The University of Akron
The Processing and
Capabilities of Shape
Memory Plastics
Melt-spinning of a Triblock Copolymer
Robert DeChurch
11
ABSTRACT
In this senior design project, a tri-block copolymer was processed by a lab-scale extrusion
apparatus. The purpose of this project was to design a lab-scale melt-spinning process that could
effectively and efficiently convert a PS-b-PMA-r-PODA-b-PS (tri-block) copolymer into a fiber
with high-quality shape memory behavior. This project also incorporated a method of analyzing
the fiber’s shape memory behavior through a series of performance tests. The melt-spinning
apparatus used in this project was a programmable syringe pump holding a 5 milliliter glass
syringe wrapped with heating tape. This simulates an extruder that could be used on a large
industrial scale. A take up device for collection of fiber was also developed and built, which
models large-scale stretching rolls. Five trials were conducted where melt temperatures,
dispense speeds, and methods of cooling and stretching were all varied for an effective analysis.
A trial summary chart is provided and followed by a table with data collected from shape
memory testing. Calculations with equations of motion and dynamic relations are used to
determine an appropriate take-up speed for the process. The results from this senior design
project show that the PS-b-PMA-r-PODA-b-PS tri-block copolymer can be efficiently processed
on a lab-scale into a fiber with high-quality shape memory behavior. Other conclusions that can
be made are that lab-scale take-up devices can be constructed at low cost, and that take-up
devices aid in stretching fiber and improving diameter consistency.
2
TABLE OF CONTENTS
TABLE OF FIGURES……………………………………………………………………….…4-5
INTRODUCTION………………………………………………………………………………..5
BACKGROUND………………………………………………………………………………..5-7
THEORY………………………………………………………………………………………..8-9
MATERIALS AND EQUIPMENT…………………………………………………………....9-11
PROCEDURES………………………………………………………………………………12-25
DATA AND CALCULATIONS……………………………………………………………..26-30
RESULTS & DISCUSSION ……………….………………………………………………..31-32
CONCLUSION………………………………………………………………………………….33
ACKNOWLEDGEMENTS……………………………………………………………………..33
REFERENCES…………………………………………………………………………………..34
APPENDIX…………………………………………………………………………………..35-41
3
TABLE OF FIGURES
Figure 1 - SMP in coiled shaped after being quenched ............................................................................. 6
Figure 2 - SMP exhibiting shape memory behavior as temperature increases............................................ 6
Figure 3 - Schematic of melt-spinning ..................................................................................................... 7
Figure 4 – Extrudate being stretched with take-up device ....................................................................... 14
Figure 5 - Melt-spinning process layout for trials 4 and 5 ....................................................................... 16
Figure 6 - Take-up using 2 electric motors ............................................................................................. 18
Figure 7 - Fiber produced in trial 1 ........................................................................................................ 19
Figure 8 - Fiber being wrapped around stir rod....................................................................................... 19
Figure 9 - Fiber produced from trial 2 .................................................................................................... 20
Figure 10 - Fiber cut for shape memory testing ...................................................................................... 20
Figure 11 - Water in beaker being heated and stirred .............................................................................. 21
Figure 12 - Temperature and stir speed settings...................................................................................... 21
Figure 13 - Knot made with fiber ........................................................................................................... 21
Figure 14 - Loosely-coiled fiber............................................................................................................. 22
Figure 15 - Tightly-coiled fiber.............................................................................................................. 22
Figure 16 - Imperfect shape-memory ..................................................................................................... 22
Figure 17 - Fiber coiled around NMR tube............................................................................................. 24
Figure 18 - Temporary coil after being quenched ................................................................................... 24
Figure 19 - Fiber returns to original permanent shape............................................................................. 24
Figure 20 - Fiber in original coiled shape ............................................................................................... 25
Figure 21 - Quenching straight fiber in ice water.................................................................................... 25
Figure 22 - Imperfect recovery of original coiled shape.......................................................................... 25
Figure 23 - Trial Summary Chart ........................................................................................................... 26
Figure 24 - Trial 2 Testing Results......................................................................................................... 27
Figure 25 - Take-up Analysis Using Trial 2 Flow Rate........................................................................... 28
Figure 26 - Take-up Analysis for Trials 3-5 ........................................................................................... 30
4
INTRODUCTION
The goals of this design project were to produce a fiber with shape memory behavior out of a PSb-PMA-r-PODA-b-PS tri-block copolymer, and to design a lab-scale process that could be used
to produce a quality fiber effectively and efficiently. The criterion for my design was to produce
a 6 inch long fiber with fixity and shape recovery properties of 90% in less than 30 minutes.
Other ideas I took into consideration for my design were cost, size, mobility, and simplicity of
equipment involved in a lab-scale process.
Within this design report, a brief background of shape memory polymers and fiber spinning are
discussed, followed by theory of fiber spinning. The experiments involved in this design project
consisted of five trials of fiber processing and several trials for shape memory behavior testing.
A lab-scale take-up device was designed and utilized for three of the trials. Two samples of the
same tri-block copolymer, but with different molecular weights (from two different
polymerization reactions), were used for the processing and testing of fiber. Fiber processing
was conducted at several different rates and with different take up configurations.
BACKGROUND
Shape memory polymers are kinds of responsive materials that are capable of returning from a
temporary deformation to an original shape when an external stimulus is applied. Types of
external stimuli include: temperature increases, ultraviolet light exposure, and water absorption
(Fei, 2010). When temperature is involved, the response is known as a thermally-induced shape
memory effect. To observe this effect, a shape memory polymer is first processed into a
permanent shape. Then, the polymer is programmed—heated above its transition temperature
and deformed to a temporary shape, before being quenched or cooled to retain its temporary
5
shape. Upon heating the polymer above the transition temperature again, the polymer exhibits
shape memory behavior as it relaxes to the original shape (Lendlein, 2002). Figures 1 shows an
image of a fiber in a temporary coiled shape and Figure 2 shows the same fiber demonstrating
shape memory behavior as heat is applied. This shape memory behavior makes these polymers
quite favorable for uses as actuators and sensors in a range of industries.
