Ever wondered why some materials get soaked and wet with water easily while others remain dry or you see beads of water on the surface? Or wondered why you stay dry under the rain when you wear your water-resistant clothing?
I believe you must have noticed during the summer months, beads of moisture forming on leaves early in the morning – that is before sunrise – due to dews. Did you stop to think about why the water didn’t soak into the plants? Or what property of the leaves that makes it possible for the water to form those small balls of moisture and roll of the surface?
I am curious also about the behavior of these materials when placed under wet conditions and decided to investigate. The result is this article.
I hope you have fun reading through the article while also learning about this amazing ability of materials to get wet or remain unperturbed by wet conditions. And also learn how to choose a different material for the right occasion for you.
Hydrophobic or Hydrophilic: What the heck is that?
The term “hydro” refers to water. And it has its root meaning from the Greek word hydr – used to describe something that is wet or water.
The term “philic” also comes from Greek word philia or Philos which connotes friendship or love.
When you combine both “hydro” and “philic” into one word “hydrophilic” you have something describing “water friendship” or “water loving” which means the same thing.
The term “phobic” comes from the Greek word phobos, and it means one who fears or hates.
In the same vein, the combination of “hydro” and “phobic” into one word “hydrophobic” you have a term describing “water fear” or “water frightened”.
You’d noticed I went to a great length to explain what each of the terms means – this is because they are essential terms if you want to understand the fantastic ability of materials to get wet or remain dry under a damp condition.
So one could say then that, hydrophobic materials are those materials that can resist water. This means they repel water away from their surfaces. That’s why you’d notice those beads on leaves and water running off water-resistant coats.
On the other hand is the hydrophilic materials – they are those materials that love water. They attract water and easily dissolve in water. So when you find yourself all wet and soggy, know that the clothing you are putting on is made of a water-loving material.
How do you identify hydrophobic or hydrophilic material?
You just check the labels right? But keep in mind that those labels might not 100% reflect the reality.
The most common labels are waterproof, water resistant, water repellant or weatherproof.
The question is, how do the manufacturers set those labels? Of course, they did a series of tests on the material.
The main test to determine how a material would behave under rough conditions is called the contact angle measure. Which is simply measuring the angle of the interface a liquid converges with a solid surface – in this case, the material. It is estimated using a contact angle meter.
Difference between hydrophobic and hydrophilic
Well, the underlying property that differentiates a material into hydrophobic or hydrophilic is its behavior to water. Take, for instance: salt can be said to be hydrophilic since they attract moisture when exposed to the atmosphere.
Wax or oil-based products can also be thought of as being hydrophobic since they repel water.
Hydrophilic and Hydrophobic Examples
There are several examples. Here are some of the common ones:
For hydrophilic you have water, wool, hair, milk, cellulose ( the primary ingredient used in paper, wood, and cotton) and the hydrophilic end of the soap. All of these love water very much, that’s why they’d dissolve entirely or turn soggy in water.
For hydrophobic you have waxes, fatty acids, fats and the hydrophobic end of the soap. All of these hate water and hardly mix with water.
Many tools and technical equipment are treated with coatings which makes them suitable for use in many industries.
For instance, the process of coating is applied to many surfaces such as metals, technical tools, medical tools, glass, and ceramics.
Technology allows expanding product properties. Take superglue, for example. There is waterproof superglue, which became like so due to the coating.
The water-repelling property of hydrophobic makes it desirable in the manufacture of medical and surgical tools since they make it difficult for bacteria to inhabit these tools.
They are also used in the textile industry to make water-repellent cotton and clothing.
Advantages of Hydrophobic and hydrophilic
There are many benefits derivable from either treating a substance for hydrophobic or hydrophilic and some of them include:
- Hydrophobic coatings enhance the durability of materials – for example, treated glass has been shown to last longer than ordinary bare glass.
- It boosts the corrosion-resistance ability of materials such as metals – with moisture repelling surfaces, metals can resist corrosion which is caused by a reaction between water and the metal.
- When used on medical tools – they help prevent colonization of the technical tools by bacteria.
- The hydrophobic coating is used in the manufacture of smartphone parts to improve their durability and pass certain stress tests, like the MIL-STD-810G test.
- The hydrophobic coating is applied in the instrumentation and precision industry to reduce moisture-related product loss, reduce downtime while enhancing moisture dry-down.
The material is said to be hydrophobic when it repels water while it is hydrophilic when it attracts water. The water-resisting ability of materials can be improved through coating; this has made it possible to develop materials such as water-repelling cotton, hydrophobic polyester, hydrophobic steels, glasses and so much more to boost their durability.