Test 2 Flashcards
What fiber is best suited for parachute rope?
Nylon
Which manufactured fibers are stiffness according to inital modulus?
olefin and polyester
which natural fiber has the greatest ultimate strain?
wool
which natural fiber has the greatest inital modulus (Stiffness)?
flax
the elastic stiffness of a fiber is determined from what parameters?
yield stress and yield strain
Work of Rupture describes what important characterisitcs of fiber
the total work absorbed by a fiber before it breaks
Resilience is a measure of what?
a measure of recoverable work and the ability of a fiber to return to its orginial shape
When a fiber ties into a knot..?
the fiber becomes weaker and the knot acts to increase the stress on the fiber
standard laboratatory conditions for the mechanical testing is
65 +/- 2% relative humidity and 70+/- 2 degrees fahrenheight
the yield point refers to…?
found by Merediths method for viscoelastic materials and the point where elastic deformation turns to plastic deformation.
If you are a fisherman do you want your clothes to be hydrophobic or hydrophilic?
hydrophobic
Is wool hydrophobic or hydrophilic?
hydrophilic
which fiber has the lowest melting temp?
polypropylene
glass transition temp is ..?
dependent on mositure regain and temp at which polymer chains in the amorphous part of fibers to be mobile
heat of wetting is?
heat generated when a fiber absorbs mositure
a hydrophilic fiber is one that…?
absorbs mositure readily
An oleophilic fiber is one that…?
tenaciously absorbs or holds oil
Is polyester hydrophobic or hydrophilic?
hydrophobic
Is polypropylene hydrophobic or hydrophilic?
hydrophobic
Relative humidty affects the properties of _ fibers.
hydrophillic
T or F: Cotton and wool have no melting temp because the polymers will decompose into other molecules before they become liquid.
True
Cotton is more damaged by …
Acids (low pH)
Consumers find cotton to be comfortable because…
when dry and because cotton is hydrophillic
The color of cotton is…
white, grey, light yellow
Cotton fibers are primarly from what polymer?
cellulose
the mositure regain of cotton at standard lab settings is…
8.5%
the melting point of cotton is …
cotton will decompose before it melts
T or F: cotton fiber length is highly variable due to the processing of the fiber beginning with ginning.
true
T or F: Cotton is highly flammable unless treated with a flame retardant finsihing
true
T or F: cotton is stronger than polyester
false
T or F:during a tensile test, cotton has a very low elognation at the breaking point.
true
T or F: cotton will absorb moisture and phyiscally swell
true
T or F: cotton fiber properties are highly variable because it is a natural fiber with varying growing conditions.
true
T or F: wool fiber length is highly variable due to the fact that wool on a sheep’s leg is shorter than wool on the sheeps back.
true
T or F: wool and silk will absorb mositure and phyiscally swell
true
T or F: during a tensile test, wool has a very low elongation at the breaking point
false
mositure regain of silk at standard lab conditions is
11%
consumers find silk fabrics to be comfortable
because it is hydrophilic fiber, when dry, because silk fabrics have excellent drape characterisitcs
T or F: most natural and manufactured fibers have greater breaking strength than wool.
true
T or F: individual silk filaments can have a length of several hundred meters.
true
The melting point of wool and silk
they don’t have a melting point because they will decompose before melting
the color of wool is
white, grey, brown
During melt spinning the spinneret provides what value to the process?
It creates the filament cross sectional shape
What part of the melt spinning extrusion unit forces the melted polymer to the metering pump?
the screw
In order to be formed into filaments using melt spinning, a polymer must be:
Capable of being melted, have a large degree of polymerization in order for the filament to be strong enough and not break
what part of the melt spinning extrusion unit forces the melted polymer to the spinneret with a uniform flow rate?
metering pump
