Thermal and Mechanical Analysis

1. CNMR – Athlone Institute of Technology Thermal and Mechanical Analysis Alan Murphy

2. CNMR – Athlone Institute of Technology Introduction Plastic materials are tested throughout their life: • Monomer / Reactants • Polymer / Raw Material & Additives • Product / Design • Product / Research & Development • Processing / Quality Control • Product / Service • Product / End of Life

3. CNMR – Athlone Institute of Technology Introduction A knowledge of available test methods is useful to: • Identify Research & Development requirements • Control incoming raw material quality • Quantify product specifications • Understand material data sheets • Correct manufacturing problems • Investigate customer complaints • Continuously improve the product

4. CNMR – Athlone Institute of Technology Introduction • Raw Material Testing • Control of raw material helps to assure consistent processing and end product characteristics. • Melt Flow Rate and Density are the most common raw material tests but other raw material tests may be specified if warranted by the product. Eg.1 Impact test for safety glasses. Eg.2 GPC for molecular weight control Eg 3. TGA to measure % glass content

5. CNMR – Athlone Institute of Technology Introduction • Testing during processing • QC tests, such as weight or moisture content • Troubleshooting tests, such as investigating : • Why a component is cracking during assembly • Why an extruded tube is shrinking after manufacture • Where contamination is coming from & what type

6. CNMR – Athlone Institute of Technology Introduction • Testing during service • Research and Development tests, such as comparison of alternative materials or property loss with time. • Customer complaints. eg Why has the product failed after 3 months use ? Why has the product embrittled ? Why has discolouration occurred ?

7. CNMR – Athlone Institute of Technology Thermal Analysis ANALYTICAL TECHNIQUES • Differential Scanning Calorimetry (DSC) • Dynamic Mechanical Thermal Analysis (DMTA) • Thermogravimetric Analysis (TGA) • Melt Flow Rheology (MFI) • Gel Permeation Chromatography (GPC)

8. CNMR – Athlone Institute of Technology Thermal Analysis Differential Scanning Calorimetry (DSC) DSC is a thermal method of analysis to study the thermal behaviour and thermal properties of materials (typically polymers). The material is sealed in a sample pan and subjected to a controlled temperature programme. The resulting thermograph can yield much valuable information about the properties of the material analysed. • Main use of DSC: Material Identification (Tm and DHf) based on IS EN ISO 3146:2000; Method C2

9. CNMR – Athlone Institute of Technology Thermal Analysis Differential Scanning Calorimetry (DSC)

10. CNMR – Athlone Institute of Technology Thermal Analysis Differential Scanning Calorimetry (DSC) • Other uses of DSC: • % Crystallinity determination by DSC (based on IS EN ISO 3146:2000; Method C2). • Purity and Polymorphism analysis by DSC. • Thermal Stability of materials (e.g. – oxidative induction time (OiT) of materials) by DSC.

11. CNMR – Athlone Institute of Technology Thermal Analysis Differential Scanning Calorimetry (DSC)

12. CNMR – Athlone Institute of Technology Thermal Analysis Dynamic Mechanical Thermal Analysis (DMTA) Dynamic Mechanical Thermal Analysis (DMTA) records the temperature-dependent visco-elastic properties and determines the modulus of elasticity and the damping values by applying an oscillating force to the sample. Thermal method of analysis used to determine thermo-mechanical properties of materials (i.e. – Glass Transition Temperature – Tg). Used as an alternative to DSC which is typically estimating Tg. Used to more accurately determine the Tg value, strength and temperature-dependant elongation of a material. in several modes

13. CNMR – Athlone Institute of Technology Thermal Analysis Thermogravimetric Analysis (TGA) TGA measures the weight of a substance heated at a controlled rate as a function of temperature or time. All materials ultimately decompose on heating, and the decomposition temperature and profile is a characteristic property of each material. • Main use of TGA: Inorganic Content of Material

14. CNMR – Athlone Institute of Technology Thermal Analysis

15. CNMR – Athlone Institute of Technology Thermal Analysis Thermogravimetric Analysis (TGA) • Other uses of TGA: • Material Thermal Stability. • Moisture and Volatiles Content (TG-IR). • Composition of Multi-Component Systems. • Shelf-Life Studies and Decomposition Kinetics.

