Test 2 Flashcards
What is pulp?
very short and fine cellulosic fibers
why do we use pulp in nonwovens
inexpensive and very absorbent
what is a composite
bringing together of two or more materials, one of which must be a nonwoven
what is a coform
marrying of two similar processes
why are nonwovens important in medical textile applications?
they can be made from fine fibers which will then give a fiber a high surface area and barrier properties while being breathable
how are nonwovens used in the composite industry
mold release fabrics and reinforcing fabrics that improve abrasion resistance, reduce corrosion, improve mechanical properties
why are nonwovens useful in roads and highways
they help drain water and protect against frost heaves and cracks due to water freezing
what is the major challenge in window treatments and what is done to correct this problem
light fabrics are non uniform and we will use layering and laminates
why is the polypropylene the most used fiber in nonwovens
because its density is less than other fibers and you can make more fabric from the same bale compared to other fibers
why are melt blown splitables being widely used in filters
they allow u to make very fine fibers and fabrics that will have a variety of pore shapes and size in which to trap particles
5 desirable properties for hygiene applications
lightweight, soft and comfortable, skin friendly, flexible, absorbent, breathable
5 desirable properties for crop covers
lightweight, water permeable, resistant to mold, uv resistant, air permeable, insect resistant
3 reasons nonwovens suffer in other industries
low labor, highly technical, capital intensive
how to make a low density abrasive pad
low density web sprayed with or dipped in adhesive that has abrasive particles in it. then heat the treat web to cure and assist particle/web stability
5 properties used in nonwovens analysis
fiber orientation, bond to bond distance, mass nonuniformity, number of crossovers, and pore size and shape
2 most important properties of nonwovens analysis and why
fiber orientation because it influences all other properties and mass non uniformity affects end us reliability
dry laying web production
carding and airlaying
fiber size of air laying
short or long fibers
important fiber qualities of an air laying (6)
- right length
- cohesion
- flexibility
- can use about any type of fiber
- need crimp
- standard to coarse fibers
uniformity of air-laid webs
good if properly opened
problems w airlaying (3)
- air flow leads to variability
- uniformity is highly dependent on opening
- fiber entanglement in the airstream can lead to web faults
strengths of airlaying (5)
- isotropic
- very random
- high loft and low density
- broad range of fiber type
- large range of basis wieght
important fiber qualities of carding (3)
- cohesion
- crimp
- length/ not as easy for short fibers
problems w carding (5)
- not strong
- static electricity
- low fiber to fiber cohesion ‘
- fiber breakage
- permanent fiber elognation
strength of carding (4)
- the ability to blend fibers together
- combination of multiple layers
- wide range of fibers can be carded
- wide range of basis weight
fiber qualities of wet laying (8)
- stronger
- not seek to bond together
- any natural or synthetic fiber
- don’t want it to have a lot of crimp
- need special chemical on the surface
- speciality type fibers
- low surface tension
- low fiber to fiber tension
problems of wet laying (5)
- have problem individulize because they are longer
- expensive
- requires a lot of energy
- need a high-quality fiber
- cant change from fiber type of fiber type easily
strengths of wet laying (3)
- high productivity
- broad. range of products
- can change the orientation of the fiber
2 different air laying processes and which produces what type of webs
route 1: -fiber prep -carding -bonding or cross lap to stacker - -finishing route 2: - stacking to bonding to finishing - bonding to finishing - heavier weight webs
why do we need to control fibers in airlaying?
so they dont tangle and choke up the machine
why do we trim the edges of the web after air laying?
since the velcoity on the outside of the machine is not as even as on the inside of the machine
6 properties of pulp
- bulk and absorbency
- softness
- wet strength
- value
- biodegradbale
- abrasion resistance
what are we making in carding?
webs not sliver
how do we get a uniform web in carding?
we are feeding a uniform amount of fiber to the chute
what can we do to match the bonding types in carding?
change the profile of the web
what is tacking?
similar to needlepunching just with very small needles and only enough to hold them together enough to move
how do we add a higher basis weight and more lofty when carded?
cross lap then needlepunch and then caledner to add extra strength and compress the web
can we card bi-component fibers
yes
higher speeds will cause the fibers to do what
be more in the machine direction
if u run fibers through a traditional card what do u have to do
cross lap
5 things we expect from a cross laper
- will change fiber orientation
- increase our basis weight
- improve uniformity
- composite type structure
- increase fabric width
what kind of web can we get when cross lapping?
a heavier web
what does increasing overlaps do when carding
improves uniformity and weight
what is the BIGGEST problem with cross lapping?
lack of uniformity
what defects are associated with cross lapping? (3)
- voids: spaces with not an equal amount of fibers
- creases: if it stalls it creates a crease in the fabric
- slow
after carding, if there’s a general low basis weight what kind of bonding can we do?
hydroentangle
thermal bonding
chemical bonding
NO NEEDLE PUNCHING
higher basis weight
needle punch
what is the goal is wet laying?
to increase speed
what do we want out of wet laying ?
flexible and strong
important properties of wet laying? (6)
- aspect ration
- tensile properties
- flexural resistance
- length
- shrinkage
- density
dispersion depends on (4)
- degress of fineness
- fiber stiffness in aquesous solution
- fiber crimp
- fiber wettability
in wet laying once we seperate the fibers we need them to do what
stay seperated
after wet laying what do we have to do and why
bond because they dont have any strength
what kinds of fabric defects happen in wet laying?
- logs/sticks
- ropes
- dumbbells
- fused fibers
how to make a good quality web in wet laying (4)
need good agitation
no vortex
fibers need low surface tension
low fiber to fiber tension
important fiber properties of wet laying? (6)
- length
- aspect ratio
- tensile strength/elognation
- flex resistance
- shrinkage
- density
when fiber length is increased in wet laying what happens?(3)
- less uniform
- tensile strength increases up to a max
- tear and burst strength increase up to a max
