Seminar on AQUEOUS FILM COATING. GOVARDHAN.P Department of pharmaceutics University College Of Pharmaceutical Sciences, Kakatiya university,warangal-500609. CONTENTS. INTRODUCTION AQUEOUS FILM COATING OF DOSAGE FORM Film formation mechanism Film formers Plasticizers and colours
AQUEOUS FILM COATING
Department of pharmaceutics
University College Of Pharmaceutical Sciences,
IT is the application of coating composition on to the moving bed of tablets with concurrent use of heated air to facilitate evaporation of the solvent.
Water-soluble coating materials dissolve completely in the gastrointestinal tract and
do not modify the drug release characteristics of the dosage. These polymers are applied
as aqueous solutions.
COMMON FILM FORMING MATERIALS IN
SUSTAINED RELEASE PRODUCTS
Effect of polymer molecular weight on coating properties
Property Effect of increasing polymer molecular weight
Tensile strength Increases.
Elastic modulus Increases.
Film adhesion Decreases.
Solution viscosity Significantly increases.
Polyethylene glycol (PEG)
Propylene glycol (PG)
Tributyl citrate (TBC)
Acetylated monoglyceride (AMG)
Effects of Plasticizers on the properties of film coatings
Effect of increasing plasticizer concentration
Tensile strength Decreased.
Elastic modulus Decreased.
Film adhesion May be increased, but results often variable.
Solution viscosity Increased, and magnitude of effect dependent on
molecular weight of plasticizer.
Film permeability can be increased or decreased, depending on chemical
nature of plasticizer.
Glass-transition temperature Decreased, but magnitude of effect dependent on
compatibility with polymer.
Effects of Pigments on the properties of film coatings
Effect of increasing pigment concentration
Tensile strength Decreases
Elastic modulus Increases
Film adhesion Little effect.
Solution viscosity Increases, but not substantially.
Film permeability Decreases, unless critical pigment volume concentration
This requires the coalescence of polymer particles into a continuous film.
This process involves:
Aqueous polymeric dispersions must be processed at temperatures in excess of the
glass-transition temperature of the polymer.
Film Coating Composition
Spraying air pressure:
The spraying air pressure disperse the coating liquid into droplets and effects
the droplet size distribution and droplet spreading and penetration on the tablet
The formation of adequate and adhesive film coat, the atomized droplets have
to spread completely over the surface of the tablet.
Increasing the spraying air pressure decreases the surface roughness of coated
tablets and produces denser and thinner films.
If spraying air pressure is excessive the spray loss is great. The formed droplets
are very fine and could spray dry before reaching the tablet bed, resulting in
inadequate droplet spreading and coalescence.
Spraying air pressure is insufficient, the film thickness and thickness variation
greater possibly due to change in film density and smaller spray loss.
Flow rate of coating solution
Pan air temperature
Rotating speed of the pan
Application of the film
This is an angular pan operating on a horizontal axis. Drying air is directed into the pan, through the tablet bed, and exhausted out the perforations in the
periphery of the pan.
This is similar to Accela Cota, but only a portion of the pan periphery has
perforations. Like the Accela Cota, continuous venting of the exhaust air from the
pan is still attained.
Not enough vehicle.
High atomization air.
Moving the nozzle closer to the tablet bed or
reducing the degree of atomization
REMEDY:Reduction in the liquid application rate or
increases in air dry temparature
SOLVENT FILM COATING: AQUEOUS VS. ORGANIC
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