Test 4 Flashcards
how did spun-bonded originate?
it was a modification of melt spinning
what is the cost effective way to make a fabric
spun-bonded
why is spun-bonding cost effective (3)
not a lot of processes, quick, less equipment
when did spun-bonding start
1950s
when did patents come out for spunbonding
1970s
what is the spun-bond line? (7)
liquefaction filtering extrusion cooling drawing laying on screen bonding
why do we filter in spunbonding
bc we dont want the spinnerets to get block
what is a gel
very small unmelted polymers that can get stuck in spinneret holes
why is cooling an important step in spunbonding
they need to be cold before hitting the belt
what polymers are important for spunbonding (2)
high molecular weight, medium melt viscosity
why is polypropylene used in spunbond? (2)
u can get high yield fabric with low density and can be reused
why is polyester good for spunbonding? (3)
good tensile strength, higher modulus, more heat stable
can bicompents and multicomponent be spun-bond?
yes
what are the steps of preparation of polymers before spun-bond?
crystallization
drying
additive
oxidation
what is the crystallization step of preparation in spun-bonding?
need to put in oven and heat up until it crystallizes
what is the drying step of preparation in spun-bonding?
if any moisture is left in polymer, when spinning it wont get into thin fine streams and will glob
why do we oxidize preparation in spun-bonding?
can get an OH group that something else can be attached to
where are polymer chips stored in spun-bonding and why?
in a grail silo so we can blend the polymer chips
why do we have to take fabrics right to bonding when spun-bonding?
because the fabrics are so light so we need to bond so they hold together
what is the spin pack
the spinneret, filter, metering pump, they are put together as one unit and heated to the right temperature
what happens if the polymers get too cold in spunbonding
will have to sandblast the polymer off the spinneret
what is quenching? in spunbonding
cooling before the belt, as soon as it comes out of the block it will be hit with chilled air
what does the aspirator or spreader do? in spunbonding
separate the filaments before getting to the screen, can spread in MD or CD
why is multilayering a problem in spunbonding
because the filaments are so lightweight and it would blow off
why would we do multilayering in spunbonding
to hide variations due to randomness
what does the vacuum suction do in spun-bonding?
helps hold filaments on the belt since they are so light and need to be bonded straight away
what is the difference between open and closed spun-bonding?
everything from spinneret tp belt closed in house, and they have different properties
which system open or closed is less uniform
open
what does spun-bonding make?
continuous filaments
what is meltblowing
fabric directly from polymer with high velocity air
are melt blowing or spun bonding self bonding
melt blowing
what is the process of melt-blowing?(9)
polymer extrude filter pump extra stirring spinning head lay on collecting surface calendar wind on package
what happens in the extrusion process in melt-blowing?
we have to blow hot air in dye block so we can keep polymer hot as long as possible
what is the goal of melt blowing
to make a fine fiber
what kinds of polymers are made with spunbond
special polymers with a low viscosity
what is different about the melt blowing screw?
much longer and smaller in diameter
what are the 3 polymers of the dye assembly>
polymer feed distribution, die nosepiece, air manifolds
what is the polymer feed distribution?
controls how the polymer flows across the block because we dont want dwell times to be too high and control the flow rate
2 types of polymer feed distribution
coat hanger and T type
what is the dye nosepiece?
wide, hollow, tapered that holds holes that polymer flow to form fibers
what are the capillary type dye nosepiece?
drill slots in both sides and match them up
what are the drilled holes dye nosepiece?
drilled holes straight through, requires a lot of precision
what are the air manifolds?
gaps on both sides of the dye piece and allows us to blow hot air and hit the polymer as soon as it comes out
why is air a major cost in meltblowing
being pressurized and heating
if we reduce the capillary size what happens to fiber size
reduces fiber size
what is a drum used for in melt blowijg
get electrostatic charge, helps save space
why do we calendar bond in melt blowing
to help collapse pore size and improve filtration efficiency
what are shots in melt bloiwng
small particles of polymer that did not melt
what is the output rate in melt blowing
how much polymer is being pushed through the block
small fibers = _ throughout ratw
low
what needs to be changed before u start the melt blowing process?
air gap
air angle
die setback
die hole size
are melt blowing highly oriented?
no because they are weak
what is the difference in air between spun and melt
spun need small volume of ambient air
melt needs large volume of very high temp
where is spun bond drawing force applied
at the attenautor
where is melt blowing drawing force applied
at the die tip right when the polymer comes out of the dye
why do we finish nonwovens?
to change appearance, enhance performance, and alter functionality
why do we use dry processing a lot in finishing?
to reduce cost, enviromental
what is shrinking used for?
