Effect of temperature on thermo-mechanical properties of Macro-Defect-Free cement-polymer composite

In this work thermo-mechanical properties of MDF cements have been analyzed under complex thermal hystories. In particular the temperature sensitivity of the material has been investigated using dynamical-mechanical analysis. Several tests have been performed to investigate the behaviour of the material from room temperature to 250 degrees C at a fixed frequency (1 Hz). The viscoelastic behaviour of the composite was then analyzed at different frequencies: it was observed that the material exhibits two main transitions, around 60 degrees C and 160 degrees C. For comparison with differential scanning calorimeter analysis the first peak was attributed to the glass transition of the PVAAc while the second one was associated to the melting of the crystalline part of the polymer. In addition, dynamical-mechanical analysis that included complex thermal hystories, were performed both on pure polymer films, and on the MDF cements, confirming that the drop of mechanical properties with temperature is essentially due to the nature of the viscoelastic component. Results obtained are in agreement with the picture of a composite in which a polymeric thermoplastic matrix surrounds partially hydrated cement particles. (C) 1999 Kluwer Academic Publishers.