# Smart Firefighters PPE: Impact of Phase Change Materials
## 2 Materials and Methods
### Evaluation of PCM Thermal Performance--Preliminary Tests  
This study analyzed three different encapsulated phase change materials with varying intrinsic properties, such as melting point and heat storage capacities, Table 1. Within the under-study phase change materials, PCM 1 and PCM 2 possess similar heat-storage capacities but different melting points, and both are in powder form. Regarding PCM 3, it presents a lower melting point and heat storage capacity and is encapsulated as a granulate.  
Six grams of these materials were integrated into a membrane pouch (7 \(\times\) 7 cm) made from a membrane of expanded polytetrafluoroethylene laminated with an aramid non-woven thermal barrier to evaluate the PCM thermal performance. This pouch was placed in a multilayer system composed of an outer shell fabric, a 3D knit fabric, an outer shell/cork matrix (to insert the pouch), and an outer shell layer, which simulates the architecture of the developed vest. Subsequently, these ensembles were tested in an experimental set-up built for simulating convective heat exposure, Figure 1e (procedure adapted from ISO 6942:2002 [20]). The sample was placed in a frame (i.e., 6 \(\times\) 6 cm; Figure 1b) and exposed for 60 min to a heat source (i.e., 1500 W heat gun, Esco tornado 1500; Figure 1a). The cooling process was then studied by turning the heat source off. A thermocouple was placed at the center of the sample, on the surface not exposed to the heat source (Figure 1c), to monitor the temperature evolution during heating and cooling periods.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**PCM** & **Commercial Name** & \begin{tabular}{c} **Melting/Freezing** \\ **Temperature Range,**\({}^{\circ}\)**C** \\ \end{tabular} & \begin{tabular}{c} **Heat Storage** \\ **Capacity, kJ/kg** \\ \end{tabular} & **Form** & **Composition** \\ \hline PCM & \begin{tabular}{c} RUBITHERM\({}^{\circledR}\) \\ PX82 \\ \end{tabular} & 77-85/85-77 & 105 & \begin{tabular}{c} Microencapsulated \\ (powder) \\ \end{tabular} & \begin{tabular}{c} -60\% organic \\ material (PCM) \\ 40\% inorganic material \\ (hydrophilic silica) \\ \end{tabular} \\ PCM & \begin{tabular}{c} RUBITHERM\({}^{\circledR}\) \\ PX52 \\ \end{tabular} & 49-53/52-48 & 100 & \begin{tabular}{c} Microencapsulated \\ (powder) \\ \end{tabular} & \begin{tabular}{c} material (PCM) \\ 40\% inorganic material \\ (hydrophilic silica) \\ \end{tabular} \\ PCM & \begin{tabular}{c} RUBITHERM\({}^{\circledR}\) \\ GR42 \\ \end{tabular} & 38-43/43-37 & 55 & \
\begin{tabular}{c} Encapsulated \\ (granulate) \\ \end{tabular} &
\begin{tabular}{c} material (PCM) \\ 70\% inorganic material (natural \\ porous mineral particle) \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table}
Table 1: Properties and characteristics of the PCMs.  
Figure 1: Experimental set-up used for the thermal performance assessment of PCM pouches: (**a**) heat source (at 15 cm from the sample); (**b**) sample frame (6 \(\times\) 6 cm metal frame); (**c**) thermocouple (type K) location; (**d**) temperature acquisition device (Fluke 51 II); (**e**) entire set-up.