Figure 1 - SMP in coiled shaped after being
quenched
Figure 2 - SMP exhibiting shape memory
behavior as temperature increases
Fiber spinning is one processing technique that involves the uniaxial deformation of polymer
extrudate into fibers. The uniaxial deformation results in structuring of the polymer’s molecular
chains and improves the fiber’s tensile strength (Isayev, 2006). Fiber spinning can be
accomplished through three methods: melt spinning, wet spinning, or dry spinning. All methods
utilize screw extrusion for the conversion of particulate solids into a melt, but melt spinning is
the simplest. In melt spinning, the polymer melt exits the extruder through a die with multiple
holes called a spinneret. The extrudate leaves the spinneret as fibers that are cooled, drawn, and
wound up on a take up device (Jana, 2010). As shown in Figure 3, multiple take up devices, inline heating, and varying take up speeds can be used to further stretch the fibers and aid in
molecular configuration. Wet spinning involves dissolving the polymer in a solvent, and
extruding the material out of a spinneret and into a chemical solution. Similarly, dry spinning
6
requires the polymer to be dissolved in a solvent, but the extruded fibers are not fed into a
chemical solution. The solvent evaporates after exiting the spinnerets (Tadmor, 2006).
Figure 3 - Schematic of melt-spinning
7
THEORY
The Processing of the polymer converts solid plastic particulates into a polymeric melt. To
effectively analyze the melt spinning process of fiber, fundamental fluid equations and dynamic
equations can be used to fully understand the flow and characteristics of the polymer.
Equation of Motion:
The mass flow rate of polymer is constant throughout the melt-spinning process.
(1)
Where:
(2)
(3)
(4)
To fully analyze the flow of polymer in melt spinning, the equations of motion using cylindrical
coordinates (r, θ, z) are written as:
(5)
(6)
(7)
With the extruder’s processing rate and the extrudate diameter known, the velocity of the
polymer at the die exit can be determined using a fundamental volume flow rate relation.
(8)
As the extrudate leaves the die, the material undergoes stretching and a reduction in diameter.
With a constant mass-flow rate and a diameter reduction, the material will speed up as it moves
farther away from the die. The velocity can be determined using the following equation.
8
(9)
Where:
And
The diameter changes with the distance the fiber travels from the exit of the die. The reduction
in diameter or reduction in radius can be expressed as:
(10)
To determine an appropriate motor(s) for the take up of a polymer fiber, a fundamental dynamic
equation can be written as:
(11)
Where:
MATERIALS AND EQUIPMENT
Material:
The material that was used was Poly(styrene-block-methylacrylate-co-octadecylacrylateblock-styrene) Shape Memory ABA Triblock Copolymer (PS-b-PMA-r-PODA-b-PS)
Equipment:
For Melt Processing:
Braintree Scientific Inc.
o BS-8000/9000
o Multi-PhaserTM
9
o Programmable Syringe Pump
Glass Hamilton Syringe – 1000 Series
o Syringe volume – 5 mL
o Inner barrel diameter – 10.301 mm
Traceable Expanded-Range Thermometer (VWR)
Barnstead Electrothermal Heater
Heating Tape (narrower width tape was used in 2 nd , 3rd, 4th, and 5th trials)
For Take up:
Metal needle – used to keep fiber from sticking to end of capillary
Plastic Ziploc bag (trials 1 and 2)
Glass jar (trial 1 only)
Glass Pyrex container (trial #2 only)
Chair (to set take up device on)
Metal plate
Lab cart (to position ac-dc converter)
Scotch tape
2 wire nails
2 tacks
0.5’ x 1’ wood board (pine)
o Source/supplier: Home Depot
Wood screws
o Source/supplier: Home Depot
Wooden yarn spools
o Source/supplier: Michael’s Arts and Crafts
Plastic butt connectors (Home Depot – electrical department)
2 1 hole aluminum fastener(3/4‖ dia)
o Source/supplier: Home Depot
2 2 hole brass pipe straps (1‖ dia)
o Source/supplier: Home Depot
2 2 hole brass pipe straps (1 ¼ ‖ dia)
o Source/supplier: Home Depot
2 electric gearhead motors
o Input voltage: 4VDC up to 18VDC
o Motor shaft: .2" dia. x .39"L "D" shaft
o Motor dimensions about 2.43"L (excluding shaft) x 1.3" dia. (at maximum dia. at
gearhead).
o Speed ratings:
 3RPM at 6VDC with a no load current of 75mA.
10
 6RPM at 12VDC with a no load current of 75mA.
o Additional specifications:
 Gearhead has 3 tapped holes for mounting
 Brand new
AC to DC converter
o Manufacturer:
o Voltage conversion: 120 VAC to 13.8 VDC
o Max rated current: 4 Amps
2 1 Kilo-ohm linear potentiometers
o Source/supplier: Philcap Electronics
Electrical wire
For Cooling:
Metal coat hanger (Mine)
o Wire cutters were used to cut a 12‖ straight section from the hanger
Wooden yarn spool
o Source/supplier: Michael’s Arts and Crafts
Aluminum baking bread pan
o Source/supplier: Wal-Mart
Thermometer (checking temperature of water bath)
For Testing:
2 Dual Function (heating and magnetic stirring) Plate with temperature control/feedback
2 magnetic stir rods
3 glass beakers
Thermometer
Glass NMR sample tube (Trials #3-5 testing)
Glass stir rod (Trial #2 testing)
Razor blade
Two sets of tweezers
Scotch tape
A set of calipers
Ruler
11
PROCEDURES
A. Fiber Processing
Procedure for Melt-Spinning (Trials #1-5):
