Effect of temperature on thermo-mechanical properties of Macro-Defect-Freecement-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 mate rial from room temperature to 250 degrees C at a fixed frequency (1 Hz). Th e viscoelastic behaviour of the composite was then analyzed at different fr equencies: it was observed that the material exhibits two main transitions, around 60 degrees C and 160 degrees C. For comparison with differential sc anning calorimeter analysis the first peak was attributed to the glass tran sition of the PVAAc while the second one was associated to the melting of t he crystalline part of the polymer. In addition, dynamical-mechanical analy sis that included complex thermal hystories, were performed both on pure po lymer films, and on the MDF cements, confirming that the drop of mechanical properties with temperature is essentially due to the nature of the viscoe lastic component. Results obtained are in agreement with the picture of a c omposite in which a polymeric thermoplastic matrix surrounds partially hydr ated cement particles. (C) 1999 Kluwer Academic Publishers.