4.1 Thermal conductivity and interfacial property of PTFE and PES
membrane.
PTFE and PES both have good mechanical stability and outstanding
chemical
resistance50-52. In
addition, they both exhibit excellent reliability for rapid temperature
floatation and for long-term usage as reported53. The measured
thermal conductivity of PTFE and PES hollow fiber membranes are shown in
Figure 5a. PTFE membrane possesses higher thermal conductivity
(0.1712±0.025 W/m·K, average value in the measured temperature range)
than that of PES membrane (0.1246±0.013 W/m·K). And the thermal
conductivity of PTFE membrane increases from 0.1464 W/(m·K) to 0.1959
W/(m·K) when the temperature increases from 10 ℃ to 80 ℃; while, the
thermal conductivity of PES membrane is relatively stable when the
temperature increases. Generally, the thermal conductivity of the
membrane is influenced by the nature of the membrane material (solid
phase) and the pores distributed of in the membrane (gas phase). The
large void structure in the membrane will be a convective heat transfer
heat transfer and a radiation heat transfer
mode54,55.
The XRD patterns of the two membranes in Figure 5b indicates that the
PTFE membrane possesses a semi-crystalline structure, whose thermal
conductivity changes greatly with temperature56-58. While, PES
membrane has an amorphous polymer, which the glass transition
temperature is as high as 230 °C51. Below this
temperature, the temperature has no significant impact on PES membrane’s
thermal conductivity. In the temperature operation range of 5 to 40 °C
during MACC, the two hollow fiber membranes both have a stable thermal
conductivity, which is important for the nucleation control at a wide
temperature operation window.