Particle Bonding Mechanism in granulation, What do you mean?

Particle Bonding Mechanism:  The particles which form bond between themselves help to build up granules. So particle bond is essential to form effective granules which prevent breaking of granules during transportation. Particles are primarily form bond between themselves then number of particle form granules. There are several ways to form bond between the particles. Types […]

Particle Bonding Mechanism: 

The particles which form bond between themselves help to build up granules. So particle bond is essential to form effective granules which prevent breaking of granules during transportation. Particles are primarily form bond between themselves then number of particle form granules. There are several ways to form bond between the particles.

Particle Bonding Mechanism
Types of Particle Bonding Mechanism

In the context of granulation, particle bonding mechanism refers to the processes by which individual particles adhere to each other to form larger agglomerates or granules. Granulation is a process widely used in various industries such as pharmaceuticals, food processing, and fertilizer production to create granular materials with improved properties such as flowability, compressibility, and dissolution characteristics.

  • Several mechanisms contribute to particle bonding in granulation
  • Mechanical interlocking
  • Van der Waals forces
  • Capillary forces
  • Chemical bonding
  • Sintering
  • Electrostatic attraction


Mechanical interlocking:

 This process involves the physical entanglement of particles due to their irregular shape or surface properties. When particles come into contact, the irregularities mesh together and bonds form between adjacent particles.

Mechanical entanglement is an interesting phenomenon in which the irregular shape or surface properties of particles lead to physical entanglement. Imagine a scenario where you have a pile of Lego blocks. Each brick has a unique shape and surface texture, including projections, ridges, and edges. If you stack these bricks on top of each other, you will notice that they are not just stacked on top of each other. Rather, they are intertwined. Cracks in one brick lie over cracks in the other brick, forming a strong bond between the two bricks. This is a perfect example of a mechanical lock in action.

Also consider the structure of the Velcro. Velcro fasteners consist of two strips. One has a small ring (called the “male” side) and the other has a small ring (called the “female” side). When these strips are tied together, the loops on one side form a strong connection with the loops on the other side. This connection is purely mechanical and uses interlocking hooks and rings to hold the strips together.

Another example of mechanical interlocking in construction is the use of interlocking bricks or blocks. These bricks have a unique shape that allows them to fit together like puzzle pieces, creating a stable structure without the need for mortar or glue. The irregularities and projections on the surface of each brick mesh with adjacent bricks, preventing them from easily moving or separating.

Simply put, mechanical locks play an important role in many aspects of our daily lives, from simple activities like playing with LEGO bricks to more complex applications in design and manufacturing. This highlights the importance of understanding how the physical properties of materials can affect their behavior and interactions.


Van der Waals forces:

Van der Waals forces are weak attractions that exist due to temporary dipoles between molecules or particles. These forces can attract nearby particles to each other and contribute to particle bonding.

Van der Waals forces, named after Dutch scientist Johannes Diederick van der Waals, describe the weak but significant attractive forces that occur between molecules or particles. These forces arise from temporary fluctuations in the distribution of electrons within the molecule, resulting in temporary dipoles. Although van der Waals forces are weaker than ionic or covalent bonds, they play an important role in various phenomena such as the cohesion of liquids, the formation of molecular aggregates, and the adhesion of materials.

Let’s take the example of geckos, fascinating creatures known for their incredible ability to climb vertical surfaces and even walk upside down on rooftops. This extraordinary result is made possible by the complex interplay of van der Waals forces. Tiny hair-like structures called setae cover the gecko’s legs, and each bristle is divided into hundreds of smaller structures called spades. These spatulas create a large surface area, maximizing the potential for van der Waals interaction with the surface. When a gecko presses its paws against a surface, the weak van der Waals forces between the spatula and the surface combine to create an adhesive force that allows the gecko to cling tightly.

In everyday life, van der Waals forces also play a role in phenomena such as the condensation of a gas into a liquid, where molecules are held together by this weak attraction. For example, water vapor condenses in a glass of cold water, forming droplets due to van der Waals forces between water molecules. Similarly, coordination between molecules in liquid water is facilitated by surface tension and van der Waals forces, which contribute to the droplet forming ability.

Additionally, van der Waals forces are largely involved in interactions between molecules in biological systems. For example, the structure of DNA, the genetic blueprint of living organisms, is based, among other things, on the stacking of base pairs governed by van der Waals forces. Moreover, the folding of proteins into functional three-dimensional conformations is influenced by van der Waals interactions between amino acid side chains.

In summary, van der Waals forces may individually be weak, but their cumulative effects can be profound, shaping the behavior of molecules in a variety of situations, from the motion of a gecko to the structure and function of biological macromolecules.


Capillary forces:

Capillary forces arise due to the presence of liquid bridges between particles. When a liquid binder is added to the granulation process, it fills the voids between particles and creates liquid bridges. These bridges can solidify through processes such as evaporation or cooling, forming bonds between particles.

