Lecture 2: Powders and Granules Flashcards
Powder
-physical form of solid material composed of particles
-dosage form for internal or external use
Powder dosage forms
-oral
-topical
-inhalation
physiochemical properties of powders
-particle size
-shape
-density
-solid-state properties
Particle size affects
-“processability” (flow, mixing, tableting)
-formulation performance (content uniformity, dissolution)
Particle size affects
-dissolution
-suspendability of suspensions
-uniformity of mixture in liquids or powders
-particles aerosol behavior for inhalation
-segregation may occur if powders have wide size distributions
Particle size measurements
-sieving (mass based size)
Particle size distribution
-D10: 10% of particles are smaller
-D50: 50% are smaller
-D90: 90% are smaller
-span= (D90-D10)/D50
Width of size distribution
span= (D90-D10)/D50
Mircoscopy
physical size?
Projected area diameter
-equivalent diameter corresponding to diameter of a circle with same projected area as the irregularly shaped particle
Laser diffraction
-volume based size
Particle density
-true density = mass/true volume
-bulk density = mass/bulk volume
-cohesive vs non cohesive
Powder flowability
-how easy powder moves to another location
-important for material conveying, transportation, and capsule and tablet die filling
flowability of smaller particles
poor
flowability of spherical particles
-better than needle and plate shaped particles
milled particles
-cohesive (sticky)
-poor flowability
Measurements of powder flowability
-angle of repose
-Carr index
Angle of repose
-tanx = 2h/D
-30 degrees = great flow
>60 degrees = poor
Carr index
=(tapped density- poured density)/ tapped density
-5-15%= great flow
->40%= poor
Cohesive vs noncohesive
-cohesive sticks to side of tubes and to self
-noncohesive settles at the bottom of the tube
Powder comminution
-particle size reduction
-improve dissolution, absorption, and mixing homogeneity
-effects of size reduction depend on design of equipment, energy, and sheat inputs of properties of the material
Powder comminution methods (mechanical milling)
-ball
-hammer
-jet
Ball mill
-materials + grinding medium in rotating mill
Hammer mill
idk
Jet mill
-generate fine particles down to 1 um
-used for inhalation powders
-compressed grinding air + powder
Powder mixing (blending)
-unit operation involving manipulation of heterogenous physical system with the goal of making it homogenous
Types of mixtures
-unmixed
-ideal
-random
-segregation
Major types of blending
-tumble blender (V-blender, tote blender, turbula blender)
-blade blender (high shear blender)
Granules
-dry aggregates of particles
-can be used as dosage form
-mostly for making tablets and capsules
-improve powder flowability, reduce dusts, enhance compactibility
Wet granulation process
- blending
- adding binder
- granulation
- Drying
- Sieving
Dry granulation process
- blending
- compression
- Size reduction
wet granulation
-high shear granulation
Dry granulation
-no liquid
-less processing steps and fewer risks than wet granulation
-lose some compactibility for tableting
Roller compaction
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