Pharmaceutical Manufacturing Handbook: Production and

1082 TABLET PRODUCTION SYSTEMS
[78, 84, 83] . Most recently, partial melting of drugs could be analyzed for materials
whose melting temperature is as high as 94 ° C [87] , and the reversible transgression
of a glass transition temperature of 80 ° C was determined [162] .
All results indicated that temperature increase depends on the material. Further
temperature increase during tableting can contribute to slight changes in material
structure [85] .
6.4.9
ANALYSIS OF FINAL TABLET FORMATION
This characterization of the process of tablet formation has to be completed by
analyzing the changes induced by tableting.
Most important is the elastic recovery of the tablets which starts during decompression
and is fi nished dependent on the material after several days. Elastic recovery
can be defi ned as [163] .
Ht−H ER ( % ) = 100 ×
H
where H min is the minimum height of the tablet under load and H t the height of the
tablet at different times t after tableting.
Elastic recovery gives information on the remaining elasticity of the materials
which is only slowly released. Further it can indicate structural changes inside the
materials and tablets. Structural changes induced by tableting have to be analyzed
by physicochemical techniques, such as spectroscopic and thermoanalytical methods,
X - ray diffraction, scanning electron microscopy, and transmission electron microscopy
[35, 36, 85, 164 – 166] . The analyzed changes will help to better understand the
process of tablet formation and identify the reasons for compactibility of materials.
However, these changes are not the subject of this chapter.
6.4.10 COMPLETE DESCRIPTION OF PROCESS
OF TABLET FORMATION
On the whole, the process of tablet formation can fully be described by combining
the analysis of the tableting process with the fi nal formation of the tablets. The
methods which gives most detailed information of the whole process and simultaneously
is a fast method is the 3D modeling technique in combination loith calculating
the elastic recovery of the tablets. In addition, by combining both these methods
and calculating general plasticity P from time plasticity d , pressure plasticity e , twisting
angle ω , and elastic recovery ER, a more general tool for analysis of the process
of tablet formation is available [3, 4] .
Finally the crushing force of the tablets after relaxation gives information on
the formed bonds inside the material and the compactibility. Compactibility has
been described by Leuenberger [167] . For the future it can be expected that a
prediction of compactibility as a result of the process of tablet formation is
possible.
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