Tear strengths, determination

There are a number of different-shaped samples that are specified for carrying out the tear strength determination. The exact shape and test method used needs to be specified for any values quoted. 

Tear Strength, Elmendorf Sometimes called the Elmendorf tear, this tear strength determines the force required to propagate a single-rip tear starting from a cut in a specimen using a falling-pendulum type (Elmendorf) apparatus. 

The second parameter, tear strength, describes the film resistance to tear propagation. It is measured with a special apparatus, the Ehnendorf Tear Tester (ASTM D1922), and defined as the weight of a loaded pendulum capable of tearing a notched piece of film. Two values are usually measured for each film sample. One determines tear propagation in the machine direction of the film, the other in the transverse direction. 

Tables 4—6 Ust ASTM methods used for the characterization of PB and PMP. A number of specialized methods were developed for testing particular articles manufactured from polyolefins several of these determine the performance of PB and PMP film, including the measurement of the film s dart impact strength and tear strength. Dart impact strength is measured by dropping a heavy dart with a round tip on a stretched film. Tear resistance, which reflects the film s resistance to tear propagation, is measured with the Ehnendorf tear tester. Two values for the tear strength are usually reported, one in the machine dkection of the film and the other in the transverse dkection. Pipes manufactured from PB are tested by pressurizing them internally with water the time-to-burst failure is determined at various temperatures (46). The standard test method for haze and luminous transmittance (ASTM D1003) is used for the measurement of PMP optical characteristics.

Although a variety of test methods, eg, Dk, modulus, and tear strength, exist to determine key properties of potential contact lens materials, a number of properties, eg, wettabihty and deposition, have no predictive methodology short of actual clinical experience. 

Determination of mechanical properties like tensile strength, tear strength, modulus, and elongation at break are the most common methods adopted to determine the cured properties of short fiber-mbber composites. Murty and De [133] discussed the technical properties of short fiber-mbber composites whereas Abrate [8] reviewed the mechanism of short fiber reinforcement of mbber. Fiber concentration in the matrix plays an important role in the optimization of the required... 

ISO 34-1 2004 Rubber, vulcanized or thermoplastic - Determination of tear strength -Part 1 Trouser, angle and crescent test pieces... 

Tensile and tear strengths were determined using ASTM standards D412 and D1004, respectively, at a crosshead speed of 0.42 mm/s (1 In/mln) values reported are the average for 3 specimens. The elastic and Inelastic (plastic) components of the total elongation... 

The quantity directly measured in a tear test is the force on the test piece during testing. Particularly with the trouser method, this force will fluctuate along the tear path. ISO 34 takes the maximum force reached in the case of crescent, angle and Delft methods but for the trouser method a median force is determined in accordance with procedures given in ISO 6133147, Analysis of multi-peak traces obtained in determinations of tear strength and adhesion strength. 

ISO 34 Part 2, 1996. Determination of tear strength - Small (Delft) test pieces. 

ISO 6133, 1998. Analysis of multi-peak traces obtained in determinations of tear strength and adhesion strength. 

In tensile strength determinations, the material has to completely break through the cross-section, whereas the tear strength test indicates the resistance to the propagation of a defect, such as a nick, in the polyurethane. The way that elastomers tear under different conditions has led to a number of different tests. 

Part 1 Trouser, angle, and crescent test pieces Part 2 Small (delft) test pieces Standard test method for tear strength of conventional vulcanized rubber and thermoplastic elastomers Testing of rubber and elastomers Determination of the tear strength of elastomers Trouser test piece... 

The analytical techniques discussed previously can be used to study the EPDM network as such or its formation in time as well as to determine relationships between the network structure and the properties of the vulcanisates. In a preliminary approach some typical vulcanised EPDM properties, i.e., hardness, tensile strength, elongation at break and tear strength, have been plotted as a function of chemical crosslink density (Figure 6.6). The latter is either determined directly via 1H NMR relaxation time measurements or calculated from the FT-Raman ENB conversion (Table 6.3). It is concluded that for these unfilled, sulfur-vulcanised, amorphous EPDM, the chemical crosslink density is the main parameter determining the vulcanisate properties. It is beyond the purpose of this review to discuss these relationships in a more detailed and theoretical way. 

To determine whether or not changes in color were accompanied by fiber damage, unexposed fabric and several fabrics exposed to the xenon-arc source for 550 kj/m2 (AE from 1 to 3) were tested for tearing strength by the Elmendorf method (11). Before exposure, the tearing strength of the blue wool fabric was 2040 g in the warp and 1710 g in the fill direction. For all other fabrics tested after exposure to light, the... 

The effect of synthesized modifiers on fluorosiloxane rubbers is determined on the basis of fluorosiloxane rubber CKTFT-100 As seen fix)m data presented in Table 3, characteristics of fluorosiloxane rubber depend on quantity of introduced modifier and its molecular mass Properties of rubber compounds are highly dependent on modifier concentrations. Optimal modifier content amounts to 6 - 7%. Increase in molecular mass of modifier on transition from modifier II to modifier VI leads to increase in tear strength and relative elongation in comparison to the control specimen (modifier concentration = 0). Also, after thermal treatment at 250 °C for 24 h in the presence of modifier VI, improvement of all fluorosiloxane rubber compound properties is observed. 

The amount of water used in flexible urethane foam formulations, together with the corresponding amount of TDI, largely determines the foam density. As the amount of water increases, with a corresponding increase in TDI, the density decreases. If water content is increased without increasing the TDI, foams may be obtained with coarse cells and harsh textures. Lower tensile and tear strengths and compression moduli result, while the compression set tends to increase. Another important... 

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