Injection Molding Vectra® Liquid Crystal Polymers (LCP)

Transcription

Injection Molding
Vectra® Liquid Crystal Polymers (LCP)
Processing and Mold Design
© 2013 Celanese LCP-007 AM 10/13
Celanese Maintains Leading Position in
Engineered Materials
Service temperature
Engineering Polymers
High-Performance
Polymers (HPP)
(TI1 > 150°C)
Engineering
Polymers (ETP)
(TI1 90 – 150°C)
Basic
Polymers
LCP
– Vectra® /Zenite®
PPS
– Fortron®
PCT
– Thermx®
PET
– Impet®
PBT
– Celanex®
PBT Alloy
– Vandar®
TPC-ET
– Riteflex®
POM
– Hostaform®/Celcon®
UHMW-PE
– GUR®
Long Fiber and
Continuous Fiber
Reinforced Thermoplastics*
Amorphous
LFRT
– Celstran®, Factor ®
Compel®
CFR-TP
– Celstran® Tapes,
Rods and Profiles
Partially crystalline
TI1 = Temperature Index
* with Matrix Polymers: PP, PA, PPS, PBT, POM and others on request
2
Liquid Crystal Polymers are Very Unique
► Melting range rather than sharp melt point and very low heat
of fusion.
► High chain continuity, ordered molecular structure in both solid
and melt phase.
► Flows extremely well under shear within the
melting range.
► Inherently flame resistant.
► High heat deflection temperatures.
► Reinforcement reduced anisotropy increases load bearing
capability.
3
LCP vs Semi-Crystalline Polymer
Vectra® LCP maintains same molecular order in both the melt and solid phase.
Nematic Liquid Crystal
Random Coil
Melt
Extrusion
Solid State
Extended chain Structure
► High Chain Continuity
► High Mechanical Properties
► Inherent Property Anisotropy
Lamellar Structure
► Low Chain Continuity
► Lower Mechanical Properties
4
Vectra® LCP– A History of Innovation
340
S resin (S135)
HDT@ 1.8 MPa, °C
320
300
T resin (T130)
280
J resin
(30% GF)
Ei resin (E130i)
260
C resin (C130)
240
A resin (A130)
L resin (L130)
220
200
1980
1985
1990
1995
2000
2005
2010
Continuous Innovation to Meet Customer Needs
5
The Heat Deflection Temperature vs. Tm
30-35% Glass Reinforced Grades
Reflow Peak Temp
350
DTUL/A @ 1.8 MPa
330
310
290
Vectra S135
PPA
270
PPS
Vectra E130i
PA HTN
PA 46
250
Reflow Peak Temp
PCT
Vectra A130
230
210
240
260
280
300
320
340
360
380
Melting Temperature °C
Reflow Peak Temperature is a Big Factor for Part Failure
6
Vectra® LCP Products
Fillers and reinforcements – to match performance with
application needs
Filler Reinforcement
Effect(s)
Fiberglass
Stiffness and strength
Carbon fiber
Enhanced stiffness and strength
Mixed fillers/fibers
Wear resistance and stiffness
Mineral fillers
Flatness and surface appearance
Graphite flake
Wear and chemical resistance
Carbon black
Electrostatic dissipation
Proprietary fillers
Improved platability
Pigments
Color concentrates
7
Vectra® LCP Grades
Glass Fiber
A115
A130
A150
Carbon Fiber
A230 D3
Fiber / Filler
A430 FDA
A435 FDA
E130i
E150i
E480i
E130G
S135
E440i
E 463i /E471i
E473i
E488i
S471
S475
E540i
Mineral
Graphite
A625
Conductive
A700
A725
A230-D3
J540
S540
S625
E820i Pd
E830i Pd
E840i LDS
Plateable
Unreinforced
A950
LCP Alloy Blend
V140
V143 XL
V143 LC
HDT Increases
8
Spiral Flow vs. Other Resins (30-40% GF)
Vectra E130i
PPS
PCT
PPA
PET FR
0
50
100
150
Spiral Flow (Inches)
Each molded at manufacturer’s recommended conditions and three injection
pressures normalized to 30K psi. Cavity thickness = 0.125 in.
