Tenacity and Elongation

Table 2. Tenacity and Elongation of Commercial Acetate and Triacetate Fibers...

To accommodate the various uses in 100% form and in blends, the tenacities and elongations of the nylon staple offerings range from 0.3 to 0.6 N /tex (3—7 g/den) and from 50 to 100% elongation. Most other fiber properties of nylon staple differ tittle from those of the continuous filament property characteristics of nylon-6 and nylon-6,6 are similar (see Polyamides, general). 

In the coupled process (Fig. 7c), the draw ratio, which affects the tenacity and elongation, lowers with increasing spinning speed. As draw ratio is increased, tenacity and initial modulus increase and elongation decreases. 

Fig. 8. Tangent modulus (T), tenacity ( ), and elongation (A ) as a function of take-up velocity for nylon-6. To convert N /tex to g/den (gpd), multiply by...

Brown and Chuah [84] and Oppermann el ol. [36] studied the spinning of partially oriented yam (POY) as a function of take-up speed from 500 to 5000m/min. Figures 11.18 and 11.19 show, respectively, development of the tenacity and elongation as a function of spinning speed. Tenacity increases with increasing... 

As expected, the residual extensibility of the fiber decreases at higher draw ratios. What is not so predictable is that the true stress at failure increases as the draw ratio increases fiber failure strength is improved by drawing the yarn. If a curve is drawn to connect the end points of the stress-strain curves, it is seen that there is an inverse relationship between tenacity and elongation to break (eb). The form of this relationship is as follows ... 

Stiffness or tensile modulus at break was determined from the value of tenacity and elongation at break using the following relation ... 

Relative changes in the properties of ethyl cellulose are given in Fig. 51. Modulus, tenacity and elongation decrease with dose for rayon, cotton and cellulose acetate, whereas stiffness increases for acetate and rayon. 

For the various POY yams textured at constant tension to a fixed tenacity and elongation target (3.3 grams per denier tenacity 18% elongation), the number of broken filaments generated by the texturing operation decreases with Increased yam stmcture (Table 1). Interestingly, the best POY structure versus PTY broken filament number correlation Is achieved with the reciprocal product of amorphous orientation (fa) and crystalline content (x) ... 

FIGURE 3.37 Tenacity and elongation versus take-up velocity for two CR polypropylenes. (From Jack, H.P. McKinley, J.R. Symposium on Polypropylene—Growth Fiber of the Eighties, New York, September 1981. With permission.)... 

Rosenthal [209] has given an empirical expression for the relation between tenacity and elongation ... 

Figure 11.6 shows the typical stress-strain curve for either cellulose acetate or triacetate yarn [35]. The linear part of the curve under low stresses is not as steep as that for cotton or rayon. At about 0.9 g/den stress, the curve starts to show large increments of strain for very small increments of stress. This continues until the fiber breaks at about 1.36 g/den and 26% strain or elongation. Tenacities and elongations for various acetate and triacetate fibers may be slightly different, depending on the particular manufacturing conditions. 

The dimensions of the fibrils and microvoids seen in the uncollapsed drawn fiber can be traced back to the structure of the freshly coagulated fiber. Knudsen [268] has shown that the reduction of the spin-bath temperature gives a denser and finer structure in both the first roll and drawn uncollapsed fiber, and furthermore, the tensile properties are improved. In Figure 12.32, the breaking tenacity and elongation are shown as a function of the draw ratio for different spin-bath temperatures. The lower spin-bath temperature produces a stronger and stiffer fiber. The lateral properties of the finished fiber are also improved by having the denser structure. The number of cycles-to-fail in a multifilament flex-abrasion test increases by a factor of 2-3 x when the spin-bath temperature is lowered from 55 to 0°C. This is attributed to an increase in the number of lateral interconnections between fibrils in the drawn fiber as the bath temperature is reduced. 

Textile Fibers. PTT POY is spun using PET POY or SDY fiber spinning machines. Table 5 shows the tenacities and elongations of PTT fiber as a function of spinning speed (64). Tenacity increases while the elongation decreases with increasing speed. The PTT fiber stress-strain curve, unlike PET, has an inflexion point like a knee (45,65). A fully oriented PTT fiber has a modulus of 2.58 GPa (374,000 psi) compared to 9.15 GPa (1.33 x 10 psi) of PET (45). 

An isophthalic general purpose resin, offering good chemical resistance, flexibility, high tenacity and elongation, with low water absorption. 

Polypropylene (PP) fiber was supplied from Kolon Glotech Co., Ltd., Korea. The specific gravity and the melting point of PP fiber were 0.91 and 160-165°C, respectively. And the tenacity and elongation of the PP fiber were 1.5-4.5 g/denier and 50-350%,... 

The still defficient properties of PO fibers may be improved by the production of PO, through metallocene catalysis. In these cases, polydispersity decreases from 4.5 to 2.5, the MFI index is improved, as well as tenacity and elongation to break. 

Spandex fibers are weak but highly extensible fibers with tenacities of 0.5-2 g/d (4.5-18 g/tex) dry with slightly weaker wet tenacities, and elongations at break of 400%700% Spandex exhibits nearly complete recovery from high elongations and is quite resilient. The fibers have... 

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