Abstract
Purpose: To study the mechanical and dynamic swelling properties of grewia gum, evaluate its compression behaviour and determine the effect of drying methods on its properties.Methods: Compacts (500 mg) of both freeze-dried and air-dried grewia gum were separately prepared by compression on a potassium bromide (KBr) press at different pressures and subjected to Heckel analysis. Swelling studies were performed using 200 mg compacts of the gum (freeze-dried or air-dried) compressed on a KBr press. The mechanical properties of the films of the gum prepared by casting 1 % dispersions of the gum were evaluated using Hounsfield tensiometer. The mechanical properties of grewia gum films were compared with films of pullulan and guar gum which were similarly prepared. The effect of temperature on the water uptake of the compacts was studied and the data subjected toSchott’s analysis. Results: Drying conditions had no effect on the yield pressure of the gum compacts as both air-dried and freeze-dried fractions had a yield pressure of 322.6 MPa. The plots based on Schott’s equation for the grewia gum samples showed that both samples (freeze-dried and air-dried) exhibited long swelling times. Grewia gum film had a tensile strength of 19.22±3.61 MPa which was similar to that of pullulan films (p > 0.05). It had an elastic modulus of 2.13±0.12 N/mm2 which was significantly lower (p < 0.05) than those of pullulan and guar gum with elastic moduli of 3.33±0.00 and 2.86±0.00 N/mm2, respectively.Conclusion: The type of drying method used does not have any effect on the degree of plasticity of grewia gum compacts. Grewia gum obtained by either drying method exhibited extended swelling duration. Matrix tablet formulations of the gum will likely swell slowly and promote sustained release of drug.Keywords: Grewia gum compact, Films, Heckel analysis, Swelling behaviour
Highlights
There is a renewed interest in films made from natural polymers [1]
The tensile strength of grewia gum films decreased with increasing concentration of polyethylene glycol, and becoming less brittle with a more translucent appearance
PEG is capable of plasticising grewia gum films and the effect is concentration-dependent
Summary
There is a renewed interest in films made from natural polymers [1]. This is because they are renewable resources and are environmentally friendly. Relationships where either the compaction pressure or the volume is transformed, have been used to describe the compressibility of powders [7]. Most of these equations are of limited practical value [8]. Natural polysaccharides are formed by various sugar units or monosaccharides which are capable of promoting intra- and inter-molecular bonds. They exhibit large variation in their functional properties [3]. Plasticisers must be added to modify the mechanical properties of the films These compounds decrease inter- and intramolecular attractive forces and increase chain mobility thereby improving flexibility [5]
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