Fiber natural

The term natural fibers covers a broad range of vegetable, animal, and mineral fibers. However, in the composites industry, it usually refers to wood fiber and plant-based bast, leaf seed, and stem fibers. These fibers often contribute greatly to the structural performance of the plant and, when used in plastic composites, can provide significant reinforcement. Below is a brief introduction to some of the natural fibers used in plastics. More detailed information can be found elsewhere [1-4]. 

Flax is the most used natural fiber (excluding wood) in the European automotive industry, most of which is obtained as a by-product of the textile industry [5]. However, other natural fibers such as jute, kenaf sisal, coir, hemp, and abaca are also used. Natural fibers are typically combined with polypropylene, polyester, or polyurethane to produce such components as door and trunk liners, parcel shelves, seat backs, interior sunroof shields, and headrests [6]. 

European consumption of natural fibers in automotive composites was estimated at 26000 tons in 2003 and is expected to grow by 10% per year [7]. Worldwide consumption in all applications by 2010 has been estimated at 110 000-120 000 tons per annum in a variety of applications including automotive, building, appliances and business equipment, and consumer products. 

The major steps in producing natural fibers for use in plastics include harvesting of the fiber-bearing plants, extraction of the fibers, and further processing of the raw fiber to meet required purity and performance aspects for use in plastic composites. 

Fiber extraction procedures will depend on the type and portion of plant the fibers are derived from (e.g., bast, leaves, wood) as well as the required fiber performance and economics. Fiber-bearing plants have very different anatomies (e.g., tree versus dicotyledonous plants) and often fibers are derived from agricultural residues or byproducts from industry [8]. Consequentiy, the processing needs can differ greatiy. 

Mercedes-Benz (among other companies) has studied many materials and is using animal hair and fibers made from flax, sisal, coconut, and cotton, in upholstery, door panels and rear shelves of its cars. The company is looking to replace glass fiber with natural fiber alternatives, but has found it difficult. Not only are natural materials usually sensitive to temperature, but they also tend to absorb water and often exhibit extreme variation in quality that is not good for an automobile manufacturer. For over a century results of studies and evaluations of the different natural fibers continue not to be practical for use in the RP industry. 

Ford is using hemp fibers as a replacement for chopped strand glass mat in the parcel shelf for the high roof model of the Transit. It is molded by resin injection molding (RTM). Depending on results, the auto company sees a wide range of components in both vans and cars using hemp as the reinforcement. 

Hemcore does not see the product as meeting every application need of the fiber-RPs industry, but it considers that the fiber could find some price/performance gaps. No yield figures have yet been published, but it is possible that, in common with other natural fibers, a very large area of land will be needed to produce viable quantities. 

This is one of the most important natural fibers. It is produced in India, Bangladesh, Thailand, Vietnam, and other countries. It contains 56-64 wt% cellulose, 29-25% hemicellulose, 11-14% lignin, and a small proportion of fats, pectin, ash, and waxes. Application of jute fiber in RPs with matrices of TS resins such as unsaturated polyester or vinyl ester resins has been widely studied. To date the poor adhesion to hydrophobic TPs, such as polyethylene and polypropylene, has to date limited application in TPs. 

Jute fiber (JF) has been popular since the start of this century, principally as a filler and as a reinforcement with TP matrices. These low-cost natural fibers consist mainly of cellulose and hemicellulose chains running parallel to the fiber direction and lignin. High performance, average unidirectional-oriented tensile strength (T ) is 500 MPa, elastic modulus (E) is 40 GPa, and elongation is 1.7%. Other fiber properties are density 1.45 and weight 0.21 g/m. 

The annual change in fiber consumption is depicted in Fig. 2.4. It is apparent that 

According to Fig. 2.5, natural fibers can be divided into three major categories plant-derived, animal, and mineral fibers. The most important examples of each category are cotton, wool, and asbestos. Natural fibers are produced in almost every country in the world, depending on climatic and geographical factors. In this chapter, only the fiber materials most important for industrial production are discussed. 

For fibers with circular cross section-for example, wool or glass-the diameter in micrometers is often used as characterizing parameter. More details concerning fiber and yarn numbering can be found in Section 3.4. 

1 Seed Fibers 1 Bast Fibers 1 Hard Fibers 1 Wool 1 1 Fine Animal Hair 1 Coarse Animal Hair 1 1 Silk 1 

Cotton Fiax (Linen) Aioe Hemp Sheep Wooi Aipaoa Cattle Hair Silk 

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In terms of the number of scientists and engi neers involved research and development in polymer chemistry is the principal activity of the chemical in dustry The initial goal of making synthetic materials that are the equal of natural fibers has been more than met it has been far exceeded What is also im... 

In general, the geometric properties of the natural fibers are highly variable from fiber to fiber, both within a given lot and among lots of the same fiber type. In the synthetic fibers, the geometric properties are extremely uniform in view of the production control possible in a chemical plant but not in an agricultural product. 

