Backpack Material Definition of Terms
The definition of "Warp" is the threads attached lengthwise in
a loom to be crossed by the weft.
The definition of "Weft" is the horizontal threads woven across
a warp to make a fabric, also known as Woof.
The definition of "Denier" is a measure of fibre fineness: a
unit of fineness of silk and some artificial fibres, such as Nylon,
equal to one gram per 9,000 metres of yarn. The strict definition
of denier is the weight in grams of 9,000 meters of the yarn. For
example, 9,000 meters of a 450 Denier thread weighs 450 grams. Denier
is a direct numbering system in which the lower numbers represent
the finer sizes and the higher numbers the coarser sizes, for example
a 450 denier yarn is twice as fine as 900 denier yarn. Material
Weight or Fibre Thickness is an important consideration in the materials
utilized for backpack construction. It is obvious, that the higher
the Denier in a particular material the higher the strength of the
fabric, and the higher the weight as well. Most of the higher quality
backpacks identify the denier of the material on promotional information.
Does this mean a higher Denier is better? Not necessarily, this
would depend on the material, for instance 600D Polyester Material
would not be as strong as 420D Nylon Material.
There is an additional factor you should be aware of - tenacity.
Tenacity is a measure of the fabric's ability to resist additional
tearing once a tear has started. Nylon is available in two types
of tenacity. Type 6 Nylon commonly used in backpacks and classified
as low tenacity, or lower strength nylon (tenacity of 3.0 to 6.0
grams per Denier), or Type 66 Nylon considered high tenacity and
is much stronger (tenacity of 6.0 to 9.5 grams per Denier). Can
you tell the difference? Unfortunately, there is no way to tell
the difference without testing the material in a laboratory.
The definition of "Polyurethane" is any group of thermoplastic
polymers used in coatings, insulation, adhesives, foams and fibres.
The term "polyurethane elastomers" includes such diverse products
as thermoplastic polyurethane, cast elastomers and Reaction Injection
Moulded (RIM) products. Thermoplastic Polyurethane Major Applications
include, Architectural Glass Lamination, Auto-Body Side Moulding,
Automotive Lumbar Supports, Caster Wheels, Cattle Tags, Constant
Velocity Boots (Automotive), Drive Belts, Film and Sheet, Fire Hose
Liner, Flexible Tubing, Food Processing Equipment, Footwear - sport
shoe soles, Hydraulic Hoses, Hydraulic Seals ,Inflatable Rafts,
In-Line Skates, Magnetic Media, Medical Tubing / (+IV) Biomedical
Apparatus, Mining Screens, Sporting Goods, Swim Fins and Goggles,
Coated Fabrics, Wire and Cable Coatings.
Tensile Strength Test ATSM D5034
The definition of "Tensile" relates to tension, capable of being
drawn out, stretched or pulled out of shape. Testing textile tensile
material properties applies to yarns, twisted threads and cords,
flat structured specimens such as fleece, knitwear and fabrics.
Common tests include seam slippage resistance, tear propagation,
needle tear out resistance, and grab method.
Breaking Strength and Elongation Test ASTM D5034
The grab and modified grab test procedures determine breaking
strength and elongation of wet or dry textile fabric samples. A
grab test is really a tensile test where the centre of the specimen
width is gripped in the clamps. The modified grab test is similar
- lateral slits are made mid-length of the specimen severing all
yarns bordering that portion of the specimen held between the two
clamps. The grab test applies to woven, non-woven, and felted fabrics,
while the modified grab test .is best used for woven fabrics. The
test is not recommended for glass fabrics, knitted fabrics or high
stretch fabrics. A four-inch wide material specimen must be mounted
in the centre of upper and lower grips and force applied until the
specimen breaks. There are two types of specimens used, grab and
modified grab. For the Grab Test the front grip face must measure
1 inch by 1 or 2 inches, the longer dimension along the vertical.
The grab test determines the effective strength of the fabric: the
strength of the yarns in a specified width with fabric assistance
from the adjacent yarns. It does not reflect the strength of the
yarns actually gripped between clamps. For the Modified Grab Test
the front grip face must be at least 1 inch by 2 inches, with the
longer dimension along the vertical. The modified grab test is applicable
to the determination of the breaking force of fabrics with constructions
in which the application of tensile stress on ravel strip specimens
produces further unravelling. It is particularly applicable to high-strength
Tear Strength Test ASTM D1424
The definition of "Tear" in these tests is to make a hole in
the fabric. This test method covers the determination of the force
required to propagate a single-rip tear starting from a cut in a
fabric and using a falling-pendulum type (Elmendorf) apparatus.
This method applies to most fabrics including woven, layered
blankets, napped pile, blanket, and air bag fabrics, and provided
the fabric does not tear in the direction crosswise to the direction
of the force application during the www. The fabrics may be untreated,
heavily sized, coated, resin-treated, or otherwise treated. Instructions
are provided for specimens with, or without, wetting.
Hydrostatic Pressure Test AATCC27
AATCC 127 Hydrostatic Pressure Test measures the resistance of
a fabric to the penetration of water under hydrostatic pressure.
It is applicable to all types of fabrics, including those treated
with a water resistant or water repellent finish. Water resistance
depends on the repellency of the fibers and yarns, as well as the
fabric construction. The results obtained by this method may not
be the same as the results obtained by the AATCC methods for resistance
to rain or water spray.
Colour Fastness to Daylight ISO 105-B01:2014
Specifies a method intended for determining the resistance of
the colour of textiles of all kinds and in all forms to the action