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1 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Microinjection moulding (µIM) of thermoplastic polymers :
From theory to experiment
J. Giboz1,2, T. Copponnex1, P. Mélé2
2: LMOPS - UMR CNRS 5041University of SavoieLe Bourget du LacFrance
1:HE-ARCUniversity of applied scienceSaint-ImierSwitzerland
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2 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Outline
I. Main goal� Influence of the moulding conditions in injection moulding processes:
“µpart vs Macroparts”
II. Processing techniques� Material chosen and processing conditions
III. Experimental Results / Discussion� “µpart vs Macroparts”: Difference in Structure and properties
IV.Conclusions
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3 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Main Goal
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
Chemical degradation?
Mechanical properties?
Thermal properties?
Homogeneity?
Giboz J., Copponnex T. , Mélé P. , J Micromech. Microeng., 2007, 17 R96-R109
Do the processing conditions modify the properties and the structure of polymers?
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4 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Processing techniques (1)
Babyplast 6/10®
5T Clamping force
0,15mm thick
Sesame nanomolder®
1,5T Clamping force
HDPE Borealis MG9641
x10
Moulding conditions
T = 220°C, V inj = 200 mm/sTmould = 80°C Tmould = 30°C
1,5mm thick
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
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5 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
3-Plates mould(CNC Machining)
Mould insert (Made by UV-LIGA)
Injection gates geometry
Ø: 0,2mm
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
Processing techniques (2)
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6 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Reference: 1,33
Process capability
3.72 3.73 3.74 3.75 3.76 3.770.1
1
10
40
70
95
99.5
SPC1 SPC2
R=0,988
Cum
ulat
ed fr
eque
ncy
(%)
Part length (mm)
R=0,997
3.72 3.73 3.74 3.75 3.76 3.770
5
10
15
20
Fre
quen
cy
Length (mm)
SPC 1
0.691.17Cpk
1.511.35Cp
0.0060.007σ
3.7593.747Mean
SPC 2SPC 1
The µIM process is capable to produce the part withthe specified tolerances
Two series of 300 parts
Length
Normal probability plot
Fre
quen
cyC
umul
ated
Fre
quen
cy(%
)
Length (mm)
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
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7 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Experimental results
Influence of the processing conditions on
the Microstructure and properties of Polymer
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8 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Theoretical analysis
Theoretical shear rates higher than allowable ones
Plate
Cal
cula
ted
wal
l she
ar r
ates
(s-
1 )
Speed (mm/s)
Micropart
0101
102
103
104
105
106
0 200 400 600 800 1000 1200
1
Speed (mm/s)
Maximum shear rates(≈ 40 000s-1)
0 200 400 600 800 1000 1200101
102
103
104
105
106
Speed (mm/s)
Micropart (Ø0,2mm)
Plate (0,5x6mm)
Brydson J.A., Flow properties of polymer melts, 1970, Van Nostrand Reinhold, New York
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
+=2
)12(2
WH
Q
n
nγ&
⋅+=
3
4
4
13
r
Q
n
n
πγ&
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9 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Experimental analysis
Molecular weight distribution:
Gel Permeation Chromatography
Chemical functions:
Fourier Transformed – Infrared spectroscopy (ATR mode)
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
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10 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria40
60
80
100
4000 3500 3000 2500 2000 1500 1000 500
Wave number (nm-1)
%R
efle
ctan
ce Micropart Plate Pellet
No degradation occurs with the
µIM process
Separation as a function of the molecular weight
Experimental Results
2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,50,0
Mw : 120000 g/mol
Mn : 13000 g/mol
Wei
ghtf
ract
ion
(Der
ivat
ive)
Molecular weight (log)
0,0
0,1
0,2
0,3
0,4
0,5
0,6
2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 6,50,0
0,1
0,2
0,3
0,4
0,5
0,6
Micropart Plate Pellet
Mn MwI. Goal
II. Processing techniques
III. Results
IV. Conclusion
Gel PermeationChromatography
FT-IR spectroscopy
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11 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
OM(Optical microscopy)
Polymer morphology: Crystalline structure
WAXS(Wide angle X-Ray Scattering)
DSC(Differential Scanning Calorymetry)
Multiscale relationshipsPictures from: Hobbs J., Chin J Polym Sci, 2003, 21, 135
1µµµµm
Spherolites Lamellas
The macroscopic properties of parts greatly depends on the morphology
Crystal
Scale (m)10-5 10-8 10-910-3
Plate
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
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12 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Optical microscopy (Thickness)
Plate microscopy (Half thickness)
200µm
Skin Core
CoreSkin Shear zone Post-filled zone
Mendoza R., Material PhD Thesis,ENSAM Paris, 2005
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
HDPE structure
200µm
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13 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Optical microscopy (Thickness)
A well defined “Skin-core” structureµpart morphology is more homogeneous / Macroparts
50µm
Micropart
50µm
Cryomicrotomed samples
5 µm thick
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
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14 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Temperature cycle
DSC: Experimental results
Samples’ weight: 2.4mg ± 0.1mg10°C/min
5 min
10°C/min
3 min
5 min230°C
40°C
10°C/min 10°C/min
T°
time
Smaller lamellas thicknesses for µIMDistribution of lamellae thicknesses more homogeneous for µIM
110 115 120 125 130 1350
10
20
30
40
Hea
t flo
w (
J/g.
