1. Influences of Sequential Biaxial Stretching Parameters on the Interior Structure of Polypropylene Membrane
Liang-Yu Chen, Chung-Cheng Su and Ren-Haw Chen
Department of Mechanical Engineering
National Chiao Tung University

2. Introduction

3. Application of polymer membrane
Packaging
Water filter
Battery ion exchange membranes
Barrier
Filter

4. Membrane Sequential Biaxial Stretching
Extruder
Cutting
Cooling Roller
Transverse Direction (TD) Stretching
Machine Direction (MD) Stretching
Melt extrusion die
Drawing
Stretching
Interlamellar region
Lamellar
Bridging structure
Micropores
Direction of uniaxial stretching
1μm

5. Advantage of polypropylene(PP)
Resistant to many chemical solvents
Fine mechanical strength
Low glass transition temperature
Semi-crystalline

6. Experimental

7. Heat Deflection Temperature
Materials
Polypropylene ( Sumitomo Chemical Asia, AV161)
Mold temperature 130°C
70 x 70 x 0.5 mm
Properties
Method
Unit
Value
Density
ASTM D792
g/cm3
0.9
Tensile Strength
ASTM D638
MPa 24
Rockwell Hardness
ASTM D785
HRC 88
Melt temperature
ISO 3146 °C
170
Heat Deflection Temperature
ASTM D648
114
Melt Flow Rate
ASTM D1238
g/10min 5

8. Stretching device With Controllable: Temperature Stretching Speed
Controller
Servo Motor
Heater
Plate
Grippers
Roller
With Controllable:
Temperature
Stretching Speed
Drawing Ratio

9. Stretching procedure PP Sheets Injection Molding Injection Cooling
Ejection
Heating
MD Stretching
Thermal Setting
TD Pre-stretching
TD Stretching
Dimensional Measurement
Membrane Analysis
Optical Microscopic Observation
Polarized Optical Microscopic Observation
Plastification

10. Optical microscopic observation

11. Results and Discussion

12. Effects of mold temperature on interior structure of membrane
Polarized optical microscopy micrograph cross-section of PP sheets formed at various mold temperatures. (a)90°C, (b)120°C, (c)130°C.

13. Interior structures of the membrane formed by stretching
The interior structure of membrane. (a)after MD stretching, (b)after TD stretching.
The micrographs of structure of PP sheet before stretching.
The net-like interior structure of membrane

14. Effects of MD stretching temperature on membrane’s interior structures
MD Drawing Ratio
TD Pre-stretching Temperature
Ratios of TD Pre-stretching to Total TD Stretching
TD Stretching Temperature
TD Drawing Ratio ↓
300%
90°C
60%
120°C
200%
(a)110°C, (b)120°C, (c)130°C, (d)140°C, (e)150°C MD TD

15. Effects of MD stretching temperature on membrane’s interior structures
percentage of the net-like
structure
mean size of the net-like
Structures (µm^2)
MD stretching temperature
MD stretching temperature
standard deviation of sizes
of the net-like structures (µm^2)
thickness of the
membrane (µm)
MD stretching temperature
MD stretching temperature

16. Effects of MD drawing ratio on membrane’s interior structures
260%
280%
300%
320%
340%
(a)
(b)
(c)
(d)
(e)
MD Stretching Temperature
MD Drawing Ratio
TD Pre-stretching Temperature
Ratios of TD Pre-stretching to Total TD Stretching
TD Stretching Temperature
TD Drawing Ratio
120°C ↓
90°C
60%
200%
(a)260%, (b)280%, (c)300%, (d)320%, (e)340% MD TD

17. Effects of MD drawing ratio on membrane’s interior structures
percentage of the net-like
structure
mean size of the net-like
Structures (µm^2)
MD drawing ratio
MD drawing ratio
standard deviation of sizes
of the net-like structures (µm^2)
thickness of the
membrane (µm)
MD drawing ratio
MD drawing ratio

