CNMR – Athlone Institute of Technology
Thermal and
Mechanical Analysis
Alan Murphy
CNMR –
Athlone Institute of Technology
Introduction
Plastic materials are tested throughout their life:
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Monomer / Reactants
Polymer / Raw Material & Additives
Product / Design
Product / Research & Development
Processing / Quality Control
Product / Service
Product / End of Life
CNMR –
Athlone Institute of Technology
Introduction
A knowledge of available test methods is useful to:
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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
CNMR –
Athlone Institute of Technology
Introduction
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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
CNMR –
Athlone Institute of Technology
Introduction
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Testing during processing
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QC tests, such as weight or moisture content
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Troubleshooting tests, such as investigating :
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Why a component is cracking during assembly
Why an extruded tube is shrinking after manufacture
Where contamination is coming from & what type
CNMR –
Athlone Institute of Technology
Introduction
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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 ?
CNMR – Athlone Institute of Technology
Thermal Analysis
ANALYTICAL TECHNIQUES
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Differential Scanning Calorimetry (DSC)
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Dynamic Mechanical Thermal Analysis (DMTA)
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Thermogravimetric Analysis (TGA)
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Melt Flow Rheology (MFI)
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Gel Permeation Chromatography (GPC)
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.
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Main use of DSC: Material Identification (Tm and DHf)
based on IS EN ISO 3146:2000; Method C2
CNMR – Athlone Institute of Technology
Thermal Analysis
Differential Scanning Calorimetry (DSC)
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.
CNMR – Athlone Institute of Technology
Thermal Analysis
Differential Scanning Calorimetry (DSC)
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
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.
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Main use of TGA: Inorganic Content of Material
CNMR – Athlone Institute of Technology
Thermal Analysis
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.
CNMR – Athlone Institute of Technology
Thermal Analysis
Thermogravimetric Analysis (TGA)
% Polymer
= 64.4%
% Carbon Black = 3.4%
% Glass Fibre
= 32.2%
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
CNMR –
Athlone Institute of Technology
Rheological 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
CNMR –
Athlone Institute of Technology
Mechanical 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
CNMR –
Athlone Institute of Technology
Impact 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 subzero temperatures.
Uses: QC test, material comparison, notch sensitivity
CNMR –
Athlone Institute of Technology
Aging 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
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.
CNMR – Athlone Institute of Technology
Chemical Analysis
Gel Permeation Chromatography (GPC)
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?
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Specimens were isolated and cleaned in Class
100 Cabinet
FTIR and DSC were applied to determine
the material types
CNMR – Athlone Institute of Technology
Case Study A
Contamination Issue:
%T
4 00 0.0
3 00 0
2 00 0
1 50 0
1 00 0
6 50 .0
1 /cm
Isolated White Particulate Matter: FTIR – Polytetrafluoroethylene (PTFE)
CNMR – Athlone Institute of Technology
Case Study A
Contamination Issue:
Isolated White Particulate Matter: DSC – Tm = 329oC
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.
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?
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GPC was used to
compare both ‘good’
and ‘bad’ samples.
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 preprocessed material:
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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.
CNMR – Athlone Institute of Technology
Case Study C
Recycling Issue:
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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;
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.
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FTIR determined that the
materials present were PET-based.
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PET
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.
CNMR – Athlone Institute of Technology
THANK YOU...
CNMR – Athlone Institute of Technology
Contact Details
Mr. Mark Atterbury
Senior Research Officer
Tel:
00353 9064 83070
Email: matterbury@ait.ie
Mr. Alan Murphy
Senior Research Officer
00353 9064 42575
amurphy@ait.ie