Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Technoform- A test tool to determine Thermoformability


Published on

This presentation outlines a quantitative test method and equipment to determine thermoformability of thermoplastics materials.

Published in: Technology
  • Be the first to comment

Technoform- A test tool to determine Thermoformability

  1. 1. Applications of Thermoformability Analyzer Amit Dharia Transmit Technology Group, LLC Irving, Texas
  2. 2. Objectives <ul><li>To demonstrate the need for an industry wide standard Quantitative test method for “Measuring” and “Reporting” Thermoformability of plastic materials (2005) </li></ul><ul><li>To illustrate applications of test equipment and test method in understanding and resolving issues related to Thermoformability. </li></ul>
  3. 3. Outline <ul><li>Structure-Property- Process relationship </li></ul><ul><li>Current test methods </li></ul><ul><li>Description of Technoform </li></ul><ul><li>Application and data interpretation </li></ul><ul><li>Products – Basic, Standard, Advanced </li></ul><ul><li>Conclusion </li></ul>
  4. 4. Thermoforming Process <ul><li>Extruding sheet stock </li></ul><ul><li>Heating sheet above Tg </li></ul><ul><li>Stretching heated sheet in rubbery state </li></ul><ul><li>Cooling </li></ul><ul><li>Trimming </li></ul><ul><li>Finishing </li></ul><ul><li>Regrinding and recycling scrape </li></ul>
  5. 5. Structure - Properties -Thermoformability <ul><li>Rate of change of strength with the change in strain rate at forming temperature </li></ul><ul><li>% Crystallinity – Breadth of rubbery Plateau </li></ul><ul><li>Molecular weight, Molecular weight distribution, molecular architecture (branching, crosslinking) – MFR, Melt Elasticity, Rheology </li></ul>
  6. 6. Other parameters <ul><li>Density - % filler, type of fillers, degassing </li></ul><ul><li>Geometry – Thickness, area, multi-layered structures, adhesion between layers </li></ul><ul><li>Residual stresses between and within in extruded layer sheet stock </li></ul><ul><li>Thermal diffusivity (Cp, K. Rho) </li></ul><ul><li>Extrusion quality ( gels, unmelts, thickness variation, grain patterns) </li></ul><ul><li>Color (IR absorption) </li></ul>
  7. 7. Test Methods Inconsistent results, grip extrusion, annealing Hot tensile test Repeatable, effect of temperature DMTA Repeatable, correlates with Sag test, expensive equipment Stress Relaxation No external force, geometry dependent, measure of only melt strength Sag test > Tm, cooling effect, uni-directional, not applicable to all materials Melt Tension Easy, measure of only MW MFR Major Short coming Test Method
  8. 8. Major disadvantages of current methods <ul><li>Most tests are conducted in melt or near melt phase </li></ul><ul><li>Test Specimens do not reflect actual test geometry (shape, size, clamping mode) </li></ul><ul><li>Tests do not account for orientation, thermal stresses, thickness variations </li></ul><ul><li>Isothermal environment, does not account for transient nature of heating/ cooling </li></ul><ul><li>Effects of secondary process parameters can not be evaluated </li></ul><ul><li>Results cannot be directly used. </li></ul>
  9. 9. What processors want to know? <ul><li>Will this material thermoform? </li></ul><ul><li>Will this new material process the same? </li></ul><ul><li>Will this lot process the same as the last one? </li></ul><ul><li>Why this lot does not process the same? </li></ul><ul><li>How fast material will heat? </li></ul><ul><li>What is the right forming temperature range? </li></ul><ul><li>Will melt adhesion between layers survive heating and stretching step? </li></ul><ul><li>Will material discolor, fed or degrade during heating? </li></ul>
  10. 10. What processors want to know? -II <ul><li>What is the maximum draw down? </li></ul><ul><li>How fast part can be made? </li></ul><ul><li>What is the MD and TD shrinkage? </li></ul><ul><li>Will material tear at the corners and ribs? </li></ul><ul><li>How much regrind can I use? </li></ul><ul><li>Will grains retain shape and depth? </li></ul><ul><li>Does extruded sheet have gels or unmelts? </li></ul>
