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					CNMR – Athlone Institute of Technology




      Thermal and
   Mechanical Analysis
        Alan Murphy
    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
    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
    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
    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
    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 ?
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)
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
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.

    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 sub-
zero 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?

    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




             4000.0     3000        2000          1500        1000     650.0
                                           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?

   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 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.
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;
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
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         Mr. Alan Murphy
  Senior Research Officer    Senior Research Officer
  Tel:    00353 9064 83070   00353 9064 42575
  Email: matterbury@ait.ie   amurphy@ait.ie

				
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posted:8/25/2012
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