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Drying Kinetics of Polymeric Films : theoretical and experimental studies


Academic year: 2021

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Drying Kinetics of Polymeric Films: theoretical and experimental studies

Sitaram Velaga, Dariush Nikjoo and Parameswara Rao Vuddanda

Department of Health Sciences, Luleå University of Technology, Luleå, Sweden



Drying controls physical and mechanical properties of polymeric films [1,2]. The objective of this work was to study and model drying kinetic of multicomponent films of two water soluble polymers; HPMC (amorphous) and PVA (semicrystalline).



 TGA could be used as a simple tool to

predict drying end points in drying processes like drying tunnels.

 Hill equation with three parameters well

explained drying kinetics and diffusion mechanisms of the solvent in the polymeric films.

 Bi-phasic diffusion kinetics was

observed (fickian/non-fickian).

 In situ solid state changes in the

polymer was observed to effect drying kinetics of the films.

1) Hoffmann EM, Breitenbach A, Breitkreutz J., Expert Opin Drug Deliv. 2011;8(3):299-316.

2) Zhang H, Wang Q, Li L., Polym Int. 2009;58(1):97-104.

The multicomponent films were prepared by the solvent casting method using a film applicator. A laboratory convective drying oven and thermogravimertic analysis (TGA) methods were used to study the isothermal drying kinetics. Hill equation with three parameters (Wmax,


, n) was proposed to

explain drying behaviour for the first time. Moreover, polarization and hot stage-microscopy, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were used to investigate in situ solid state of the polymeric films.


SEM of the post dried films of HPMC and PVA in TGA

at 80ºC for 60 min. Drying rates (Kd) of HPMC and PVA films before and after the characteristic time (t)

HSM images of PVA at 80 °C for (a) 10, (b) 30, (c) 60 min drying.

DSC of post dried HPMC and PVA films in TGA at 80 ºC for (a) 5, (b) 10, (c) 20, (d) 30, (e) 60 min drying.

Wloss (%) vs time for HPMC and PVA films at various temperatures in TGA


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