Abrasiveness test methods

The link between laboratory abrasion methods and road tests is now well established so that further research can concentrate on further elucidation of the basic underlying processes. This concerns particularly the interaction between filler systems and polymers, which is continuously expanding through both new polymers and new fillers. But now the link does not extend from a basic experiment to tire road testing. It can be limited to a laboratory abrasion testing method and suitable basic experiments. 

It follows that there cannot be a universal standard abrasion test method for plastics and the test method and test conditions have to be chosen to suit the end application. Also, great care has to be taken if the test is intended to provide a significant degree of acceleration. 

For many years, the only abrasion test method standardized internationally was the apparatus commonly known as the DIN abrader... 

To guarantee an objective comparison of quality between different products, it would be necessary that all test methods stress each material in the same way and, therefore, produce analog results. Figure 53 shows that this is not the case. If the abrasion value obtained for rock salt with each test method is arbitrarily defined as unity, all other results obtained for each material would have to be at the same distance above or below line 1. It can be gleaned from Figure 53 that the various test methods do stress the materials differently. For example, material B yields an abrasion value equal to 0.41 times that of rock salt if drum method 2 is applied, while with method 5 a value is determined that is more than 1.7 times higher than that obtained for rock salt. Similar, lyit less pronounced, variations are found for all other abrasion test methods. 

The main objective of the abrasion test method was to determine a link between the electrical resistance and the abrasion level, which also affects the breaking load performances. A test bench for abrasion has been developed, as shown in Fig. 23.7 based on the ASTM 4157-10 standard Test Method for Abrasion Resistance of Textile Fabrics (Oscillatory Cylinder) . This standard has been modified to measure more specifically the electrical resistance during the abrasion cycles. 

In addition to chemical analysis a number of physical and mechanical properties are employed to determine cemented carbide quaUty. Standard test methods employed by the iadustry for abrasive wear resistance, apparent grain size, apparent porosity, coercive force, compressive strength, density, fracture toughness, hardness, linear thermal expansion, magnetic permeabiUty, microstmcture, Poisson s ratio, transverse mpture strength, and Young s modulus are set forth by ASTM/ANSI and the ISO. 

There is usually more than one test method to determine a performance because each test has its own behavior and meaning. As an example there are different tests used to determine the abrasion resistance of materials. There is the popular Taber abrasion test. It determines the weight loss of a plastic or other material after it is subjected to abrasion for a prescribed number of the abrader disk rotations (usually 1000). The abrader consists of an idling abrasive speed controlled rotating wheel with the load applied to the wheel. The abrasive action on the circular specimen is subjected to a rotary motion. 

In this test for transparent plastics, the loss of optical effects is measured when a specimen is exposed to the action of a special abrading wheel. In one type of test the amount of material lost by a specimen is determined when the specimen is exposed to falling abrasive particles or to the action of an abrasive belt. In another test, the loss of gloss due to the dropping of loose abrasive on the specimen is measured. The results produced by the different tests may be of value for research and development work when it is desired to improve a material with respect to one of the test methods. The variables that enter into tests of this type are... 

The wear resistance of rubber compounds is of great practical importance for tires, but the mechanisms involved in tire wear are multiple and may vary depending on the vehicle, the driving conditions, and other extraneous variables. Many attempts have been made to develop laboratory test methods to simulate tire wear under various conditions. Whilst none can fully replicate road wear, various laboratory abrasion tests can be used to provide an indicator of wear resistance of tires under certain conditions. 

In friability tests the material s susceptibility to attrition is evaluated. But it is not as simple as it may seem at first to select the suitable test procedure. In this context Pell (1990) gave a simple thought experiment to illustrate the difficulties If we took a batch of rubber stoppers and a batch of diamonds, and rubbed them on abrasive paper, we would conclude that the diamonds were more attrition resistant. If we instead struck the particles with a hammer we would conclude that the rubber were more attrition resistant. So, different test methods can rank materials differently with respect to their attritability. This effect was for example observed by Knight and Bridgwater (1985). They subjected spray-dried powders to a compression test, a shear test and a test in a spiral classifier. They found that each test gave a different ranking of the materials. Obviously, there is no... 

The only method currently standardised internationally for plastics is the abrasive wheels method, more commonly known as the Taber abraser, which is specified in ISO 9352 [42]. A pair of abrasive wheels are in contact with a driven flat disk test piece as in Figure 6.1(d). The force on the wheels and the nature of the abradant is readily varied and the test can be carried out in the presence of liquids. 

ISO 3934 2002 Rubber, vulcanized and thermoplastic - Preformed gaskets used in buildings - Classification, specifications and test methods ISO 4649 2002 Rubber, vulcanized or thermoplastic - Determination of abrasion resistance using a rotating cylindrical drum device ISO 4664-1 2005 Rubber, vulcanized or thermoplastic - Determination of dynamic properties - Part 1 General guidance... 

ASTM D1044, Test Method for Resistance of Transparent Plastics to Surf, ace Abrasion, Vol. 8.01, ASTM, Philadelphia, Pa., 1993. 

Standard rubbers are given in several of the test method standards. Some are purely for normalizing the abrasive and have no particular service relevance. Others, such as those based on a tyre tread compound or a shoe sole type material, have the advantage of a practical significance as well as a normalizing role. There is no reason at all why, for a particular investigation, an in-house standard representative of the type of material being evaluated should not be used. 

Chapter 8 constitutes a separate specification of abrasiveness test results for a number of materials, to give the reader an idea of the range of problems that can be tackled in a laboratory using the methods described in the book. These results, not necessarily to be interpreted as hardness, could not be brought within the scope of Chapter 4 on methods. 

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