1. Introduction To Blown Film
Thomas I. Butler
Blown Film Technology, LLC
11/13/2018

2. Outline Polymer Blown Film Process Screw Die Bubble cooling Collapsing
Winding
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3. Polymer MI vs. Fabrication Process
Extrusion Coating LDPE
Cast LDPE
Cast LLDPE/m-LLDPE
Blown LDPE
Blown LLDPE/m-LLDPE
Melt Index 8 7 6 5 4 3 2 1
Coextrusion and blends of LLDPE can extend MI ranges
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4. Polymer Crystallinity (Density)
0.86 g/cc
0.88 g/cc
0.916 g/cc
0.940 g/cc
EPDM
VLDPE
LLDPE
HDPE
EPR
Non-polar
(Co)Polymers
LDPE
Elastomers
Plastomer
Metallocene-PE
EPE
Soft
MODULUS
Rigid
EVA
EMA
Polar
(Co)Polymers
EBA
EAA
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5. PE Polymer selection Blown Film Cast Film MI, dg/min 0.05 – 6.0
Density, g/cc
0.88 – 0.96
0.86 – 0.96
LCB
Very helpful
Slight effect
MWD
Broad is easier
Narrow is OK
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6. Polymer Selection – Blown Film
LLDPE
MI Typically is 1.0 to 0.5
Density depends on properties required
m-LLDPE
MI Typically is 1.0
LDPE
MI Typically is 2.0 to 0.2
Density ~ g/cc
HMW-HDPE
MI Typically is 0.05 to 0.08
Density is to g/cc
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7. Blown Film Process 1 Feeding/Dosing 2 Extrusion 3 Electrical Control7
1 Feeding/Dosing
2 Extrusion
3 Electrical Control
4 Forming
5 Cooling
6 Guiding
7 Haul Off / Turner Bars
8 Winding
9 Automation 6 3 9 1 4 2 5 8
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8. Blown Film Processes Conventional Blown Film High Stalk Blown Film
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9. Double Bubble Blown Film
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10. Blown Film Process Equipment Screw design Die diameter (Ro)
Flattened Tube DP z r
FLH, xflh
Cooling Air
h(z) Rf
Nip rolls, xnr
M, Tm
Vf , hf
Equipment
Screw design
Die diameter (Ro)
Die gap (ho)
Air ring design
Nip roll height (xnr)
Process Control
Output rate (M)
Melt temp (Tm )
Bubble size (Rf )
FLH (xflh)
Haul-off speed (Vf)
Film thickness (hf)
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11. Gravimetric Control
Multi component blend ratio controlled by gravimetric blenders (3 to 6 components are common).
Gravimetric Control
Screw Drive Speed
Output rate is
constant
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12. Metering & Barrier Screws
Metering Screw
Barrier Screw
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13. Spiral Mandrel Die Inter Mandrel Die Gap, (ho) Die diameter, (Dd)
Die Body
Die Land
Relaxation Zone
Die Gap, (ho)
Inter Mandrel
Spirals
Feed Ports
Die diameter, (Dd)
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14. Coextrusion Concentric Die
Three layer Blown Coextrusion Die - Reifenhauser
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15. Pancake Coextrusion Die
Ten layer Stacked Blown Film Die - Brampton
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16. Die Specific Output Rate (DSO)
North America
M / (p x Dd) lb/hr/inch of die circumference
Europe
M / (Dd) kg/hr/mm die diameter
M = Output rate, lb/hr (kg/hr)
Dd = Die diameter, in (mm)
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17. Blown Film Control Variables
Vf = M / (2 * p * Rf * hf * rs) > FLH
Vo = M / (2 * p * Ro * ho * rm) At die
At constant film thickness (hf) M, Rf, Vf
If: Then:
M increases Vf increase and/or Rf decrease
Rf increases Vf decrease and/or M increase
Vf increases M increase and/or Rf decrease
(Variables must also fall within range of equipment capability)
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18. Bubble Cooling Single lip Dual lip Internal Bubble Cooling (IBC)
Stacked air rings
Iris
Chimney
Chilled mandrels
Water Bath
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19. Frost Line Height FLH Air Chiller Hose Manifold Blower
Frost line should be parallel
to the die with no spikes
FLH T
Air
Hose
Blower speed relates
inversely to FLH
Chiller p
Manifold
Blower
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Maintains cooling air temperature

20. Bubble Parameters BUR = ((2/p) LF) / Dd = Db / Dd = Blow Up Ratio
DDR = Vf / Vo
= (ho / (hf * BUR))* (rm/rs)
= Drawdown Ratio
FLH = distance above die
where expansion stops
= Frost Line Height
DSO = M/(p*Dd)
= Die Specific Output T T T Tm T T
Internal Bubble Pressure, DP p
Die Pressure Drop
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21. High Stalk Bubble – Neck Height
FLH
NLH T
Air
Hose
Chiller
Blower p
Manifold
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22. Dual-Lip Air Ring
Credit: Future design
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23. Dual-lip Air Ring Bubble Ambient Air Upper Lip Air Supply
Bernoulli Effect
Cone
Lower Lip
Mounting
Bracket
Die
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24. Internal Bubble Cooling (IBC)
Air Ring
Die Body
Air
Supply
Air
Outlet
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25. Internal Bubble Cooling (IBC)
Thickness gauge
IBC cooling air
supply
IBC cooling air
exhaust
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26. Bubble Sizing IBC For High Stalk
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27. Layflat Control Layflat Bubble Diameter Width
Sonic Sensors for IBC control
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28. Bubble Collapsing Wood slats Plastic covered slats Segmented rollers
Air slide
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29. Oscillating Nip Roll Vertical Horizontal W & H Battenfeld Gloucester
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30. Winders
Center
Surface
Driven
Roll
Core
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31. Winder - Center
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32. Classical Process Variables
BUR
FLH
DDR
Die Size
Melt Temp
Output
Air Ring
Thickness
Die Gap
(None Are Independent Variables)
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33. FLH Interactions FLH Velocity Volume Temp Rel. Humidity BUR
Cooling Air
Die Gap
Thickness
Melt Temp
Output
Air ring
FLH
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34. Other Process Variables (>40)
Process time CLH, PLH, FZH
Strain MD/CD Strain Ratio
Strain Rate MD/CD Strain Rate Ratio
Residual Stress MD/CD Stress Ratio
U Cone, CLH, FLH, PLH, FLH DP
Re die, CLH, FLH, PLH De MD/CD
Nu , U We MD/CD
FLH, PLH, FZH A, X’
Ftotal, Fhaul-off, Fhoop, Fnd f, q, b
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35. Common Film Properties
Tensiles (MD/CD)
Yield
Ultimate Tensile
Elongation
Modulus
Dart Impact
Tear (MD/CD)
Haze
Gloss
COF
Block
Shrink (MD/CD)
Heat Seal
Treatment Level
Thickness Variation (MD/CD)
WVTR
OTR
Gels
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36. Polymer Property Models
Non-Oriented
Molecule
Orientation &
Crystallization
Intrinsic
Property
Oriented
Structure
Mw, MWD,
Xc , & CD
Film
Properties MD ND TD
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37. Summary Polymer selection is critical to achieving properties
Equipment design may have limitations
Fabrication conditions will influence properties
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38. Thank you
Any Questions?
11/13/2018