Extrusion of Polyethylene
Jared Stradley
CHEN 4903
December 4, 2006
Extruders
Overview
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Project objectives
Theory
Experimental setup and procedures
Results
Conclusions and Recommendations
References
Wrap up
Q&A
Project objectives
Characterize the flow of
polyethylene in cylindrical die
 Estimate the maximum flow rate
through a 1” diameter pipe die
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Theory
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Basically, it’s flow through a pipe or
an annulus
Theory cont.
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Major equations
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Pipe flow:
 r ( P1  P2 )

2L
dV
  
dr
 ( P1  P2 ) R
Q
8L
4
c
More theory
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Annular flow:
 ( P1  P2 ) R
Q
8L
4





1


4
 1  

ln 1 /   


2 2
Experimental setup
Experimental procedures
Ran polyethylene at 155, 160 and
165 °C at 3, 5, 10 and 15 rpm
 Collected samples of each run
 Ran polypropylene at 200, 205 and
210 °C at 3, 5, 10 and 15 rpm
 Also collected samples
 Calculated Q,  and dv/dr
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Results
Shear Stress vs. Velocity Gradient for Polyethylene (pipe flow)
3.0E+06
155 °C
160 °C
165 °C
τ (Pa)
2.5E+06
2.0E+06
1.5E+06
1.0E+06
5.0E+05
0.0E+00
0
2000
4000
6000
dv/dr (1/s)
8000
10000
12000
Results cont.
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Bingham plastic:
dV
  
 o
dr
Results cont.
Pressure drop (Pa)
Pressure Drop vs. Velocity for Polyethylene (annulus)
3.00E+06
155 °C
2.50E+06
160 °C
2.00E+06
165 °C
1.50E+06
1.00E+06
5.00E+05
0.00E+00
0.000
5.000
10.000
15.000
20.000
25.000
Velocity (cm/s)
30.000
35.000
40.000
Some more results
Pressure drop(Pa)
Pressure drop vs. rpm for polypropylene (pipe flow)
5.00E+06
200 °C
4.50E+06
205 °C
4.00E+06
210 °C
3.50E+06
3.00E+06
2.50E+06
2.00E+06
0
2
4
6
8
10
12
14
rpm
Maximum pressure drop: 6.40 MPa
16
18
Final result
Maximum velocity possible: 59.180 + 4.127 cm/s (95% CI)
Pressure drop (Pa)
Pressure Drop vs. Velocity for Polyethylene (annulus)
3.00E+06
2.50E+06
2.00E+06
155 °C
160 °C
165 °C
1.50E+06
1.00E+06
y = 115926x - 318281
5.00E+05
0.00E+00
0.000
y = 109967x - 235980
5.000
10.000
15.000
20.000
25.000
Velocity (cm/s)
30.000
35.000
40.000
Conclusion
Polyethylene can be extruded at a
velocity of 59.180 + 4.127 cm/s
through a 1” cylindrical pipe die
(95% CI)
 This result holds for temperatures
between 155 and 165 °C
 This value compares well with the
industrial flow rate of 0.5 m/s
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Recommendations
Run both Polyethylene and
Polypropylene at more temperatures
 Run both at higher rpm
 Take samples on same day
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References
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Bird, R. B., W. E. Stewart, E. N. Lightfoot.
Transport Phenomena. New York: John Wiley &
Sons, 1960.
Ring, T. A. Fundamentals of Ceramic Powder
Processing and Synthesis. San Diego: Academic
Press, 1996.
de Nevers, N. Fluid Mechanics for Chemical
Engineers. New York: McGraw-Hill, 2005.
www.chemfinder.com
www.nicodemus.org
www.search.com
Wrap up
Project objectives
 Theory
 Experimental setup and procedures
 Results
 Conclusions and Recommendations
 References
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Questions?