Cellulose fiber

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Cellulose fibers (/ˈsɛljʊls, -lz/)[1] are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants, or from other plant-based material. In addition to cellulose, the fibers may also contain hemicellulose and lignin, with different percentages of these components altering the mechanical properties of the fibers.

The main applications of cellulose fibers are in the textile industry, as chemical filters, and as fiber-reinforcement composites, due to their similar properties to engineered fibers, being another option for biocomposites and polymer composites.

The market for cellulose fibers has witnessed strong growth due to increasing demand from the textile industry. The demand for environmentally friendly, skin friendly and bio-degradable fabrics is a key factor driving this market.[2]

History[edit]

Cellulose was discovered in 1838 by the French chemist Anselme Payen, who isolated it from plant matter and determined its chemical formula.[3] Cellulose was used to produce the first successful thermoplastic polymer, celluloid, by Hyatt Manufacturing Company in 1870. Production of rayon ("artificial silk") from cellulose began in the 1890s, and cellophane was invented in 1912. In 1893, Arthur D. Little of Boston, invented yet another cellulosic product, acetate, and developed it as a film. The first commercial textile uses for acetate in fiber form were developed by the Celanese Company in 1924. Hermann Staudinger determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized (without the use of any biologically derived enzymes) in 1992, by Kobayashi and Shoda.

Cellulose chains linked by hydrogen bonds

Cellulose structure[edit]

Cellulose is a polymer made of repeating glucose molecules attached end to end.[citation needed] A cellulose molecule may be from several hundred to over 10,000 glucose units long. Cellulose is similar in form to complex carbohydrates like starch and glycogen. These polysaccharides are also made from multiple subunits of glucose. The difference between cellulose and other complex carbohydrate molecules is how the glucose molecules are linked together. In addition, cellulose is a straight chain polymer, and each cellulose molecule is long and rod-like. This differs from starch, which is a coiled molecule. A result of these differences in structure is that, compared to starch and other carbohydrates, cellulose cannot be broken down into its glucose subunits by any enzymes produced by animals.

Types[edit]

Natural cellulose fibers[edit]

Natural cellulose fibers are fibers that are still recognizable as being from a part of the original plant because they are only processed as much as needed to clean the fibers for use.[citation needed] For example, cotton fibers look like the soft fluffy cotton balls that they come from. Linen fibers look like the strong fibrous strands of the flax plant. All "natural" fibers go through a process where they are separated from the parts of the plant that are not used for the end product, usually through harvesting, separating from chaff, scouring, etc. The presence of linear chains of thousands of glucose units linked together allows a great deal of hydrogen bonding between OH groups on adjacent chains, causing them to pack closely into cellulose fibers. As a result, cellulose exhibits little interaction with water or any other solvent. Cotton and wood, for example, are completely insoluble in water and have considerable mechanical strength. Since cellulose does not have a helical structure like amylose, it does not bind to iodine to form a colored product.

Manufactured cellulose fibers[edit]

Manufactured cellulose fibers come from plants that are processed into a pulp and then extruded in the same ways that synthetic fibers like polyester or nylon are made. Rayon or viscose is one of the most common "manufactured" cellulose fibers, and it can be made from wood pulp.

Structure and properties[edit]

Natural fibers are composed by microfibrils of cellulose in a matrix of hemicellulose and lignin. This type of structure and the chemical composition of them is responsible for the mechanical properties that can be observed. Because the natural fibers make hydrogen bonds between the long chains, they have the necessary stiffness and strength.

Chemical composition[edit]

The major constituents of natural fibers (lignocelluloses) are cellulose, hemicellulose, lignin, pectin and ash. The percentage of each component varies for each different type of fiber, however, generally, are around 60-80% cellulose, 5–20% lignin, and 20% of moisture, besides hemicellulose and a small percent of residual chemical components. The properties of the fiber change depending on the amount of each component, since the hemicellulose is responsible for the moisture absorption, bio- and thermal degradation whereas lignin ensures thermal stability but is responsible for the UV degradation. The chemical composition of commons natural fibers are shown below,[4] and can change if the fibers are a bast fiber (obtained from the bark), a core fiber (obtained from the wood), or a leaf fiber (obtained from the leaves).

