Tear resistance test

Matched sets of folding endurance and tear resistance test specimens were prepared from each paper to be aged at several temperatures. Aging was done in forced circulation ovens that were supplied with air having a dewpoint of 53°F. At intervals, sets of test specimens were removed from the oven and tested to monitor the deterioration process. 

Breaking strength (Load) n. (1) The maximum resultant internal force that resists rupture in a tension test. The expression breaking strength is not used for compression tests, bursting tests, or tear resistance tests in textiles. 2. The load (or force) required to break or rupture a specimen in a tensile test made according to a specified standard procedure. 

This test was developed to determine the tear resistance of foam. The tear-resistance test, also known as the block method, uses the block specimen described in Figure 14-7. The block specimen is mounted by spreading the block so that each tab is held in the jaw of the tensile testing machine. The load is applied by separating the jaws at a specified speed. The force required to rupture the specimen is recorded. The tear resistance is calculated from the maximum load recorded and the average thickness of the specimen. The tear resistance is reported in newtons per meter. 

Figure 14-7. Block specimen—tear resistance test. (Reprinted with permission of ASTM.)...

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.

For both the tongue and Elmendorf test methods, it is important to observe the behavior of the specimen as the tear is propagated. In cases where the yams in the test direction are much stronger than the perpendicular yams, it is sometimes difficult or impossible to propagate the tear in the desired direction. In this case, a crosswise tear results. Tear resistance is primarily a function of fabric constmction. Loose, open weaves such as cheesecloth tend to resist tear, whereas tight weaves tend to tear easily. In the open weave, the concentrated force field at the point of tear is dissipated by the compliance of the fabric stmcture to accommodate the stress field, thereby distributing the force over a greater number of yams. 

Testing. Various test methods are provided by ASTM (16). These iaclude pigment tests of importance such as chemical analysis, presence of oversize particles, oil absorption, particle size distribution, degree of dispersion, presence of soluble components, etc. Numerous tests are also given by ASTM for the properties of filled and unfilled polymers. These iaclude, for example, such properties as impact resistance, stiffness, viscosity, tear resistance, hardness, color, and electrical resistivity. 

There are other types of impact tests for shock loading where energy is required to cause complete failure is reported. Each has their specific behaviors that can be related to specific product performance requirements. Tests include ball burst, ball or falling dart using different weights and heights, bag drop, bullet-type instantaneous impact, Charpy, dart drop, Mullen burst, tear resistance, and tub (2). 

In all of the rheometer testing of the uncured compounds, the commercial silica AZ showed the highest values with the B1 and B3 samples having the highest values among the B-series silica samples. The Mooney viscosity at 100°C increases as the number of particles in the aggregates increases. The same compounds were cured and tested, measuring tensile properties, tear resistance. 

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. 

All application verification and soil samples must be individually labeled with unique sample identification (ID) and other identifying information such as study ID, test substance name, sample depth, replicate, subplot and date of collection, as appropriate. Proper study documentation requires that sample lists and labels be created prior to work commencing in the field. Water- and tear-resistant labels should be used since standard paper labels may become water-soaked and easily torn during sample handling. Sample lists should have the same information on them as the labels and are a convenient place to record plot randomization, initials of the individual who collected the sample, and date of collection. As such, the sample list is important in establishing chain of custody from the point of sample collection until its arrival at the laboratory. 

The trapezoid test method (ASTM Dll 17) is recommended for determining the tear resistance of nonwoven fabrics. An outline of a trapezoid is marked on a 7.5 x 15 — cm specimen, and the nonparallel sides are clamped in the jaws of the tensile-testing machine. The load is applied to the specimen in such a way that the tear propagates across the specimen width. The value of the breaking load is obtained from the load—elongation curve and is determined primarily by the bonding or interlocking of the fibers of the composite structure. 

Following are the tests described in this Spec wet tensile strength, adhesion at low temp, moisture-vapor transmission rate, water-penetration rate corrosion, accelerated aging, dry tensile strength and tearing resistance... 

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. 

The two most commonly specified tests are the Die C test and the "trouser tear" (D470) test. Both of these tests measure resistance to tear propagation. Other test shapes include the crescent tear with or without end tabs. This sample shape is often nicked. The "Delft" (IS0816) sample with its internal nick is often used from samples taken from finished products. The exact size of the nick does not appear to be critical to the result. 

In a series of test runs, 15 rolls of wrap are made under carefully controlled conditions and the tear resistance of each roll is measured. The results are used as the basis of a quality assurance specification (see Problem 2.19). If X for a subsequently produced roll fails more than two standard deviations away from the test period average, the process is declared out of specification and production is suspended for routine maintenance. 

ASTM D 624-86 Standard Test Method for Rubber Property — Tear Resistance, 5 pp (DOD Adopted) (FSC 9320) (MR) (Comm D-11)... 

Consideration of what is done to the core when conducting the two tests indicates that they are somewhat similar. True, the pin used for the nail pull resistance test has a larger diameter and must tear through the paper before it crushes the core, but the basic action is to crush the core by pushing a pin into it. 

Tear resistance of irradiated sample, subjected to the notch-tear test (ASTM D 1004) was found to be unchanged after doses from 0 to 64 Mrad [430]. 

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