Polyolefin fibers

Denault J, et al. Wood and flax fiber polyolefin composites. Automotive Composites Conference, conference proceedings. Society of Plastics Engineers 2006. 

Chemical test. Solubility is a very effective test to identify fibers. Polyolefins have excellent chemical resistance to most common solvents, and they can be easily distinguished from a polyester or nylon fiber by a simple solubility test. Functional groups can also be identified using a technique such as FTIR which wiU help identify the fiber type. 

Keywords Compatibilization Composites Natural Fiber Polyolefin... 

Ichazo et al. [120] reported the mechanical properties of treated and untreated sisal fiber. Polyolefin composites were developed using 20% fiber loading. Acetic anhydride was used and acetylated treatment showed an improved tensile modulus by 30-40%. But the impact strength and elongation at break decreased because of the rigid interface between fiber and matrix [120]. 

The polyolefins production has increased rapidly in the 40 years to make polyolefins the major tonnage plastics material worldwide. In 2003, 55 million tons of polyethene and 38 million t/a polypropene were produced [1]. These products are used for packing material, receptacles, pipes, domestic articles, foils, and fibers. Polyolefins eonsist of carbon and hydrogen atoms only and the monomers are easily available. Considering environmental aspects, clean disposal can be achieved by burning or by pyrolysis, for instance. Burning involves conversion to CO2 and H2O, exclusively. 

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. 

Olefin fibers, also called polyolefin fibers, are defined as manufactured fibers in which the fiber-forming substance is a synthetic polymer of at least 85 wt % ethylene, propjiene, or other olefin units (1). Several olefin polymers are capable of forming fibers, but only polypropylene [9003-07-0] (PP) and, to a much lesser extent, polyethylene [9002-88-4] (PE) are of practical importance. Olefin polymers are hydrophobic and resistant to most solvents. These properties impart resistance to staining, but cause the polymers to be essentially undyeable in an unmodified form. 

The growth of polyolefin fibers continues. Advances in olefin polymerization provide a wide range of polymer properties to the fiber producer. Inroads into new markets are being made through improvements in stabilization, and new and improved methods of extmsion and production, including multicomponent extmsion and spunbonded and meltblown nonwovens. 

Because of the high melt viscosity of polyolefins, normal spinning melt temperatures are 240—310°C, which is 80—150°C above the crystalline melting point. Because of the high melt temperatures used for polyolefin fiber spinning, thermal stabilizers such as substituted hindered phenols are added. In the presence of pigments, the melt temperature must be carefully controlled to prevent color degradation and to obtain uniform color dispersion. 

Rayon is unique among the mass produced man-made fibers because it is the only one to use a natural polymer (cellulose) directly. Polyesters, nylons, polyolefins, and acryflcs all come indirectly from vegetation they come from the polymerization of monomers obtained from reserves of fossil fuels, which in turn were formed by the incomplete biodegradation of vegetation that grew millions of years ago. The extraction of these nonrenewable reserves and the resulting return to the atmosphere of the carbon dioxide from which they were made is one of the most important environmental issues of current times. CeUulosic fibers therefore have much to recommend them provided that the processes used to make them have minimal environmental impact. 

Other simple nickel salts of organic acids include the oxalate [20543-06-0] oleate [68538-38-5], and stearate [2223-95-2]. The latter two have been used as oil-soluble nickel forms in the dyeing of synthetic polyolefin fibers (see Driers and metallic soaps). Nickel oxalate has been used as a catalyst intermediate (59). 

Nickel also has been used as a dye site in polyolefin polymers, particularly fibers. When a nickel compound, eg, the stearate or bis(p-alkylphenol) monosulfide, is incorporated in the polyolefin melt which is subsequently extmded and processed as a fiber, it complexes with certain dyes upon solution treatment to yield bright fast-colored fibers which are useful in carpeting and other appHcations (189). Nickel stearate complexing of disperse mordant dyes has been studied (190). 

Nonwood fibers are used in relatively small volumes. Examples of nonwood pulps and products include cotton Enters for writing paper and filters, bagasse for cormgated media, esparto for filter paper, or Manila hemp for tea bags. Synthetic pulps which are based on such materials as glass (qv) and polyolefins also are used (see Olefin polymers). These pulps are relatively expensive and usually are used in blends with wood pulps where they contribute a property such as tear resistance, stiffness, or wet strength which is needed to meet a specific product requirement. 

Polyolefin—ceUulose composites also are used in nonasbestos flooring felts, waUpapers, filter media, labels, embossable papers, and other nonwoven fabrics that are made on paper machines. Use of synthetic fibers in paper has been reviewed (103,104). 

Fabrics composed of synthetic polymer fibers are frequendy subjected to heat-setting operations. Because of the thermoplastic nature of these fibers, eg, polyester, nylon, polyolefins, and triacetate, it is possible to set such fabrics iato desired configurations. These heat treatments iavolve recrystaUization mechanisms at the molecular level, and thus are permanent unless the fabrics are exposed to thermal conditions more severe than those used ia the heat-setting process. 

The most common supported tubes are those with membranes cast in place (Fig. 17). These porous tubes are made of resin-impregnated fiber glass, sintered polyolefins, and similar materials. Typical inside diameters are ca 25 mm. The tubes are most often shrouded to aid in permeate collection and reduce airborne contamination. 

Another polyolefin of interest is polystyrene, a clear, brittle plastic that, by itself, is rarely used in composites. However, several copolymers and alloys of polystyrene with acrylonitrile or butadiene have been used with fiber glass or glass spheres to form composites (7). 

Cyclopentadiene itself has been used as a feedstock for carbon fiber manufacture (76). Cyclopentadiene is also a component of supported metallocene—alumoxane polymerization catalysts in the preparation of syndiotactic polyolefins (77), as a nickel or iron complex in the production of methanol and ethanol from synthesis gas (78), and as Group VIII metal complexes for the production of acetaldehyde from methanol and synthesis gas (79). 

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