ÙÌ Ç ÙÌ ³è ëÑ ØáæÈ - LGChem Chemwide · 2015-06-09 · PipeÍ profile, film casting,...
Transcript of ÙÌ Ç ÙÌ ³è ëÑ ØáæÈ - LGChem Chemwide · 2015-06-09 · PipeÍ profile, film casting,...
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01 Introduction
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() ,
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, (Die Drool
Phenomenon) . ,
(Drool) .
116 .
Pipe profile, film casting, fiber spinning,
film/melt blowing, wire/cable sheathing
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1 | Examples of die drool Phenomenon16
(a) LLDPE, string extrusion1
(b) LLDPE, string extrusion2
(c) EVA/LLDPE compound, cable sheath extrusion3
(d) mLLDPE, string extrusion4
(e) metallocene based polyolefin elastomer resin, string extrusion5
(f) partially foamed polymer melt, string extrusion6
(g) regranulated LDPE, film blowing7
(h) unfilled HDPE, string extrusion8
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02 Die Drool Formation Mechanism
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9,
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1981 Klein 12
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13,14. Chaloupkova Zatloukal
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Suction.
Suction
4,15( 2).
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18,19 HDPE
. , HDPE
-
- slip-stick
(
)
, HDPE
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20.(3)
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(solid metal die wall, liquid
polymer melt, and air)
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driving force.
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2.
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2 | The predicted pressure field at the die exitfor the extrusion of mLLDPE.15
0.
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(
0 -negative pressure)
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driving force
suction.
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. -
16.
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driving force
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wall slip.
wall slip
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Wall slip
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slip
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no-slip condition
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, wall slip
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- Flow-Induced Molecular Weight
Fractionation Theory
- Stress-Induced Cohesive Chains
Disentanglement Theory
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3 | Separation of slip layer and polymer bulk dueto cohesive failure inside flowing polymermelt inside circular die with no adhesive slip
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03 Die Drool Causes and EliminationMethod
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04 Effect of Die Design on Die DroolPhenomenon
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[ Low Surface Energy Die Materials ]
2,17,21-23. ,
polytetrafluoroethylene
(PTFE)21PTFE22
. PTFE
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0.8
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10,
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[ Die Design Changes ]
, Foster
4 anti-drool
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frusto-conical
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15 5(c)
champering .
45 champering ,
6
. 6 (Die drool
amount, DDA).
AD
, ADie
. tD ,
tDie.
( - -
) .
5(b) Flared
25-27.
flared
flared .
HDPE
flared champering
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(champering and flared shape)
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4 | Original (left) and modified (right) die exitsurface according24
5 | Detail description of the removable capillary15
drool
conductor
plasticcovering
harmlessdrips
Cooling medium channel
DDA = AD
ADie
tD
tDie
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flared champering
(same
conclusion was found in reference27 for
mLLDPE material), HDPE
15 flared
capillary 2/15
.(7) , ,
56%,
97%15.
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6 | Dependence of the die drool amountproduced by mLLDPE extrusion on the dieexit angle (processing conditions: 400 g.hr-1, 85C, Die No. 1 - straight die, Die No. 5 -15chamfered die, Die No. 4 - 45chamfereddie)15
7 | Dimensionless build-up ratio as the functionof dimensionless flared length (processingconditions : 750 g.hr-1, 160C). LC1 is flaredlength and L is capillary length. Error barsrepresent three independent measurements19
0
1
2
3
4
5
10 20 30 40 50
Die
Droo
l Am
ount
DDA
(-)
Die No.1
Die No.5 Die No.40
1x10-4
3x10-4
2x10-4
4x10-4
6x10-4
5x10-4
7x10-4
1/15 2/15 3/15 4/15 5/15 6/15 7/15 8/15
Dim
ensi
onle
ss b
uild
up ra
tio, B
R (-)
Dimensionless flared length, LC1/L (-)Die exit angle ()
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05 Conclusion
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1 | Summary of factors inducing formation of die drool16
Method Factors inducing die drool
Die design abrupt corners at die lips
dead corners inside extrusion die (thermal degradation)
high surface energy die wall materials
high surface roughness
short die land length
Polymer material low molecular weight fractions
multimodal polymers (low molecular weight tail)
high elasticity of polymer
linear architecture of macromolecules
high content of fillers
high concentration/incompatible additives or pigments
high concentration of volatiles
dissimilar material properties in blends
high content of stearates, ester lubricants, extending oils or waxes
chemical reactions between polymer and metal barrel/screw/die (PVC or PVDC materials)
Processing high processing temperature (thermaldegradation)
draw down
intensive cooling of die exit
Other factors die swell
shark skin
wall slip
vortices (thermal degradation)
slip-stick
pressure fluctuations in screw
excessive screw/barrel wear
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