Technoform – For Rapid, Repeatable Thermoformability Analyses Dr. Amit Dharia Transmit Technology Group, LLC, TX

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 Pending TTG TECHNOFORM

Schematics of Technoform

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 Strain hardening 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

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 Temperature 35 Mil Black HIPS, 130 C,40 mm/s - No control -

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

Effect of Plug Geometry

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

Effect of forming Speed on 150 C

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

Effect of Crystallinity

Comparison of various PE

Effect of Forming Temperature

Force 100 = f (T, V, material)  F(ABS) = T (R2 =99%)  F(PMMA)= T(R2=98%)  F(PETG)= T (R2=92%)  F(HIPS)= T(R2=93%)  F(HDPE)= T (R2=86%)

Effect of Thickness PC/ABS, 40 mm/sec, 200 C

Lot to lot variation in TPO 170 C, 40 mm/second, 190 mil

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

Effect of thickness on the Heating Rate

Effect of % Regrind on formability TPO 20% regrind / Five Successive Extrusions

Effect of % Regrind in FR-ABS

Comparison of filled vs. HMS-TPO

Effect of adding HMSPP in PP

Formability of HMSPP/PP Blends

Comparison of Test Methods

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

Technoform Features BasicStandardAdvanced Fixed heaters, 120 VManual AdjustmentAutomated Adjustment = F (thickness, material) Fixed WattFixed WattsClose loop Chamber at AmbientChamber T control Speeds mm/s0-200 mm/second Plug ambient Plug T Controlled Plug mode onlyPlug and Vacuum No Vacuum modeNo Vacuum vs. depthVacuum vs. Depth record Basic softwareBasic SoftwareAdvanced 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.