Technoform – For Rapid, Repeatable Thermoformability Analyses

Dr. Amit Dharia

Transmit Technology Group, LLC, TX

www.transmit-technology.com

Outline Properties –Thermoforming Process

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

Thermoforming ProcessExtruding sheet stock Heating sheet above TgStretching heated sheet in rubbery stateCoolingTrimming 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 testsLow shear melt viscosity (MFR, RMS)Melt Tension (Draw Force –Melt

tension, Break Velocity -extension)Sag Test (sag distance, sag time)Hot Creep TestDMA (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 60

Depth, mm

For

ce,

lbs

10 min

15 min

Plug Material and ShapesTruncated 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” DiameterAll tools made of Foam Epoxy

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

- No control -

0

2

4

6

8

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12

0 50 100 150

Draw Depth, mm

Fo

rce

, L

bf Series1

Series2

Series3

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

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

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4

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12

0 20 40 60 80 100 120

Depth, mm

Fo

rce

, L

bf #1

#2

#3

#4

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

Hemi-Spherical Plug with 4 " Diameter

0

5

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15

20

25

30

35

0 10 20 30 40 50

Depth mm

Fo

rce

, lb

s\f

1

2

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

0

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5

6

0 20 40 60 80 100 120

Depth (mm)

Fo

rce

(lb

)

WF WFT Bix

Effect of forming Speed on HDPE @ 150 C

Effect of Forming Speed on HDPE

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10

0 50 100 150

Distance (mm)

Fro

min

g f

orc

e (

N)

20 mm/sec

30 mm.sec

50 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

)

PP

HDPE

HIPS

PVC

ABS

Acetal

PMMA

Nylon

Effect of Crystallinity

0

5

10

15

20

25

30

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

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0 20 40 60 80

Depth, mm

Fo

rce

, lb

f

LDPE120

LLDPE120

MDPE120

Effect of Forming Temperature

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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

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9

0 20 40 60 80 100

Depth (mm)

Fro

ce (

lbf)

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)

Fro

ce (

lbf)

1-1 1-2 1-3

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

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 20 40 60 80 100 120

Depth (mm)

Fo

rce

(lb

)

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4

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10

12

blue red Metallic

Effect of thickness on the Heating Rate

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50

100

150

200

250

0 500 1000time (sec)

Surf

ace

Tem

pera

ture

(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

Forc

e, L

bf 1st

2nd

3rd

4th

5th

Effect of % Regrind in FR-ABS

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0 20 40 60 80 100

Depth (mm)

Fro

ce (

lbf)

50% RG 100% RG

Comparison of filled vs. HMS-TPO

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50

0 20 40 60 80 100

Distance (mm)

Forc

e (

N)

40HMSTPO 20HMSTPO

40 FTPO 20FTPO

Effect of adding HMSPP in PP

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7

40 60 80 100 120 140

Forming Distance, mm

Fo

rmin

g F

orc

e,

Lb

f

10%HMSPP 20%HMSPP 30%HMSPP

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6

7

40 60 80 100 120 140

Forming Distance, mm

Fo

rmin

g F

orc

e,

Lb

f

10%HMSPP 20%HMSPP 30%HMSPP

0

1

2

3

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5

6

7

40 60 80 100 120 140

Forming Distance, mm

Fo

rmin

g F

orc

e, L

bf

10%HMSPP 20%HMSPP 30%HMSPP

Formability of HMSPP/PP Blends

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12

10 20 30

% HMSPP

thic

kne

ss (

Hig

h/L

ow

)

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

R2 = 0.9968

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12

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-3500

170 C, 40 mm/s, 190 mil

0

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0 20 40 60 80 100

Depth (mm)

Forc

e (lb

f)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.