Test 4 Flashcards
(108 cards)
1
Q
how did spun-bonded originate?
A
it was a modification of melt spinning
2
Q
what is the cost effective way to make a fabric
A
spun-bonded
3
Q
why is spun-bonding cost effective (3)
A
not a lot of processes, quick, less equipment
4
Q
when did spun-bonding start
A
1950s
5
Q
when did patents come out for spunbonding
A
1970s
6
Q
what is the spun-bond line? (7)
A
liquefaction filtering extrusion cooling drawing laying on screen bonding
7
Q
why do we filter in spunbonding
A
bc we dont want the spinnerets to get block
8
Q
what is a gel
A
very small unmelted polymers that can get stuck in spinneret holes
9
Q
why is cooling an important step in spunbonding
A
they need to be cold before hitting the belt
10
Q
what polymers are important for spunbonding (2)
A
high molecular weight, medium melt viscosity
11
Q
why is polypropylene used in spunbond? (2)
A
u can get high yield fabric with low density and can be reused
12
Q
why is polyester good for spunbonding? (3)
A
good tensile strength, higher modulus, more heat stable
13
Q
can bicompents and multicomponent be spun-bond?
A
yes
14
Q
what are the steps of preparation of polymers before spun-bond?
A
crystallization
drying
additive
oxidation
15
Q
what is the crystallization step of preparation in spun-bonding?
A
need to put in oven and heat up until it crystallizes
16
Q
what is the drying step of preparation in spun-bonding?
A
if any moisture is left in polymer, when spinning it wont get into thin fine streams and will glob
17
Q
why do we oxidize preparation in spun-bonding?
A
can get an OH group that something else can be attached to
18
Q
where are polymer chips stored in spun-bonding and why?
A
in a grail silo so we can blend the polymer chips
19
Q
why do we have to take fabrics right to bonding when spun-bonding?
A
because the fabrics are so light so we need to bond so they hold together
20
Q
what is the spin pack
A
the spinneret, filter, metering pump, they are put together as one unit and heated to the right temperature
21
Q
what happens if the polymers get too cold in spunbonding
A
will have to sandblast the polymer off the spinneret
22
Q
what is quenching? in spunbonding
A
cooling before the belt, as soon as it comes out of the block it will be hit with chilled air
23
Q
what does the aspirator or spreader do? in spunbonding
A
separate the filaments before getting to the screen, can spread in MD or CD
24
Q
why is multilayering a problem in spunbonding
A
because the filaments are so lightweight and it would blow off
25
why would we do multilayering in spunbonding
to hide variations due to randomness
26
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
27
what is the difference between open and closed spun-bonding?
everything from spinneret tp belt closed in house, and they have different properties
28
which system open or closed is less uniform
open
29
what does spun-bonding make?
continuous filaments
30
what is meltblowing
fabric directly from polymer with high velocity air
31
are melt blowing or spun bonding self bonding
melt blowing
32
what is the process of melt-blowing?(9)
```
polymer
extrude
filter
pump
extra stirring
spinning head
lay on collecting surface
calendar
wind on package
```
33
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
34
what is the goal of melt blowing
to make a fine fiber
35
what kinds of polymers are made with spunbond
special polymers with a low viscosity
36
what is different about the melt blowing screw?
much longer and smaller in diameter
37
what are the 3 polymers of the dye assembly>
polymer feed distribution, die nosepiece, air manifolds
38
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
39
2 types of polymer feed distribution
coat hanger and T type
40
what is the dye nosepiece?
wide, hollow, tapered that holds holes that polymer flow to form fibers
41
what are the capillary type dye nosepiece?
drill slots in both sides and match them up
42
what are the drilled holes dye nosepiece?
drilled holes straight through, requires a lot of precision
43
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
44
why is air a major cost in meltblowing
being pressurized and heating
45
if we reduce the capillary size what happens to fiber size
reduces fiber size
46
what is a drum used for in melt blowijg
get electrostatic charge, helps save space
47
why do we calendar bond in melt blowing
to help collapse pore size and improve filtration efficiency
48
what are shots in melt bloiwng
small particles of polymer that did not melt
49
what is the output rate in melt blowing
how much polymer is being pushed through the block
50
small fibers = _ throughout ratw
low
51
what needs to be changed before u start the melt blowing process?
air gap
air angle
die setback
die hole size
52
are melt blowing highly oriented?
