I'm looking for thermophysical properties of Galden LS 230, a liquid polymer (PFPE) produced by Solvay (https://www.solvay.com/en/markets-and-products/featured-products/Galden.html) at temperatures above 25 °C. Solvay only publishes properties at 25 °C.
I asked them for properties at higher temperatures, with no answer in three weeks. I also couldn't find other free online sources (this is a vapor phase soldering hobby project).
The properties published at 25 °C are:
- boiling point: 230 °C
- density: 1820 kg/m³
- kinematic viscosity: 4.4 cSt = 4.4 × 10-6 m²/s
- vapor pressure: 453.3 Pa
- specific heat: 973 J/kg K
- heat of evaporation at boiling point: 63 kJ/kg
- thermal conductivity: 0.07 W/mK
- coefficient of expansion: 0.0011 1/K
- surface tension: 20 dyne/cm = 0.02 N/m
- average molar weight: 1020 a.m.u
- some others that I don't expect to need for thermodynamics: dielectric strength, dielectric constant, volume resistivity.
Using the ideal gas law to calculate the density of saturated vapor at 1 bar yields about 24.4 kg/m³, which is within the range I found in some other inofficial sources and also in a pretty hard to read plot in a solvay presentation.
the wikipedia page on the temperature dependence of liquid viscosity (https://en.wikipedia.org/wiki/Temperature_dependence_of_liquid_viscosity) lists a number of models that might also apply to Galden, but I'm not sure which ones would yield reasonable results. I'd be glad if someone could shed some light on this. The solvay FAQ (https://www.solvay.com/en/markets-and-products/featured-products/galden-pfpe-faq.html) shows a plot of viscosity vs. temperature for Galden HT 230, which has the same nominal boiling point as the "LS" grade, but has higher tolerances for the molecular weight distribution. The HT grade also starts with the same viscosity at 25 °C as the LS grade. If all else fails, I might use that value.
I'm not sure if it's reasonable to assume specific heat to remain close to constant. My gut feeling is "probably".
Since Galden is a non-metal, I'd expect thermal conductivity to remain more or less constant, or to increase slightly. How large or how significant the change would be, I don't know.
I expect surface tension to decrease with increasing temperature, according to the Eötvös Rule (https://en.wikipedia.org/wiki/E%C3%B6tv%C3%B6s_rule), but to really calculate values I'd need information about the critical point of this polymer (if that even exists, anyway).
A bit more technical background
In vapor phase soldering, a printed circuit board with solder paste and components is immersed into high temperature vapor (such as that of Galden). To create this vapor, the liquid has to be heated and evaporated. This must be done carefully because Galden starts to decompose at 290 to 300 °C. All the properties above are required to calculate a Nusselt number for nucleate boiling, so that I can determine the actual temperature at the heating surface, which will be higher than 230 °C.