Physico-mechanical and free volume behaviour of guar gum filled polyurethane/polyacrylonitrile biodegradable composites

Preparation and characterization of guar gum based polyurethanes

Guar gum (plant-based polysaccharide) is a promising candidate with immense potential. It is used as emulsifier, thickener, stabilizer, and as binding agent in many industries. In the present project, it was planned to synthesize guar gum based polyurethanes by varying the amount of guar gum. Guar gum (GG) was used along with hydroxyl-terminated polybutadiene (HTPB) as soft segment, which was then reacted with isophorone diisocyanate (IPDI) to form PU pre-polymers. In last step, these -NCO terminated pre-polymers were extended with 1,4 butane diol as chain extender. The prepared polyurethane samples were then characterized by using FTIR, solid-state ¹HNMR and X-ray diffraction (XRD). Thermal behavior of the samples was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results indicated that the incorporation of guar gum in PU backbone improved its thermal behavior and crystallinity.

Guar Gum-Based Floating Microspheres of Repaglinide Using 32 Factorial Design: Fabrication, Optimization, Characterization, and In Vivo Buoyancy Behavior in Albino Rats

In this present study, floating microspheres of repaglinide were successfully fabricated by the solvent evaporation technique with varying ratios of guar gum, hydroxypropyl methylcellulose, and ethylcellulose with polyvinyl alcohol. Microspheres were characterized by production yield, particle size, in vitro buoyancy, entrapment efficiency, in vitro drug release, and in vivo floating behavior in albino rats. The formulation process was optimized for stirring speed (X₁) and concentration of polymer ratio (X₂) on dependent variables such as percentage entrapment efficiency, percentage yield, in vitro buoyancy, and percentage of drug release by the 3² factorial Design-Expert^® 12, trial version, software. The optimized formulation was characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, differential scanning calorimetry, and scanning electron microscopy and was successfully formulated with the highest percentage of cumulative drug release (94.26 ± 3.10), entrapment efficiency (74.70% ± 2.16%), and particle size (50.34 ± 3.67 μm) and remains buoyant for 24 h in simulated gastric fluid (0.1N HCL) with high in vitro buoyancy percent (84.90 ± 2.88). When the drug-polymer solution of dichloromethane and ethanol is dropped in polyvinyl alcohol solution, it leads to the formation of a shell and produces cavities, creating the buoyant nature of floating microspheres. X-ray imaging indicates the uniform distribution and buoyant nature of microspheres in the gastric fluid for a 10-h period.