Direct compression test

Deformation Under Loa.d. The mechanical behavior of coal is strongly affected by the presence of cracks, as shown by the lack of proportionahty between stress and strain in compression tests or between strength and rank. However, tests in triaxial compression indicate that as the confirming pressure is increased different coals tend to exhibit similar values of compressive strength perpendicular to the directions of these confining pressures. Except for anthracites, different coals exhibit small amounts of recoverable and irrecoverable strain underload. 

Triaxial compression tests are another means of determining shearing strength of a soil. A complex device is used to apply pressure along the sides of a cylindrical specimen and axially down the axis of the cylindrical specimen. In general, triaxial tests are superior to direct shear tests since there is better control over intake and discharge of water from the specimen. 

Direct shear test of soils under consolidated drained conditions Consolidated-undrained triaxial compression test on cohesive soils One-dimensional consolidation properties of soils One-dimensional consolidation properties of soils using controlled-strain loading... 

Shallow convex tablets (jin) containing 300 mg HPMC K15M and 1% magnesium stearate were prepared by direct compression. Disintegration tests were performed in triplicate, using the BP 1988 method, in 600 ml of media at 37°C using discs. Tests were run for a maximum of 2 h. 

In this study, the influence of several formulation factors on the release kinetics of potassium chloride from directly compressed matrices is investigated. Formulations containing hydrophilic (methylcellulose, carbomer), plastic (polyvinyl chloride) and wax (glycerol palmitostearate) matrix materials at concentrations of 10%, 15% and 20%, and insoluble excipients, were prepared and tested using the USP XXI-NF XVI rotating paddle method. 

With the exception of the formulation obtained by direct compression in a rotary machine, the dissolution profiles were well fitted by the Weibull function. A high density in the centre of the tablets may explain the sigmoid dissolution profiles. A percentage of the drug remains imprisoned in the matrix after the dissolution test. It is possible to suppose that, in the densified central zone of the tablet, the diameters of the pores are smaller than the diameters of the drug particles covered by the inert polymers. 

Gohel MC, Jogani PD. Functionality testing of a multifunctional directly compressible adjuvant containing lactose, polyvinylpyrrolidone, and croscarmellose sodium. Pharm Technol 2002 64-82. 

In summary, when tested, the grades of calcium phosphate dibasic discussed above exhibited mechanical properties that were very appropriate for tablet compaction and thus for formulation processing by direct compression, dry granulation, or wet granulation. With this in mind, it is easy to understand the popularity of DCP in pharmaceutical tablet formulations. 

As can be seen from the results, the composite formed from monomer/-polymer 114a with Celion G30-500 8HS fabric exhibited excellent mechanical properties [28], To a first approximation it would appear that the inherent fracture toughness of the matrix resin has been carried over to the composite panels. The CAI (compressive strength after impact) and OHC (open hole compression) tests are a direct measurements of the toughness of the composite part, the value of 332 MPa for the CAI compares very favorably to the value of 300 MPa typical for the thermoplastic composites. The OHC values under hot-wet test conditions would seem to indicate that the composite has very good retention of its mechanical properties at both 177°C and 203 °C. 

The manufacturing process used to make the test product should be described briefly to provide information on the method of manufacture (e.g., wet granulation vs. direct compression). A list of excipients used, the amount used, and their intended functions should be provided. Excipients used in the test product should have been used previously in FDA-approved IR solid oral dosage forms. 

Plane strain compression tests (Fig. 12.2b) may be also used. One principal dimension remains constant thus a = vo2, where a2 ar d 03 are the principal stresses in the three directions x, y and z. This test has to be performed with care, due to different breadth dies, and friction coefficients, but it is nevertheless used to complete the yielding criteria curves (see below). 

As discussed above, testing to conform to pharmacopeia requirements may not be sufficient to assure excipient quality in the manufacture of low-dose formulations. Often, excipients make the bulk of the dosage form and if a dry blending and direct compression is utilized, the functional properties of excipients become even more critical compared to a granulation process. Typical functional properties to be tested for excipients include the following ... 

Reid and Schey studied the role of substrate composition and other factors in the formation and performance of films on various metal substrates, including copper, aluminium, titanium and mild steel, tested against themselves and against an alloy steel. They used a twist-compression test to assess performance, and concluded that substrate hardness and composition had the greatest influence on film formation and life. They believed that film formation and especially durability are improved by chemical reaction if a substrate, such as copper or iron, has a strong tendency to react to form a sulphide, provided that the reaction kinetics are favourable. However, they found no direct evidence of reaction or of sulphide formation. Their conclusions were based on the fact that the durability of the films was found to be in the sequence aluminium, titanium, iron, copper, which is the same as the order of the free energies of formation of their sulphides. 

Twenty lubricants for effervescent tablets were tested for lubrication efficiency in direct compression of a standard effervescent formulation. The lubricant concentration was high as compared to traditional tablet lubricants. By increasing the lubricant concentration... 

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