High Flow = Thinner Walls and Complex Parts
9
Dimensional Stability
Stable dimensions after exposure to surface mount technology temperatures (reflow
soldering)
► Change of length vs. 4.149-inch tool dimension
► SIMM molded at manufacturer’s recommended conditions
► SMT simulated by hot oil bath exposure at 260°C
4.5
SHRINKAGE (mils/inch)
4
As molded
SMT @ 260°C
3.5
3
2.5
2
1.5
1
0.5
0
Vectra E130i
PPS 40GF
PPS 40GF HF PPA 33GF V0
HTN 35GF V0
Dimensional Variations Can Cause Contact Failure
10
Water Absorption
Cross section of blistering
sample (connector housing)
Water Absorption (ppm)
40000
LCP GF30
35000
Water Absorption (ppm)
LCP GF30
PPS GF40
PA9T GF33
PA9T GF33
PA6TGF30
PA46 GF40
30000
25000
20000
15000
10000
5000
0
40000
PPS GF40
PA6TGF30
20
40
PA46 GF40
60
Time (hours)
80
100
Condition: 60°C; 95%RH
35000
30000
25000
20000
15000
10000
5000
0
20
40
60
80
Time (hours)
Condition: 35°C; 85%RH
100
PA 6T GF30FR
PA 46 GF30FR
Condition:
40°C; 95%RH; 96 hrs;
IR Reflow @ 265°C
High Water Absorption + Temp = Quality and Reliability Problems
11
Automotive
E&E
Technology
MID/LDS
High
Performance
Connectors
LCP
Cookware
Electronic
Packaging
Medical
Tech Fibers
12
Challenges on Materials for
Interconnects
Trends in
Interconnects
Typical Design for
Interconnects
Lead-free soldering
(ROHS and WEEE)
Material
Requirements
Higher heat
resistance
High flow
Improved flatness
Miniaturization
(complex, thinner)
Stronger weldlines
Higher frequency
Electrical properties
V-0 Halogen free
Agency compliance
13
Challenges in Materials for Electronics
Halogen-Free Materials
Elimination of Halogen Flame Retardants
Must Have Both Properties
High Temperature
Halogen-Free Polymers
Increased Thermal Stability to Meet
Lead-Free Soldering Requirements
Lead-Free Soldering Process
RoHS and WEEE
14
Molding
Processing Recommendations
► Drying
► General Processing Guidelines
► Equipment
► Additional Considerations
15
Molding
Drying Conditions
► LCP resins must be dried before molding to reduce the possibility
of hydrolytic degradation.
► Dry LCP at 150 - 170°C for a minimum of 6 hours; overnight
drying of LCP is preferred. Drying for up to 24 hours is
acceptable and will not harm LCP.
► A dehumidified hopper dryer must be capable of maintaining
-40°C dew point. Insure that filter element is clean and
there is good air flow (>1 ft/sec. space velocity across
the surface of pellets). Hopper dryers with dual desiccant
cartridges (one active while the other is regenerated)
are highly recommended for all grades.
High Performance Applications Require Attention to Details
16
Molding
Processing Temperatures
Processing Temperatures in °C
1
2
3
4
D
M
W1, W2
A Series
Ei Series
S Series
270 to 280
315 to 325
330 to 350
275 to 285
315 to 325
340 to 360
280 to 290
325 to 335
345 to 365
285 to 295
335 to 345
355 to 370
290 to 300
335 to 345
355 to 370
285 to 295
335 to 345
360 to 370
80 to 120
80 to 120
80 to 120
Note: Processing conditions for V143XL / LC same as for Ei series
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Molding
Molding Variables – Injection Pressure.
