Hydrophilic vs. Hydrophobic

[peterjaw]

Hi captains,
While considering the waxes, sealants, cleaners ....I found this video from Japan
https://www.youtube.com/watch?v=RdcPGS-u21Y

On the right side, the surface is coated with hydrophobic sealant, and the left side is with hydrophilic sealant.
The tester put a drop of cooking oil on both side and started to spread water for simulating the rain drops.

On ther other hand, while everybody talks about "beading" effect, it reminds me that with countless of water beads
on the gel coat, they become Convex Lenses under the sun light. I don't mean the gel coat will be "burned" but the surface
could be easily damaged.

With these 2 thinkings above, I start to think if the beading effect from either wax or sealant is suitable for boat? Should
I use hydrophilic products for the gel coat? I can wash my car whenever/wherever I want to, but not my boat.

Does anybody think about this? Or I am just over reacting?

 

[Marine Reflections]

I think about it, too much!

The main concern is the TDS / deposits in the water that are left on a surface once 'the bead' has evaporated, leaving behind a scaly water spot.
You can get around this by using polished water or drying the surfaces down after a wash (if you can reach them).

Hydrophilic waxes and sealants are not the norm, most would want a surface to reject as they are so much easier to wash and dry. Think absorbing drying cloth and rejecting surface.
But, as you quite rightly ponder, would you be better off without those beads if the same level of UV inhibiting was available.

It would be a trade off and would depend on the circumstances. Having the water self dry by sheeting off of the surface would be good, but also it could mean that the surface is accepting guests rather than rejecting them.

I'd love to have a lab and test the pro's and cons of each, but there are many variables to study.

Things start to get interesting when the contact angle (how a droplet sits on a surface) is engineered to be greater than 150º deeming it 'Super-hydrophobic'. Water doesn't splat, it bounces.

That has kind of been the carrot on a stick in the industry for many decades, never wash your car again etc etc, things are getting closer to 150º but close isn't quite the same.

Tony

 

[Marine Reflections]

 

[peterjaw]

Hi Tony,
I agree that it all depends on the circumstances. The rain drops are not such a pure water shown in the vedio after all. Other than
the rain drops, there are still dew water, bird drops, moisture in the air ... etc.

 

[Marine Reflections]

Hi Tony,
I agree that it all depends on the circumstances. The rain drops are not such a pure water shown in the vedio after all. Other than
the rain drops, there are still dew water, bird drops, moisture in the air ... etc.

Not sure what to make of that.

Do you mean that the water in the video wasn't pure water?
At first, the water is just coloured so we can see what is happening under the hydrophobic properties of the surface, in the second part they show it with added microscopic ferrous particles added.

 

[peterjaw]

...

Do you mean that the water in the video wasn't pure water? ...

No, I meant that in real world the water from the sky is never pure. After the water evaporate there must be some residue on the hydrophobic surface even the water was beaded.

 

[Marine Reflections]

No, I meant that in real world the water from the sky is never pure. After the water evaporate there must be some residue on the hydrophobic surface even the water was beaded.

Ah, I see.

You're right there is.

A different animal to that from within the pontoon water. Diesel, salt, aviation fuel, dust and general fall out.
With a hydrophobic surface though there's a good chance this will self clean to a degree (depending on the current contact angle of interaction) whereas the deposits from a pontoon hose (scale) will grab and bond quickly and is very difficult for the surface to rid itself of it.