Pellets friability

Other Tests. The so-called tumbler tests are usually used for testing material like coke, coal, iron ore pellets or tablets. They can be divided into drum tests and ball mill type tests. The latter type is used to derive both the Hardgrove Index and the Bond s Work Index, which are often used to classify the material friability as described in Sec. 3. They are generally more suited to coarse material. The Hardgrove Grindability test requires an initial size range form 595 to 1190 microns. 

The physical properties of pellets have been widely used to determine an acceptable yield of pellets. These include shape indices, size and size distribution, densities, pore volume and distribution, flow properties, and friability. Of course, drug release from the pellets is a critical parameter to be monitored in order to ensure potency and uniformity of drug distribution. 

Although surface fractal dimension was found inadequate as a roughness factor to indicate the friability of tablets, it has been reported to be useful in other situations such as describing the roughness of pellets made in a rotary processor by wet granulation. ... 

It is usually relatively simple to find the optimum conditions for a single response that does not depend on more than four factors once the coefficients of the model equations have been estimated, provided, of course, that the model is correct. Real problems are usually more complex. In the case of pellet formation, it is not only the yield of pellets that is important but also their shape (how near to spherical), friability, smoothness, and ease of production. The optimum is a combination of all these. 

Vertommen, J. Kinget, R. Influence of Five Selected Processing and Formulation Variables on the Particle Size Distribution, and Friability of Pellets Produced in a Rotary Processor. Drug Dev. Ind. Pharm. 1997, 23 (1), 39 6. 

With all four of the granulating methods in Table 172, copovidone usually gives hard tablets or pellets of low friability. Since it is soluble, the drug normally dissolves rapidly, whether in gastric or intestinal juice [132,644] and frequently relatively independently of the compression force, as can be seen in Fig. 109. Like in the case of povidone K 30 it can be expected that copovidone enhances the dissolution of many drugs as shown with griseofulvin [528]. 

Breakdown by confined compression can be tested in a compression cell similar to that in compaction tests, except that the normal forces used are greater here. A British Standard method59 packs a sample of specified quantity and size grade into a steel cylinder, 150 mm nominal diameter a plunger is inserted into the open end of the cylinder and the whole compressed in a compression testing machine. The load is slowly increased up to 400 kN and the product is then sized. A similar test has been used in assessing friability of pellets and coal. 

We continue with the example of extrusion-spheronization. A formulation has been developed containing the drug substance, a plastic diluent and a binder. We want an optimized process and the response that most interests us is the percentage mass yield of pellets having a particle size between 900 pm and 1100 pm. We are not concerned for the present with other characteristics such as the shape, surface quality or friability of the pellets (potentially interesting as these may be). Factors that may affect the yield (and quality) of the resulting pellets are ... 

Vertommen, 1. and Kinget, R. (1997). The influence of five selected processing and formulation variables on the particle size, particle size distribution, and friability of pellets produced on a rotary processor. Drug Dev Ind Pharm, 23,39-46. 

Several processing factors can affect the binder performance during extrusion and spheronization processes including hydration level, extruder speed, shape, hole size, spheronizer speed, and residence time. While the use of microcrystalline cellulose alone or in combination with lactose is widely adopted, the addition of binders can aid in the formation of a plastic mass than can be easily extruded and spheronized. Increasing the PVP or starch/gelatin level increases the pellet size and decreases their friability (59). 

ASTM E279-97 (2005) Standard Test Method for Determination of Abrasion Resistance of Iron Ore Pellets and Sinter by the Tumbler Test ASTM C421-05 Standard Test Method for Tumbling Friability of Preformed Block-Type Thermal Insulation... 

Particles in gas streams vary so widely in terms of size, density, shape, stickiness, friability, erosiveness, surface charge, and other characteristics that no one method of separation, and not one type of separator, is suitable for processing the entire spectrum of materials. Thus the separation equipment must be capable of processing a very wide variety of material—from pellets to sub-micron powders, from hard minerals, like garnet sand, to soft food products like rolled oats. Some of these materials are very free-flowing, others tend to compact or cake. The products and types of particles shown in Figs. 1.2.1 and 1.2.2 are rather typical of the myriad of substances that can, and have been, successfully conveyed and subsequently classified or separated in modern separation equipment, including cyclones, bag filters and electrofilters. 

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