by Tash Hughes of
hematite, minerals in drilling fluids, some membranes,
glucose/sugar and many other substances are known as
hydrophilic. In comparison, oils, proteins, colloids,
greases and clays are hydrophobic.
What does this
mean? Does it really matter to non-scientists?
water loving. Such compounds have an affinity to water
and are usually charged or have polar side groups to
their structure that will attract water.
water hating. These compounds are repelled by water and
are usually neutral (no charge.)
In more depth,
these terms have much to do with the structure of water
itself. Water consists of two hydrogen atoms joined to
one oxygen atom, all in a triangular pattern. The oxygen
is negatively charged whilst the hydrogen end is
positively charged. Thus, water molecules are actually
attracted to each other and form hydrogen bonds.
Water Molecule Water
are very important to living things as these bonds allow
the strands of DNA to hold together, proteins to form
and water to behave as it does.
Adding drops of
oil or particles of clay or grease to a container of
water will not result in a solution as adding sugar
particles would. In fact, there will be a ball of oil or
clay formed; forming a ball reduces the overall amount
of surface area exposed to the water. Although it may
appear that the oil is gathering into a drop, the
reality is that water is highly attracted to other water
molecules and ignores the hydrophobic molecules; the oil
molecules are then squeezed together to allow the water
to form more hydrogen bonds. Non-polar molecules are
neither attracted to nor repelled by each other so the
pull between water molecules is much stronger.
molecules attract the water molecules and they blend
together, making water a very good solvent in many
properties of certain substances can be of great use in
industry, especially in terms of keeping essential areas
For instance, a
hydrophilic membrane will not be fouled with oil, grease
or other hydrophobic substances. The membrane is highly
attractive to water so the water molecules will push
away other molecules in order to gain access to the
membrane. Once formed, hydrogen bonds are quite stable
and reluctant to break apart. This keeps contaminants
away from the membrane so it remains clean and
functioning for longer.
coatings or materials become wet very easily, and
maintain the wetness for longer than a hydrophobic
equivalent would. Thus, using hydrophilic coatings or
materials for tubes and hoses eliminates the need for
additional lubricants. This is of particular usefulness
where sterility or cross contamination issues may arise.
coatings of rubber can increase the power of plugs and
o-rings, etc to stop water escaping to cause leaks. The
water is attracted to the coating and less available for
seeping through gaps. This is the basis for waterstop
and sealant products.
On the other
hand, hydrophilic grouts are less useful than
hydrophobic ones in wet areas. Hydrophobic grouts absorb
only enough water to bind the compounds; it is stable
once in use. Hydrophilic grouts are prone to lose and
attract water as conditions vary and thus contract and
expand. This movement can be destructive and absorption
of water may add contaminants to the grout; hydrophilic
grouts generally donít last as long as their hydrophobic
counterparts. Hydrophilic grouts are great for stopping
leaks, but not for filling in large voids.
Other uses of
hydrophilic substances are catheters, contact lens
cleaners, gums in frozen dough, waterproofing outside
materials (e.g. horse blankets,) surface treatment of wet
wipes and nappies, wound dressings and scientific
testing for proteins and the like.
has a science degree and experience in major engineering
companies. As well as having written Expressions of
Interest, Tash has written analytical and procedural
documents. All technical and business writing needs are
met by www.wordconstructions.com.au