Prior to DSC measurement of the blends, DSC measurements were performed on the physical mixtures (Figures ). All three mixtures display an initial endothermic peak in the first upscan, which most likely corresponds to surface water loss as phosphate glasses xNa2O-(1-x)P2O5 with x < 0.5 are hygroscopic. For the 1:1 physical mixture, a weak glass transition feature at 212 °C and 213 °C was observed in the second and third DSC upscans respectively, before onset of decomposition. Similar results were obtained for the 1:3 physical mixture, in which a single Tg at 211 °C and 213 °C was found in the second and third DSC upscans respectively before Td. After the initial endothermic feature in the 1:6 physical mixture in the first upscan, the inorganic Tg is visible at 193 °C before a second Tg at 241 °C. Again, a single Tg at 208 °C is evident in both the second and third DSC upscans, with Tgs also visible on cooling. Tg values of 211 °C and 215 °C are obtained from the first DSC upscans of the corresponding blends for the 1:1 and 1:3 samples respectively, but no discernible Tg can be assigned for the 1:6 sample (Figures A feature resembling the form of a Tg can be observed around 253 °C in the first upscan, but this feature was not reproduced in the second upscan. The second DSC upscans display a single Tg at 212 °C, 212 °C and 217 °C for the 1:1, 1:3 and 1:6 Zn:P blends respectively, as observed in the DSC traces of the physical mixtures (Figure ). Interestingly, the Tgs of the physical mixtures and corresponding blends were shifted higher than the inorganic glass Tg by more than 25 °C (Table ). Overall, the strength of the DSC signal at Tg varies according to the mass of the phosphate glass phase.