1. Put on safety goggles
2. Gather all melt-spinning equipment
3. Acquire enough polymer material to fill half of 5mL syringe, and then place polymer into
syringe
4. Wrap and secure heating tape around filled portion of syringe
5. Install syringe into syringe pump, and position syringe pump vertically to allow for
downward dispensing
6. Move syringe pump to counter-top edge, and make sure pump is stable or fastened down.
7. Plug heating tape into Barnstead Electrothermal heater, and then plug heater into wall
socket
8. Rotate heater knob to ―4‖ for initial heating (tape should get hot within a 1-2 minutes)
- Use thermal gloves when handling heating tape and syringe
9. Turn ON Traceable Expanded-Range Thermometer (VWR), and place thermometer tip
into heating tape pore to measure melt temperature on outside of syringe
10. Monitor heating tape temperature, and look for stability before readjusting temperature
with knob control
11. Set temperature to a value/range above the melting temperature of polymer (above 120°C
worked well for processing fiber)
12. After polymer has had enough exposure to heat, polymer melt will begin to build up and
fall slowly at the exit of the syringe capillary due to gravity.
13. Plug in Syringe pump’s cord into wall outlet, and turn ―ON‖ pump by flicking switch on
back of syringe pump
14. Using control buttons on front display of Syringe pump, set syringe diameter (10.301
mm) and dispensing rate.
15. Press start button to begin process
*****After this step, procedures vary for each trial. Procedures are continued for each
trial following.
Above Procedures (continued)
Trial 1:
16. As extrudate flows downward, use glass jar to support fiber. Move jar downward as fiber
becomes longer
17. When material is used up, press the ―Start/Stop‖ button to stop pump dispensing
18. Place fiber into a plastic Ziploc bag until fiber testing is attempted
12
19. Turn OFF syringe pump by flicking switch on back of syringe pump, and then unplug
device
20. Clean up work space, and bring back equipment to the respective areas.
Trial 2:
Initial Setup Step: Fill ¾ of a glass Pyrex beaker with water
Above Procedures (continued)
16. As extrudate flows downward, use glass Pyrex container (with water) to support and cool
fiber. Move container downward as fiber becomes longer
17. When material is used up, press the ―Start/Stop‖ button to stop pump dispensing
18. Place fiber into a plastic Ziploc bag until fiber testing is attempted
19. Turn OFF syringe pump by flicking switch on back of syringe pump, and then unplug
device
20. Clean up work space, and bring back equipment to the respective areas.
Trial 3:
For Trial 3, only one take-up device used (no water bath)
Setup procedures for take-up device
i. Position chair up against counter (with back support end away from counter)
ii. Place metal plate on top of chair seat
iii. Place take-up device on plate, and position device so that it is up against counter wall and
in-line with syringe die
Above Procedures (continued)
16. As extrudate flows downward into the water bath, grab the fiber with a hand and wind it
around take-up spool. Do not pull it too fast, or the fiber will break near the syringe
capillary exit
17. Plug in AC-DC converter, and flip switch ON to begin power supply to electric motors.
18. Adjust speed of take-up motor #1 to an appropriately low value with the potentiometer
19. Continue to pull fiber, and begin winding fiber around slowly-rotating take-up spool
13
Figure 4 – Extrudate being
stretched with take-up device
20. Adjust take-up speed with potentiometer to a rate that allows for effective stretching, but
no breaking
***If needed, the syringe dispensing rate can also be adjusted
21. When material is used up, press the ―Start/Stop‖ button to stop pump dispensing
22. Turn OFF syringe pump by flicking switch on back of syringe pump, and then unplug
device
23. Turn OFF first take-up spool by adjusting potentiometer for maximum resistance
24. Once all the remaining fiber has been wrapped onto second motor shaft, flip AC-DC
converter switch OFF
25. Unplug AC-DC converter.
26. Remove spools from motor shafts, and place spools into containers until fiber testing is
attempted.
27. Clean up work space, and bring back equipment to the respective areas.
Trials 4 and 5
For Trials 4 and 5, take-up devices and water baths were used.
Setup procedures for the take-up and cooling devices are as follows:
i. Position chair up against counter (with back support end away from counter)
ii. Place metal plate on top of chair seat
iii. Using a straight 8‖ section of coat hanger wire, poke one small hole on both sides of the
aluminum bread pan.
14
** The holes should be made about 3.5‖ above the base of the pan and about 2.25‖ from
one end of the pan.
iv. Slide the coat hanger wire through one of the holes, and then slide wooden spool over
wire
v. Continue to slide wire through other hole so that wire is positioned symmetrically across
pan width.
vi. Wrap tape around ends of coat hanger wire to restrict axial movement.
vii. Position aluminum baking bread pan (with wooden spool) on top of plate, and up against
wall supporting the counter
*** The pan should be configured as shown in Figure 5 with its longest distance
perpendicular to the counter, and spool end near the counter wall. The pan should be directly
in-line with the syringe.
viii.
Fill the pan with cool tap water so that approximately ¾ of the volume is occupied
ix. Place 2 ¼‖ high cardboard box on top of metal plate, and position right in front of
aluminum pan
x. Place the take up device on top of cardboard box, and position wooden base to align takeup spool with spool on coat hanger rod in aluminum pan.
15
Figure 5 - Melt-spinning process layout for trials 4 and 5
16
Trial 4:
Above Procedures (continued)
16. As extrudate flows downward into the water bath, grab the fiber with a hand and pull it
under the spool that is set in the water. Do not pull it too fast, or the fiber will break near
the syringe capillary exit
17. Plug in AC-DC converter, and flip switch ON to begin power supply to electric motors.
18. Adjust speed of take-up motor #1 to an appropriately low value with the potentiometer
19. Continue to monitor process, and readjust take-up and dispense speeds when appropriate
20. When material is used up, press the ―Start/Stop‖ button to stop pump dispensing
21. Turn OFF syringe pump by flicking switch on back of syringe pump, and then unplug
device
22. Turn OFF first take-up spool by adjusting potentiometer for maximum resistance
23. Once all the remaining fiber has been wrapped onto second motor shaft, flip AC-DC
converter switch OFF
24. Unplug AC-DC converter.
25. Remove spools from motor shafts, and place spools into containers until fiber testing is
attempted.
