Search tips
Search criteria 


Logo of aapspharmspringer.comThis journalToc AlertsSubmit OnlineOpen Choice
AAPS PharmSciTech. 2007 September; 8(3): E152–E157.
Published online 2007 August 31. doi:  10.1208/pt0803071
PMCID: PMC2750567

Effect of curing on water diffusivities in acrylate free films as measured via a sorption technique


Studies were performed to investigate the effect of curing on the diffusion coefficients of water, as measured via the sorption technique, in acrylate polymeric films. The mathematical model selected for obtaining diffusion constants from the vapor-phase sorption studies was derived from the longtime Fourier equation used for diffusion into a planar sheet. For Eudragit NE films, the diffusion coefficients of water decreased continuously until a constant minimum value was reached. Diffusion coefficients in Eudragit RS films decreased initially but increased beyond 4 hours of curing at 70δC and 90°C. This latter result suggested the possible evaporation of plasticizer, which also results in a more dramatic increase in glass transition temperature with curing for the Eudragit RS free film in comparison to the Eudragit NE free film. Such loss of plasticizer could also lead to the formation of molecular-scale channels within the films, which would result in increased film permeability. To verify this proposed explanation, the amounts of triethyl citrate plasticizer in Eudragit RS free films were determined using Fourier-transform infrared spectrophotometry. An optimal curing condition was predicted for Eudragit NE and Eudragit RS films based upon the curing conditions at which a minimum value of the diffusion coefficient was reached.

Keywords: Curing, acrylate coating, sorption, diffusion coefficient, glass transition temperature

Full Text

The Full Text of this article is available as a PDF (321K).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
1. Harris MR, Ghebre-Sellassie I. A water based coating process for sustained release. Pharm Technol. 1986;10:102–107.
2. Hutchings D, Clarson S, Sakr A. Studies of mechanical properties of free films prepared using an ethylcellulose pseudolatex coating system. Int J Pharm. 1994;104:203–213. doi: 10.1016/0378-5173(94)90161-9. [Cross Ref]
3. Hutchings D, Kuzmak B, Sakr A. Processing considerations for an EC latex coating system: influence of curing time and temperature. Pharm Res. 1994;11:1474–1478. doi: 10.1023/A:1018960310144. [PubMed] [Cross Ref]
4. Bodmeier R, Paeratakul O. The effect of curing on drug release and morphological properties of ethylcellulose pseudolatex coated beads. Drug Dev Ind Pharm. 1994;20:1517–1533. doi: 10.3109/03639049409050195. [Cross Ref]
5. Bodmeier R, Paeratakul O. Process and formulation variables affecting the drug release from chlorpheniramine maleate-loaded beads coated with commercial and self-prepared aqueous ethyl cellulose pseudolatexes. Int J Pharm. 1991;70:59–68. doi: 10.1016/0378-5173(91)90164-J. [Cross Ref]
6. Amighi K, Moës AJ. Influence of plasticizer concentration and storage conditions on the drug release rate from Eudragit RS30D film-coated sustained-release theophylline pellets. Eur J Pharm Biopharm. 2007;42:153–245.
7. Lippold BH, Sutter BK, Lippold BC. Parameters controlling drug release from pellets coated with aqueous ethyl cellulose dispersions. Int J Pharm. 1989;54:15–25. doi: 10.1016/0378-5173(89)90160-9. [Cross Ref]
8. Struik LCE. Physical Aging in Amorphous Polymers and Other Materials. New York, NY: Elsevier; 1978.
9. Laot CM, Marand E, Schmittmann B, Zia RKP. Effects of cooling rate and physical aging on the gas transport properties in polycarbonate. Macromolecules. 2003;36:8673–8684. doi: 10.1021/ma021720o. [Cross Ref]
10. Pekarski P, Hampe J, Bohm I, Brion HG, Kirchheim R. Effect of aging and conditioning on diffusion and sorption of small molecules in polymer glasses. Macromolecules. 2000;33:2192–2199. doi: 10.1021/ma990642a. [Cross Ref]
11. Jacobs MH. Diffusion Processes. New York, NY: Springer-Verlag New York Inc; 1967.
12. Vieth RW. Diffusion In and Through Polymers. Piscataway, NJ: Oxford University Press; 1991.
13. Crank J, Park GS. Diffusion in Polymers. New York, NY: Academic Press; 1968.
14. Lehman KOR. Polymethacrylate coating systems. In: McGinity J, editor. Aqueous Polymeric Coatings for Pharmaceutical Dosage Forms. 2nd ed. New York, NY: Marcel Dekker Inc; 2007. pp. 101–173.
15. Wheatley TA, Steuernagel CR. Latex emulsion for controlled drug delivery. In: McGinity JW, editor. Aqueous Polymeric Coatings for Pharmaceutical Dosage Forms. 2nd ed. New York, NY: Marcel Dekker Inc; 1997. pp. 1–54.
16. Verhoeven J, Schaeffer R, Bouwstra JA, Junginger HE. The physicochemical characterization of poly (2-hydroxyethyl methacrylate-comethacrylic acid), 2: effect of water, PEG 400 and PEG 6000 on the glass transition temperature. Polym. 1989;30:1946–1950. doi: 10.1016/0032-3861(89)90371-6. [Cross Ref]
17. Rowe RC. Reappraisal of the equations used to predict the internal stresses in film coatings applied to tablet substrates. J Pharm Pharmacol. 1983;35:112–113. [PubMed]
18. Guma NC, Kale K, Morris KR. Investigation of film curing stages by dielectric analysis and physical characterization. J Pharm Sci. 1997;86:329–334. doi: 10.1021/js9603008. [PubMed] [Cross Ref]

Articles from AAPS PharmSciTech are provided here courtesy of American Association of Pharmaceutical Scientists