Poly(vinyl alcohol) and poly(vinylpyrrolidone) blends: 2. Study of relaxations by dynamic mechanical analysis

Blends of poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) were studied by dynamic-mechanical analysis (DMA). PVA with different degrees of hydrolysis (88 and 99 wt%) and PVP with different molecular weights (10.000 and 360.000 g/mol) were used to prepare the blends. DMA results showed that blends were miscible over the whole composition range studied. However, the E" modulus curves exhibit relaxations at the same temperature range below Tg for all blends, suggesting the presence of microenvironments in the blends. These microenvironments are associated to the hydrogen bonding between PVA-PVA in the crystalline and amorphous phase and PVP-PVA in the amorphous phase and in the amorphous-crystalline interface. The stiffness and the flexibility of these blends at 200 degrees C depend strongly on the blends composition, the molecular weight of PVP and the hydrolysis degree of the PVA as determined by the E' modulus curves. (C) 1999 Elsevier Science Ltd. All rights reserved.