Determination and modeling of contact angle of Canola oil and olive oil on a PTFE surface at elevated temperatures using air or steam as surrounding media

- A decreased CAs of each system was observed as temperature increased.
- Surrounded media had no effect on CAs of Canola and olive oils.
- Girifalco-Good-Fowkes-Young equation better predicted CAs of Canola oil.
- Olive oil data was better fitted by GGFY modified with Eötvös equation.
- CA and interfacial tension of oil-air systems correlated linearly.

Contact angles (CAs) of unused Canola and olive oils on polytetrafluoroethylene (PTFE) were measured, and the effect of oil type, surrounding media, and temperature evaluated. CAs were compared to values predicted by Girifalco-Good-Fowkes-Young (GGFY) equation, and GGFY combined with the Eötvös equation (GGFY-E). Finally, a relationship between the CA and interfacial tension for each oil type was obtained. CAs were measured by the sessile drop method (ramé-hart instrument co.). For oil-air systems, measurements were performed at 23 ± 1 °C, 40 °C, and then every 20 °C until reaching the oils' smoke point (olive oil: 180 °C, Canola oil: 200 °C). The same procedure was followed for oil-steam systems with first and second temperatures of 110 and 120 °C, respectively. Temperature and oil type had a significant effect (P < 0.05) on CAs, while no significant effect of surrounding media was observed. CAs decreased linearly as temperature increased (approximately 0.2°/°C). Error (E%) values were less than 10% for the majority of Canola oil systems and olive oil-air predicted CAs. Using Zisman plots, PTFE's surface tension estimates were determined using Canola and olive oil air systems (16.0 and 18.2 mN/m respectively); both systems showed a linear correlation (r2 = 0.99) between interfacial tension and CA.