Trial 5:
Above Procedures (continued)
16. As extrudate flows downward into the water bath, grab the fiber with a hand and pull it
under the spool that is set in the water. Do not pull it too fast, or the fiber will break near
the syringe capillary exit
17. Plug in AC-DC converter, and flip switch ON to begin power supply to electric motors.
18. Adjust speed of take-up motor #1 to an appropriately low value with the potentiometer
19. Continue to pull fiber, and begin winding fiber around slowly-rotating take-up spool
20. Adjust take-up speed with potentiometer to a rate that allows for effective stretching, but
no breaking
***If needed, the syringe dispensing rate can also be adjusted
17
Figure 6 - Take-up using 2 electric motors
21. After fiber has been wrapped once on the first take-up spool, continue to pull fiber slowly
to the second take-up spool
22. Adjust speed, initially, so that it is equal to the first motor’s speed
23. As shown in Figure 6, begin winding fiber on second take-up spool
24. Increase take up speed slightly, so that additional stretching can take place between the
first and second take-up spools. Monitor process, and readjust take-up and dispense
speeds when appropriate
25. When material is used up, press the ―Start/Stop‖ button to stop pump dispensing
26. Turn OFF syringe pump by flicking switch on back of syringe pump, and then unplug
device
27. Turn OFF first take-up spool by adjusting potentiometer for maximum resistance
28. Once all the remaining fiber has been wrapped onto second motor shaft, flip AC-DC
converter switch OFF
29. Unplug AC-DC converter.
30. Remove spools from motor shafts, and place spools into containers until fiber testing is
attempted.
31. Clean up work space, and bring back equipment to the respective areas.
18
Shape Memory Testing Procedures
Trial #1 Testing
Date: Tuesday, October 12, 2010
@ 3:30 pm
until 3:55 pm
Purpose: To test shape-memory properties of fiber made in first trial
Equipment:
Safety glasses
Hotplate
Glass stir rod
Glass beaker (filled with ice water)
One set of tweezers
Testing Procedure:
1. Put on safety glasses
2. Gather and setup all testing equipment and materials
3. Place fiber on hot plate
4. Wrap hot fiber around glass stir rod (Figure 8)
5. Quench fiber in ice water for approximately 30 seconds
6. Slide fiber off of glass stir rod (use tweezers to break initial adhesive forces if necessary)
7. Place fiber on hot plate and observe relaxation
8. Record observations
9. Clean up workspace and put back all equipment
Observations: After being placed on the hot plate, the coiled fiber relaxed to a relatively
straight fiber (shape memory behavior is evident).
Figure 7 - Fiber produced in trial 1
Figure 8 - Fiber being wrapped around
stir rod
19
Trial #2 Testing
Date: Tuesday, November 2, 2010 @ 2:00 pm
until 4:30 pm
Purpose: To test shape-memory properties of fiber made in second trial
Equipment:
Dual function (heating and magnetic stirring) Plate with temperature control/feedback
2 glass beakers:
o One for hot water (set at 65°C)
o One for ice water (measured at 3°C)
Thermometer
Razor
Magnetic stir rod for achieving more even temperature distribution in hot water beaker
Glass rod
2 sets of tweezers
A set of calipers
Ruler
Three Tests
Initial Procedures:
Cut fiber (Figure 9) into four sections with razor as shown in Figure 10
Figure 9 - Fiber produced from trial 2
Figure 10 - Fiber cut for shape memory
testing
Put on safety glasses
Gather and set up all testing equipment and materials
20
Figure 11 - Water in beaker being heated and
stirred
Figure 12 - Temperature and stir speed settings
I. Knot (Tie/Untie) Test
Procedure:
1. With tweezers in both hands, place fiber sample in the hot water beaker for 5-10 seconds,
while stretching sample.
2. Remove fiber from hot water, and tie fiber in a loose knot
3. Quench fiber in ice water bath for 10+ seconds
4. Place fiber sample back into hot water
5. Watch for shape memory properties
Observations: Fiber did not exhibit any tying capabilities or untying capabilities on its
own. However, after opening up the knot loop, it did relax back to a more straight fiber.
The fiber did not fully recover its initial straightness.
Figure 13 - Knot made with fiber
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II. Coil Test
Procedure:
1. With tweezers in both hands, place fiber sample in the hot water beaker for 5-10 seconds,
while stretching sample.
