Tablet mechanical strength

Pellets or tablets (1.5-10 mm in diameter), rings (6-20 mm) and multichanneled pellets (20-40 mm in diameter and 10-20 mm high) are used when a high mechanical strength is required. They are produced by compressing a mixture of the support powder and several binders (kaolin day, stearic acid) and lubricants (graphite) in a press. 

Some of the more common antifrictional agents are listed in Table 10. Many of these are hydrophobic and may consequently affect the release of medicament. Therefore, lubricant concentration and mixing time should be kept to the absolute minimum. Lubricants may also reduce significantly the mechanical strength of the tablet (see Fig. 12) [29,81]. Stearic acid and its magnesium and calcium salts are widely used, but the... 

In order to produce an adequate tablet formulation, certain requirements, such as sufficient mechanical strength and desired drug release profile, must be met. At times this may be a difficult task for the formulator to achieve, due to poor flow and compactibility characteristics of the powdered drug. This is of particular importance when one only has a small amount of active material to work with and cannot afford to make use of trial-and-error methods. The study of the physics of tablet compaction through the use of instrumented tableting machines (ITMs) enables the formulator to systematically evaluate his formula and make any necessary changes. 

To produce tablets that are uniform in weight and content and exhibit a certain degree of mechanical strength, one needs a mixture of powders with (a) good flow properties (b) a minimum tendency for segregation, and (c) the ability to be compressed. To achieve these ends, granulation with other excipients is often necessary. 

Evdokimov IA, Serov AN. Effect of compaction parameters on mechanical strength of lactose tablets. Izvestiya Vysshikh Uchebnykh Zavedenii Pishchev Tekhnol 2000 (5-6) 60—61. 

During compaction, primary particles are packed, re-arranged and can undergo deformation and possibly breakage. These events can occur sequentially or in parallel. The mechanical strength of a tablet may strongly depend on the mechanical properties of the primary particles and the particle-particle interactions within it. It is essential that the particles deform plastically or rupture since the stored elastic strains can weaken the tablet on release (Roberts and Rowe, 1987). 

The carrier can be in the form of a powder used for slurry reactions or a particulate such as a sphere, cylinder, or tablet (typically a few mm in diameter) used in fixed bed reactors. The size and shape depend very much on what is anticipated to be the rate-limiting step. For example, for a reaction limited by pore diffusion it is customary to use a smaller particle in the shape of a star, trilobe, or wagon wheel to decrease the diffusion path while increasing the external geometric surface area. Mechanical strength and solubility... 

Tablets are often coated to protect the drug from the external environment, to mask bitter tastes, add mechanical strength, or to enhance ease of swallowing. A coating can also be used for aesthetic or commercial purposes, improving product appearance and identity.

Binder A material with a high bonding ability can be used as a binder to increase the mechanical strength of the tablet. A binder is usually a ductile material prone to undergo plastic (irreversible) deformation. Typically, binders are polymeric materials, often with disordered solid-state structures. Of special importance is the deformability of the peripheral parts (asperities and protrusions) of the binder particles [5],... 

Adolfsson, A., Gustafsson, C., and Nystrom, C. (1999), Use of tablet tensile strength adjusted to surface area and mean interparticulate distance to evaluate dominating bonding mechanism, Drug Dev. Ind. Pharm., 25,753-764. 

The physical and mechanical properties of tablets, such as density and mechanical strength, are significantly affected by the process. Since tablet compression relies on the ability of particulates to be compacted, the need to control the critical properties of the materials with respect to readiness or ability to compact is an important issue to the formulator. 

Single pellet crush testing has played an integral part in industry for many years. Pharmaceutical companies, for example, consider the mechanical strength of medicinal tablets to be an important property. (1)... 

The mechanical strength of the tablets and lubricant sensitivity were found fo be dependenf upon fhe marmifol confenf and fhe processing... 

Stanley, P. Rowe, R.C. Newton, J.M. Theoretical considerations of the influence of polymer film coatings on the mechanical strength of tablets. J. Pharm. Pharmacol. 

The mechanical strength of a tablet plays an important role in the development and control procedures. Crushing strength is the most widely used test of mechanical strength. It is defined as the compression force that, when applied diametrically to a tablet, just fractures it. Tablet hardness depends on the weight of material and the space between the upper and lower punches at the moment of compression. Inconsistent hardness values are likely to result from variation in these parameters. The fundamentals of powder compression are given in a report by Leuenberger and Rohera. ... 

The strength is usually assessed as the force required to fracture a tablet in a deflned direction e.g., its diameter. This has traditionally been referred to as the hardness of the tablet, which is incorrect terminology in this context. In material science, hardness is a surface property related to resistance to indentation. Terms such as physical strength or mechanical strength are more appropriate. 

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