This fact sheets
covers the antistatic advantages
of ZQ Merino
made from
MERINO FIBRE
zqmerino.com
Anti-static
Introduction
Table 1. Triboelectric series of various materials
Column 1 Insulator name.
Column 2 Charge affinity in nC/J (nano ampsec/wattsec of friction).
Column. 3: Charge acquired if rubbed with metal
(W=weak, N=normal, or consistent with the affinity).
Static electricity is the accumulation of electrical charges on the
surface of a material, usually an insulator or non-conductor of
electricity. It is called “static” because there is no current flowing, as
there is in alternating current (AC) or direct current (DC) electricity.
Typically, two materials are involved in static electricity, with one
having an excess of electrons or negative (−) charges on its surface
and the other material having an excess of positive (+) electrical
charges. Atoms near the surface of a material that have lost one or
more electrons will have a positive (+) electrical charge.
Static electricity arises when two dissimilar materials rub together,
creating an electrical charge and is the imbalance of positive and
negative charges. During this rubbing, friction causes positive
charges to accumulate on one surface, and negative charges on the
other. When the materials are good conductors of electricity, the
charges are readily dissipated away. However, in instances where
they don’t, an unpleasant, and potentially dangerous, electrical
discharge may occur resulting in static electric shock to people.
There are a number of factors that can influence the potential for
static electricity generation in textiles such as:
• Low humidity caused by seasonality, country and/or internal air conditioning
• Friction causes by the rubbing contact between two surfaces
• Low material moisture content that occurs in synthetic fibres such as nylon, polyester and acrylic
Static electricity is formed much better when the air is dry or the
humidity is low. When the air is humid, water molecules can collect
on the surface of various materials. This can prevent the build up of
electrical charges. The reason has to do with the shape of the water
molecule and its own electrical forces.
To understand this further, various materials can be ranked
according to their tendency to gain or lose electrons. This is known as
the triboelectric series. It usually lists materials in order of decreasing
tendency to charge positively (lose electrons), and increasing
tendency to charge negatively (gain electrons). Somewhere in the
middle of the list are materials that do not show strong tendency to
behave either way (Table 1).
Polyurethane foam
Sorbothane
Box sealing tape (BOPP)
Hair, oily skin
Solid polyurethane, filled
Magnesium fluoride (MgF2)
Nylon, dry skin
Machine oil
Nylatron (nylon filled with MoS2)
Glass (soda)
Paper (uncoated copy)
Wood (pine)
GE brand Silicone II (hardens in air)
Cotton
Nitrile rubber
Wool
Polycarbonate
ABS
Acrylic (polymethyl methacrylate)
Epoxy (circuit board)
Styrene-butadiene rubber (SBR, Buna S)
Solvent-based spray paints
PET (mylar) cloth
PET (mylar) solid
EVA rubber for gaskets, filled
Gum rubber
Hot melt glue
Polystyrene
Polyimide
Silicones (air harden & thermoset, but not GE)
Vinyl: flexible (clear tubing)
Carton-sealing tape (BOPP), sanded down
Olefins (alkenes): LDPE, HDPE, PP
Cellulose nitrate
Office tape backing
UHMWPE
Neoprene (polychloroprene, not SBR)
PVC (rigid vinyl)
Latex (natural) rubber
Viton, filled
Epichlorohydrin rubber, filled
Santoprene rubber
Hypalon rubber, filled
Butyl rubber, filled
EDPM rubber, filled
Teflon
+60+N
+58-W
+55+W
+45+N
+40+N
+35+N
+30+N
+29+N
+28+N
+25+N
+10-W
+7-W
+6+N
+5+N
+3-W
0
-W
-5
-W
-5
-N
-10-N
-32-N
-35-N
-38-N
-40-W
-40+W
-55-N
-60-N
-62-N
-70-N
-70-N
-72-N
-75-N
-85-N
-90-N
-93-N
-95-N
-95-N
-98-N
-100-N
-105-N
-117-N
-118-N
-120-N
-130-N
-135-N
-140-N
-190-N
Anti-static performance or good electrical conductivity is an
important criterion in apparel, interior and technical textiles for a
number of reasons:
Starting Voltage
80
Residual Voltage
Why Antistatic
performance is Important
100
60
40
20
• Preventing static cling of garments for comfort
• Safety with respect to prevention of static charges
• Prevention of electrical interference with the operation of electronic equipment
For both fashion and technical apparel systems, good anti-static
performance is a key criterion for wearer comfort, personal safety
and equipment safety. This has particular important ramifications
for first response and professional risk takers who rely on garment
systems that protect them from internal and external dangers.
