# Thermal Characterization of Phase Change Materials by Differential Scanning Calorimetry: A Review
## 4 PCM Properties Achieved by DSC
### Transition Temperatures
[8], who were not able to detect solid-solid transition of paraffin when measuring with high scanning rates. [PERSON] et al. [62] considered three paraffin-based PCMs and one bio-based PCM with different heating rates and masses. They chose the maximum peak of the Cp curve as a melting temperature and observed a shift of the melting point to lower temperatures by decreasing the heating rate. This study is among the few ones based on the IEA (International Energy Agency) protocol for DSC measurements. Figure 10a,b displays an example of the influence of the mass sample and heating rate on the transition temperature and heat flow curve of adipic acid. The IEA method helps to determine the appropriate heating rate, which minimizes the heating rate effect on the DSC results, and finally, represents the enthalpy curve versus temperature for each PCM. [PERSON] et al. [63] performed a combined experimental and theoretical analysis of the heat transfer characteristics of a PCM inside an emulsion. They considered three PCMs, namely, hexadecane (T\({}_{\text{m}}\) = 18.0 \({}^{\circ}\)C), heptadecane (T\({}_{\text{m}}\) = 21.8 \({}^{\circ}\)C), and octadecane (T\({}_{\text{m}}\) = 28 \({}^{\circ}\)C), all mixed in an emulsifying medium. In their physical model, some parameters were measured experimentally, such as heat capacity and thermal conductivity, and several heat exchange coefficients were found by a genetic algorithm. The liquid fraction of the PCM sample could be deduced at any time, leading to the determination of the transition temperatures. The authors concluded that the peak temperature is only the plate temperature when the energy exchange is maximum and it does not highlight experimentally the end of transition. On the contrary, according to the maximum value of liquid fraction (one by convention), the end of transition could be found more accurately. Furthermore, they quantified the influence of the heating rate both numerically and experimentally and concluded that by increasing the heating rate, the thermal gradients inside the DSC cell increase, so the peak temperature shifts to a higher value and the melting range becomes broader. They also showed that in the case of a mixture of PCMs, high heating rates hide essential information about the kinetics of melting. [PERSON] et al. [64] proposed a new methodology to determine the melting range of a PCM with a focus on finding the actual endset temperature of melting, namely, the partially melted DSC measurement. They heated the sample from a starting temperature below the melting point to the maximum heating temperature according to the melting range of the PCM. For RT 27, the heating started from 20 \({}^{\circ}\)C to a range between 25 \({}^{\circ}\)C and 32 \({}^{\circ}\)C, with a temperature interval of 0.5 \({}^{\circ}\)C. By calculating the enthalpy of melting and solidification for each ending temperatures and considering the PCM latent heat, they determined a temperature in which PCM could adsorb and release all of its latent heat. The endset temperature was found to be independent of the heating rate for this method. However, applying this method for PCMs with supercooling effect and the DSC without cooling accessories would be more challenging. According to [PERSON] et al. [64], the actual ending temperature determined by partially melted DSC measurement is almost the same as the temperature achieved by low heating rate measurements. The summary of all these works concerning the transition temperature of PCMs by DSC method can be seen in Table 6. The DSC calibration is an important step toward reliable data. Regarding the temperature calibration, multipoint calibration, including a calibrant with a melting point close to that of the sample, is recommended [39; 54]. The same conditions for both the sample measurement and the regular calibration should be imposed. Unfortunately, in PCM studies, the calibration procedure is not generally mentioned [54]. Furthermore, as stated by [PERSON] et al.