°C)
Temperature (°C)
Micropart Plate Pellet
Second heating
EndoEndo
1100
10
20
30
40
Hea
t flo
w (
J/g.
°C)
110 115 120 125 130 1350
Temperature (°C)
110 115 120 125 130 1350
10
20
30
40
Micropart Plate Reference (Pellet)
Hea
t flo
w (
J/g.
°C)
Temperature (°C)
EndoEndo
First heating
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
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15 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
00,00
0,02
0,04
0,06
0,08
0,10
W
eigh
t dis
trib
utio
n (n
m-1)
C)(J/flow Heat :dTdE °
:T0mMelt temperature ofa perfect crystal (°K)
:M Crystal weight (g)
:eσ Surface energy (J.m-2)
*: Albérola et al., J Polym Sci B: Polym Phys 1990. 28, 569
Crystallite thickness in µIM are smaller / conventional processThickness distribution of crystallites is narrower
Gibbs-Thomson relation
Distribution of lamellas thicknesses
⋅−= ∞
m
e0m
∆Hl
2σ1TT
0 10 20 30 40
Lamellas thickness (nm)
Crystal thickness distribution*
( )MT2σ
ρTTdTdE
) l (f0me
c20
m
⋅⋅
⋅−⋅=
0 10 20 30 400,00
0,02
0,04
0,06
0,08
0,10
Lamellae thickness (nm)
Wei
ght d
istr
ibut
ion
(nm
-1)
Micropart Plate
0 10 20 30 400,00
0,02
0,04
0,06
0,08
0,10
Lamellae thickness (nm)
Wei
ght d
istr
ibut
ion
(nm
-1)
Micropart Plate
Second heatingFirst heating
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
Thermal and Shear effect?
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16 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
*: Giboz, J., P. Mélé, T. Copponnex, “On the morphology of microinjection moulded thermoplastics polymer”
Submitted to Polymer
WAXS: Crystalline structure
40mm 1,5mm
Bragg’s law: Determination of the crystalline structured = n.λ / 2sin(θ)
110
200
No change in the crystalline structureLamellae thickness lower (as for DSC measurements)
002
12 16 20 24 360,0
0,1
0,2
0,8
0,9
1,0
Micropart Plate
Inte
nsity
(C
ount
s (A
.U)
2 Theta (deg)
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
Cristallinity(%)
Micropart 66 ± 3
Plate 58 ± 3
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17 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Conclusions
I. Goal
II. Processing techniques
III. Results
IV. Conclusion
• Mould• Mould insert
Physical modification
• “Skin-core” structure• Crystallinity more important• Thinner crystalline entities• More homogeneous crystalline structure
• Small scale Productions• Capable process
Thermal VS Shear effects?
Polymerproperties
Development
Processing
Chemical modification
• No degradation
Part properties?
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18 4M 2007 Conference, 3-5 October 2007, Borovets, Bulgaria
Conclusions
Thank you for your attention