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Hydroxypropyl methylcellulose (HPMC) and polyvinyl alcohol (PVA) are important polymers in pharmaceutical, food and other industries being largely used as encapsulation agents. The characterization of two reference grades of HPMC (Pharmacoat Ò 603 and Pharmacoat Ò 615) and one reference grade of PVA (Mowiol Ò 4-98), through X-ray diffraction (XRD) and thermogravimetry (TG) is described. Specific analyses were performed by means of dynamic vapour sorption analysis of water adsorption/ desorption from vapours at 10, 25, 40, 55 and 70°C. Guggenheim-Anderson-de Boer (GAB), Brunauer-EmmettTeller (BET), Park and n-layer BET models were successfully used to fit the experimental data. The glass transition temperature as function of water content was measured by means of differential scanning calorimetry (DSC). The experimental data were analysed according to Linear, Gordon-Taylor, Fox and Roos equations. XRD

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