12 Questions
What is the primary reason for increasing the size of particles in a mixture?
To reduce the dust hazard and improve flow properties
What method is used to create larger particles by fusing them together?
Sintering
What type of force is responsible for the attraction between molecules?
Van der Waals forces
What is the effect of increasing the partial pressure of a vapor on the surrounding atmosphere?
It increases the thickness and strength of the adsorbed layers
What is the result of the overlapping of adsorbed layers on particles in contact?
A bonding force between the particles
What is the purpose of creating a defined metered quantity of active ingredient?
To provide a precise amount of active ingredient
What are the 4 types of liquid states mentioned by Newitt and Conway-Jones (1958)?
Pendular, funicular, capillary, droplet
In which type of liquid state do the liquid bridges have fewer curved surfaces and boundaries for surface tension to act on?
Droplet
What results from the curved liquid surfaces in a liquid bridge, as per Newitt and Conway-Jones (1958)?
Capillary pressure
What is the interstitial space between particles known as, according to Newitt and Conway-Jones (1958)?
Porosity
Which forces do not require contact between particles and can act over long distances in granulation processes?
Electrostatic forces
What kind of bridges can be formed between particles if the material is soluble in the liquid used to create granules?
Magnetic bridges
Study Notes
- Size enlargement is the process of combining smaller particles to form larger masses while still retaining the identity of the original particles.
- There are several reasons for increasing particle size, including reducing dust hazards, preventing caking and lump formation, improving flow properties, increasing bulk density for storage, and creating a uniform mixture of ingredients.
- Methods for enlarging particle sizes include granulation, compaction (e.g., tabletting), extrusion, sintering, spray drying, and prilling.
- Interparticle forces that play a role in size enlargement include van der Waals forces, forces due to adsorbed liquid layers, forces due to liquid bridges, electrostatic forces, and solid bridges.
- Van der Waals forces refer to the attractive forces between molecules and can be calculated using the Hamaker constant, radius of the sphere, and the gap between the sphere and plane.
- Forces due to adsorbed liquid layers result from the presence of a condensable vapor on the surface of particles, leading to bonding forces between particles.
- Forces due to liquid bridges are influenced by the type of liquid state (pendular, funicular, capillary, or droplet) and can affect the interparticle distance and strength of the structure.
- Electrostatic forces arise from friction and collisions between particles during processing and can be attractive or repulsive.
- Solid bridges within the granule can be formed by removing liquid from the original granule, resulting in crystalline bridges, liquid binder bridges, or solid binder bridges.
Learn about the process of increasing the size of particles by putting them together to form larger masses while still maintaining the original particles' identity. Understand the reasons for enlarging particle size such as reducing dust hazards, improving flow properties, and creating a uniform mixture of ingredients.
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