Tabletting technology Part II

Friends,

In continuation to my earlier inputs about tabletting technology and techniques today let us see about.

Mechanisms of granule formation in wet granulation

The four key mechanisms of granule formation as originally outlined include:

1. Wetting and nucleation

This is the first and an important phase in granule formation. It involves the initial wetting of powder bed and existing granules by the granulating fluid to form nuclei. This step is largely influenced by spray rate or fluid distribution as well as feed formulation properties, in comparison with mechanical mixing. It is worth noting that the nucleation process, that is, the initial coalescence of primary particles in the immediate vicinity of the larger wetting drop is strongly linked with the wetting stage.

2. Coalescence or ball growth

In the coalescence or ball growth stage, partially wetted primary particles and larger nuclei come together to form granules composed of several particles. The more general term of coalescence refers to the successful collision of two granules to form a new, larger granule.

3. Consolidation

As granules increase in size, they are consolidated by compaction forces due to bed agitation. The extent of the consolidation depends on the agitation in the granulation equipment and the resistance of the granules to deformation. This phase in granule formation controls internal granule porosity, and therefore final properties of the granules e.g., granule strength, hardness, or dissolution.

4. Attrition or breakage

At this stage, formed granules break into fragments which bind to other granules forming a layer of material over the surviving granule.

The above mechanisms can occur simultaneously in all processes of wet 

granulation. However, certain mechanisms may dominate in a particular manufacturing process depending on the type of equipment used.

Steps in wet granulation method of tablet production

Let us get to know in detail about the following four important steps Of wet granulation in the next article till then.....

Step 1: Weighing and mixing of formulation ingredients (excluding the lubricant).

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Step 2: Preparing the damp mass.....

Step 3: Wet screening/ Screening the dampened powder into pellets or granules.........

Step 4: Drying of moist granules.....

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Step 5: Sizing the granulation by dry screening......

In the next article we will discuss in detail about the above 5 steps

Till then bidding a good bye

Cheers

Santhanam srikanth

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