Type of fiber Cellulose (%) Lignin (%) Hemicellulose (%) Pectin (%) Ash (%)
Bast fiber Fiber flax 71 2.2 18.6 – 20.6 2.3
Seed flax 43–47 21–23 24–26 5
Kenaf 31–57 15–19 21.5–23 2–5
Jute 45–71.5 12–26 13.6–21 0.2 0.5–2
Hemp 57–77 3.7–13 14–22.4 0.9 0.8
Ramie 68.6–91 0.6–0.7 5–16.7 1.9
Core fiber Kenaf 37–49 15–21 18–24 2–4
Jute 41–48 21–24 18–22 0.8
Leaf fiber Abaca 56–63 7–9 15–17 3
Sisal 47–78 7–11 10–24 10 0.6–1
Henequen 77.6 13.1 4–8

Mechanical properties[edit]

Cellulose fiber response to mechanical stresses change depending on fiber type and chemical structure present. Information about main mechanical properties are shown in the chart below and can be compared to properties of commonly used fibers such glass fiber, aramid fiber, and carbon fiber.

Fiber Density (g/cm³) Elongation (%) Tensile strength (MPa) Young's modulus (GPa)
Cotton 1.5–1.6 3.0–10.0 287–597 5.5–12.6
Jute 1.3–1.46 1.5–1.8 393–800 10–30
Flax 1.4–1.5 1.2–3.2 345–1500 27.6–80
Hemp 1.48 1.6 550–900 70
Ramie 1.5 2.0–3.8 220–938 44–128
Sisal 1.33–1.5 2.0–14 400–700 9.0–38.0
Coir 1.2 15.0–30.0 175–220 4.0–6.0
Softwood kraft 1.5 1000 40.0
E–glass 2.5 2.5–3.0 2000–3500 70.0
S–glass 2.5 2.8 4570 86.0
Aramid 1.4 3.3–3.7 3000–3150 63.0–67.0
Carbon 1.4 1.4–1.8 4000 230.0–240.0

Applications[edit]

Composite materials[edit]

Matrix Fiber
Epoxy Abaca, bamboo, jute
Natural rubber Coir, sisal
Nitrile rubber Jute
Phenol-formaldehyde Jute
Polyethylene Kenaf, pineapple, sisal, wood fiber
Polypropylene Flax, jute, kenaf, sunhemp, wheat straw, wood fiber
Polystyrene Wood
Polyurethane Wood
Polyvinyl chloride Wood
Polyester Banana, jute, pineapple, sunhemp
Styrene-butadiene Jute
Rubber Oil palm

Composite materials are a class of material most often made by the combination of a matrix and a fiber. This combination mixes the properties of the matrix and the fiber to create a new material that may be stronger than the fiber alone. Recently, cellulose fibers have begun to be used as a fiber-reinforcement material, especially in conjunction with polymers (as can be observed in the table[5]), in biocomposites and fiber-reinforced plastic. The macroscopic characteristics of fibers can influence the behavior of the resulting composites. Of interest are the following physical and mechanical properties of cellulosic fibers:

  • Dimensions: The relationship between the length and diameter of the fibers is a determining factor in the transfer of efforts to the matrix. Another interesting point is the irregular cross-section of plant fibers as well as their fibrillated appearance, which can exert a positive influence on the anchoring of the fibers with the fragile matrix.
  • Void volume and water absorption: Because of the large volume of permeable voids within the material, absorption is very high within the first moments of immersion. As a direct consequence, comes negative interference in relation to water, such as the binder matrix swelling and subsequent shrinkage of the fiber. On the other hand, the high void volume contributes to reduced weight, increased acoustic absorption and low thermal conductivity the obtained components.
  • Tensile strength: Similar, on average, to the polypropylene’s fibers.
  • Elastic modulus: Cellulosic fibers are classified as low modulus determining the factor for its use in building components working in post-cracked stage, with high energy absorption and resistance to dynamic forces.

