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3 Challenges in Plastics Testing: Melt Flow, Heat Deflection Temperature, & Impact

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This presentation addresses the changes and trends in key standards; factors that influence results and solutions; and increasing lab efficiency and throughput in regards to melt flow, heat deflection temperature (HDT), & impact testing.


Published in: Engineering
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3 Challenges in Plastics Testing: Melt Flow, Heat Deflection Temperature, & Impact

  1. 1. The 3 Challenges in Plastics Testing Melt Flow, HDT & Impact
  2. 2. 2 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Agenda Overview • Testing Standard • Changes and Trends in Key Standards • Melt Flow • HDT & Vicat Tests • Challenges • Factors that Influence Results and Solutions • Melt Flow • HDT & Vicat Tests • Impact • Increasing Lab Efficiency and Throughput • HDT & Vicat Tests • Impact
  3. 3. 3 Melt Flow Index Polymer Melt Extrudate MFI = MFR = Fluidity = Inverse of Viscosity Ability of material melt to flow under pressure • ISO 1133 • ASTM D1238
  4. 4. 4 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. ISO 1133-1,2 • Latest Revision in 2011 • Reference for most local standards on melt flow tests worldwide • Similar to ASTM D1238, but differs in technical content What’s Changed? Testing Standards Reviewed – Melt Flow
  5. 5. 5 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. 2005 2011 TEMPERATURE ACCURACY TEMPERATURE VERIFICATION / CALIBRATION PISTON GEOMETRY Max absolute deviation, defined for all materials and as a function of different temperature ranges One simple procedure required for all applications Head diameter defined by difference from barrel diameter, sharp lower edge Evolution of ISO 1133 Max absolute deviation + relative distribution along the barrel (for sensitive materials) over the entire temperature range More complex procedure added for sensitive materials (part 2) Absolute tolerance on head diameter, rounded lower edge = Significant
  6. 6. 6 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Temperature Tolerance Specified by 2011 Revision of Standard Temperature Tolerances ISO 1133-1: • Maximum deviation at 10 mm above die surface: ± 1°C (all temperatures) • Maximum deviation between 10 - 70 mm above die surface : ± 2°C to ± 3°C (depending on temperature) • No maximum relative distribution specified Temperature Tolerances ISO 1133-2: For all temperatures, between 0 - 70 mm above die surface: • Maximum deviation from set temperature: ± 1°C • Maximum relative distribution of the temperature: ± 0.3°C
  7. 7. 7 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. TEMPERATURE ACCURACY TEMPERATURE VERIFICATION / CALIBRATION PISTON GEOMETRY RESULTS METHOD EFFICIENCY PRODUCT Changes How Will These Changes Impact You?
  8. 8. 8 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Heat Deflection Temperature Test • A stress is applied on a sample in a 3-point bending mode while temperature is raised at uniform rate HDT value for the material under test
  9. 9. 9 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Vicat Softening Temperature • A standard indenter penetrates into the surface of a plastic test specimen when the temperature is raised at a uniform rate VST value for the material under test
  10. 10. 10 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Testing Standards Reviewed – HDT & Vicat • ISO 75-1,2 • ISO 75-3 • ASTM D648 • JIS K7207 • ISO 306 • ASTM D1525 • JIS K7206
  11. 11. 11 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. ISO 75-1,2 • The most common plastics Heat Deflection Temperature (HDT) standard worldwide • Latest revision in 2013 • Not technically equivalent to ASTM D648 What’s Changed?