Capillary forces result from the formation of liquid bridges between particles, a phenomenon commonly observed in a variety of natural and industrial situations. For example, consider the granular process of pharmaceutical manufacturing. When a liquid binder, such as a solution of water and a polymer, is introduced into the dry powder mixture, it enters the spaces between the particles, effectively filling the voids and forming liquid crosslinks.

This process is similar to the way water flows through a sponge, sticking to the surface of the material and creating bonds between the fibers. In the granulation process, these liquid cross-links play an important role in shaping the properties of the final product. When the liquid binder penetrates the particle composite, it wets the surface, reduces interfacial tension, and promotes particle reorganization. This allows the powder mixture to dissolve into a cohesive aggregate.

Subsequent solidification of these liquid cross-links further solidifies the granular structure. This solidification can occur through a variety of processes depending on the type of liquid binder and environmental conditions. For example, if water acts as a binder, evaporation from heat or air flow will gradually remove the moisture, causing the liquid bridge to solidify and bond between adjacent particles. Similarly, in cooling processes such as freeze granulation, a drop in temperature causes the liquid binder to phase change from a liquid state to a solid state, causing the particles to stick together.

In essence, capillary forces and the addition of liquid binders ensure the coagulation of the granular material, allowing it to form a cohesive structure with appropriate properties. This phenomenon applies not only to the pharmaceutical industry but also to many other fields, from food processing and construction to ceramics and metallurgy. Manipulating particle interactions through liquid bridges is critical to achieving desired material properties and product performance.


Chemical bonding:

In some cases, chemical reactions may occur between particles or between particles and the binder. These reactions can form chemical bonds that provide strong adhesion between particles.

Chemical reactions can occur under a variety of conditions, particularly between particles or between particles and binders. These reactions are very important because they favor the formation of chemical bonds, creating strong adhesion between particles.

Consider the concrete curing process as a real-life example. When water is added to cement, a chemical reaction occurs between the water and cement particles to form hydrated calcium silicate gel (C-S-H). This gel acts as a binder and forms strong chemical bonds with the aggregate particles present in the mixture. As a result, concrete hardens and gains strength over time due to the chemical bonds formed between the components. This demonstrates how chemical reactions contribute to the cohesion and stability of materials, improving their structural integrity and performance in real-world applications.



An important process in materials science and manufacturing, sintering involves partial melting that occurs at the surface of particles when they are exposed to high temperatures. This heat treatment triggers a transformation step in which adjacent particles are exposed to heat and undergo surface liquefaction upon exposure, resulting in the formation of molecular bonds that bind them together.

To illustrate this concept, let us consider ceramic tile production. In the sintering stage of ceramic production, fine particles obtained from raw materials such as clay, silica and other additives are compressed into the desired shape. When these compressed particles are fired in a high-temperature furnace, typically in the range of 1,000 to 1,500°C, sintering is initiated by heat. At these high temperatures, the particle surfaces begin to soften and slightly melt, allowing intermolecular compounds to fuse and form. As a result, the separated particles gradually fuse to form a hard and dense ceramic structure. This process not only increases the strength and durability of ceramic tiles, but also helps develop desirable properties such as smoothness and uniformity of surface texture. Sintering therefore constitutes a fundamental technology for achieving the structural integrity and functional properties required for a wide range of industrial applications, from ceramics to metallurgy and beyond.


Electrostatic attraction:

Electrostatic forces can play an important role in particle bonding, especially in processes where particles become charged. Conversely, charged particles can attract one another and form bonds. Understanding and controlling these bonding processes is important to optimize the granulation process and achieve desired granulation characteristics such as size, shape, strength, and dissolution rate.

Electrostatic forces have a significant impact on particle bonding, especially in charged particle situations. When particles carry opposite charges, they exert a mutual attraction force, promoting bonding between particles. This phenomenon has wide application in various practical situations, such as granulation processes in pharmaceutical manufacturing.

Take tablet production as an example, where granulation is a critical step. In this process, powdered ingredients are combined and mixed with a binder to form granules. These particles must have specific characteristics such as size, shape, strength and dissolution rate to ensure the quality and effectiveness of the final product. During the granulation process, electrostatic forces are exerted when charged particles interact with each other. Conversely, charged particles are attracted to each other, promoting bonding and cohesion between particles.

Granulation Method Advancements

Understanding the complexity of electrostatic interactions and their impact on particle bonding is important for optimizing granulation processes. By controlling these bonding mechanisms, manufacturers can tailor particle properties to their desired specifications. This level of control allows the production of tablets with uniform active ingredient content, consistent dissolution profile, and improved bioavailability.

The same principles also apply to industries other than pharmaceuticals, such as ceramics or pesticide production. By using electrostatic forces to bind particles together, manufacturers can improve the quality, functionality, and performance of their products, ultimately meeting the diverse needs of consumers and industry.

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