Molding by position transfer or pressure transfer is preferred using high injection
speed. Data acquisition equipment and pressure transducers in the tool to monitor
process is recommended
"E130i
Lot 1HMV"
Lot 2
"E130i"
Typical processing conditions
Max. residence
time in barrel
If possible <5 min, typically 3-5 min
(depends on temperature)
Injection pressure
PSP = 50 to 150 MPa
Holding pressure
PN ~ PSp
Back pressure
PSt < 10 bar
Screw speed
ns = vs/d · π
Vs (periph. velocity of screw) ~ 0.1 to 0.3 m/s
Injection speed
Very high
Nozzle
Open or shut off nozzle
1.5
1.55
1.6
1.65
1.7
1.75
1.8
1.85
1.9
Screw Retraction Time, s
Data acquisition recommended to monitor
process and quality control.
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Molding
Molding Variables – Injection Pressure
► Melting range rather than sharp melt point. Low heat of fusion results in very fast
cure and cycle times. Typical cure time is a few seconds with a cycle time range
of 4 to 13 seconds for small part molding (depending on cavitation).
Very Low Heat of Fusion –
The solid and nematic fluid
phases have very similar
structure.
19
Molding
Molding Variables
Injection Speed vs. Flow Length (0.1 mm Test Bar)
Injection speed is a function of shear
30
Vectra E130i
Flow Length (mm)
25
20
Low MV at high shear
► Long flow length
► Minimize filling pressure
15
10
PPS 40% GF
5
0
0
50
100
150
200
250
Injection Speed (mm/sec)
20
Molding
Injection Molding Equipment
► Reciprocating screw injection molding machines:
‒ Barrel utilization 10-35% of machine capacity. For complex/critical designs increase barrel
utilization between 20-50% of machine capacity. (Note: short consistent SRT is critical)
► Screw design guidelines:
‒
Feed zone: 1/2 of screw length
‒
Compression zone: 1/4 of screw length
‒
Metering zone: 1/4 of screw length
‒
L/D ratio: 16:1 to 24:1
‒
Compression ratio: 2.5:1 to 3.5:1
‒
Optimum clearance between screw and barrel
‒
0.0015″ per side
► Nozzle tip:
‒
Reverse taper, small orifice diameter, 1.5 to 2.5 mm depending on grade and material selection
‒
Heater band with independent temperature controller
► Check ring – must hold 1 to 3 mm cushion
► Clamping systems – toggle or hydraulic system
‒
Clamp force – 2.0 to 3.5 tons per square inch cavity area depending on wall thickness
21
Molding
Purging
► Switching from another material:
‒ Purge the material out of the machine with low MFI HDPE, then raise temperatures for
molding Vectra LCP.
‒ Begin molding when material is flowing cleanly from the nozzle.
‒ Switching between grades of Vectra LCP:
‒ One grade of Vectra LCP can be used to purge another without using a purge compound. When the
new grade is flowing cleanly, begin molding.
► Shutting down a machine:
‒ It is necessary to purge with another material if Vectra LCP is molded when machine is
reheated.
‒ If a different polymer is to be molded, purge with HDPE.
‒ If the screw is to be pulled, purging with purge compound or HDPE is suggested.
22
Molding
Regrind
Extremely stable to reprocessing, 50% regrind UL listing. (Seven pass regrind study)
► Grinding process
‒ Hot feed
‒ Slow speed, shear cutter
‒ Close tolerance cutter*
‒ Closed loop system preferred
* Per manufacturer specifications
Note: Regrind must be dried before molding if not used in a closed loop system. Allow two hours longer than drying conditions recommended for the virgin material.
23
Molding
Key Processing Tips
► Dry Vectra LCP grades < .01 percent and use on-line dehumidified hopper dryer.
► Use close tolerance screw and barrel.
► Inspect check valve for wear on a routine basis.
► Use press with good process control.
