Sheath/core fibers

Shaving products Shaw process Shear breeding Shear energy Shearlings Shearometer Shear plane Shear rate Shear stresses Shear test Shear thinning behavior Shear viscosity Sheath-core fiber... 

Fig. 14. Bicomponent spinneret for sheath-core fiber, where A represents copolymer B, homopolymer and D, bicomponent fiber capillary exit. If...

A number of polymer and fiber modifications have been devised to overcome this problem, although none has been successful enough to allow acrylics to compete in successfully easy-care apparel markets. The fibers may be treated with compounds such as ammonium sulfide [433], hydrazine derivatives [434,435], thiosemicarbazides [436], silicone oils [437], and emulsions of polysiloxane and polyepoxide [438]. Some success has been achieved by incorporating comonomers that increase the wet glass transition temperature of the polymer or make the copolymer more water-resistant [439-444]. Sheath-core fibers have been reported [445] in which the core polymer is stable under hot-wet conditions and the sheath polymer is used to compensate for deficiencies in dyeability. 

Although bicomponent fibers are usually based upon crystalline polymers, crystallinity is not required in both components. For example, in a recent study, Han (1973) coextruded several sheath-core bicomponent systems based on polyethylene and polystyrene, respectively. Han found that the interfacial curvature in the sheath-core fibers became more circular... 

Chemical vapor deposition on hot filament surfaces Solid surface of carbon, graphite or metal filaments o Short diamond/carbon and diamond/metal sheath/core fibers 0 Diamond microtubes, microcoils... 

Short diamond/carbon whiskers (Figure 6), the first truly discontinuous sheath/core fibers [28], were made by a two step process. The short vapor grown carbon core fibers were produced by pyrolysis of H2/CH4 mixtures in the presence of iron catalysts [25]. These vapor grown carbon fibers were then ultrasonically polished, and diamond was deposited by a microwave plasma-enhanced chemical vapor deposition technique [28]. 

This subchapter deals with experimental sheath/core fibers made by conventional as well as plasma enhanced chemical vapor deposition, and by plasma enhanced physical vapor deposition. 

This transient operating cycle [7] minimizes devitrification as the melt passes from refining to fiberizing conditions. The low pressures which are independently applied to each crucible facilitate the formation of solid concentric sheath/core fibers and prevent the formation of hollow fibers. The core diameters can range from 8.4 to 75.1 pm and the overall fiber diameter, including sheath or clad, can range from 140 to 149 pm. 

Sheath-core fibers n. Bicomponent fibers of either two polymer types, or two variants of the same polymer. One polymer forms a core and the other surrounds it as a sheath. 

The results presented indicate that uniform sheath-core fibers of nano dimensions can be produced from two polymers by carefully adjusting the spinning conditions, in particular the applied voltage. As it is generally known, the polymer solution flow rates and concentrations directly controlled the core-sheath fractions and, therefore, the overall fiber size. 

Sheath-Core Fibers Bicomponent fibers of either two polymer types, or two variants of the same polymer. 

Staple bicomponent fiber capacity is fairly equally distributed throughout North American, Europe, and Asia. The lines are small as compared to standard staple lines. Two major products are produced. One is sheath/ core fibers with a low melt sheath that is used for binder fibers in carded, thermally bonded nonwovens.The other product is side-by-side fibers (usually polyester and co-polyester) that are self-crimping and used for fiberfill. Production is approximately equal between these two products. 

Nanoparticles such as carbon nanotubes can be added to the matrix for achieving conductivity. Semi-conducting metal oxides are often nearly colorless, so their use as conducting elements in fibers has been considered likely to lead to fewer problems with visibility than the use of conducting carbon. The oxide particles can be embedded in surfaces, or incorporated into sheath-core fibers, or react chemically with the material on the surface layer of fibers. 

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