ElectroStatic Discharge or ESD awareness is particularly important
for anyone associated with electronics. As integrated circuits
become more compact, and feature sizes shrink, active devices as
well as some passive devices are becoming more prone to damage
by the levels of static that exist. To combat its effects, industry is
investing heavily in anti-static interior systems such as flooring and
interior textiles. Within this sphere of anti-static protection, we can
also include anti-static garment systems to ensure that people are
not carrying and transmitting static and provide protection to both
the wearer and electronically sensitive equipment.
Previous
options
(Limitations of other fibres)
Most people, having experienced the nuisance of static cling or
felt the zap of a shock, assume that static is something that can
be seen and felt. Yet it takes 3500 Volts of static electricity for
human beings to perceive the effects of a static discharge. To put
that number in perspective, sensitive electronic components can
be damaged or destroyed by a discharge of fewer than 25 Volts.
Random static discharge and field effects caused by such common
events as sliding a chair, rising from a seated position or walking
across a floor can wreak havoc on computers and sophisticated
telephone systems.
Figure 1 demonstrates the ability of various materials to dissipate
static charge. The lesser this ability, the greater the potential for
static electricity to discharge through a user’s body, resulting in an
electric shock.
0
Wool
Nylon
Acrylic
Polyester
Figure 1. Static charge leakage after 15 minutes at 15% RH, from fabric
manufactured from different fibres. Source (Leeder, 1984)
Merino Wool Solution
Merino wool has the ability to absorb up to 35% of its own weight
in water with this water vapour absorption being an intrinsic fibre
quality and hence independent of fabric structure (Massie and
Mehta, 1980) with hydroscopic fibres having the ability to absorb,
transport and desorb moisture from/to the vapour phase (Benisek
et al, 1987) as opposed to non-hydroscopic fibres. Hydroscopic
fibres also have the ability to store moisture within their fibre
structure in reasonably significant quantities that can then act as
a reservoir for buffering humidity variations of the surrounding
environment.
Natural fibres such as wool are able to actively absorb and retain
moisture from both the internal (skin) and external environment,
with their absorption properties being much greater than most
synthetic fibres (Figure 2). This confers natural fibres the ability to
conduct charge away relatively efficiently in comparison to nonhydroscopic synthetic fibres.
contact
18
16
% moisture by fibre weight
14
The New Zealand Merino Company Ltd
12
Level 2
114 Wrights Road
PO Box 25-160
Christchurch
New Zealand
10
8
6
4
Ph +64 27 479 2594
Fax +64 3 335 0912
2
0
Wool
Nylon
Polyester
Acrylic
Polypropylene
Figure 2. Moisture absorbance of wool and synthetic fibres (Collie and
Johnson, 1998)
Summary
Because of its unique moisture retention properties, wool is less
prone to build up of static electric charge than synthetic fibre
Use of wool textiles provides a safer and more comfortable wool
environment than synthetic products, particularly in applications
where static electricity is of particular concern – aircraft carpets,
buildings with sensitive electronic equipment, fuel transfer facilities,
etc.
It is also possible to further improve static resistance by the
incorporation of conductive fibres or the use of specialised surface
treatments
References
l Benisek., L, Harnett., P.R. and Palin., M.J., 1987, The influence of
fibre and fabric type on thermophysiological comfort, Melliand
Textilberichte 68, pp. 878-888.
Collie, S.R. and Johnson, N.A.G., 1998, The benefits of wearing wool
rather than man-made fibre garments. Lincoln, Christchurch, New
Zealand, WRONZ.
Leeder, J., 1984, Wool – Nature’s wonder fibre, Australasian
Textiless Publishers
Massie, D.S. and Mehta, P.N., 1980. Moisture transport properties
of underwear fabrics. Ilkley, Yorkshire, UK, International Wool
Secretariat, Technical Centre.