tabletting 2 Flashcards
what is powder compressibility?
‘it’s propensity, when held within a confined space, to reduce in volume when subjected to a load”
what is plastic deformation?
when particles stay deformed and cohesion is kept
what is elastic deformation?
cohesion is lost and particles return to original shape
how is compression is plastic material?
particles flow and voids are filled so more contact area for bonding
compression of elastic materials?
the particles deform once pressure is applied but store the energy. they then release the energy, causing the tablet to expand, providing a stress form within which weakens the tablet
examples of elastic materials?
disintegrants
compression of brittle materials?
particles shatter, the voids are filled and increases contact area for bonding
what is viscosity a combo of?
elastic and plastic behaviour
what are the types of bonds formed during tabletting?
‘mechanical interlocking, melting at contact points, molecular bonding where surfaces meet’
what two things can be adjusted on a tabletting machine?
dwell time, maximum pressure
what is the linear region?
hardness depends on pressure applied and pressure can be adjusted
what is lamination?
horizontal layers ad cracks forming because of over compression
what is the A region?
the loose compacted region
little bonding of particles
no strength
called the powder plug used to fill in capsules
what is the B region of tabletting machine?
linear region
inter-particulate bonding
more pressure so more tablet strength
air in the voids of the tablet
what is the C region of tabletting machine?
maximum compaction
maximum bonding of particles
maximum bonding
maximum air in voids
what is the D region of tabletting machine?
excess compression
bonds break because extra energy no longer used to make more bonds
lamination occurs which reduces the strength of the tablet
why do plastic materials need more dwell time?
because they flow with time so more internal bonds can be made therefore stronger tablets
what is capping?
the top of the tablet comes off because of lamination
what is chipping/sticking?
chipped sides of the tablet and holes in tablet form sticking to the punch
what are stress cracks in tablets?
cracks caused by too much elastic expansion
what is friability?
during transportation:
the edges erode
powder is shedded
problems in formulations?
too much elastic ingredient
too much compressible drug
drugs that have a low melting point
drugs that react with excipients
wrong quantity of lubricant or mixed for a wrong time period
consequences of too much elastic ingredient?
‘stress cracks and friable’
consequences of too much compressible drugs?
lamination or capping or friability occurs
consequences of drugs with low melting points?
sticks to punches and melts during tabletting because of the heat
consequences of drugs reacting with excipients?
doesn’t happen often because discovered in pre-formulating studies
consequences of lubrincants?
not enough lubrication leads to struggle of ejection of tablet
too much lubricant leads to fewer inter-particulate bonds so weaker tablets therefore more friable
what are the types of tablet machines?
single punch, rotary, compaction simulator
what are the properties of single punch?
50 tablets per minute
rarely used
what are the properties of rotary machines?
multiple punches
20,000 tablets made per minute
small machines used for lab and pilot scale
big ones used for full scale manufacturing
what are the properties of compaction simulator?
single punch
one tablet at a time
lots of sensors
advantages of compaction simulator?
‘needs few grams of drug since it makes one tablet so useful in early development when new drug is in short supply’
disadvantages of compaction simulator
very expensive
options of coating tablets?
slide 17
tablets and tabletting part 2 ppt
how is a tablet sugar coated?
coating liquid poured onto the bed of the tablet
rotation coats the tablets evenly
coat is left to dry before next coating
what are the variables of sugar coating tablets?
rotation speed
air flow
air temperature
rate of pouring in the liquid
what is the process of polymer film coating?
coating liquid sprayed into tablet bed
drum rotated to spread coating on the surface
evaporation of liquid to form solid polymer firm
variables of polymer film coating?
spray rate
drum rotation speed
temperature
air flow
what does the liquid for film coating contain?
polymer latex
plasticiser
colour
surfactant
separating agent
what is the polymer latex for?
no organic solvent
what is plasticiser for?
help polymer particles coalesce
what is colour for?
‘as a fine suspension lake’
what is the surfactant for?
‘to help liquid spread quickly’
what is the separating agent for?
so tablets don’t stick together during drying
how does a film coat form?
‘latex suspension sprayed onto the tablet, liquid evaporates, latex particles coalesce to form a polymer film’
how does compression coating and multilayer coating happen?
‘powder compressed into weak tablet
coating formulation compressed onto it
double compression forms strong tablet’
properties of compression coating and multilayer coating
special tabletting machine required