► Data acquisition and pressure transducers are best.
► Use independent nozzle heater control.
► Decompression < 3mm – none is preferred.
► Do not use sprue break.
► Use fast injection speed and moderate screw speed.
► Verify melt temperature is within the suggested range.
24
Part Design
Part and Mold Design
► Runner Design
► Venting Design
► Additional Considerations
25
Part Design
Recommended Runner Design for Vectra LCP
Traditional Design
► Larger gates and runners
area easier to fill
► Full round runner is best
► Cold-slugs wells
► Straight geometry
► Venting added before first shots
Recommended Design
► Smaller is better
► Modified Trapezoid is best
► Remove cold-slug wells
► Curvy geometry
► Venting of the cavity added after first
shots is critical and will lower the
pressure to fill the cavity
Why? Insulated by one piece of steel vs. two (easier to control temperature).
It also removes potential errors by only cutting one half of the tool.
26
Part Design
Runner Sizes
Traditional Runner Design
► Runner sizes started around 0.200″
(5.1 mm)
► Large runner sizes with E-Series
cause too much pressure loss in the
runner system. When the material
reaches the part, there’s not enough
pressure to push it into the intricacies
of the design.
Recommended Runner Design
► Runner sizes start around 0.060″
(1.5mm) and stepping down 0.010″
(0.25 mm) at each split.
► The reduction of runner size,
properly sized, adds shear in a
controlled manner to a material
that thrives on shear.
► It also keeps the material flowing
with a constant pressure (without
pressure drops). The material
shear increases the heat in the
runner system.
► All steps must be smoothly
transitioned to eliminate any sudden
pressure drops.
27
Part Design
Runner Design
Traditional Runner
► Imbalanced flow, doubled cavitation
adds shear
Preliminary 24-Cavity Runner Design
Improved Solution
► Balanced flow, improved quality
Recommended 24-Cavity Runner Design
28
Part Design
Venting Design
► Since LCP has very low shrinkage, polish vent lands in cavity, polish runner and
runner vents and allow adequate draft to aid mold release.
► Add abundant inserts so venting and wall thickness can be adjusted
to balance flow without recutting the tool.
► Create short shots to help locate vent
(size and depth) location.
‒ Place vents where dark flow
lines appear in the part.
‒ Increase venting for runners
until flash appears in the
land area.
29
Part Design
Gate Design
► Typical runner/gate:
‒ Conventional cold runner
‒ Hot runner with cold sub-runner
‒ Direct hot runner (Ø as small as possible)
► Very narrow runner cross sections
►
►
►
►
(round, trapezoidal, half-round) for
high shear (and material saving)
Gate usually at the front (in the main stress direction)
As few gates as possible, preferably one
Usually a pin gate, for flat components also a
film gate, small dimensions
(e.g., Ø 0.3 - 0.5 mm)
Avoid sharp corners and edges (external radii 1.5 x s,
internal radii 0.5 x s)
Gates and Runner are Very Important Component of the Part Design
30
Part Design
Redesigned sprue and
runner and resolved
knit line, gassing and
bow issues.
31
Part Design
Flex Modulus vs. Wall Thickness for Vectra E130i
30000
E130i
25000
MPa
20000
15000
10000
5000
0
0
1
2
3
Thickness, mm
4
5
32
Part Design
Mechanical properties are proportionally better in thinner wall
sections than thick ones.