  11. 11. What Industry Needs? <ul><li>A standard test method which reflects all unit steps – heating, 3D stretching, forming, and cooling </li></ul><ul><li>A test equipment which can be precisely controlled, is rapid, easy to use, provides repeatable and quantitative information, using the least amount of material. </li></ul><ul><li>Easy to use “Thermoformability Index” standard for comparing, contrasting effects of selected process/ material variables </li></ul>
  12. 12. Variables Shrinkage Extrusion, storage Additive package impurity % of fillers Forming speed % regrind Type of fillers Plug temperature Volatiles Rho, k, Cp Plug material Color η o , η el Plug geometry Layers % LCB, % Xl Part geometry Residual stresses Tg, Tm, % Xc Forming Method Thickness Molecular Structure Process Feed Stock Material
  13. 13. Desired Test Method <ul><li>MEANINGFUL </li></ul><ul><li>Rapid </li></ul><ul><li>Easy to use </li></ul><ul><li>Quantitative </li></ul><ul><li>Repeatable </li></ul><ul><li>A good problem solving tool </li></ul>
  14. 14. Output Range Input Temp. vs. Time Plug assist, Vacuum Method Force vs. Time Any type Resin Type Test Input – Output Variable Plug Dwell time 10- 180 mm/second Forming Speed Variable Cooling Time 100 lb Maximum Force 23 C to 120 C Plug temperature Force vs. Depth Epoxy, Polished Aluminum Plug Material Force at Max Draw Depth Variable Heat Soak time Draw vs. time 60 C to 280 C Forming Temperature Force vs. Draw Depth 10 mil to 375 mil Sheet Thickness
  15. 15. Typical GUI Screen Sag Elastic Plastic Strain hardening Thinning
  16. 16. Results V,T
  17. 17. Technoform
  18. 18. Schematics of Technoform
  19. 19. Melt Strength = Resistance to Deformation @ T Melt Elasticity =Capability to deform @ T Stress (Force) % Draw or A/Ao Strain Hardening
  20. 20. Heating rates for various plastic materials (Heater at 600 C, 3” from upper, 2” from lower)
  21. 21. Effect of Crystallinity
  22. 22. Comparison of various PE
  23. 23. Effect of Forming Temperature
  24. 24. Force 100 = f (T, V, material) <ul><li>F(ABS) =9.2348 -0.0547 T (R2 =99%) </li></ul><ul><li>F(PMMA)=7.1587 -0.0341 T(R2=98%) </li></ul><ul><li>F(PETG)=10.096 -0.0601 T (R2=92%) </li></ul><ul><li>F(HIPS)=9.6782 - 0.0503T(R2=93%) </li></ul><ul><li>F(HDPE)=5.2771 -0.0266 T (R2=86%) </li></ul>
  25. 25. Effect of Melt Strength (% HMSCOPP in COPP)
  26. 26. HMSCOPP
  27. 27. COPP vs. HMSCOPP
  28. 28. Isothermal vs. Non-Isothermal 20 mm/s, 130 C, HIPS
  29. 29. Effect of Plug Temperature HIPS 35 mil, 130 C, 40 mm/s, No control
  30. 30. Effect of Plug Temperature-II 35 mil HIPS, 130 C, 40 mm/s, Plug at 23 C
  31. 31. Effect of Plug induced cooling -III HIPS (with and without hole)
  32. 32. Effect of Plug Material 35 mm HIPS, 40 mm/s, 130 C
  33. 33. Effect of Sheet Thickness on heating rates
  34. 34. Effect of Sheet Thickness
  35. 35. Effect of Color on heating Rate
  36. 36. Effect of Color CoPP, 35 mil, 40 mm/s, 160 C
  37. 37. Effect of Lot to Lot Variation 170 C, 40 mm/s, 190 mil TPO
  38. 38. Effect of Regrind (FR-ABS) 125 mil, 160 C, 40 mm/sec
  39. 39. Effect of Regrind (GPPS) 125 mil, 190 C, 40 mm/sec
  40. 40. Processing Window of Commercial TPOs
  41. 41. COPP- Nano clay Composites
  42. 42. CoPP-Nano Clay Composites
  43. 43. How to Standardize? <ul><li>Thermoforming Index (TFI) </li></ul><ul><ul><li>Force required to draw a sheet of thickness X at speed Y mm/second using a Plug of specified geometry G at Temperature T f to area ratio A (or volume ratio V), with plug temperature Tp. </li></ul></ul><ul><li>TFI = [Force (M, Tm)/ Force (GPPS, Ts)] </li></ul>
  44. 44. Thermoforming Index (example) <ul><li>125 mil, GPPS, 40 mm/s force to draw to 45 mm depth @ 160 C is 7 lbs. </li></ul><ul><li>125 mil, PP, 40 mm/s Force required to draw to 45 mm depth @ 170 C is 3.5 lbs. </li></ul><ul><li>TFI of PP = F 45,PP * thickness (GPPS) </li></ul><ul><ul><ul><ul><ul><li>F 45, GPPS * thickness (PP) </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>= 3.5*0.125/ 7* 0.325 </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>= 0.5 </li></ul></ul></ul></ul></ul>
  45. 45. Conclusions <ul><li>Easy and rapid test method with overall operation similar to actual Thermoforming process </li></ul><ul><li>Economical vs. Field trials </li></ul><ul><li>Test equipment and method can be applied to wide range of Industrial applications </li></ul><ul><li>TFI offers one simple number (like MFI) representing material’s Thermoformability </li></ul><ul><li>Test equipment and method can be applied to wide range of Industrial applications </li></ul>