the cellulose is removed and compressed into sheets (this removes excess caustic soda) and treated with carbon disulfide (nerve gas requiring adequate ventilation).
- The mixture (viscose solution) is filtered and converted into strands (by being pushed through a spinneret). From here, the strands soak in sulfuric acid to produce filaments, eventually spun into yarn.
The end product is a semi-synthetic fabric, which is an affordable silk-substitute.
An alternative method is the “closed-loop” process. The end product is organic because the cellulose structure remains the same (chemically). This process uses N-methylmorpholine-N-oxide to convert bamboo cellulose into lyocell fibers.
- After the extraction into a viscose solution, hydrogen peroxide is added to the mixture, pushed through spinnerets, forming thinner strands, and eventually spun into yarn.
This process is more expensive, but the chemicals are less hazardous (to humans), and most are reusable.
How Bamboo Fibers Are Made Into Powder
Adding to an impressive resume, bamboo fibers also come in an edible variety. Although not technically a fiber in its final form, the powder is a derivative of the fibers.
The process of converting fibers into food-fortifying powder includes:
- Harvesting young (edible) bamboo shoots.
- Cutting, crushing, and breaking the culms into smaller fragments. The edible parts are removed from the non-edible parts and cut smaller.
- The bamboo fragments are “blanched” (boiled) and dried at roughly 1580F for 20 to 30 minutes.
- Pulverising and grinding into flour. The ground powder should pass through a sieve with a mesh size of around 100.
The result is a white powder full of various nutrients, which many people add to other types of flour (i.e., not a complete replacement, but an additive/fortification).
It’s important not to confuse bamboo powder for bamboo flour. The flour is ground-up fibers mixed with polyurethane (or other plastics) to create a composite filler.
Conclusion
Bamboo is immensely versatile. Once harvested, bamboo fibers are produced mechanically, chemically, or through a combination of the methods used in producing composites (mixed with resin or cement), textiles, or food fortifications. These fibers are strong, nutritious, and provide a sustainable alternative to traditional materials.