pmcimagazine.com
UNDERSTANDING
TECHNICAL FABRICS
Pictures Courtesy of UF PRO and Project GECKO
When we review clothing products we talk a lot about their performance and technicality; is this
all just clever “marketeering” or is there some genuine basis in cold hard fact and science? This
month we get down to basics as ‘Beardy’ Bill Thomas debunks some fabric myths.
So, what are we really talking about when we use the
phrase “technical fabrics”? Basically we are looking at fabric
technologies with a very specific end use in mind that
balance the three key areas of waterproofness (read general
weatherproofness), breathability and durability.
I’ll use the well-known GORE-TEX products as an example
here as they really are a market leader and Gore are continually
developing new, ground breaking fabric technologies to meet
the needs of their Brand partners; you only have to look in our
“Gear on Test” section each month to see examples of this!
Breaking it down W L Gore and Associates use two main
forms of construction in their garments, Two and Three Layer
(although there are other specific constructions in their massive
portfolio). Two Layer construction essentially means that
their ePTFE (expanded Polytetrafluoroethylene) membrane is
attached directly to an outer face fabric with a loose lining;
Three Layer construction means that the face fabric, membrane
and inner lining fabric are all bonded together. Many prefer the
Three Layer construction as it’s is easier to get on and off as a
loose mesh liner can sometimes snag on gear.
Different seam tapes (to ensure seams are 100% waterproof
and do not let water in through stitch holes) are used in the
different constructions; Two Layer seam sealing tape is applied
to the GORE-TEX membrane directly, whilst in Three Layer the
sealing takes place over the inner lining fabric. Seam sealing is
an art form in itself!
24
Keeping the Weather at Bay
Let’s take a look first at waterproofness and how technical
fabrics achieve this. The GORE-TEX membrane is the heart of all
their excellent products. It contains over 9 billion microscopic
pores per square inch. These pores are 20,000 times smaller
than a water droplet, but 700 times larger than a water vapor
molecule, which makes the membrane durably waterproof,
while allowing perspiration (moisture as a vapour) to escape
from the inside. An oleophobic, or oil-hating, substance is
integrated into the membrane, preventing the penetration of
body oils, insect repellents and the like.
Simply put imagine an elephant, a mousehole and an
ant! The mousehole is the microscopic pore in the membrane,
the ant is a water vapour molecule and the elephant a water
droplet; it’s pretty easy to see that although the ant can escape
through the mousehole with ease, there is NO WAY that you
could push the elephant through it without breaking the wall
down! In garment terms that would mean tearing a ruddy great
hole in your jacket!
So, water cannot penetrate the membrane, or can it? Logic
dictates that eventually any fabric technology can be pushed
to a point of failure and this can be tested; in this case the
applicable British Standard is ‘BS EN 343:2003 Protective
Clothing. Protection against Rain’.
The Standard describes the tests that should be carried out
to ascertain a garment’s level of waterproofness and sets out
the performance standards that items carrying this description
should meet. A Test House would carry out these tests in order