Fibers density values

Typical textile fibers used, for example, in a needle-punched filter fabric, are a blend of 3.3- and 6.6-dtex (3- and 6-denier) polyester staple. These fibers are - 5 cm long, have diameters ranging from 18 to 25 pm, mass-per-unit-length or linear density values ranging from - 350 to 650 mg per 1000 m, and length-to-width ratios in the order of 1000 to 1. 

The amorphous phase differs from the mesophase and the crystalline phase by a clearly lower value of density. The amorphous phase density depends on the internal orientation of the fiber. Us value is in the range 1.335-1.357 g/cm. In the case of a very high orientation, it can even reach the value 1.363 g/cm-. ... 

Two helices are packed antiparallel in the orthorhombic unit cell. Association of the helices occurs through a series of periodic carboxylate potassium water - carboxylate interactions. An axial projection of the unit-cell contents (Fig. 23b) shows that the helices and guest molecules are closely packed. This is the first crystal structure of a polysaccharide in which all the guest molecules in the unit cell, consistent with the measured fiber density, have been experimentally located from difference electron-density maps. The final / -value is 0.26 for 54 reflections, of which 43 are observed, and it is based on normal scattering factors.15... 

Tests for Fire Resistance of Roof Covering Materials, 1983. (similar to ASTM E 108) Tests for Flame Propagation and Smoke Density Values for Electrical and Optical Fiber Cables in Spaces Transporting Environmental Air, 1991. 

The density of fibers is a very important attribute. We mentioned above the use of linear density or mass per unit length. That term is really suitable for giving m idea of the fiber size. Bulk density or mass per unit volume tells us how heavy a material is. Bulk density values of some important fibers are given in Table 2.2. The reader can easily verify that if we divide the linear density of a fiber by its... 

Oxidative degradation appears to be the main mechanism governing humification. In determining the degree of decomposition or humification of peat materials the estimation of total fiber content correlates well with relative biodegradability and is a more reliable method than either the pyrophosphate index or bulk density values. 

The strain values observed at the maximum load point during a biaxial test are lower than in the case of the uniaxial test performed with same dimension samples and this for the two directions. As a consequence, the strains at which the load is maximum are lower than 4.5% in the weft direction during the uniaxial test. These strain values represent the limit from which a loss of fiber density takes place in the tows and this phenomenon should probably be avoided by keeping the tensile strain in the tetrahedron preform lower than these values. 

Moreover, long(>200 cm) fibers 1 mm in diameter were formed from thermoplastic gels ofY-123 ceramics and PVA." Calcined fibers exhibited values of = 92-94K. These fibers form materials characterized by different values, depending on the degree of saponification (DS) and the Y-123 ceramic content of these materi-als." The minimum critical current density occures when DS = 67 mol%, and the maximum value (J = 3.5 X 10 Acm, 77K) when DS = 81 mol%. The critical current density is also affected by the conditions of treatment (calcination and pyrolysis), which is associated with the peculiarities of the distribution of the ceramics over the fibers. High-T). superconductor nanocomposites have also been prepared by polymerization of acrylic acid in an aqueous solution of Y + nitrate and Ba + and Cu " acetates. " ... 

The shell-side Sherwood number strongly depends on the fiber density. There is an optimal value of diameter to pitch ratio. In loosely packed modules the distance that the solute molecules must travel is too long. On the other hand, in tightly packed modules the disadvantageous fiber-to-fiber interaction takes place.Even in uniformly packed modules wide residence time distribution of fluid elements does exist... 

The development of high-performance fiber composites leads to plastic designs with excellent corrosion resistance, density values lower than aluminum, and cyclic loadability comparable to steel. However, it is generally harder to achieve reproducible properties with composites than with metals. That is why special attention must be paid to processing and quality assurance [645]. 

With only a few exceptions, most of the open literature on yarns from electrospun fibers focuses on the process of yarn formation, mih i than on the yarns obtained. Although the process is certainly an mq)ortant aspect, researchers should bear in mind that ultimately the intended end-user of their results will be the fibers and textiles manufacturing indushy. With this in mind, future research should pay more attention to the properties of the yarns obtained, and report more on these with specific focus on tenacity, elasticity and linear density values. 

Fig. 3 Refraction values of both (0°+ 90°) fiber directions with respect to impact energy per layer. The fiber/matrix debonding of CFRP laminates correlates significantly to the impact energy per volume (energy density).

---