Materials and methods
CA-398-10NF-EP with acetyl content at 39.4% and CA-398-10TG (technical grade) with acetyl content at 40.3% (Eastman Chemical
Company, Kingsport, TN) were used in the study. The plasticizer (Pz) investigated was polyethylene glycol 3350 (PEG 3350,
Sigma Aldrich, St Louis, MO). High-purity acetone (B&J Brand, Burdick & Jackson, Muskegon, MI) and deionized water (NANOpure
water system, Barnstead, Van Nuys, CA) were used as the solvent system. When applying CA onto tablets, the coating formulations
were the same as those casting films. The tablets to be coated consisted of 98.5% of POLYOX water-soluble resins with a molecular
weight of 5,000,000 (Dow Chemical, Midland, MI), 0.5% of colorant (Sensient Technologies Corp., St. Louis, MO), and 1.0% of
magnesium stearate (Mallinckrodt Baker Inc., Phillipsburg, NJ). All of these materials were used as received.
Preparation of CA-free films.
The CA-free films were prepared using a solvent evaporation method. PEG 3350 was dissolved in water for 1.5 h, then most
of needed acetone was added to the PEG/water solution. CA was gradually added to the solvent system under stirring. After
all CA was added, stirring continued for another 2 h to allow CA to dissolve completely. The remaining needed acetone was
added to the above mixture, followed by stirring for 30 min. After the CA solution was degassed for about 3 h, the solution
was ready to be used to cast films. The film-cast method and procedures can be found in reference (12). The film formulations
were developed based on an experiment design; the design space was that water varied from 0.0–10.0% and the ratio of Pz to
polymer varied from 0.00 to 0.29. There were three repeated points (center point) for CA-398-10NF-EP and one center point
for CA-398-10TG. The design was constrained with water, which must be in the formulation whenever Pz is present. Table I lists
all of the free films prepared.
Table I: List of CA- free films studied.
Characterization of CA-free films.
The prepared films were characterized, and film properties such as film morphology, glass transition temperature, oxidative
and thermal stability, mechanical strength and elongation, contact angle, and water vapor transmission rate were determined
according to the methods described in a previous article (12).
Preparation of model tablets.
POLYOX with (molecular weight of 5,000,000), blue dye, and magnesium stearate were blended in a V-blender (The Patterson
Kelly Co. Inc, East Stroudsburg, PA) for 3 min with the intensifying bar on for 15 s. The above mixture was then compressed
into 250.0-mg tablets on a rotary tablet press (D3B 16 station, Manesty, England) under 200-lb compression force.
CA coated on the model tablets.
The CA coating formulations at 6.0% solid level were prepared following the same procedures used to prepare CA-free film
except there was no degas step. Table II lists the coating formulations having four repeat points (center point) for CA-398-10NF-EP
and one center point for CA-398-10TG based on the same experimental design as the free films.
Table II: Coating formulations.
All of the coating runs, with a target coating weight at 10.0 wt% relative to the tablet weight, were performed in a pan coater
(COMPU-LAB, Thomas Engineering, Inc., Hoffman Estates, IL) with one spray gun under the processing conditions indicated in
Table III. For each run, 800.0 g of tablets were coated, and all coating runs were repeated at least twice.
Table III: Coating processing conditions.
Testing of CA-coated tablets.
Eight tablets from each coating run were randomly selected and tested in deionized water at 37 °C to determine water uptake
using a standard disintegration tester. At selected time intervals, the tested tablets were taken out, gently dried with a
tissue, and weighed. The water uptake was calculated using the following equation:
Water uptake at time t =
(tablet weight at time t) – (tablet weight at time 0)