2. Remove fiber from hot water, and wrap fiber around narrow glass rod
o Fiber can be wrapped loosely or tightly as shown in Figures 14 and 15
3. Quench fiber in ice water beaker for 10+ seconds
4. Slide fiber coil off rod, and place fiber into hot water
5. Watch for shape memory properties
Repeat ―coil test‖ a second time- this time stretching fiber approximately 3 times its original
length
Observations: Fiber did exhibit shape memory properties. Fiber relaxed to a straighter
fiber, but did not show full recovery as shown in Figure 16
Figure 14 - Loosely-coiled fiber
Figure 15 - Tightly-coiled fiber
Figure 16 - Imperfect shape-memory
22
III. Stretch Test
Procedure:
1. Mark a segment on fiber sample
2. Measure segment length with ruler and record value in notebook
3. With tweezers in both hands, place fiber sample in the hot water beaker for 5-10 seconds,
while stretching fiber to a length that is approximately 2 times its original length
4. Remove fiber from hot water, and quickly quench fiber in ice water for 10+ seconds
5. Measure and record segment length
6. Let Fiber sit at ambient conditions for 10 minutes
7. Measure and record segment length
8. Place fiber sample back into hot water for 10+ seconds
9. Remove fiber from hot water
10. Watch for shape memory properties
11. Measure segment length and compare to initial segment length
Repeat ―stretch test‖ a second time- this time stretching fiber approximately 3 times its original
length
Trial #3-5 Testing
Date: Thursday April 21, 2011
@ 3:40 pm
until
5:15 pm
Purpose: To test shape-memory properties of fiber made in trials #3-5
Equipment:
2 Dual function (heating and magnetic stirring) Plate with temperature control/feedback
3 glass beakers:
o One for very hot water (set at 90°C)
o One for hot water (set at 55°C)
o One for ice water (measured at 5-7°C)
Thermometer
Razor blade
2 Magnetic stir rods (for achieving even temperature distribution in 2 hot water beakers)
NMR tube
2 sets of tweezers
Initial Procedures
Put on safety glasses
Gather and setup all testing equipment and materials
23
I. Straight Test
Procedure:
Cut small (1.5-2.5‖) piece of fiber from trial sample
Using tweezers, stretch fiber to straight shape in 55°C water bath
Quickly place stretched fiber in 90°C water bath, and allow for relaxation (20-30 sec)
Quench straight fiber in ice water for approximately 20 seconds
Place fiber in 55°C water bath, and coil fiber around NMR tube as shown in Figure 17
- One end of fiber may need to be taped to NMR tube to make coiling easier
6. Quench fiber (still wound on NMR tube) in ice water to keep coiled shape (20 seconds)
7. Take fiber out of ice water and observe coil shape
8. Slide fiber off of NMR tube (use tweezers to break initial adhesive forces if necessary)
9. Place fiber back into 55°C water and observe behavior
10. Record observations
11. Clean up workspace and put back all equipment
1.
2.
3.
4.
5.
Figure 17 - Fiber coiled around NMR tube
Figure 18 - Temporary coil after being
quenched
Figure 19 - Fiber returns to original
permanent shape
24
II. Coil Test
Procedure:
1. Heat fiber in 55°C water bath for 10 seconds
2. Take out of water bath and quickly wrap warm fiber around NMR tube
- One end of fiber may need to be taped to NMR tube to make coiling easier
3. Place end of NMR tube with fiber into 90°C water bath to allow for relaxation of fiber
chains (20-30 sec)
4. Quench fiber (still coiled on NMR tube) in ice water for approximately 20 seconds
5. Take fiber out of ice water bath and slide coiled fiber off NMR tube (use tweezers if
necessary). Figure 20 shows the coiled fiber after being removed from NMR tube.
6. Using 2 sets of tweezers, place coiled fiber into 55°C water bath and stretch fiber to a
straight shape (20 seconds)
7. Quench straight fiber in ice water bath (20 seconds)
8. Take fiber out of ice water bath and observe straight shape
9. Place fiber into 55°C water bath and make observations
10. Record observations
11. Clean up workspace and put back all equipment
Figure 20 - Fiber in original coiled
shape
Figure 21 - Quenching straight fiber
in ice water
Figure 22 - Imperfect recovery of
original coiled shape
25
DATA AND CALCULATIONS
Date
Material
TRIAL 1
10/12/2010
PS-b-PMA-rPODA-b-PS
Figure 23 - Trial Summary Chart
TRIAL 2
TRIAL 3
TRIAL 4
10/29/2010
4/15/2011
4/21/2011
PS-b-PMA-r- PS-b-PMA-r- PS-b-PMA-rPODA-b-PS
PODA-b-PS
PODA-b-PS
TRIAL 5
4/21/2011
PS-b-PMA-rPODA-b-PS
Molecular
Weight (g/mol)
Melt Temp.
(°C)
Dispensed
Volume (μL)
100,000
100,000
80,000
80,000
80,000
130-140
150-165
125-135
130-145
145-155
511.9
922.2
980.3
997.2
1934
Dispense Rate
(μL/min)
90
50
Range: 10-30
Best: 22
Cooling
Ambient Air
Water bath
(20°C)
Ambient Air
None
None
1 take-up
wheel
Range: 10-15
Best: 15
Water bath
(20°C)
1 take-up
wheel
Range: 15-20
Best: 18
Water bath
(20°C)
2 take-up
wheels
1.31-1.73
1.52-1.81
0.29-0.34
0.23-0.33
0.17-0.22
Length
30cm (11.8in)
43cm (16.9in)
1165-2400cm
(459-945in)
5088-8520cm
(2003-3354in)
Observations
Thick fiber
with
inconsistent
dia.
Thick fiber
with
inconsistent
dia.
1019-1484cm
(401-584in)
Thin fiber
with
consistent
dia.
Thin fiber
with
consistent dia.
Thin fiber
with
consistent dia.
Collecting
device
Average Fiber
Dia. (mm)
** Note that the melt/process temperatures varied considerably from trial to trial. All trials were
conducted with the same material, but trials #1 and 2 used material with higher molecular weight
than material used in trials #3, 4, and 5. The dispense rate was varied from trial to trial. Trials
#2, 4, and 5 incorporated water baths for methods of cooling fiber after exiting syringe. Tap
water at a temperature of 20°C was used for the water baths. Take up devices were employed in
trial #3, 4, and 5. The above figure shows that use of a take up device can decrease fiber
diameter and enhance fiber diameter consistency.
26
No quantitative shape memory testing was conducted with fibers processed in trial 1, 3, 4, or 5.
However, quantitative shape memory testing was conducted with fibers processed in trial 2, and
the accompanying results are shown in Figure 24.
