Backpack Construction
Definition of Terms
Warp
The definition of "Warp" is the threads attached lengthwise in
a loom to be crossed by the weft.
Weft
The definition of "Weft" is the horizontal threads woven across
a warp to make a fabric, also known as Woof.
Polyurethane
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. Further technical information
is available at:
http://www.polyurethane.org/
Tensile Strength
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 & Elongation by the Grab Test per 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.
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.
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 fabrics.
A four-inch wide 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.
Grab test: the front grip face must measure 1 inch by 1 or 2
inches, the longer dimension along the vertical.
Modified grab test: the front grip face must be at least 1 inch
by 2 inches, with the longer dimension along the vertical.
Tear Strength
The definition of "Tear" in these tests is to make a hole in the
fabric.Tear Strength of Fabrics by Falling-Pendulum Type (Elmendorf)
Apparatus as per ASTM D1424
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 test method applies to most fabrics including woven, layered
blankets, napped pile, blanket, and air bag fabrics, provided the
fabric does not tear in the direction crosswise to the direction
of the force application during the test. The fabrics may be untreated,
heavily sized, coated, resin-treated, or otherwise treated. Instructions
are provided for testing specimens with, or without, wetting.
Further technical information is available at:
ASTM International
Standards Worldwide
Denier
The definition of "Denier" is a measure of fibre fineness in
silk and some artificial fibres, such as Nylon, equal to one gram
per 9,000 metres of yarn. Denier is a measurement of fibre weight
used to describe the thickness of a thread or yarn. The higher the
denier, the larger the fibres and the stronger the material.
Information on Thermoset Polymers and Thermoplastic Polymers
MatWeb - This page allows you to quickly access all of
the polymers/plastics, metals, and ceramics/other engineering materials
in the MatWeb material property database.
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