Dynamic mechanical thermal analysis of aqueous sugar solutions containing fruct...

• Autor(es): Cruz, Isabel B. ; Oliveira, Jorge C. ; MacInnes, William M.
• Data: 2001
• Identificador Persistente: http://hdl.handle.net/10400.14/6857
• Origem: Veritati - Repositório Institucional da Universidade Católica Portuguesa
• Assunto(s): Biomaterials science; Frequency-response analysis; Glass transition; Molecular mobility; WLF equation
• Tipo de Documento: Artigo
• Idioma: Inglês

Descrição

The glass transition of glucose, fructose, lactose, maltose and sucrose solutions at maximum cryo-concentration was studied by Dynamic Mechanical Thermal Analysis (DMTA), using the disc bending technique. The glass transition temperatures were determined from the peaks in the loss modulus E′′, which corresponds theoretically to the resonance point (Maxwell model) for several input frequencies. The frequency dependence was well described by both an Arrhenius-type model and by the WLF (Williams, Landel and Ferry) equation, yielding glass transition temperatures for an average molecular vibration time of 100 s, which were similar to published midpoint temperatures determined by DSC scans. Some sugar mixtures were studied, yielding results that were well described by the Gordon–Taylor equation, using literature data. The frequency dependence of the viscoelastic ratio was also well approximated by an Arrhenius-type equation, with activation energies similar to those of the glass transition temperature and corresponded well to published values of the endset of glass transition.