Figure 24 - Trial 2 Testing Results
Stretch Test Data
Lengths
2 x Stretch (mm) 3 x Stretch (mm)
Initial Length (L1)
19.42
19.32
Quenched Length (L2)
38.12
63.32
Length after 10 minutes in ambient (L3)
37.37
61.86
Final Length (L4)
19.63
23.18
%
%
Shape Memory Characterization
Maximum Strain (εm)
96.29
227.74
Fixed Strain (εu)
92.43
220.19
Residual Strain (εp)
1.08
19.98
Percent Fixity (Rf)
95.99
96.68
Percent Recovery (Rr)
98.88
91.23
Calculations from Trial #2 Testing for Shape Memory Characterization:
Maximum Strain (ε m):
Fixed Strain (ε u):
Residual Strain (εp):
Percent Fixity (R f):
Percent Recovery (Rr):
As shown in the above calculations, the percent fixity and percent recovery are both above 90%
27
Figure 25 - Take-up Analysis Using Trial 2
Flow Rate
Determining take-up (winding) speed
Known Quantities
volume flow rate (Q)
Guessed Values
Init. extrudate dia.
(d0)
motor shaft dia. (D1)
motor shaft rad. (R1)
Determined Values
Init. Crss-sctn area
(A0)
Init. Exit vel. (V0)
1st stretched vel. (V1)
#1 Motor vel. (w1)
Chosen Values
Draw ratio
Units
μL/min
50
3
50 mm /min
3
0.833 mm /sec
mm
1.5
5 mm
2.5 mm
1.77
mm2
0.47 mm/sec
1.89 mm/sec
113.18 mm/min
45.27 rad/min
7.205 rpm
4.000
*****In Figure 25, the motor speed required for take-up was determined using a known
volume flow rate and estimated values for initial extrudate diameter, motor shaft diameter,
and draw ratio
Sample Calculations used in determining speed needed for take-up device(s)
Using trial 2 as a starting point, 50
was selected as the volume flow rate and then converted
into units of mm3 per unit second.
The exact extrudate diameter was not measured during melt-spinning, but measurements with
calipers revealed that the fiber produced in trial 2 had an inconsistent diameter that ranged
28
between 1.52 and 1.81mm after cooling (this is listed in Figure 23). To act as a starting point, a
value of 1.5 mm was chosen for the extrudate diameter.
The area is then determined to be:
Area:
Then initial exit velocity of the extrudate is determined using the Q=VA relation.
Extrudate exit velocity:
Referring back to the Theory section, draw ratio is defined as
If
.
, then the velocity of the fiber at the take-up wheel is
Converting to units of mm per minute, the velocity becomes
The motor shaft diameter was measured as 0.2 inches, which is approximately 5 mm. Using 5
mm as the motor shaft diameter, the motor speed can then be determined which the angular and
linear velocity relation
.
Motor speed:
Based on results from trial 2 and calculations for a take-up speed, two identical electric motors
with an allowable input voltage range of 4 – 18 VDC and given rated operating speeds of 3 rpm
(at 6 V) and 6 rpm (at 12 V) were selected for use in the take-up device. The AC-DC converter
29
supplies 13.8 VDC, so linear extrapolation was used to determine that the electric motors’
operating speeds would be 6.9 rpm.
With the motor speed and other process variable values governing trials 3-5, draw ratios were
determined using an analysis conducted in Excel. Figure 29 shows this analysis.
Figure 26 - Take-up Analysis for Trials 3-5
Take-up Analysis
Known Quantities
volume flow rate (Q)
22
15
22
15
0.367
0.250
1.7
5
2.5
1.7
17
8.5
Units
18 μL/min
3
18 mm /min
3
0.300 mm /sec
Guessed Values
1.7 mm
17 mm
8.5 mm
Init. extrudate dia. (d0)
motor shaft dia. (D1)
motor shaft rad. (R1)
Determined Values
Init. Crss-sctn area
(A0)
2.27
2.27
2.27
Init. Exit vel. (V0 )
0.16
0.11
0.13 mm/sec
6.14 mm/sec
1st stretched vel. (V1)
#1 Motor vel. (w1)
Chosen Values
Draw ratio
mm2
1.81
6.14
108.38 368.51 368.51 mm/min
43.35 43.35 43.35 rad/min
6.900 6.900 6.900 rpm
11.182 55.763 46.469
** In trials 3-5, the take-up speed used was 6.9 rpm,
which shows that the draw ratios were 11.182, 55.763, and
46.469, respectively.
30
RESULTS & DISCUSSION
In this experiment, five trials of melt-processing were performed to produce fibers out of a PS-bPMA-r-PODA-b-PS triblock copolymer. A summary of the trials is presented in Figure 22 and
shows the difference in molecular weights of the polymer used in trials 1 and 2 and trials 3 -5.
Dispense rates of the material were also varied in each trial. In trials 1 and 2, no take-up device
was used to collect and stretch the fiber extrudate. In these trials, the fibers produced were
relatively thick and exhibited good shape memory behavior. The fiber produced in trial 2 was
subjected to a stretch test, and the results in Figure 23 show that the percent fixity and recovery
were both above 90%, which was a goal of this design project. Quantitative shape memory
testing of the fibers produced in trials 3-5 was attempted, but was unsuccessful. Qualitative
testing (Figures 16-21) involving coiling and straightening fibers was utilized, and further
demonstrated the polymer’s shape memory ability.
The processing of the fiber was conducted with the use of a programmable syringe pump. An
alternative to this set-up would have been to use a capillary rheometer. With a capillary
rheometer, the rheological properties could have been obtained. However, in this particular
project, the main goal was to determine if a triblock copolymer could be processed into a fiber.
The programmable syringe pump was capable of accomplishing this, as well, as the pump
offered greater portability over a capillary rheometer. Students at The University of Akron have
access to a capillary rheometer located in the Polymer Academic Center, but an individual who is
not enrolled in the university may have an issue with trying their own experiments. According to
Sherman, benchtop capillary rheometers can range in price from $30,000-40,000 up to $100,000
(Sherman, 2004). A programmable syringe pump, similar to the one used in this design project,
31
can be purchased for $275.00 at www.braintreesci.com (Products, 2001). With a much smaller
initial capital investment, lab-scale experimentation can be performed adequately.
