compression and consolidation

Views:
 
Category: Education
     
 

Presentation Description

No description available.

Comments

By: Halleluyah777 (72 month(s) ago)

Sir plzzz send me this presentation

Presentation Transcript

CONTENTS:

CONTENTS DEFINATIONS DERIVED PROPERITIES OF POWDERED SOLID EFFECT OF APPLIED FORCES ON COMPRESSION STRENGTH OF GRANULES COMPRESSION AND CONSOLIDATION UNDER HIGH LOADS REFERENCES

DEFINATIONS::

DEFINATIONS: COMPRESSION - Compression means reduction in the bulk volume of the material as a result of displacement of the gaseous phase . CONSOLIDATION - An increase in the mechanical strength of the material resulting from particle/particle interaction .

Derived properties of powdered solids:

Derived properties of powdered solids The solid-air interface Angle of repose Flow rates Mass-volume relationships Density

THE SOLID-AIR INTERFACE:

THE SOLID-AIR INTERFACE COHESION : Attraction between like particle. Experienced by particles in bulk. ADHESION : Attraction between unlike particle. Experienced by particles at surface. Resistance to movement of particles is affected by two factors: a) Electrostatic forces. b) Adsorbed layer of moisture on particles

ANGLE OF REPOSE::

ANGLE OF REPOSE: DEFINITION: The maximum angle possible between the surface of pile of the powder and the horizontal plane.

PowerPoint Presentation:

a. Fixed funnel and free standing cone method. b.Tilting box method. c. Revolving cylinder method . METHODS TO MEASURE ANGLE OF REPOSE

FORMULA FOR MEASURING ANGLE OF REPOSE:

FORMULA FOR MEASURING ANGLE OF REPOSE Θ = tan -1 (h/r) here, h= height of pile r= radius of the base of the pile Θ = angle of repose ANGLE OF REPOSE (Ø) (Degrees) FLOW < 25 EXCELLENT 25-30 GOOD *30-40 PASSABLE >40 VERY POOR Adding glidant,0.2% aerosil may improve

ANGLE OF REPOSE :

ANGLE OF REPOSE STATIC ANGLE OF REPOSE KINETIC/DYNAMICANGLE OF REPOSE It is angle of repose determined by 1 st two methods (a. & b.) It is angle of repose determined by the 3 rd method ( c.)‡ It is preferred since they most closely mimic the manufacturing situation in which powder is in motion.

FLOW RATES :

FLOW RATES Compressibility index (Carr's consolidation index) I = [1-v/vo]x100 here, V= Tapped Volume V0= Volume before tapping CONSOLIDATIONINDEX (Carr, % ) FLOW 5-15 EXCELLENT 12-16 GOOD *18-21 FAIR TOPASSABLE *23-35 POOR 33-38 VERY POOR >40 VERY VERY POOR Adding glidant,0.2% aerosil may improve flow.

TYPES OF VOLUME :

TYPES OF VOLUME True volume (Vt) Granule volume (Vg) Bulk volume (Vb) Relative volume (Vr ) Vr =V/Vt Vr tends to become unity as all air is eliminated fromthe mass during the compression process

MASS-VOLUME RELATIONSHIPS :

MASS-VOLUME RELATIONSHIPS TYPE OF VOIDS OR AIR SPACES : Open intra particulate voids Closed intra particulate voids Inter particulate voids

METHODS TO MEASURE VOLUME OF POWDER. :

METHODS TO MEASURE VOLUME OF POWDER. Helium pycnometer Liquid displacement method (specific gravity bottle method)

DENSITY :

DENSITY DIFFERENT TYPE OF DENSITY: True density ρ t =M/v t Granule density ρ g =M/v g Bulk density ρ b =M/v b relative density ρ r = ρ / ρ t

Compression:

Compression Powder fluidity required to transport the material provide adequate filling of the dies to produce tablets of consistent weight and strength. Powder compression Depends on density and packing characteristics of powder When external mechanical forces are applied to a powder mass, there is reduction in bulk volume as follows, 1.Repacking 3.Brittle fracture: e.g., sucrose 2.Particle 4.microquashing deformation e.g., acetyl salicylic acid, MCC - when elastic limit or yield point is reached. Microsquasing : Irrespective of the behavior of larger particles smaller particles may deform plastically. Elastic deformation Plastic deformation

PowerPoint Presentation:

1. Initial repacking of particles. 2. Elastic deformation of the particles until the elastic limit (yield point) is reached. 3. Plastic deformation and/or brittle fracture then predominate until all the voids are virtually eliminated. 4. Compression of the solid crystal lattice then occurs. Stages involved in compression On Decompression

:

Repacking Load Deformation If elastic If plastic Load Load Load 17

Compression process:

Compression process In particle deformation and rearrangement the following three principal modes of deformation are as follow 1. Elastic deformation : A spontaneously reversible deformation of the compact in which, upon removal of the load, the powder mass reverts back to its original form. Most materials undergo elastic deformation to some extent. Compression of rubber would be by elastic deformation.

Compression process:

Compression process 2.Plastic deformation : After exceeding the elastic limit of the material (yield point), the deformation may become plastic, that is, the particles undergo viscous flow. This is the predominant mechanism when the shear strength between the particles is less than the breaking strength. Plastic deformation is a time-dependent process. 3 . Brittle fracture: Upon exceeding the elastic limit of the material (yield point), the particles undergo brittle fracture if the shear strength between the particles is greater than the breaking strength. Under these conditions, the larger particles are sheared and broken into smaller particles.

Consolidation process :

Consolidation process Cold welding: when the surfaces of two particles approach each other closely enough, their free surface energies results in strong attractive force, a process known as cold welding. Fusion bonding: Multiple point contacts of the particle upon application of load produces heat which causes fusion / melting. Upon removal of load it gets solidified and increase the mechanical strength of mass.

Consolidation process:

Consolidation process Mechanical theory : As the particles undergo deformation, the particle boundaries that the edges of the particle intermesh, forming a mechanical bond Intermolecular forces theory : Under pressure the molecules at the point of true contact between new, clean surface of the granules are close enough so that Vander Waals forces interact to consolidate the particle. E.g. microcrystalline cellulose is believed to undergo significant hydrogen bonding during tablet compression. Liquid-surface film theory: Thin liquid films form which bond the particles together at the particle surface. The energy of compression produces melting of solution at the particle interface followed by subsequent solidification or crystallization thus resulting in the formation of bonded surfaces

Factors affecting consolidation:

Factors affecting consolidation The chemical nature of the material The extent of the available surface The presence of surface contaminants The inter surface distance

METHODS TO DETERMINE STRENGTH OF GRANULE: :

METHODS TO DETERMINE STRENGTH OF GRANULE: Compressive strength or crushing strength. Abrasion tests.

Compression and consolidation under high load::

Compression and consolidation under high load : Relationship between upper punch FA& lower  punch forces F L : F L = F A × e -KH/D here, K = constant, H & D= height & diameter of tablet

REFERENCES::

REFERENCES: Marshall, K., Compression and consolidation of powdered solids. In : The Theory and Practice of Industrial Pharmacy. Lachman, L., Lieberman, H. A. and Kanig, J. L. (Eds.) 3 rd Edition (1986) Lea & Febiger, Philadelphia , pp. 66-99. Bodga, M. J. (2002) Tablet compression: Machine theory, design and process troubleshooting. In: Encyclopedia of Pharmaceutical Technology. Swarbrick J and Boylan J (Eds). Marcel and Dekker Inc., USA . Vol. 3: 2669 – 2688. British Pharmacopoeia (1998) HMSO, London .

authorStream Live Help