Get used to the word “super-hydrophobic”, it’s going to change the way we live our lives. From water repellent fabrics to hulls of the biggest ocean liners in the world, benefit from superhydrophobic and water repellent coatings, alike. Superhydrophobic surfaces are extremely repellent towards water, so that water not only doesn’t cling but simply bounce off without leaving slightest of a trace. Water repellent fabrics are among the most discussed superhydrophobic materials, for obvious reasons. These fabrics are so amazing that you can completely immerse them in water but they do not get wet.
Although scientists use all kind of fancy techniques to fabricate these materials. If you are smart enough you can do just that with the chemicals that you can find at your home. I accidently found this method when I was doing an experiment. It was a pleasant surprise and I’m going to share it with you. Required materials are very easy to find and cheap as well. The hydrophobic solution can be easily used as a water repellent coating for fabric, water repellent spray for shoes (canvas shoes), waterproof fabric spray and tent waterproofing spray. You can even experiment and see what else it can make superhydrophobic. If you are not sure, test it on a small piece of a fabric to see anything goes wrong.
The stuff you need
A silicone sealant (look for RTV or room temperature vulcanizing type, and great if you can find the clear sealant, if you are not sure ask from your local hardware owner)
A bottle of paint thinner or mineral spirit ( any brand of NC thinner would do, just make sure that you haven’t mixed water in to it accidently)
A glass bottle with cap to mix the ingredients and a plastic cup to treat the fabric
Piece of a fabric to treat ( woven or knitted, use cotton for best effects)
Pair of gloves and a mask (mask is optional if you do this outdoors)
How to make the hydrophobic solution
Making hydrophobic solution is quite easy. Here is how.
Get about 50 ml of paint thinner to the bottle
Squeeze out about 5 grams of RTV silicone sealant in to the glass bottle containing thinner ( the amount may depend on the weight and structure of the fabric, but I’ve found that 5 grams usually does the trick, you can experiment further if you want)
Close the cap and shake the bottle hard as you can to mix the two items. Stop when you see a turbid solution without any leftover RTV silicone on the bottom
Pour the solution in to the plastic container and immerse the fabric. You must make sure the fabric is completely covered with the liquid
Leave it for five minutes, and keep under sunlight until completely dry
Test it by pouring some water on it, you will see water rolls off like it does on a lotus leaf indicating superhydrophobicity
How it works
Although seems surprising, nanotechnology is at work here. When I first observed this it took me by surprise and I investigated further with methods that I have in my dispose. An electron microscope image of the treated fibers show that fibers are completely covered with the coating. More interestingly, surface is also covered with uniformly distributed small particles.
To understand the effect further, we need to look at the material composition of the RTV silicone. Silicone sealant is a specially modified type of a silicone polymer which comes under the class of polydimethylsiloxanes. These polymers are known for their very low surface energy, which means that these surfaces are very difficult to wet. RTV silicone sealant also contain a material call hydrophobic fumed silica as a filler which plays another key part in this effect. These small particles, also have very low surface energy and they go and deposit on the surface of the fibers. These small particles create a micro level mountain like structures on the cotton fiber surface. So when a water droplet falls on to the cotton fibers, it would essentially be suspended on the tip of these mountains, maintaining an air gap between the water and the surface of the fiber. This make water droplets to bead and roll off when the fabric is tilted. The same phenomenon, with even more stunning detail, exists on the surface of a lotus leaf.
You can try this homemade water repellent coating and let me know how it went. You can try to make a water repellent fabric, water repellent shoe (canvas shoe) or make your tent hydrophobic with it. Use it as a spray if you have a spraying device. Just make sure you wear masks.
Try this at home!
Thank you for number of encouraging comments you’ve given and i’m very glad to hear the amazing experiences you’ve had with this method. The one that really moved me was this one,
|hey !! it helped me a lot !! thank u soo much !! i got first prize by doing this !!|
and this one,
|Used Dow Corning 785 with white spirit and took the canvas tent out last weekend, it poured down and we stayed nice and dry, thanks for the info and for saving us lots of cash.|
Dow Corning 3138356 732 Clear Multi-Purpose Sealant, 90 mL will give you the best results with basic NC thinner.
See few other DIY nanotechnology activities