For trials 3-5, a take-up device was built at low-cost and utilized to accomplish a full lab-scale
melt-spinning process. A schematic of the device is shown in Figure A17, and a list of the parts
and expenses associated with the construction of the take-up device is found in Figure A19.
With the addition of this device, the processing of the tri-block copolymer became much more
effective. The stretching of the fiber created a much thinner strand than had been produced in
trials 1 and 2. Proper adjustment of the take-up speed also resulted in a fiber with a much more
uniform diameter. As mentioned in the Background section of this report, the stretching involved
in fiber spinning aids in the structuring of the polymer’s molecular chains. This structuring will
improve the fiber’s strength in the axial direction. Further optimization was attempted with the
addition of a water bath (20°C) in trials 4 and 5, and with the use of a second take-up spool for
extra cold-drawing. From Figure 22, definite improvements in stretching are evident when
observing the reduction in diameter between consecutive trials.
32
CONCLUSIONS
The results obtained from the experimental trials and performance tests indicate the
accomplishment of meeting the initial criteria set forth in my design project. In each of the five
trials, a fiber longer than 6 inches was produced within 30 minutes. The shape memory testing
showed that the PS-b-PMA-r-PODA-b-PS triblock copolymer fiber had fixity and shape
recovery properties greater than 90%. The take-up is important in stretching the fiber and
improving the diameter consistency of the fiber, and the cost of producing an effective lab-scale
take-up device is relatively inexpensive. Based on the success of this project, there is
justification that a large-scale melt-spinning process is viable for shape memory polymers.
Recommendations that could be made are to continue experimentation of melt-processing PS-bPMA-r-PODA-b-PS triblock copolymer fiber, and to possibly attempt solution processing (wet
and dry spinning). With the continuation of more melt-processing testing, attempts to increase
the process/take-up speed and modify the setup should be made. In addition, more samples of
the same polymer should be polymerized, processed, and tested to determine if there is a definite
effect of molecular weight on shape memory behavior under one specified set of conditions.
Also, a different polymer could be experimented with and tested to better evaluate this lab-scale
melt-spinning process.
ACKNOWLEDGEMENTS
The author would like to acknowledge and thank all who offered advice and assistance in this
Senior Design Honors Project. Special thanks go to the College of Engineering and Honors
College at The University of Akron, Dr. Kevin Cavicchi, Dr. Robert Weiss, Dr. Hendrik Heinz,
Pengzhan Fei, and Seth Haney for all their support.
33
REFERENCES
Fei, P. a. (2010). Synthesis and Characterization of a Poly(Styrene-block-methylacrylate-cooctadecylacrylate-block-styrene) Shape Memory ABA Triblock Copolymer. Akron: American
Chemical Society.
Isayev, P. D. (2006). Rheology: Concepts, Methods, & Applications. Toronto: ChemTec
Publishing.
Jana, Sadhan. ―Lecture 23: Shaping by Stretching Flows.‖ Polymer Processing. The University
of Akron, Akron, OH. 24 November, 2010.
Lendlein, A. a. (2002). Shape-Memory Polymers. Weinheim: Angewandte Chemie - WileyVCH.
Products. (2001). Retrieved April 26, 2011, from Braintree Scientific Web Site:
http://www.braintreesci.com/Products/OEMPump.asp#JustInfusion
Sherman, L. M. (2004, May). "Rheometers: Which Type is Right for You?". Retrieved April 26,
2011, from Plastics Technology: http://www.ptonline.com/articles/rheometers-which-type-isright-for-you
Tadmor, Z. a. (2006). Principles of Polymer Processing. Haifa, Israel and Newark, New Jersey:
Wiley-Interscience.
34
APPENDIX
TABLE OF FIGURES
Figure A1 – Take-up Analysis for Volume Flow Rate of 50 μL………………………………………….36
Figure A2 – Take-up Analysis for Volume Flow Rate of 25 μL ………………………………………....37
Figure A3 – Input Voltage versus Motor Speed ……………….………………………………………....38
Figure A4 – Plot of Motor Speed vs. Input Voltage …………...…………………………………………38
Figure A5 – DC Electric gear head motor ……………………………………………………………..…39
Figure A6 – 5mL glass syringe ………………………………………………………………..…...……..39
Figure A7 – Heating tape …………………………………..……………………………………………..39
Figure A8 – Electrothermal Heater …………………………………………………………………...…..40
Figure A9 – Programmable Syringe ………………………………………………………………….…..40
Figure A10 – Hot plate used in trial 1 testing ………………………………………………………….....40
Figure A11 – Take Take-up device board with …………………………………………………………..41
Figure A12 – Test equipment (NMR tube and tweezers)L ……………………………………...………..41
Figure A13 – Magnetic stir rod …………………………………………………………………….……..41
