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Development of hot-melt extrusion as a novel technique for the ...

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However, <strong>the</strong> DSC <strong>the</strong>rmograms <strong>of</strong> <strong>the</strong> PM showed broad endo<strong>the</strong>rmic transitions from127-163 o C and 124-151 o C that correspond to INM and FMT, respectively (Fig. 2.5 b-e). Theabsence <strong>of</strong> sharp <strong>melt</strong>ing endo<strong>the</strong>rms in <strong>the</strong> active <strong>for</strong>mulations suggests that both drugs arepartially dissolved in <strong>the</strong> <strong>melt</strong>ed polymers.Fig. 2.5a: MTDSC <strong>the</strong>rmograms <strong>of</strong> pure polymers and drugs.In <strong>the</strong> c<strong>as</strong>e <strong>of</strong> INM/VA64 extrudates, a single Tg w<strong>as</strong> observed <strong>for</strong> both loadingsindicating drug – polymer miscibility. When <strong>the</strong> two components are miscible <strong>the</strong> Tg <strong>of</strong> <strong>the</strong>extruded sample should, according to <strong>the</strong> Gordon – Taylor equation [29] be between <strong>the</strong>ir Tgs.For INM 20% and 40% loadings, <strong>the</strong> Tgs were lowered to 56.2 o C and 57.2 o C, respectivelydenoting INM – VA64 miscibility. The INM gl<strong>as</strong>s transition temperature h<strong>as</strong> been previouslyestimated at 42.3 o C. The presence <strong>of</strong> a single Tg <strong>for</strong> <strong>the</strong> INM/VA64 extrudates suggests <strong>the</strong>presence <strong>of</strong> a gl<strong>as</strong>sy solid solution where INM is molecularly dispersed within <strong>the</strong> polymermatrices.31 | P a g e

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