Tensile strength and elongation

Tensile strength testing is by far the most popular method of evaluating of filled materials. This can be seen from the numerous publications which analyze the subject. The information in this section is organized to provide the following information  

A general equation describes the effect of the volume fraction of a filler on tensile strength  

Without knowing the values of these coefficients, it is not possible to predict if tensile strength of the composite increases or decreases as the volume fraction of the filler increases. It is also obvious from the form of the equation that constants can be selected to describe certain features of the filler s behavior. For example, constant a is usually related to stress concentration. In composites, in which the filler has very poor adhesion, a = 1.21 or a = 1.23 for non-spherical particles. The constant b is usually assigned the arbitrary value of 0.67. Constants c and d relate to the effect of particle size. The smaller the particle size, the larger are the values of these constants. When the values of these four constants are known or approximated, it makes it possible to predict the tensile strength of various composites. Since the last term in Eq 8.1 is positive, a decrease in the particle size of the filler 

For low concentrations of filler, the Einstein equation usually fits experimental data  

In the Einstein equation, b = 1 for spherical particles at low concentration and a depends on the adhesion between the matrix and the filler. This equation predicts that the addition of filler increases tensile strength which was found to be not always the case, so this equation has been modified by various researchers. The Nicolais and Narkis equation is a common modification in which a=1.21 and 

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Modified ETEE copolymer has excellent weather resistance tensile strength and elongation ate not affected. On the other hand, tensile and elongation properties of the glass-reiaforced compound show a significant reduction. 

Like other perfluoropolymers. Teflon PFA is not highly resistant to radiation (30). Radiation resistance is improved in vacuum, and strength and elongation ate increased more after low dosages (up to 30 kGy or 3 Mrad) than with FEP or PTEE. Teflon PEA approaches the performance of PTEE between 30 and 100 kGy (3—10 Mrad) and embrittles above 100 kGy (10 Mtads). At 500 kGy (50 Mrad) PTFE, FEP, and PFA ate degraded. The effect of radiation on tensile strength and elongation is shown in Table 7. 

Tensile Strength and Elongation. The tensile strength of latex mbber foam has been shown to depend on the density of the foam (149,177) and on the tensile strength of the parent mbber (177,178). At low densities the tensile modulus approximates a linear relation with density but kicreases with a higher power of density at higher densities. Similar relations hold for polyurethane and other flexible foams (156,179,180). 

Types of Latex Compounds. For comparison with dry-mbber compounds, some examples of various latex compounds and the physical properties of their vulcanizates are given in Table 23. Recipes of natural mbber latex compounds, including one without antioxidant, and data on tensile strength and elongation of sheets made from those, both before and after accelerated aging, are also Hsted. The effects of curing ingredients, accelerator, and antioxidant are also Hsted. Table 24 also includes similar data for an SBR latex compound. A phenoHc antioxidant was used in all cases. 

Fast, low temperature curing mbber compounds can be prepared by initial heat prevulcanisation of the Hquid latex and are marketed commercially (Revultex, Doverstrand Corporation). Rubber deposited from these often needs tittle more heat than that required to dry the deposit, to achieve optimum tensile strength and elongation. Such compounds are often used by small companies manufacturing thin-wall dipped medical latex products, such as examination gloves, as few compound preparation facilities are needed by the dipping company. 

Table 7. Effect of Stretch Ratio on Tensile Strength and Elongation of a VDC—VC Copolymer ...

Fig. 2. Tensile strength and elongation retention after aging of FZ. Aging temperature D, 150°C A, 175°C O, 200°C. To convert MPa to psi, multiply by...

Table 10.3 Effect of straining rate on the measured tensile strength and elongation at break of two samples of polyethylene...

S-B, Polystyrene 1,2-Polybuta diene Polystyrene Polybutylene Improved tensile strength and elongation... 

Tensile strength and elongation at break has been determined by an Instron mechanical analyzer, and the results are as shown in Fig. 10, 11, and 12. 

To introduce some interfacial physico-chemical linkage between EVA and PRP, blends were made by adding different quantities of M AH-PP. Some results are demonstrated in Table 12, The physico-mechanical properties of the PRP-EVA compositions modified with MAH-PP showed that properties are influenced by MAH-PP concentration. Compositions with better impact strength and improved brittleness can be prepared by varying the modifier concentration. Tensile strength and elongation are not significantly influenced by the addition of a modifier. An increase in the modifier con-... 

Compatibility and various other properties such as morphology, crystalline behavior, structure, mechanical properties of natural rubber-polyethylene blends were investigated by Qin et al. [39]. Polyethylene-b-polyiso-prene acts as a successful compatibilizer here. Mechanical properties of the blends were improved upon the addition of the block copolymer (Table 12). The copolymer locates at the interface, and, thus, reduces the interfacial tension that is reflected in the mechanical properties. As the amount of graft copolymer increases, tensile strength and elongation at break increase and reach a leveling off. 

Fig. 5.8 Effect of temperature on the tensile strength and elongation of tantalum...

Mechanical properties, such as elastic modulus and yield point, that depend on crystallinity per se are not seriously affected by low to moderate doses of ionizing radiation. On the other hand, those mechanical properties that are sensitive to interlamellar activity are most dramatically affected by the low to moderate radiation doses. This is seen in the ultimate tensile strength and elongation at failure of the polyolefins. It is also reflected in the large change in melt index between 0 and 18 Mrad, which indicates formation of cross-links that increase with increasing... 

The mechanical test data show an increase in ultimate elongation for several of the B1 through B8. Samples Bl, B3, and B6 in particular showed similar tensile strength and elongation as the A2 and A3 samples. The tear resistance values were also similar for the Bl and B3 samples compared to A2 and A3 samples. 

Data are presented which illustrate that the tensile strength and elongation-at-break depend significantly on the extension rate even when the stress remains in equilibrium with the strain prior to fracture. A crude estimate was made of the threshold (lowest possible) values of the true stress-at-break and the elongation-at-break for the TIPA elastomer. The estimated quantities are about 26% less than those found at an extension rate of about 0.01 min-1 at 30°C. 

ISO 527-4 1997 Plastics - Determination of tensile properties - Part 4 Test conditions for isotropic and orthotropic fibre-reinforced plastic composites ISO 527-5 1997 Plastics - Determination of tensile properties - Part 5 Test conditions for unidirectional fibre-reinforced plastic composites ISO 1798 1997 Flexible cellular polymeric materials - Determination of tensile strength and elongation at break... 

For three- and ten-year outdoor exposures of 3-mm-thick samples, retentions of tensile strength and elongation at break can be, for example ... 

After 15-year outdoor exposures of 0.1-0.15 mm thick films, the retentions of tensile strengths and elongations at break range from 91% up to 125% without visible change. These results are examples only and cannot be generalized. 

Figure 4.124 shows two examples of the retention of tensile strength and elongation at break for a film exposed to the Weather-Ometer. 

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