Technoform – For Rapid, Repeatable Thermoformability Analyses

Dr. Amit DhariaTransmit Technology Group, LLC, TXwww.transmit-technology.com

Outline® Properties –Thermoforming Process

relationship ® Current test methods ® Description of Technoform ® Application and data interpretation® Products – Basic, Standard, Advanced® Conclusion

Thermoforming Process®Extruding sheet stock ®Heating sheet above Tg®Stretching heated sheet in rubbery state®Cooling®Trimming ®Finishing

Structure - Properties -Thermoformability® Rate of change of strength with the

change in strain rate at forming temperature

®% Crystallinity – Breadth of rubbery Plateau

® Molecular weight, Molecular weight distribution, molecular architecture (branching, crosslinking) – MFR, Melt Elasticity

Other parameters® Density - % filler, type of fillers, degassing® Geometry – Thickness, area, multi-layered

structures, adhesion between layers® Residual stresses between and within in

extruded layer sheet stock® Thermal diffusivity (Cp, K. Rho)® Extrusion quality ( gels, unmelts,

thickness variation, grain patterns)® Color (IR absorption)

Current tests®Low shear melt viscosity (MFR, RMS)®Melt Tension (Draw Force –Melt

tension, Break Velocity -extension)®Sag Test (sag distance, sag time)®Hot Creep Test®DMA (Relaxation time)

Major disadvantages of current methods® Most tests are conducted in melt or near melt

phase ® Test Specimens does not reflect actual test

geometry (shape, size, clamping mode)® Tests does not account for orientation, thermal

stresses, thickness variations® Isothermal environment, does not account for

transient nature of heating/ cooling ® Effects of secondary process parameters can not

be evaluated® Results cannot be directly used.

What processors want to know?® Will this material thermoform? ® Will this new material process the same? ® Will this lot process the same as the last one?® Why this lot does not process the same?® How much time is needed to heat the sheet?® How fast material will heat?® What is the right forming temperature range?® Will melt adhesion between layers survive

heating and stretching step?® Will material discolor, fed or degrade during

heating?

What processors want to know? -II®What is the maximum draw down?® How fast part can be made? ®What is the MD and TD shrinkage?®Will material tear at the corners and ribs?® How much regrind can I use?®Will grains retain shape and depth?® Does extruded sheet have gels or

unmelts?

What Industry Needs?® A standard test method which reflects all unit

steps – heating, 3D stretching, forming, and cooling

® A test equipment which can be precisely controlled, is rapid, easy to use, provides repeatable and quantitative information, using the lease amount of material.

® Easy to use “Thermoformability Index” standard for comparing, contrasting effects of selected process/ material variables

TECHNOFORM TM

Patent PendingTTG

TECHNOFORM

Schematics of Technoform

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Typical Data input® Mode of operation – Plug Assisted, Vacuum® The heating element distance from the sheet

surface® The heating element temperature® The sheet temperature® Heat Soak time at given temperature® Plug velocity (2 to 200 mm/second)® Plug Delay Time ® Plug Temperature® Part Cooling time

Typical user Input Screen

Sag Distance

Thinning

Strainhardening

Forming Depth mm

Thermoformability Index=slope

Typical Data Output® Heating rate (Delta C/ time) = f (thickness)® Sag distance ® Forming force (Stress) vs. forming

distance (strain)® Forming Force vs. time® Yield force® Forming force vs. actual temperature® Shrinkage (manual measurements)

Effect of Heating time Force vs. Depth (180 C, Isothermal)4" dia hemi-spherical plug, 20 ipm

(effect of pre-heat time)

01020304050

0 20 40 60Depth, mm

Forc

e, lb

s

10 min15 min

Plug Material and Shapes®Truncated cone with flat end (2.5” Top

D, 0.75 “ Bottom D, 4” Height)®Truncated cone with Rounded End (2.5”

Top D, 1” D bottom, 4” Height)®Hemisphere of 3.5” Diameter®All tools made of Foam Epoxy

Effect of Plug Temperature35 Mil Black HIPS, 130 C,40 mm/s

- No control -

0

2

4

6

8

10

12

0 50 100 150

Draw Depth, mm

Forc

e, L

bf Series1Series2Series3

Effect of controlling Plug TemperatureHIPS, 40 mm/second with T control

HIPS @130 C, 40 mm/secondPlug cooled for five minutes

0

2

4

6

8

10

12

0 20 40 60 80 100 120

Depth, mm

Forc

e, L

bf

#1#2#3#4

Effect of Plug GeometryForce vs. Depth 180 C, 40 mm/s

Hemi-Spherical Plug with 4 " Diameter

05

101520253035

0 10 20 30 40 50

Depth mm

Forc

e, lb

s\f

12

Effect of plug materialHIPS, 170 C, 40 mm/second, 35 mil

0

1

2

3

4

5

6

0 20 40 60 80 100 120

Depth (mm)

Forc

e (lb

)