The physical properties of these fibers are compared with those of natural fibers and other synthetic fibers in Table 1. Additional property data may be found in compilations of the properties of natural and synthetic fibers (1). Apart from the polyolefins, acryhcs and nylon fibers are the lightest weight fibers on the market. Modacryhcs are considerably more dense than acryhcs, with a density about the same as wool and polyester. 

Staple is produced by cutting a crimped tow into short lengths (usually 4—5 cm) resembling short, natural fibers. Acetate and triacetate staple are shipped in 180—366 kg bales, but production is quite limited. Conventional staple-processing technology appHed to natural fibers is used to process acetate and triacetate staple into spun yam. 

Fibers for commercial and domestic use are broadly classified as natural or synthetic. The natural fibers are vegetable, animal, or mineral ia origin. Vegetable fibers, as the name implies, are derived from plants. The principal chemical component ia plants is cellulose, and therefore they are also referred to as ceUulosic fibers. The fibers are usually bound by a natural phenoHc polymer, lignin, which also is frequentiy present ia the cell wall of the fiber thus vegetable fibers are also often referred to as lignocellulosic fibers, except for cotton which does not contain lignin. 

J. G. Cook, Handbook of Textile Fibers I. Natural Fibers, 5th ed., Merrow Publishing, Durham, UK, 1984. 

Thermoplastic Fibers. The thermoplastic fibers, eg, polyester and nylon, are considered less flammable than natural fibers. They possess a relatively low melting point furthermore, the melt drips rather than remaining to propagate the flame when the source of ignition is removed. Most common synthetic fibers have low melting points. Reported values for polyester and nylon are 255—290°C and 210—260°C, respectively. 

In conjunction with the increased use of synthetic fibers and blends of synthetic and natural fibers, and the modernisation of appHcation processes which has taken place simultaneously, the technique of textile whitening has been improved considerably. 

A selection of fiber property data is given ia Table 2 as an illustration of the range of fiber properties available commercially for use ia manufacturiag nonwoven fabrics. In general, fiber diameters range from 5 to >40 p.m for natural fibers, and from less than 10 p.m (microdenier) to as high as needed for manufactured fibers. 

Bags of various constmctions are used in the storage and transportation of dry chemicals. The choice of which type of bag to use should be based on the needs of the product for adequate protection and the requirements of the distribution network. To a certain degree, bags can be custom-made for a particular product indeed, almost any shipping requirement can be satisfied by one of many combinations of paper, plastic, and natural fibers incorporated in the design of bags. 

Textile. Textile bags are made from natural fibers such as cotton and burlap (see Fibers, vegetable). Burlap or Hessian cloth is woven from jute fibers. Because the supply of jute and, consequendy, its price have been uncertain for many years, textile bags gradually have been replaced by various combinations of textile components with plastic or paper, multiwaH paper bags, or plastic bags (see Textiles). 

Staple is used directly in the manufacturing of nonwoven fabrics (qv) (127) and spun into yam through the cotton, worsted, and woolen systems in 100% form or in blends with other synthetic or natural fibers (128,129). 

Nonabsorbable Natural Sutures. Cotton and silk are the only nonabsorbable sutures made from natural fibers that are stiH available ia the United States. Cotton suture is made from fibers harvested from various species of plants belonging to the genus Gossipium. The fiber is composed principally of ceUulose. The seeds are separated from the cotton boUs, which are carded, combed, and spun iato yams that are then braided or twisted to form sutures ia a range of sizes (Table 4). The suture is bleached with hydrogen peroxide and subsequendy coated (finished or glaced) with starch and wax. The suture may be white or dyed blue with D C Blue No. 9. 

Fibers have been used by humans for thousands of years, but only in the twentieth century has there been such an explosion in fiber types available to the textile manufacturer. The advent of synthetic fibers possessing improved resiliency and dimensional stability has placed natural fibers, particularly cotton (qv), at an ostensible disadvantage. Before synthetics, various means to control the shrinkage, dimensional stability, and smooth-dry performance of cotton had been investigated, but the appearance of synthetics such as polyester has placed a greater sense of urgency on cotton interests to focus on the perceived deficiencies of natural fibers. 

Treatments with Chemicals or Resins. Resin treatments are divided into topical or chemical modifications of the fiber itself. Most chemical treatments of synthetic fibers are topical because of the inert character of the fiber itself and the general resistance of the fiber to penetration by reagents. By contrast, ceUulosics and wool possess chemical functionality that makes them reactive with reagents containing groups designed for such purchases. Natural fibers also provide a better substrate for nonreactive topical treatments because they permit better penetration of the reagents. 

Early waterproofing treatments consisted of coatings of a continuous layer impenetrable by water. Later water-repellent fabrics permitted air and moisture passage to improve the comfort of the wearer. Aluminum and zirconium salts of fatty acids, siUcone polymers, and perfluoro compounds are apphed to synthetic as well as natural fibers. An increase in the contact angle of water on the surface of the fiber results in an increase in water repeUency. Hydrophobic fibers exhibit higher contact angles than ceUulosics but may stiU require a finish (142). 

ASTM D629 describes procedures for determining cross-sectional shapes for natural fibers using microscopic analysis. Cross-sectional shape of synthetic fibers also can be verified by using microscopic analysis. 

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