Polyolefin fibers Properties

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. 

Elastic recovery or resilience is the recoveiy of length upon release of stress after e xtension or compression. A fiber, fabric, or carpet must possess this property in order to spring back to its original shape after being crushed or wrinkled, Polyolefin fibers have poorer resilience than nylon this is thought to be partially related to the creep properties of the polyolefins. 

The following list summarizes some of the main properties and characteristics of polyolefin fibers ... 

Polyolefin fibers are characterized and tested using most of the common synthetic liber techniques. It is beyond the scope of this chapter to discuss all techniques in detail. It is, however, important to mention the following properties, which are essential in understanding the identification and performance of polyolefin fibers. 

Tenacity. It is the stress at which the fiber breaks, expressed in grams per denier. It is a very important property of polyolefin fibers, and it can range between 3.5 and 8 g/d (grams per denier) or 31-81 g/tex [10]. General textile use PP fibers can have a tenacity of 40.5-50 cN/dtex, whereas high tenacity yams used in ropes and nets can have tenacities up to 81 cN/dtex [11]. 

Polyolefin fibers include both polyethylene (PE) and polypropylene (PP), and the latter is commonly used. PP has good mechanical properties, hydrophilic properties, and a... 

Recently, the use of Raman spectroscopy to characterize polymeric products has been the subject of two patents. Van Wijk et al. [1] patented the use of Raman spectroscopy with chemometrics for quality control of fiber spinning. They claim that Raman spectroscopy can predict dye uptake, structural properties, and mechanical properties once an appropriate chemometrics model has been developed for that polymeric type and the application. Aratake et al. [2] patented polyolefin fibers in which the skin had a low orientation and the core had a high orientation. They determined the ratio of the intensities of the 810-cm" band to the 840-cm band of polypropylene when the laser was polarized parallel to the fiber axis and for the same intensity ratio when the laser was polarized... 

The mechanical and physical properties of polyolefins are influenced, sometimes profoundly, by molecular weight. For example, paraffinic alkanes are incapable of forming fibers or films possessing useful mechanical properties. On the other hand, polyolefin fibers and films constitute a major segment of the polymer industry and find broad utility in everyday life. 

Vinyon fiber is chemically inert and possesses chemical properties similar to polyolefin fiber. Vinyon is only slowly attacked by ultraviolet rays in sunl ight. Vinyon fiber melts with decomposition at 135°-1 SOX, with vinyon containing comonomer having a lower melting/decomposition temperature. 

Antistatic finishes and antioxidants normally used on synthetic fibers are added to the polymer melt prior to polyolefin fiber formation. The most common antioxidants used include hindered substituted phenols, organo-metallic antioxidants, and substituted phenols. Blending of comaiomers with polyolefin prior to fiber formation is used not only to improve dye-abil ity but al so to plasticize the fiber and improve other fiber properties. Polyolefins may be effectively made flame retardant through incorporation of a metal oxide such as antimony oxide in conjunction with a brominated hydrocarbon or brominated organophosphate. 

Fibers from synthetic polymers make up approximately 80% of the total production of chemical fibers in Germany and about 90% worldwide (2000). The most important synthetic fibers are polyamide (Wulfhorst, 1997), polyester (Tetzlafi", 1997), and polyacrylonitrile (Wulfhorst, 1998). Because of their very specific properties, polyvinyl chloride (Koch, 1968), polytetrafluoroethylene, polyolefin fibers (such as polyethylene and polypropylene) (Wulfhorst, 1989b), and polyvinyl alcohol are used mostly for technical textiles. At the end of this section, an overview is given of synthetic polymers featuring the chemical structures, specific properties, and various applications (Table 2.7). The physical characteristics of chemical fibers from synthetic polymers are summarized later in Table 2.8. 

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. 

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