WF WFT Bix

Effect of forming Speed on HDPE @ 150 C

Effect of Forming Speed on HDPE

0

2

4

6

8

10

0 50 100 150Distance (mm)

From

ing

forc

e (N

)

20 mm/sec30 mm.sec50 mm/sec

Heating rates for various plastic materials(Heater at 600 C, 3” from upper, 2” from lower)

30

80

130

180

230

0 20 40 60 80

t (seconds)

T (c

)PPHDPEHIPSPVCABSAcetalPMMANylon

Effect of Crystallinity

05

1015202530

50 70 90 110 130

Forming distance, mm

Forc

e (N

)HDPE PP HIPS PETG ABS PMMA PVC

Comparison of various PELDPE, LLDPE, MDPE @ 60 mm/s

0

510

1520

2530

35

0 20 40 60 80

Depth, mm

Forc

e, lb

f LDPE120LLDPE120MDPE120

Effect of Forming Temperature

0

2

4

6

8

10

12

14

125 145 165 185

Temperature (C)

Fo

rce

(N)

ABS

PP

HDPE

HIPS

PETG

PMMA

ACETAL

Force100 = f (T, V, material)®F(ABS) =9.2348 -0.0547 T (R2 =99%)®F(PMMA)=7.1587 -0.0341 T(R2=98%)®F(PETG)=10.096 -0.0601 T (R2=92%)®F(HIPS)=9.6782 - 0.0503T(R2=93%)®F(HDPE)=5.2771 -0.0266 T (R2=86%)

Effect of ThicknessPC/ABS, 40 mm/sec, 200 C

0123456789

0 20 40 60 80 100

Depth (mm)

Froc

e (lb

f)

95 150 250

Lot to lot variation in TPO170 C, 40 mm/second, 190 mil

0123456789

10

0 10 20 30 40 50 60 70

Depth (mm)

Froc

e (lb

f)1-1 1-2 1-3

Effect of Color Co PP, 160 C, 40 mm/second, 35 mil

00.10.20.30.40.50.60.70.8

0 20 40 60 80 100 120

Depth (mm)

Forc

e (lb

)

0

2

4

6

8

10

12

blue red Metallic

Effect of thickness on the Heating Rate

050

100150200250

0 500 1000time (sec)

Surfa

ce

Temp

eratur

e(C)

100 mil 150 mil 250 mil

Effect of % Regrind on formability TPO20% regrind / Five Successive Extrusions

0123456

40 60 80 100 120

Forming Distance, mm

Form

ing Fo

rce,

Lbf

1st2nd3rd4th5th

Effect of % Regrind in FR-ABS

0

2

4

6

8

10

12

14

0 20 40 60 80 100

Depth (mm)

Froc

e (lb

f)

50% RG 100% RG

Comparison of filled vs. HMS-TPO

0

10

20

30

40

50

0 20 40 60 80 100

Distance (mm)

Forc

e (N

)40HMSTPO 20HMSTPO

40 FTPO 20FTPO

Effect of adding HMSPP in PP

01234567

40 60 80 100 120 140Form ing Dist ance, mm

Form

ing

Forc

e, L

bf

10%H MSPP 20%HMS PP 30% HMSPP

01234567

40 60 80 100 120 140Form ing Dist ance, mm

Form

ing

Forc

e, L

bf

10%H MSPP 20%HMS PP 30% HMSPP

01234567

40 60 80 100 120 140

Forming Distance, mm

Form

ing

Forc

e, L

bf10%HMSPP 20%HMSPP 30%HMSPP

Formability of HMSPP/PP Blends

02468

1012

10 20 30

% HMSPP

thic

knes

s (H

igh/

Low)

Comparison of Test MethodsRelaxation Time (s) Vs. Force @ 75 mm depth

R2 = 0.9968

02468

1012

0 2 4 6 8

Relaxation Time (sec)

Form

ign

Froc

e (7

5 m

m)

PP, 165 C

HDPE,140CHIPS,160 C

Processing window for E-3500170 C, 40 mm/s, 190 mil

0

10

20

30

0 20 40 60 80 100

Depth (mm)

Force

(lbf)

170 180 190 170TPO

Technoform FeaturesBasic Standard Advanced

Fixed heaters, 120 V Manual Adjustment Automated Adjustment = F (thickness, material)

Fixed Watt Fixed Watts Close loop

Chamber at Ambient Chamber T control Chamber T control

Speeds 0-120 mm/s 0-200 mm/second 0-200 mm/second

Plug T @ ambient Plug T @ ambient Plug T Controlled

Plug mode only Plug and Vacuum Plug and Vacuum

No Vacuum mode No Vacuum vs. depth Vacuum vs. Depth record

Basic software Basic Software Advanced features

Conclusions® Technoform is a simple to operate test

equipment is which closely reflects all unit steps of the typical thermoforming process and generates quantitative and repeatable information in short time.

® The test data can be used in raw form to compare or contrast various materials, process parameters or can be further modeled as a design or predictive tool.