Friability test methods

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... 

While friability is a property that may be attributed to crystals and many chemical compounds, tests devised thus far pertain only to coals however, the same tests may be used on other materials having the same relative degree of friability. Several methods have been used to determine friability, and are based on two procedures (a) Measurement of work done in reducing coal of a given size to a smaller size, or (b) subjecting the coal to a definite amount of work and measuring the reduction in coal size due to such work. 

ASTM C 421-88 Standard Test Method for Tumbling Friability of Preformed Block-Type Thermal Insulation, 2 pp (Comm C-lQ... 

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. 

At present, there is no official guidance defining what percentage of asbestos in soil would constitute a health risk and how this figure might depend upon the asbestos type, product, material, friability or moisture content etc. However, the UK HSE is also reviewing the test methods for asbestos materials in contaminated land and may provide additional guidance as part of this future documentation. 

The friability of a rigid foam is not an easy property to determine, and it is seldom used as a quality control measurement. However, for certain materials such as phenol-formaldehyde foam it can be a useful tool in formulation work to ensure that the product is suitable for the application area. In certain instances the test method is best adapted to the foam being tested, for example the time duration of the test may be shortened if the material is being abraded too harshly. 

The Roche Friabilator is one of the most common methods used to test for resistance to abrasion [147], In this case, a minimum of 6 g (often 20 tablets) of dedusted and weighed tablets are placed in a 12 in. high drum, which is then rotated for 100 revolutions. A... 

In the United States, a number of physical tests are performed on silicon carbide using standard AGA-approved methods, including particle size (sieve) analysis, bulk density, capillarity (wettability), friability, and sedimentation. Specifications for particle size depend on the use for example, coated abrasive requirements (134) are different from the requirements for general industrial abrasives. In Europe and Japan, requirements are again set by ISO and JSA, respectively. Standards for industrial grain are approximately the same as in the United States, but sizing standards are different for both coated... 

Several methods of estimating relative strength or friability or grindability utilize a porcelain jar mill in which each coal may be ground for, say, revolutions, and the amount of new surface is estimated from screen analyses of the feed and of the ground product. Coals are then rated in grindability by comparing the amount of new surface found in the test with that obtained for a standard coal. 

The method employs a cylindrical porcelain jar mill fitted with three lifters that assist in tumbling the coal. A sample (usually 1000 g) of sized coal is tumbled in the mill for a specified time at a specified number of revolutions per minute. The coal is then removed and screened and the friability is reported as the percentage reduction in the average particle size during the test. For example, if the average particle size of the tumbled coal was 75% that of the original sample, the friability would be 25%. As with several other tests, the test parameters can be adjusted to suit the purpose of the investigation, but the precise parameters must be reported with the data. 

Breakdown of particles on impact can be tested either on single particles or on a quantity of the bulk solid, and the result is a measure of particle friability. The available tests have been well reviewed in the recent attrition report by the Board54 and only a mention of the main methods is given here. 

A drop shatter test has also been described for determining the friability of coal (ASTM, 2011e) which is similar to the standard method used as a shatter test for coke (ASTM, 2011m). In this method, a 50 lb sample of coal (2-3 in. [4.5-7.6 cm]) is dropped twice from a drop-bottom box onto a steel plate 6 ft below the box. The materials shattered by the two drops are then screened over round-hole screens with 3.0 in. (76.2 mm), 2.0 in. (50.8 mm), 1.5 in. (38.1 mm), 1.0 in. (25.4 nun), 0.75 in. (19.05 mm), and 0.5 in. (12.7 mm) openings and the average particle size is determined. 

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