  12. 12. 12 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. ISO 75-1, 2 Both flatwise with 64 mm span or edgewise with 100 mm span Only one mercury-in-glass thermometer Between 20 - 23°C SPECIMEN POSITION AND SPAN INITIAL TEMPERATURE TEMPERATURE- MEASURING HEATING EQUIPMENT Practically only oil bath were available Any suitably calibrated temperature-measuring device is allowed (A device for each station is recommended) 64 mm span no longer allowed for edgewise tests Liquid bath, fluidized bed or an air- oven systems Below 27°C ISO 75:1974 (1st edition) 1987 (2nd edition) 2004 2013 1993/Split Part 1, 2 and (3) = Significant
  13. 13. 13 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. How Will These Changes Impact You? HEATING EQUIPMENT SPECIMEN POSITION AND SPAN TEMPERATURE MEASURING INITIAL TEMPERATURE RESULTS METHOD EFFICIENCY PRODUCT Changes
  14. 14. 14 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. ISO 306 • The most common plastics Vicat Softening Temperature (VST) standard worldwide • Latest revision in 2013 • Equivalent to ASTM D1525 What’s Changed?
  15. 15. 15 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. ISO 306 Mercury-in-glass thermometer Between 20 - 23°C Initial Temperature Temperature- measuring Heating Equipment Practically only oil bath were available Load applied after preconditioning (5 minutes) phase Test Procedure Any suitably calibrated temperature-measuring device. One per station, as close as possible to both the indenting tip and specimen Liquid bath, direct-contact or fluidized bed systems Below 25°C Load applied before pre-conditioning (5 minutes) phase 1974 (1st edition) 1987 1994 2004 2013 = Significant
  16. 16. 16 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. How Will These Changes Impact You? HEATING EQUIPMENT TEST PROCEDURE TEMPERATURE MEASURING INITIAL TEMPERATURE RESULTS METHOD EFFICIENCY PRODUCT Changes
  17. 17. 17 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Other Standards • ASTM D648 • 2000, 2001, 2004, 2006 and 2007 (latest) • No significant changes observed • Current ballot to incorporate fluidized bed as alternative heat transfer medium • ASTM D1525 • 1987, 2000, 2006, 2007, 2009 (latest) • From 2009 it is including fluidized powder as heat transfer medium • Technically equivalent to ISO 306
  18. 18. 18 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Why are my results inconsistent or incorrect? What influences results?
  19. 19. 19 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Factors That Influence Results MFI Temperature Accuracy Preparation of Sample (Moisture) Sample Compacting Method Parameters Temperature Stability Choice of Procedure Encoder Accuracy Extrudate Cutting Precision Melt Density Value Manual Operations within Test Maintenance of Die & Piston Cleaning Procedures = Most common
  20. 20. 20 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Manual vs. Automatic • Controlled Compacting • Better reproducibility and less scattering of results • No physical effort required by operator (reduces risk of injury) • Post-test automatic purging • Reduces total test time • Operator is ready to run next test more quickly • Cleaning • Thorough cleaning extends life of equipment and helps to maintain consistent results
  21. 21. 21 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Material • Has the material been pre-conditioned according to procedure? • Hygroscopic materials give unreliable test results if they are not dried in consistent manner • Moisture tends to generate bubbles and trigger degradation of sample • Temperature and length of drying time must be consistent • Is the melt density being used in the MFR calculations correct? • Is the amount of material being tested consistent? • Was the material compacted properly (or were there air bubbles)?
