Friability test

The large number of experiments that are termed attrition tests can be divided into two major fields of application, namely tests of material friability and experiments to study attrition phenomena. They will be separately discussed in the following subsections. The various test devices will be discussed afterwards. 

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 

Friability tests can be used for various purposes. They are widely used in quality control. Here, samples of produced material are subjected to a more or less arbitrary but well defined stress. The attrition extent is assessed by comparison with a standard value and a decision is reached whether the material meets the standard. Moreover, friability tests are often used for comparison of different materials to select the most attrition-resistant one. This is a usual procedure in the case of catalyst development. For example, Contractor et al. (1989) tested anew developed fluidized bed VPO-catalyst in a submerged-jet attrition test (described below). Furthermore, the specific attrition rate of a material in a certain process can be roughly estimated by friability tests. In this case the stress must be similar to that occurring in the process and the obtained degradation extent must be compared with those of other materials from which the process attrition rate is known. 

Results that are obtained by different friability tests are usually not comparable. All these tests give only a relative attrition resistance and numerical results are only useful in connection with detailed information about the test considered. 

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Size stability refers to the abihty of coal to withstand breakage during handhng and shipping. It is determined by twice dropping a 23-kg (50-lb) sample of coal from a height of 1.8 m (6 ft) onto a steel plate. From the size distribution before and after the test, the size stabdity is reported as a percentage factor (see ASTM D 440). The friability test... 

Pneumatic Conveying Tests. In contrast to fluidized bed tests, no standard equipment exists that simulates the stress on particles in pneumatic conveying lines. There is no friability test quoted in the pertinent literature that is based on a specific pneumatic conveying system. 

Friability test 3 (alternate for EIDS bullet impact test)... 

Friability is of interest primarily because friable coals yield smaller proportions of the coarse sizes that may (depending on use) be more desirable, and there may also be an increased amount of surface in the friable coals. This surface allows more rapid oxidation hence, conditions are more favorable for spontaneous ignition, loss in coking quality in coking coals, and other changes that accompany oxidation. These economic aspects of the friability of coal have provided the incentive toward development of laboratory friability tests. 

A. typical, tabulation of a friability test is shown in Table 86. 

Table 86—Results of Friability Tests on a Certain Coal...

Numerous methods are required to characterize drug substances and drug products (Chapter 10). Specifications may include description identification assay (of composite sample) tests for organic synthetic process impurities, inorganic impurities, degradation products, residual solvents, and container extractables tests of various physicochemical properties, chiral purity, water content, content uniformity, and antioxidant and antimicrobial preservative content microbial tests dissolution/disintegration tests hardness/friability tests and tests for particle size and polymorphic form. Some of these tests may be precluded, or additional tests may be added as dictated by the chemistry of the pharmaceutical or the dosage form. 

Hardness and friability tests are two additional tests usually performed as in-process controls during manufacturing. They will be required for product release when the characteristics of hardness and friability have a critical impact on the quality of the product. Carbamazepine is also available as a chewable tablet and because the hardness is an important characteristic of the tablet, a hardness test is required for batch release. 

Stop the drum and collect two samples. Allow them to dry, either on an open tray or using any type of drier. Use one sample to determine the particle size distribution, and the other to run the friability test. 

Collect two samples, like in the drum agglomerator experiment and follow fhe same procedure, that is, use the first sample to determine the particle size distribution and the second one to run the friability test. 

From friability testing determine friability as the difference of weighed samples at the different conditions before and after the test. Express the friability in weight loss percentage. 

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