Ramie fibers

The family is essentially tropical with a few temperate species familiar as slinging nettles, which often produce painful sensations on contact with the leaves. Otherwise fibers (ramie) and a few edible leaves are known in the family. 

Fiber, ramie A strong natural fiber of vegetable origin, sometimes used as a filler or reinforcing material providing high shock resistance and strength. 

Kulshreshtha et al. [83], as well as Mitra and Mukherjee [118], postulate the existence of paracrystallinity in ramie, jute, and hemp. The latter claim to have developed refinements to the techniques of measurement of parameters of the three-phase model for cellulose I [117]. Subsequently, by measuring the structural parameters relative to [002], [101], and [101] reflections, they show that the degrees of crystallinity and paracrystallinity determined for each of the three reflections are different (anisotropy) for each of the three fibers (ramie, jute, and hemp) [122]. The results also confirm that the greater the paracrystalline distortion, the smaller the paracrystallite size. 

X-ray analysis reveals that the hemp fiber structure is very similar to the other fibers (ramie, flax), which have low lignin content. The spiral structure of hemp is comparable to that of ramie [58] and the spiral angle has been estimated to be to be 7.5° [35]. 

Ramie reinforced PLA biocomposite with flame retardancy by using APP on preserving the environmental fiiendly character of biocomposites has been studied. Here, natural fibers can be used as char formers in association with APP to increase the char yield of biocomposites. The flame retardancy of biocomposites is obtained by three means (Fig. 4.36). PLA is blended with APP, then the resulting flame-retarded PLA is combined with ramie fibers (ramie fibers with flame retardant treatment by APP is compoimded with PLA) PLA and ramie both of which have been flame-retarded by APP are blended together. 

Among the bast textile fibers, the density is close to 1.5 g/cm, or that of cellulose itself, and they are denser than polyester, as shown iu Table 5. Moisture regain (absorbency) is highest iu jute at 14%, whereas that of polyester is below 1%. The bast fibers are typically low iu elongation and recovery from stretch. Ramie fiber has a particularly high fiber length/width ratio. 

The microfibrils iu vegetable fibers are spiral and parallel to one another iu the cell wall. The spiral angles iu flax, hemp, ramie, and other bast fibers are lower than cotton, which accounts for the low extensibiUty of bast fibers. 

Fig. 3. Cross sections (500x) of bast fibers (a), fiax (b), hemp (c), jute (d), kenaf and (e), ramie.

Traditional uses for ramie have been for heavy industrial-type fabrics such as canvas, packaging material, and upholstery. Increased production of the fiber in Asia, particularly China, has promoted the use in blended fabrics with silk, linen, and cotton which can now be found on the market. 

There is Httle difference between the wet and the dry stress—strain diagrams of hydrophobic fibers, eg, nylon, acryHc, and polyester. Hydrophilic protein fibers and regenerated cellulose exhibit lower tensile moduH on wetting out, that is, the elongations increase and the strengths diminish. Hydrophilic natural ceUulosic fibers, ie, cotton, linen, and ramie, are stronger when wet than when dry. 

Elod and Schmid-Bielenberg86 observed that the speed of acetylation of dry native fibers increases with decreasing degree of micellar (crystallite) orientation. Arranged in order of increasing reactivity the dry native fibers were flax, hemp, ramie and cotton. On being pretreated with water or acetic acid, however, the fibers were alike in rates of reac-... 

Acetylation rates have also been studied by Centola37 who treated natural and mercerized ramie fibers for varying times with acetic anhydride and sodium acetate and examined the reaction products chemically and by X-ray diffraction. The reagent was considered to penetrate into the interior of fibers. A heterogeneous micellar reaction was believed to occur that converted a semi-permeable elastic membrane around the micelles into the triacetate. The rate of acetylation of mercerized ramie was observed to be faster than that of unmercerized fiber. Centola concluded that about 40 % of the cellulose in native ramie is amorphous and acetylates rapidly. 

Figure 1. X-ray diffraction pattern of ramie cellulose I. Fiber axis is vertical.

Plant fibers such as cotton, abaca, agave, flax, hemp, kapok, jute, kenaf, and ramie are still in use but even cotton is no longer king. ... 

Fiber or Fibre is any tough substance composed of threadlike tissue, especially when capable of being spun or woven. Fibers may be divided into animal (wool or silk), vegetable (cotton, hemp, flax, ramie, esparto, jute, sisal etc), mineral (asbestos, glass fiber) and artificial (Rayon, Nylon, Orion, Vinyon, Saran etc)... 

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