16. CNMR – Athlone Institute of Technology Thermal Analysis Thermogravimetric Analysis (TGA) % Polymer = 64.4% % Carbon Black = 3.4% % Glass Fibre = 32.2%

17. CNMR – Athlone Institute of Technology Rheological Analysis Melt Flow Rate (MFR) to ISO 1133. Grams of material that flow through a simple die in 10 minutes using a loaded piston and a set temperature. Is a measure of Shear Viscosity and is directly proportional to the average molecular weight. Uses: Raw material control; processing quality; regrind studies; useful troubleshooting test

18. CNMR – Athlone Institute of TechnologyRheological Analysis Capillary Rheometry: uses motor driven pistons to produce high pressures and two barrels with dies to measure shear viscosity and elongational viscosity. Mimics processing conditions; gives information on average molecular weight and molecular weight distribution. Uses: mould and die design; new material validation; troubleshooting; raw material control

19. CNMR – Athlone Institute of TechnologyMechanical Analysis Tensile Testing to ISO 527 Measures the strength of a material and its flexibility (elongation). Also used to measure peel strength, bond strength, weld strength. Carried out on dumbbell specimens or actual product. Uses: QC control for material or product

20. CNMR – Athlone Institute of TechnologyImpact Analysis Izod and Charpy Impact Testing to ISO 179/180. These are pendulum impact tests generally done on test bars but can be adapted for small products. Usually notched, testing can be done at ambient or sub-zero temperatures. Uses: QC test, material comparison, notch sensitivity

21. CNMR – Athlone Institute of TechnologyAging Studies Use of elevated temperatures to accelerate the aging process of plastic products. Based on a 10ºC rise in environmental temperature produces a twofold increase in the degradation rate. Humidity can be applied too if considered a factor. Uses: shelf-life studies; product data; regrind analysis and the affect of other influences on product lifespan

22. CNMR – Athlone Institute of Technology Chemical Analysis Gel Permeation Chromatography (GPC) GPC causes separation by various pore sizes in the column packing material, separating on the basis of molecular size, not molecular weight. Main use of GPC (or SEC): Measuring average molecular weight (Mp) and molecular weight distribution (Mw) of a material. Typical Detection methods used are UV-vis and Refractive Index.

23. CNMR – Athlone Institute of Technology Chemical Analysis Gel Permeation Chromatography (GPC)

24. CNMR – Athlone Institute of Technology Case Study A Contamination Issue: The client sent one sample of their product with particulate on the bottom of the container. How was it resolved? • Specimens were isolated and cleaned in Class 100 Cabinet • FTIR and DSC were applied to determine the material types

25. CNMR – Athlone Institute of Technology Case Study A Contamination Issue: Isolated White Particulate Matter: FTIR – Polytetrafluoroethylene (PTFE)

26. CNMR – Athlone Institute of Technology Case Study A Contamination Issue: Isolated White Particulate Matter: DSC – Tm = 329oC

27. CNMR – Athlone Institute of Technology Case Study A Outcome: The client checked their materials list and equipment associated with this product. The PTFE Source was determined to have come from a stirring bar used during manufacture of the solution.

28. CNMR – Athlone Institute of Technology Case Study B Processing Issue: A batch of parts were cracking in service after normal pressure was put on the end of the part. How was it resolved? • GPC was used to compare both ‘good’ and ‘bad’ samples.

29. CNMR – Athlone Institute of Technology Case Study B Processing Issue: Therefore we looked at the process and decided to look at the moisture content of the pre-processed material: • Using Karl Fischer Coulometry we determined that the material had not been dried sufficiently. • This then led to the materials’ molecular weight being affected during processing causing the material in the part to be weakened.

30. CNMR – Athlone Institute of Technology Case Study C Recycling Issue: • A manufacturer using regrind polyethylene material experienced difficulties with contamination of screen plates within an extruder. • The problem was thought to be caused by contamination of the regrind feedstock. CNMR were requested to: (1) Identify the contaminant; (2) Determine the source of contamination if possible;

31. CNMR – Athlone Institute of Technology Case Study C Recycling Issue: • Debris from the screen plates was examined under an optical microscope. It was determined that the contamination was not compatible with the matrix and could be removed easily. • FTIR determined that the materials present were PET-based. PET

32. CNMR – Athlone Institute of Technology Case Study C Recycling Issue: DSC confirmed that the contamination had a Tm at ca. 250oC. This is typical of the melting characteristics demonstrated by PET. Material from two silos were analysed. The granules were separated simply according to density. Only one material from one of the silos was found to contain dense particles. These particles had the same thermal characteristics as the contaminant.

33. CNMR – Athlone Institute of Technology THANK YOU...

34. CNMR – Athlone Institute of Technology Contact DetailsMr. Mark Atterbury Mr. Alan MurphySenior Research Officer Senior Research OfficerTel: 00353 9064 83070 00353 9064 42575Email: matterbury@ait.ieamurphy@ait.ie