Tenacity, tensile strength

Sometimes, mechanical properties of polymer fibers can be found as an example, tenacity (tensile strength, in MPa) and tensile modulus (in GPa). It should be clear that these values cannot be used for design calculations unless the fibers are kept in their original form. The fibers display such high mechanical properties because of the high degree of orientation of the polymer chains in the fiber. The influence of the polymer type apparently is of secondary importance and only becomes important when the material is melted again. 

Zugfestigkeit, /. tensile strength, tenacity, zugfrei, a. free from drafts, zugiessen, v.t. fill up by pouring pour to, pour in. 

As for the tenacity, which describes the fiber s resistance to the action of the tensile force, the quantitative index assumed most often is the tensile strength (crj (cN/tex). For the quantitative assessment of tenacity an index of mechanical long life (t) is used, proposed by Zurkow and Abasow [46,47]. This index defines the time after which, when applying a definite tensile strength and a definite temperature, the fiber breaks. 

A recent approach was based on the DMAc/LiCl and N-methyl-2-pyrrohdone/IiCl solvent systems [252,253] that enabled better dry tensile strengths although they did not provide adequate wet tenacities, due to poor crystallinity and poor consohdation of the fibre. A further problem was the... 

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

TENACITY. Strength per unit weight of a fiber or filament, expressed as g/deiuer. It is the rupture load divided by the linear density of the fiber. See also Tensile Strength. 

A very important diagram for fibres and yams is the stress—strain diagram, where the specific stress is plotted as a function of the elongation (extensional strain) in %. The curve starts at an elongation of zero and ends in the breaking point at the ultimate specific stress (=tensile strength or tenacity) and the ultimate elongation (=strain at break). 

The very wide range of the numerical values of the mechanical properties is evident. The modulus of organic polymer fibres varies between 1 and 350 GPa. The tenacities or tensile strengths may even vary from about 0.07 GPA (0.05 N/tex) for the weakest (cellulose acetate) to about 7 GPa (4 N/tex) for the strongest fibre (PIPD or M5 ) the compressive strengths reaches up to 1.7 GPa and the temperature resistance up to 400 °C. The ultimate elongation may vary from about 1% for the stiffest fibre (carbon) to about 600% for the most rubber-elastic. 

Fig. 18. Correlation between carbon fiber tensile strength and stabilized fiber tenacity. = AN/VBr optimized (cf. Sea. 5)...

Table VI compares the key properties of these two types of thermotropic polymers category by category. The samples compared had the same melting ranges, but were very different in reduced viscosities and solubility characteristics. The data compared were those processed under the most favorable conditions. Interestingly enough, the as-spun fibers from the polyester-carbonate can be heat-treated more efficiently than those fibers (of same tenacity) spun from the polyester. Both of them gave fiber properties far superior to those of nylons and polyethylene terephthalate. These two classes of polymers also had comparative properties (such as tensile strength, tensile modulus, flex modulus, notched Izod impact strength) as plastics and their properties were far superior to most plastics without any reinforcement.

The oriented film specimens were mounted on aluminum frames and exposed on an Atlas Weather-Ometer, Model 65WR. An 18 minute spray cycle together with an 102 minute cycle at 55% relative humidity and approximately 65°C was used. At regular intervals, the test specimens were removed from exposure and their tensile strength measured on an Instron Model 1102. A decrease in tensile strength, expressed as tenacity, over the tensile strength of the same formulation before exposure, is a measure of the deterioration of the physical properties of the polymer. "Failure" in this test is defined as a loss of 50% or more of the initial sample tenacity. 

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