"Blendas de poli(alcool vinilico) e poli(vinil pirrolidona) : estudo do comportamento de fases"

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

The phase behavior of the blends of poly(vinyl alcohol). PVAI, and poly(vinyl pirrolidone), PVP, were studied by differential scanning calorimetry, DSC, infrared spectroscopy using Fourier transform-attenuated transmission reflectance, FTIR-ATR and dynamic-mechanical analyser, DMA. The molecular weight influence of PVP and hydrolysjs degree of PVAI were studied with respect to the phase behavior. The samples were prepared by casting of PVAI and PVP, on Petri plates. PVAl is a crystalline polymer whose blends with PVP show a crystalinity degree which is dependent on the mixture composition. DSC and DMA results show a single gIass transition temperature, which occurs at an intermediate temperature in relation to Tg of the pure polymers for alI compositions studied, independently of the molecular weight of PVP or the hydrolysis degree of PVAl. The dependence between the Tg and the blends composition is compIex and partially described by the Gordon-Taylor equation. The Dcp in the gIass transition, as well as the gIass transition width, are strongly dependent on the blends composition. The melting point depression was the criterion used to evaluate the miscibilíty of the blends. The PVAI cristalline phase is a function of the blends composition. The value of the polymer-polymer interaction parameter was negative for alI blends. The miscibility is assigned to intermolecular hydrogen bonding interaction in the system. From FTIR-ATR results, a shift of the band assigned to the PVP carbonyl is observed when the PVAl is present meanwhile the PVAI hydroxyl band is algo dislocated, indicating interactions between these groups. DMA results show secondary relaxations in the blends which were attributed to the hydrogen bonding reorganization. Studies of the influence of the molecular weight of PVP and hydrolysis degree of PVAI in the blends on lhe viscoelastic behavior showed that high moIecular weight PVP acts as a reinforcement to the mechanical properties in a region between the glass transition and the melting, while Iow molecular PVP, in spite of being more rigid than PVAI, acts favouring its flowing.

ASSUNTO(S)

misturas polimeros solução(quimica)

ACESSO AO ARTIGO

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