Physical Ageing of Amorphous Indapamide Characterised by Differential Scanning Calorimetry

The objective of this study was to characterise amorphous indapamide (IND) subjected to the physical ageing process by differential scanning calorimetry (DSC). The amorphous indapamide was annealed at different temperatures below the glass transition, i.e., 35, 40, 45, 65, 75 and 85 °C for different lengths of time, from 30 min up to a maximum of 32 h. DSC was used to characterise both the crystalline and the freshly prepared glass and to monitor the extent of relaxation at temperatures below the glass transition (Tg). No ageing occurred at 35, 40 and 45 °C at the measured lengths of times. Molecular relaxation time constants (τKWW) for samples aged at 65, 75 and 85 °C were determined by the Kohlrausch-Williams-Watts (KWW) equation. The fragility parameter m (a measure of the stability below the glass transition) was determined from the Tg dependence from the cooling and heating rates, and IND was found to be relatively stable (“moderately fragile”) in the amorphous state. Temperature-modulated DSC was used to separate reversing and nonreversing processes for unaged amorphous IND. The enthalpy relaxation peak was clearly observed as a part of the nonreversing signal. Heat capacities data for unaged and physically aged IND were fitted to Cp baselines of solid and liquid states of IND, were integrated and enthalpy was presented as a function of temperature.

Effects of Hard Segment Contents on Dynamic Mechanical Properties of Gap-Based Polyurethane Elastomers

Gap-based polyurethane elastomer (GAPE) with different hard segment contents are synthesized with 44-Diphenylmethane diisocyanate (MDI), 1,4 butylene glycol (BDO) as hard segments and GAP as soft segments. Dynamic mechanical analysis (DMA) is applied to investigated the dynamic mechanical properties and the mechanical properties of GAPE are studied by materials laboratorial instrument. The results show that GAPE-2 with 33 wt% hard segment has better mechanical properties, of which the tensile strength is 11.3MPa and elongation at break is 460.5%.As shown in DMA, T g of GAPE-2 is-18.4°C, and the low-temperature fragility parameter and activation energy of GAPE-2 are lower, 55.6 and 271.0 KJ·mol-1 respectively. Elastomer with good stiffness and flexibility is obtained.

Glass Forming Ability and Non-Isothermal Crystallization Kinetics of Zr64Al10.1Cu11.7Ni14.2 Metallic Glass

The glass forming ability, thermal stability and non-isothermal crystallization kinetics of Zr64Al10.1Cu11.7Ni14.2 glass forming alloy were investigated. Its maximum glass forming dimension is up to 5mm and its critical cooling rate is less than 40Ks-1. The apparent activation energies derived from the Kissinger for Eg, Ex, Ep1 and Ep2 are 244.97±12.90, 264.63±10.18, 268.75±40.10 and 222.34±24.12 KJmol-1, respectively. The fragility parameter m is about 20.27, indicating its better thermal stability and glass forming ability.

Comparison of bulk metallic glass formation between Cu-Hf binary and Cu-Hf-Al ternary alloys

Optimized compositions for bulk metallic glass (BMG) formation have been determined for the Cu−Hf binary and Cu−Hf−Al ternary systems. The Cu−Hf−Al BMG-forming composition region is identified to correlate with the (L → Cu10Hf7 + CuHf2 + CuHfAl) eutectic reaction. The eutectic temperature is reduced by nearly 50 K relative to that of the binary eutectic, demonstrating the significant role of the third element Al in stabilizing the liquid. The fragility parameter D* of the Cu55Hf45 binary and Cu49Hf42Al9 ternary supercooled liquid was determined from relaxation time measurements, indicating that Al incorporation also leads to a “stronger” liquid. The combination of these thermodynamic and kinetic effects is responsible for the dramatic enhancement of glass-forming ability from the Cu−Hf binary to the Cu−Hf−Al ternary.