Effect of wall thickness on rigidity (Vectra E130i Natural )
250
Tensile strength
200
150
100
50
0
4mm
3.2mm
1.6mm
0.8mm
0.7mm
0.6mm
Thickness of the test bar
Uniform Wall Thickness Will Improve Mechanical Performance
33
Vectra® LCP Selection Criteria
► Thermal requirements. Lead free
‒ Heat deflection temperature (HDT/A) 300°C
‒
Impact strength, even at cryogenic
temperatures
‒
Very low coefficient of thermal expansion
► Non-stick or friction requirements
‒ Minimal wear with low coefficient of friction
► Chemical resistance
► Low outgassing
► Sterilization resistance
‒ Resistant to all sterilization methods: hot
steam, radiation or chemical
► Flammability requirements
‒ Inherently flame-retardant UL-V0
► Biological compatibility
► Easy flowing
‒ Fills long, thin-walled moldings
► Output rate
‒ Fast cycles
‒
High replication accuracy
► Dimensional requirements
‒ Very low mold shrinkage
‒
Excellent shape retention throughout the
service temperature range
‒
Dimensionally stable because of low water
absorption
► Mechanical property requirements
‒ High strength in thin-walled designs
► Barrier properties
‒ Minimal fuel, H2, O2 and H2O permeability
Meet Two or More Requirements, Vectra LCP Can Be a Solution
34
Thank you.
Questions?
For Additional Information Contact:
Cory Pierson, Field Technical Service
[email protected]
Edson Ito, Vectra® LCP Technical Marketing
[email protected]
Contact Information
Disclaimer
This publication was printed on 1 October, 2013 based on
Celanese’s present state of knowledge, and Celanese
undertakes no obligation to update it. Because conditions of
product use are outside Celanese’s control, Celanese makes
no warranties, express or implied, and assumes no liability in
connection with any use of this information. Nothing herein is
intended as a license to operate under or a recommendation
to infringe any patents.
Copyright © 2013 Celanese or its affiliates.
All rights reserved.
Americas
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Product Information Service
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Customer Service
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Customer Service
t: +86 21 3861 9266 f: +86 21 3861 9599
36
Typical Design Checklist
1. What is the function of the part?
2. What is the expected lifetime of the part?
3. What agency approvals are required? (UL, FDA, USDA, NSF, USP, SAE, MIL
spec)
4. What electrical characteristics are required and at what temperatures?
5. What temperature will the part see? And, for how long?
6. What chemicals will the part be exposed to?
7. Is moisture resistance necessary?
8. How will the part be assembled? Can parts be combined into one plastic part?
9. Is the assembly going to be permanent or one time only?
10. Will adhesives be used? Some resins require special adhesives.
11. Will fasteners be used? Will threads be molded in?
37
12. Does the part have a snap fit? Glass filled materials will require more force to close
the snap fit, but will deflect less.
13. Will the part be subjected to impact? If so, radius the corners.
14. Is surface appearance important? If so, beware of weld lines, parting line, ejector
location, and gate vestige.
15. What color is required for the part? Is a specific match required or will the part be
color coded? Some glass or mineral filled materials do not color as well as unfilled
materials.
16. Will the part be painted? Is a primer required? Will the part go through a high
temperature paint oven?
17. Is weathering or UV exposure a factor?
18. What are the required tolerances? Can they be relaxed to make molding more
economical?
19. What is the expected weight of the part? Will it be too light (or too heavy)?
20. Is wear resistance required?
21. Does the part need to be sterilized? With what methods (chemical, steam, radiation)?
38
22. Will the part be insert molded or have a metal piece press fit in the plastic part?
Both methods result in continuous stress in the part.
23. Is there a living hinge designed in the part? Be careful with living hinges designed
for crystalline materials such as acetal.
24. What loading and resulting stress will the part see? And, at what temperature and
environment?
25. Will the part be loaded continuously or intermittently? Will permanent deformation
or creep be an issue?
26. What deflections are acceptable?
27. Is the part moldable? Are there undercuts? Are there sections that are too thick
or thin?
28. Will the part be machined?
29. What is the worst possible situation the part will be in? (For example, the part
may be outside for an extended period of time and intermittently put in water, or
the part may see a constant high load while submerged in gasoline at 150°F.)
Parts should be tested in the worst case environment.
39

Injection Molding Vectra® Liquid Crystal Polymers (LCP)

Transcription

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