Polyolefins fibers

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. 

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). 

The total 1997 U.S. production of polyolefin fibers, including polypropylene fibers, was approximately 2.5 billion pounds. 

Polymer types employed Urethanes polyolefins (fiber phase) Urethanes polyolefins (fiber phase) Urethanes Various... 

Polyolefin containers, fluorine surface treatment of, 11 846 Polyolefin dust, 20 230 Polyolefin fibers, 11 224 24 614. See also Olefin fibers... 

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. 

Thermal and Oxidative Stability. In general, polyolefins undergo thermal transitions at much lower temperatures than condensation polymers thus, the thermal and oxidative stability of polyolefin fibers are comparatively poor. Preferred stabilizers are highly substituted phenols such as Cyanox 1790 and lrganox 1010, or phosphites such as Ultranox 626 and Irgafos 168. 

One of the most recent developments in the use of polyolefin fibers is in composites of spunbond (SB) and melt-blown systems. Some examples of structures being made are SB/MB, known as SM, SB/MB/SB, or SMS, and other combinations of SB and MB. The... 

Polyolefins. Polyolefin fibers are produced from the polymerization of ethylene or propylene gas. The catalysis research of Ziegler and Natta led to the development of these polymers to form crystalline polymers of high molecular weight. Hercules Inc. produced the first commercial fibers in 1961. The fibers made from these polymers are melt-spun. The cross-sections are round, and the fibers are smooth. They have extremely low dye affinity and moisture absorbance. Colored fiber is normally produced by mixing pigments in the melt polymer prior to extrusion. 

Polypropylene and polyethylene are perhaps the two most important polyolefin fibers. Polyethylene has a simple, linear chain structure consisting of a carbon backbone and small hydrogen side groups. Such a structure makes it easy to crystallize. There are three common grades of polyethylene low density polyethylene (LDPE), high density polyethylene (HDPE), and ultra-high molecular... 

Polymeric fibers are popular for reinforcing concrete matrices because of their low density (more number of fibers for a prescribed volume fraction), high tensile strength, ease of dispersion, relative resistance to chemicals, and relatively low cost compared to other kinds of fibers. Polypropylene and polyolefin fibers are typically hydrophobic, resulting in a relatively poor bond with concrete matrices compared to some other types of fibers. Treatment of polypropylene with an aqueous dispersion of colloidal alumina or silica and chlorinated polypropylene enhances the affinity of these fibers toward cement particles. Treatment of polypropylene fibers with a surface-active agent provides better dispersion of the fibers and a stronger bond between cement and fiber. The earlier attempts at surface treatments of polypropylene fibers have had only limited success and have not been commercially attractive. 

Significantly improved UV light stability is found with polymeric substrates stabilized with bis(2,2,6,6-tetramethyl-piperidinyl-4) sebacate, an example of hindered-amine class light stabilizers, compared with those stabilized with conventional light stabilizers. Application areas covered include polyolefin fibers, films and molded sections, polyurethane, and styrenics. Synergistic performance with o-hydroxyphenyl benzotriazoles in these polymers is apparent. 

The seventh trend is the increasing use of novel processing methods. For example, there is growing use of supercritical fluids (e.g., supercritical carbon dioxide and nitrogen gases) to foam polyolefin blends for density reduction. There is use of ultrasound to, for example, devulcanize cross-linked rubber. There is use of solid-state shear mechanical processing to break the polyolefin blend material into submicron particles to make environment friendly (water-based) polyolefin dispersions. There is use of electrospinning technique to make polyolefin fibers and in particular nanofibers. 

Aromatic-aliphatic bromine compounds, like the bis(dibromopropyl)-ether of tetrabromobisphenol A, or bromoethylated and aromatic ring-brominated compounds, such as l,4-bis-(bromoethyl)-tetrabromobenzene, combine the high heat stability of aromatic-bound bromine with the outstanding flame retardancy of aliphatic-bound bromine. They are used mainly as flame retardants for polyolefins, including polyolefin fibers. 

Fiber processing development Unusual plastic fibers such as polyolefin fibers are produced by a spurted or melt-blown spinning technique. A variety of directly formed nonwovens with excellent filtration characteristics is produced. Original development was by... 

---