Suberin fatty acids isolated from outer birch bark improve moisture barrier properties of cellulose ether films intended for tablet coatings.
We showed that the addition of suberin fatty acids (SFAs) even at small concentrations significantly improves the water vapor barrier properties of hydroxypropyl methylcellulose (HPMC) films. SFAs were isolated from the outer birch bark using extractive hydrolysis. The effects of SFAs on the film formation of aqueous HPMC were investigated with free films plasticized with polyethylene glycol (PEG 400). Special attention was paid on the physical solid-state, moisture barrier and mechanical stress-strain properties of films intended for tablet film coatings. Topography and surface morphology, glass transition temperature (Tg), tensile strength, Young's modulus, and water vapor permeation (WVP) of films were studied. The addition of SFAs lowered the Tg of films suggesting partial enhancement in film plasticization. The WVP of films decreased with increasing SFAs concentration up to 15% (calculated as a % w/w from a polymer weight). The WVP value for a non-suberized reference film and suberized film plasticized with PEG 400 was 2.13×10(-6) and 0.69[×10(-6) g/(mm(2)×h)×mm/Pa], respectively. The addition of SFAs impaired the mechanical stress-strain properties of HPMC films by reducing the deformation capacity of film. In conclusion, the film properties and performance of aqueous HPMC can be modified by including SFAs in the films.
Department of Pharmacy, Faculty of Medicine, University of Tartu, Nooruse 1, 50411 Tartu, Estonia. Electronic address: jyrki.heinamaki@ut.ee.
Jyrki
J
Heinämäki
Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56 (Viikinkaari 5E), FI-00014, Finland. Electronic address: anna.halenius@helsinki.fi.
Anna
A
Halenius
Department of Pharmacy, Faculty of Medicine, University of Tartu, Nooruse 1, 50411 Tartu, Estonia. Electronic address: maaja.paavo@ut.ee.
Maaja
M
Paavo
VTT Technical Research Centre Finland, P.O. Box 1000, FI-02044 VTT Espoo, Finland. Electronic address: sami.alakurtti@vtt.fi.
Sami
S
Alakurtti
VTT Technical Research Centre Finland, P.O. Box 1000, FI-02044 VTT Espoo, Finland. Electronic address: pauliina.pitkanen@vtt.fi.
Pauliina
P
Pitkänen
VTT Technical Research Centre Finland, P.O. Box 1000, FI-02044 VTT Espoo, Finland. Electronic address: minni.pirttimaa@vtt.fi.
Minni
M
Pirttimaa
Department of Pharmacy, Faculty of Medicine, University of Tartu, Nooruse 1, 50411 Tartu, Estonia. Electronic address: urve.paaver@ut.ee.
Urve
U
Paaver
Department of Geology, Institute of Ecology and Earth Sciences, University of Tartu, Ravila 14a, 50411 Tartu, Estonia. Electronic address: kalle.kirsimae@ut.ee.
Kalle
K
Kirsimäe
Department of Pharmacy, Faculty of Medicine, University of Tartu, Nooruse 1, 50411 Tartu, Estonia. Electronic address: karin.kogermann@ut.ee.
Karin
K
Kogermann
Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56 (Viikinkaari 5E), FI-00014, Finland. Electronic address: jouko.yliruusi@helsinki.fi.
Jouko
J
Yliruusi
D029662:Betula; D055119:Elastic Modulus; D065347:Hypromellose Derivatives / Q000737:chemistry*; D008055:Lipids / Q000737:chemistry* / Q000302:isolation & purification; D010539:Permeability; D024301:Plant Bark / Q000737:chemistry; D010968:Plasticizers / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D013607:Tablets; D013718:Tensile Strength; D044366:Transition Temperature; D014867:Water / Q000737:chemistry*
D008055:Lipids; D010968:Plasticizers; D013607:Tablets; D014867:Water; D065347:Hypromellose Derivatives; D011092:Polyethylene Glycols; C065875:suberin
Birch bark; Free films; Hydroxypropyl methylcellulose; Mechanical properties; Suberin fatty acids; Water vapor permeation