Figure A14 – Calipers …………………………………………………………………………...………..42
Figure A15 – Water bath (aluminum pan and wooden spool on metal coat hanger)……………………..42
Figure A16 – AC-DC Voltage Converter ………………………………………………………….……..42
Figure A17 – Schematic of Take-up Device ………………………………………………………….…..43
Figure A18 – Schematic of Set-up for Trials 4 and 5……………………………………………………..44
Figure A19 – Take-up Device Expenses …………………………………………………………..……..45
Figure A20 – SMP sample before processing …………………………………………………………....46
Figure A21 – School Spirit (SMP cut into "UA" shape)…………………………………...……………..46
35
APPENDIX (Continued)
Figure A1 – Take-up Analysis for Volume Flow Rate of 50 μL
Determining take-up (winding) speed
Known Quantities
volume flow rate (Q)
50
50
50
50
50
50
50
50
50
50
50
50
50
50
0.833 0.833 0.833
0.833
0.833
0.833
0.833
Units
50 μL/min
3
50 mm /min
3
0.833 mm /sec
Guessed Values
Init. extrudate dia. (d0)
motor shaft dia. (D1)
motor shaft rad. (R1)
Determined Values
1.5
5
2.5
1.5
6
3
2
5
2.5
2
6
3
1.5
5
2.5
1.5
6
3
2
5
2.5
Init. Crss-sctn area (A0)
1.77
1.77
3.14
3.14
1.77
1.77
3.14
Init. Exit vel. (V0)
0.47
0.47
0.27
0.27
0.47
0.47
0.27
1st stretched vel. (V1)
#1 Motor vel. (w1)
Chosen Values
Draw ratio
2 mm
6 mm
3 mm
2
3.14 mm
0.27 mm/sec
1.89
1.89 1.06 1.06
3.77
3.77
2.12
2.12 mm/sec
113.18 113.18 63.66 63.66 226.35 226.35 127.32 127.32 mm/min
45.27 37.73 25.46 21.22 90.54 75.45 50.93 42.44 rad/min
7.205 6.004 4.053 3.377 14.410 12.008 8.106 6.755 rpm
4.000
4.000 4.000 4.000
8.000
8.000
8.000
8.000
*****This chart shows speed values for several cases (varying init. Extr. Dia., motor shaft
dia., and draw ratio)
36
APPENDIX (Continued)
Figure A2 - Take-up Analysis for Volume Flow Rate of 25 μL
Determining take-up (winding) speed
Known Quantities
volume flow rate (Q)
25
25
25
25
25
25
25
25
25
25
0.417 0.417 0.417 0.417
0.417
Units
25
25
25 μL/min
3
25
25
25 mm /min
3
0.417 0.417 0.417 mm /sec
Guessed Values
Init. extrudate dia. (d0)
motor shaft dia. (D1)
motor shaft rad. (R1)
Determined Values
1.5
5
2.5
1.5
6
3
2
5
2.5
2
6
3
1.5
5
2.5
1.5
6
3
2
5
2.5
Init. Crss-sctn area (A0)
1.77
1.77
3.14
3.14
1.77
1.77
3.14
Init. Exit vel. (V0)
0.24
0.24
0.13
0.13
0.24
0.24
0.13
1st stretched vel. (V1)
#1 Motor vel. (w1)
Chosen Values
Draw ratio
2 mm
6 mm
3 mm
2
3.14 mm
0.13 mm/sec
0.94 0.94 0.53 0.53
1.89
1.89 1.06 1.06 mm/sec
56.59 56.59 31.83 31.83 113.18 113.18 63.66 63.66 mm/min
22.64 18.86 12.73 10.61 45.27 37.73 25.46 21.22 rad/min
3.603 3.002 2.026 1.689 7.205 6.004 4.053 3.377 rpm
4.000 4.000 4.000 4.000
8.000
8.000 8.000 8.000
*****This chart shows speed values for several cases (varying init. Extr. Dia., motor shaft
dia., and draw ratio)
37
APPENDIX (Continued)
Figure A3 – Input Voltage versus Motor Speed
DC Voltage Input
(Volts)
6
12
13.8
Motor Shaft Speed
(RPM)
3
6
6.9
Figure A4 – Plot of Motor Speed vs. Input Voltage
Motor Speed (rpm)
Motor Speed versus Input Voltage
8
7
6
5
4
3
2
1
0
6.9
6
3
0
5
10
15
DC Voltage Input (V)
38
APPENDIX (Continued)
Figure A5 - DC Electric gear head motor
Figure A6 - 5mL glass syringe
Figure A7 - Heating tape
39
APPENDIX (Continued)
Figure A8 - Electrothermal Heater
Figure A9 - Programmable Syringe
Figure A10 - Hot plate used in trial 1 testing
40
APPENDIX (Continued)
Figure A11 - Take-up device board with
motors and speed control
Figure A12 - Test equipment (NMR tube and
tweezers)
Figure A13 - Magnetic stir rod
41
APPENDIX (Continued)
Figure A14 - Calipers
Figure A15 - Water bath (aluminum pan
and wooden spool on metal coat hanger)
Figure A16- AC-DC Voltage Converter
42
APPENDIX (Continued) - This is the schematic page (AutoCAD drawing of Take-up device)
43
APPENDIX (Continued)
Figure A18 - Schematic of set-up
44
APPENDIX (Continued)
Figure A19 - Take-up Device Expenses
Part
6VDC 3rpm
Gearhead Motor
Quantity Used
2
Product/Model #
G15492
P-11B
Supplier
Electronic
Goldmine
(Scottsdale, AZ)
Philcap Electronics
Total Cost
$46.48 ($24.00
w/o shipping
fees)
$10.28
Linear 1 kΩ
potentiometer
1 ¼‖ steel-copper
tube strap
1‖ steel-copper
tube strap
1 in. x 6 in. x 6 ft.
Whitewood Board
Crown Bolt zinc
plated wood
screws #12 x ¾‖
(10-pcs)
Halex 3/4 in. 1Hole Conduit
Straps (4-Pack)
Crown Bolt #16 x
1-1/4 in. Wire
Nails 1.75 oz.
Zinc Plated
Wood Spools (3pack)
Wall tacks
Speaker wires
Scotch Matte
Finish Magic™
tape
CWI Solid State
Regulated DC
Power Supply
TOTAL COST
2
2
Model 501-5PK
Home Depot
$0.56
2
Could not find
Home Depot
$0.38
1
Model # 914762
Home Depot
$5.37
8
Model # 20971
Home Depot
$5.24
2
Model # 96152
Home Depot
$0.88
2
Model # 45144
Home Depot
$1.30
3
754246105462
Michaels
$1.49
2
2
2 small pieces
N/A
N/A
N/A
Found at home
Donated by friend
Found at home
Free
Free
Free
1
Model # PS-4AR
Donated by father
free
$71.98
45
APPENDIX (Continued)
Figure A20- SMP sample before processing
Figure A21 – School Spirit (SMP cut into "UA" shape)
46