  22. 22. 22 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Factors That Influence Results HDT/Vicat Temperature Accuracy LVDT Measurement Accuracy Specimen Dimensions – Wrong Weights (HDT) Span (HDT) Oil Not Properly Selected System Cooling Between Tests Pre- Conditioning Material Residual into the Bath Stress Applied (HDT) Method Parameters Unstable Temperature Rate Control Oil Degradation = most common sources of issues
  23. 23. 23 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Oil Selection & Degradation • Selection of the right oils helps obtain more consistent results • Oil that is intended for testing at higher temperatures will be too viscous for sufficient circulation at lower temps • Extending the life of your oil: • Nitrogen valve can be activated to prevent oil contact with oxygen and prevent premature degradation • Specimen cages reduce oil degradation due to materials into bath • Bonus: saves operator time
  24. 24. How Much Time Can You Gain? Increasing Laboratory Efficiency
  25. 25. 26 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Solutions to Improve Throughput 6 stations system Automation Manual 3 stations system Cost Effectiveness Water Chiller
  26. 26. 27 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Manual vs. Automated Test Time 6 stations Automatic Chiller 6.5 minutes 5 minutes 180 minutes 45 minutes Preheating cooling Station preparation up to specimens in bath Test time (example up to 300°C) Ideal Setup Total Cycle Time: 235 minutes Total Cycle Time: 270 minutes 6 stations Manual tap water cooled 180 minutes 5 minutes 9.5 minutes 75 minutes Manual Setup Cycle time reduced by about 30 minutes
  27. 27. 28 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Factors That Influence Results Impact Specimen Notching Method Micrometers - Dimensional Measurement Accuracy of Equipment Hammer Capacity Environmental Losses Specimen Notching Speed Hammer Design Frame Design Method Parameters Indirect Verification Calipers – Dimensional Measurement Specimen Conditioning = most common sources of issues
  28. 28. 29 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Bad Notch Affecting Impact Results? • At what speed are you notching specimens? • What is the depth of every pass? • Are you using a linear notching knife? • Is your knife profile within tolerance? • When did you last change the notching knife? 40 30 20 10 0 0.25 0.5 1 2 4 8 16 32 PVC Nylon POM ABS PMMA Notch Tip Radius (mm) ImpactStrength(kJ/m2) Good Notch Bad Notch
  29. 29. 30 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Bad Notch Affecting Impact Results? Linear Cutter Rotary Cutter 0.224 0.235 0.221 0.26 0.26 0.26 0.19 0.2 0.21 0.22 0.23 0.24 0.25 0.26 0.27 0.28 0.29 0.3 0.31 0 1 2 3 4 NotchBaseRadius(mm) Number of specimens Notch Radius Tolerance = 0.25 +/- 0.05 mm Linear cutter Rotary cutter
  30. 30. 31 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Specimen Conditioning • Are you impacting the specimen within 5 seconds after taking it out of the refrigerator/ Cryodispenser /cooling unit? • Are you handling the specimen with conditioned tongs and gloves?
  31. 31. 32 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Izod Vice Clamping • Some plastics are sensitive to clamping pressure • Differences in clamping pressure between tests and/or operators will reduce results repeatability Manual Tightening Tightening with a Lever Pneumatic Tightening
  32. 32. Increasing Laboratory Efficiency How Much Time Can You Gain?
  33. 33. 34 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Types of Setups IDEALTYPICAL Motorized Impactor • Integrated micrometer • Automatic hammer release • Automatic positioning of hammer Manual Impactor • Non-integrated Micrometer • Manual release of hammer • Manual positioning of hammer
  34. 34. 35 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. 1. Measure specimen dimensions 2. Enter specimen dimensions 3. Place specimen on the vice 4. Close the safety door 5. Release hammer manually 6. Brake the test 7. Open the safety door 8. Reposition the hammer manually 1. Place specimen under micrometer (Dimensions are automatically sent to the machine) 2. Place specimen on the vice 3. Close the safety door 4. Release hammer pneumatically with a click (Hammer is repositioned automatically) SPECIMEN HANDLING AND MEASUREMENT INITIATION OF TEST PREPARATION FOR NEXT TEST INCREASED USER INTERACTION MINIMIZED USER INTERACTION The Differences
  35. 35. 36 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Cycle Times Minutes 1 2 3 50s 30s 15s 40s 20s 40s Test Time with Hammer Release/Reposition Test PreparationSpecimen Measurement IDEAL SETUP TYPICAL SETUP > 32% FASTER! Total Cycle Time: 75 seconds Total Cycle Time: 110 seconds
  36. 36. 37 All content remains the intellectual property of Instron. Copying and distributing is strictly prohibited. Thank you for your time! Please contact Instron® if you have any questions Visit www.instron.com for more information

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