Textile[edit]

In the textile industry regenerated cellulose is used as fibers such as rayon, (including modal, and the more recently developed Lyocell). Cellulose fibers are manufactured from dissolving pulp.[6] Cellulose-based fibers are of two types, regenerated or pure cellulose such as from the cupro-ammonium process and modified cellulose such as the cellulose acetates.

The first artificial fiber, known as artificial silk, became known as viscose around 1894, and finally rayon in 1924. A similar product known as cellulose acetate was discovered in 1865. Rayon and acetate are both artificial fibers, but not truly synthetic, being made from wood. Although these artificial fibers were discovered in the mid-nineteenth century, successful modern manufacture began much later.

Filtration[edit]

The cellulose fibers infiltration/filter aid applications can provide a protective layer to filter elements as powdered cellulose, besides promoting improved throughput and clarity.[citation needed] As ashless and non-abrasive filtration, make cleanup effortless after the filtering process without damage in pumps or valves. They effectively filter metallic impurities and absorb up to 100% of emulsified oil and boiler condensates. In general, cellulose fibers in filtration applications can greatly improve filtration performance when used as a primary or remedial precoat in the following ways:

  • Bridging gaps in the filter septum and small mechanical leaks in the gaskets and leaf seats
  • Improving the stability of the filter-aid cake to make it more resistant to pressure bumps and interruptions
  • Creating a more uniform precoat with no cracks for more effective filtration surface area
  • Improving cake release and reducing cleaning requirements
  • Preventing fine particulate bleed-through
  • Precoating easily and rapidly and reducing soluble contamination

Comparison with other fibers[edit]

In comparison with engineered fibers, cellulose fibers have important advantages as low density, low cost, they can be recyclable, and are biodegradable.[7] Due to its advantages cellulose fibers can be used as a substituent for glass fibers in composites materials.

Environmental issues[edit]

What is often marketed as "bamboo fiber" is actually not the fibers that grow in their natural form from the bamboo plants, but instead a highly processed bamboo pulp that is extruded as fibers.[6] Although the process is not as environmentally friendly as "bamboo fiber" appears, planting & harvesting bamboo for fiber is much more sustainable and environmentally friendly than harvesting more slow growing trees and clearing existing forest habitats for timber plantations.

See also[edit]

References[edit]

  1. ^ "Cellulose Fiber- definition of cellulose fiber in the Free Online Dictionary". The Free Online Dictionary. Retrieved December 7, 2014.
  2. ^ Cellulose Fibers Market Analysis and Growth Forecasts
  3. ^ Cellulose : molecular and structural biology : selected articles on the synthesis, structure, and applications of cellulose. Brown, R. Malcolm (Richard Malcolm), 1939-, Saxena, I. M. (Inder M.). Dordrecht: Springer. 2007. ISBN 9781402053801. OCLC 187314758.
  4. ^ Xue, L. G.; Tabil, L.; Panigrahi, S. (2007). "Chemical Treatments of Natural Fiber for Use in Natural Fiber-Reinforced Composites: A Review". Journal of Polymers and the Environment. 15 (1): 25–33. doi:10.1007/s10924-006-0042-3.
  5. ^ Saheb, D. N.; Jog, J. P. (1991). "Natural fiber polymer composites: A review". Advances in Polymer Technology. 18 (4): 351–363. doi:10.1002/(SICI)1098-2329(199924)18:4 (inactive 2018-07-04).
  6. ^ a b 1971-, Fletcher, Kate, (2008). Sustainable fashion and textiles design journeys. London: Earthscan. ISBN 9781849772778. OCLC 186246363.
  7. ^ Mohanty, A. K.; Misra, M.; Hinrichsen, G. (2000). "Biofibres, biodegradable polymers and biocomposites: An overview". Macromolecular Materials and Engineering. 276-277 (1): 1–24. doi:10.1002/(SICI)1439-2054(20000301)276:1<1::AID-MAME1>3.0.CO;2-W.

External links[edit]