Properties of fibers

Fabrics are two-dimensional materials made from fibers. Their primary purpose is to cover things and they are commonly used in clothes, carpets, curtains, and upholstery. The motive for covering may be aesthetic, thermal, or acoustic. Fabrics are made out of or twisted bundles of fibers. The spinning of yams can occur in two ways staple fibers can be twisted into a thread ( spun yam ) or monofilaments can be twisted into a similar usable thread ( filament yam or continuous filament yam ). All these definitions are important in order to understand the conversation of the fiber industry. 

Polymer Tenacity (g/denier) Tensile Strength (kg/cm ) Elongation (%) 

In general, you should recall that the tensile strength and modulus of fibers must be much higher than that for plastics and their elongation must be much lower. Synthetic fibers are usually stretched and oriented uniaxially to increase their degree of parallel chains and increase their strength and modulus. 

Besides the high tenacity, a number of other properties are considered necessary for most fiber applications. Although no one polymer is superior in all of these categories, the list in Table 17.3 represents ideals for polymers being screened as fibers. 

Proper Tg and T. A low Tg aids in easy orientation of the fiber. The should be above 200°C to accept ironing (as a textile) but below 300°C to be spinnable. 

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An important aspect of the mechanical properties of fibers concerns their response to time dependent deformations. Fibers are frequently subjected to conditions of loading and unloading at various frequencies and strains, and it is important to know their response to these dynamic conditions. In this connection the fatigue properties of textile fibers are of particular importance, and have been studied extensively in cycHc tension (23). The results have been interpreted in terms of molecular processes. The mechanical and other properties of fibers have been reviewed extensively (20,24—27). 

Attention must also be focused on the noncrystalline domains. Many important properties of fibers can be directly related to these noncrystalline or amorphous regions. For example, absorption of dyes, moisture, and other penetrants occurs in these regions. These penetrants are not expected to diffuse into the crystalline domains, although there may be adsorption on crystaUite surfaces. The extensibUity and resUience of fibers is also directly associated with the noncrystalline regions. 

Noncrystalline domains in fibers are not stmctureless, but the stmctural organization of the polymer chains or chain segments is difficult to evaluate, just as it is difficult to evaluate the stmcture of Hquids. No direct methods are available, but various combinations of physicochemical methods such as x-ray diffraction, birefringence, density, mechanical response, and thermal behavior, have been used to deduce physical quantities that can be used to describe the stmcture of the noncrystalline domains. Among these quantities are the amorphous orientation function and the amorphous density, which can be related to some of the important physical properties of fibers. 

Optical Properties. When light falls on an object, it is either partially absorbed, reflected, or transmitted. The behavior of the object as it relates to each of these three possibiUties determines visual appearance. Optical properties of fibers give useful information about the fiber stmcture refractive indexes correlate well with fiber crystalline and molecular orientation and birefringence gives a measure of the degree of anisotropy of the fiber. 

Optical properties of fibers are measured by light microscopy methods. ASTM D276 describes the procedure for fiber identification using refractive indexes and birefringence. Other methods for determining fiber optical properties have been discussed (3,38—44). However, different methods of determining optical properties may give different results (42). 

Stress—Strain Curve. Other than the necessity for adequate tensile strength to allow processibiUty and adequate finished fabric strength, the performance characteristics of many textile items are governed by properties of fibers measured at relatively low strains (up to 5% extension) and by the change ia these properties as a function of varyiag environmental conditions (48). Thus, the whole stress—strain behavior of fibers from 2ero to ultimate extension should be studied, and various parameters should be selected to identify characteristics that can be related to performance. 

J. Aveston, G. A. Cooper, and A. Kelly, ia The Properties of Fiber Composites, IPC Science Technology Press, The National Physical Laboratory, 1971, pp. 15-26. 

Ethers, esters, amides and imidazolidines containing an epithio group are said to be effective in enhancing the antiwear and extreme pressure peiformance of lubricants. Other uses of thiiranes are as follows fuel gas odorant (2-methylthiirane), improvement of antistatic and wetting properties of fibers and films [poly(ethyleneglycol) ethers of 2-hydroxymethyl thiirane], inhibition of alkene metathesis (2-methylthiirane), stabilizers for poly(thiirane) (halogen adducts of thiiranes), enhancement of respiration of tobacco leaves (thiirane), tobacco additives to reduce nicotine and to reduce phenol levels in smoke [2-(methoxymethyl)thiirane], stabilizers for trichloroethylene and 1,1,1-trichloroethane (2-methylthiirane, 2-hydroxymethylthiirane) and stabilizers for organic compounds (0,0-dialkyldithiophosphate esters of 2-mercaptomethylthiirane). The product of the reaction of aniline with thiirane is reported to be useful in the flotation of zinc sulfide. 

J. M. Whitney and M. B. Riley, Elastic Properties of Fiber Reinforced Composite Materials, AIAA Journal, September 1966, pp. 1537-1542. 

J. J. Hermans, The Elastic Properties of Fiber Reinforced Materials when the Fibers are Aligned, Proceedings of the Koninklijke Nedertandse Akademie van Weten-schappen, Amsterdam, Series B, Volume 70, Number 1, 1967, pp. 1-9. 

Orientation of fibers relative to one another has a significant influence on the strength and other properties of fiber-reinforced composites. With respect to orientation three extremes are possible as shown in Fig. 5. Longitudinally aligned fibrous composites are inherently anisotropic, in that, maximum strength and reinforcement are... 

Among the basic mechanical properties of fibers are their deformability and tenacity. When an axial stretching force is applied to the fiber, the principal quantitative indices of deformability are the axial elastic modulus (E)... 

The role of the matrix is to protect the filler from corrosive action of the enviroment and to ensure interactions between the fibers by mechanical, physical and chemical effects. The mechanical properties of fiber composites are dependent on the mutual position of the fibers in the monolithic materials. 

Joslin, CG Stell, G, Bounds on the Properties of Fiber-Reinforced Composites, Journal of Applied Physics 60, 1607, 1986. 

Geomembrane blowing operations, 20 174 Geometric mean, 18 136 Geometric properties of fibers, 11 166-167 of staple fibers, 11 166-167 Geon balanced vinyl chloride process, 25 636, 672... 

Normalized frequency, 11 132 Normalized mechanical properties, of fibers, 11 182... 

Kelly, A. and Tyson, W. R., Tensile properties of fiber reinforced metals copper tungsten and copper/molybdenum,. /. Mech. Phys. Solids, 13, 329 (1965). 

Ho, H. and Drzal, L. T., Evaluation of interfacial mechanical properties of fiber reinforced composites using the microindentation method, Composites, A, 27, 961 (1996). 

The mechanical properties of fiber-matrix interfaces 3.2.1. Introduction... 

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