no because they are weak
53
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
54
where is spun bond drawing force applied
at the attenautor
55
where is melt blowing drawing force applied
at the die tip right when the polymer comes out of the dye
56
why do we finish nonwovens?
to change appearance, enhance performance, and alter functionality
57
why do we use dry processing a lot in finishing?
to reduce cost, enviromental
58
what is shrinking used for?
to relieve stresses, remove disortions and promote dimensional stability
59
what are the pros to shrinkage? (3)
higher basis weight, higher density or bulk, increases strength
60
what is dry shrinkage primarily used with? (2)
high percent of synthetic fibers
| low melt fibers
61
what is compacting?
sliding fibers closer together
62
what are the pros for compacting? (2)
remove paper feel, increase volume of fabric,
63
what fibers are best used for compacting? (4)
wet fabric, hydrophilic fiber, heat stability, MD webs are best
64
what is creping?
very similar to compacting just at a lower temperature and dry
65
what does creping improve?
basis weight up to 50% and elongation
66
what is glazing, calendaring and pressing?
calendaring process that uses smooth roll to get stiff highly polished fabric
67
what are the pros to glazing, calendaring and pressing?
can reduce pore size, stiffen lightweight web, can change visual effect of fabric
68
what is perforating?
hot needles to poke holes in webs, heated needles will cause area around needle to fuse around the hole
69
what is slitting? and what does it improve
roller with small blades and improves softness
70
what is splitting?
used to take dense needle-punched fabric and split it to make a synthetic leather like fabric
71
what is suede finishing?
after splitting we calendar or emboss to give a velour look
72
what is shearing and raising?
making loops on the surface and shearing and plucking them to raise them higher, gives feel of carpet
73
what is singeing?
burn off protruding fibers from needle-punched fabric to get smooth surface, makes it easier to clean
74
what is sewing and quilting?
joining 2 webs together
75
what can we weld?
two thermoplastic materials today
76
what is washing?
normal washing just with full width washers and dryers
77
what is dyeing?
combining chemical bonding and dyeing
78
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
79
what can stiffening accomplish?
can add 300% of web weight, but u need to apply several layers
80
what is flocking?
lay down pattern and adhesive and have short fibers to stand up where the pattern is
81
what is a composite
combination of two or more materials with an interface
82
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
83
how are composites economical?
eliminates steps and can replace products
84
when making a composite what fiber properties do we need to consider (6)
```
fiber type
fiber length
fiber diameter
porosity
airflow
cross-sectional shape
```
85
what is a fuzzy interface?
when two fibers mix together, not easy to pull apart
86
what is a clear interface?
can peel apart, veeners
87
what is a veener?
low melt in between and will cause it to stick and can peel apart
88
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
89
what was wrong with the original medical blue
not breathable, had absoportion and barrier properties
90
what is an extrusion coating?
marrying a nonwoven w a film on
91
how do we add active ingredients to a web
either bonded within the fiber itself or put in the web and hoping it stays
92
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
93
how do we activate carbon?
lay down low density web, intermingle particles in air web system and then lay down another layer
94
how do we much sure activated carbon last longe?
make sure particle sizes are larger than your fiber size
95
what do we use in automotive composites?
hemp of kenalp because it is very stiff
96
what is a depth filter?
have different layers responsible for picking up different size particles, each layer can have different chemistry.
97
what is caking?
when it gets clogged because the small particle layers are on top
98
what is stitch bonded
low melt yarn that melts and is abrasive part, stitch bond also serves to hold it together
99
spunbonded open system characteristics (5)
```
high filament speed
finer fibers
flexible
most polymers
shorter height
```
100
spunbonded closed system characteristics (5)
```
better bonding
good uniformity
well defined process
mostly PP
not affected by room air
```
101
typical process of melt blowing (5)
```
extruder
metering pump
die assembly
web formation
winding
```
102
processing material variables in melt blowing (5)
```
polymer type
molecular weight
molecular weight distribution
melt viscosity
polymer additives
```
103
processing machine variables in melt blowing (6)
```
polymer/die temperature
air temp
die to collector distance
collector speed
polymer throughput
air throughput
```
104
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
```
105
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
106
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
```
107
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
```
108
lamination methods of composites
```
thermal bonding
ultrasonic bonidng
adhesive bonding
extrusion coating
needlepunching
hydroentanglingn
```