to relieve stresses, remove disortions and promote dimensional stability
what are the pros to shrinkage? (3)
higher basis weight, higher density or bulk, increases strength
what is dry shrinkage primarily used with? (2)
high percent of synthetic fibers
low melt fibers
what is compacting?
sliding fibers closer together
what are the pros for compacting? (2)
remove paper feel, increase volume of fabric,
what fibers are best used for compacting? (4)
wet fabric, hydrophilic fiber, heat stability, MD webs are best
what is creping?
very similar to compacting just at a lower temperature and dry
what does creping improve?
basis weight up to 50% and elongation
what is glazing, calendaring and pressing?
calendaring process that uses smooth roll to get stiff highly polished fabric
what are the pros to glazing, calendaring and pressing?
can reduce pore size, stiffen lightweight web, can change visual effect of fabric
what is perforating?
hot needles to poke holes in webs, heated needles will cause area around needle to fuse around the hole
what is slitting? and what does it improve
roller with small blades and improves softness
what is splitting?
used to take dense needle-punched fabric and split it to make a synthetic leather like fabric
what is suede finishing?
after splitting we calendar or emboss to give a velour look
what is shearing and raising?
making loops on the surface and shearing and plucking them to raise them higher, gives feel of carpet
what is singeing?
burn off protruding fibers from needle-punched fabric to get smooth surface, makes it easier to clean
what is sewing and quilting?
joining 2 webs together
what can we weld?
two thermoplastic materials today
what is washing?
normal washing just with full width washers and dryers
what is dyeing?
combining chemical bonding and dyeing
what are the challenges of dyeing? (2)
need to make sure binders are compact-able with dyes, and difficult to dye when web contains blends of different fibers
what can stiffening accomplish?
can add 300% of web weight, but u need to apply several layers
what is flocking?
lay down pattern and adhesive and have short fibers to stand up where the pattern is
what is a composite
combination of two or more materials with an interface
what do have an interface in composites?
to maintain the distance properties of each material , we want them to bond while still maintaining the properties
how are composites economical?
eliminates steps and can replace products
when making a composite what fiber properties do we need to consider (6)
fiber type fiber length fiber diameter porosity airflow cross-sectional shape
what is a fuzzy interface?
when two fibers mix together, not easy to pull apart
what is a clear interface?
can peel apart, veeners
what is a veener?
low melt in between and will cause it to stick and can peel apart
what was the process of the original medical blue?
spun laced, carded web and tissue paper web that we hydroentangle then coat it with polyurethane to give the barrier properties
what was wrong with the original medical blue
not breathable, had absoportion and barrier properties
what is an extrusion coating?
marrying a nonwoven w a film on
how do we add active ingredients to a web
either bonded within the fiber itself or put in the web and hoping it stays
how do we make a 3D needle-punched composite?
lay down needle-punched web and put down a layer of carbon and selectively needle-punch to connect the 2 webs, making pockets
how do we activate carbon?
lay down low density web, intermingle particles in air web system and then lay down another layer
how do we much sure activated carbon last longe?
make sure particle sizes are larger than your fiber size
what do we use in automotive composites?
hemp of kenalp because it is very stiff
what is a depth filter?
have different layers responsible for picking up different size particles, each layer can have different chemistry.
what is caking?
when it gets clogged because the small particle layers are on top
what is stitch bonded
low melt yarn that melts and is abrasive part, stitch bond also serves to hold it together
spunbonded open system characteristics (5)
high filament speed finer fibers flexible most polymers shorter height
spunbonded closed system characteristics (5)
better bonding good uniformity well defined process mostly PP not affected by room air
typical process of melt blowing (5)
extruder metering pump die assembly web formation winding
processing material variables in melt blowing (5)
polymer type molecular weight molecular weight distribution melt viscosity polymer additives
processing machine variables in melt blowing (6)
polymer/die temperature air temp die to collector distance collector speed polymer throughput air throughput
what does a high DCD cause (5)
bulkier and softer web better fiber cooling less tendency to disturb fiber lay down less web uniformity used for heavy basis weight fabric
what does a low DCD cause (4)
more compact/stiffer web
balance if process air and suction capability
more uniformed web
used for light basis weight fabric
how to reduce shots (5)
reudce output ratw reduce air temp/ increase air flow replace die tip if necessary reduce melt temp check for resign quality
product characterisitcs of a melt blown (7)
random fiber orientation low to moderate web strength high cover factor fiber diameter ranges from .5 to 30 microns basis weight ranges from 8 to 350 g/m2 fibers have a smooth surface texture microfibers provide high surface area
lamination methods of composites
thermal bonding ultrasonic bonidng adhesive bonding extrusion coating needlepunching hydroentanglingn