18. Effects of TD pre-stretching temperature on membrane’s interior structures
MD Stretching Temperature
MD Drawing Ratio
TD Pre-stretching Temperature
Ratios of TD Pre-stretching to Total TD Stretching
TD Stretching Temperature
TD Drawing Ratio
120°C
300% ↓
60%
200%
(a)80°C, (b)90°C, (c)100°C, (d)110°C, (e)120°C MD TD

19. Effects of TD pre-stretching temperature on membrane’s interior structures
percentage of the net-like
structure
mean size of the net-like
Structures (µm^2)
TD pre-stretching temperature
TD pre-stretching temperature
standard deviation of sizes
of the net-like structures (µm^2)
thickness of the
membrane (µm)
TD pre-stretching temperature
TD pre-stretching temperature

20. Effects of ratio of TD pre-stretching to total TD stretching on membrane’s interior structures
20%
40%
60%
80%
100%
(a)
(b)
(c)
(d)
(e)
MD Stretching Temperature
MD Drawing Ratio
TD Pre-stretching Temperature
Ratios of TD Pre-stretching to Total TD Stretching
TD Stretching Temperature
TD Drawing Ratio
120°C
300%
90°C ↓
200%
(a)20%, (b)40%, (c)60%, (d)80%, (e)100% MD TD

21. Effects of ratio of TD pre-stretching to total TD stretching on membrane’s interior structures
percentage of the net-like
structure
mean size of the net-like
Structures (µm^2)
10% % %
10% % %
ratios of TD pre-stretching
to total TD stretching
ratios of TD pre-stretching
to total TD stretching
thickness of the
membrane (µm)
standard deviation of sizes
of the net-like structures (µm^2)
10% % %
10% % %
ratios of TD pre-stretching
to total TD stretching
ratios of TD pre-stretching
to total TD stretching

22. Effects of TD stretching temperature on membrane’s interior structures
MD Stretching Temperature
MD Drawing Ratio
TD Pre-stretching Temperature
Ratios of TD Pre-stretching to Total TD Stretching
TD Stretching Temperature
TD Drawing Ratio
120°C
300%
90°C
60% ↓
200%
(a)110°C, (b)120°C, (c)130°C, (d)140°C, (e)150°C MD TD

23. Effects of TD stretching temperature on membrane’s interior structures
percentage of the net-like
structure
mean size of the net-like
Structures (µm^2)
TD stretching temperature
TD stretching temperature
standard deviation of sizes
of the net-like structures (µm^2)
thickness of the
membrane (µm)
TD stretching temperature
TD stretching temperature

24. Effects of TD drawing ratio on membrane’s interior structures
180%
200%
220%
240%
260%
(a)
(b)
(c)
(d)
(e)
MD Stretching Temperature
MD Drawing Ratio
TD Pre-stretching Temperature
Ratios of TD Pre-stretching to Total TD Stretching
TD Stretching Temperature
TD Drawing Ratio
120°C
300%
90°C
60% ↓
(a)180%, (b)200%, (c)220%, (d)240%, (e)260% MD TD

25. Effects of TD drawing ratio on membrane’s interior structures
percentage of the net-like
structure
mean size of the net-like
Structures (µm^2)
TD drawing ratio
TD drawing ratio
standard deviation of sizes
of the net-like structures (µm^2)
thickness of the
membrane (µm)
TD drawing ratio
TD drawing ratio

26. Conclusions

27. For sequential biaxial stretching process
MD stretching
Increasing the orientation of the structure of the membrane
TD pre-stretching (with low temperature)
Separating the interior structure of the membrane
TD stretching
Leads to a net-like interior structure

28. During MD stretching Increasing MD stretching temperature
The uniformity of the structure of the membrane would increased
Improves the generation of fibers in the net- like interior structure
Increasing MD drawing ratio

29. During TD pre-stretching
Increasing TD per-stretching temperature
Significantly reduces the number of net-like structures
Increasing the ratio of TD pre-stretching to total TD stretching
Increases the number of net-like structures and improves the consistency of their sizes

30. During TD stretching Increasing the stretching temperature
Reduces the amount of net-like structures formed
Increasing TD drawing ratio
Increases the size of the formed net-like structures

31. Thanks for your kind attention!