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Transcript of Polymer Film Testing
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Oil, Chemicals and Agri (Caleb Brett Division) March 2007
Polymer Film Testing
(Techniques and Analysis)
Polymer films are widely used in our every day lives. Today we
will learn about the most common testing techniques used for
polymer films and thin sheeting and the type of data that can be
generated from those tests.
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Industries That Commonly Use
Polymer Films
Packaging Food
Non-Food
Building & Construction Trash Disposal (City and Town)
Film Photography
Electronics
Adhesives (Tape)
Medical
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Organizations for Test
Standards
There are two primary standard organizations thatgovern the methodology of most plastics testing:
ASTMAmer ican Society for Testing & Materials
ISO
International Organization for Standardization
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Polymer Film Testing
1. What is a film?2. Specimen Preparation
3. Mechanical: Tensile, Puncture, Impact, Tear
4. Physical: Identification, Gage, Coefficient of Friction, SurfaceEnergy, Density, Permeability, Blocking
5. Electrical: Dielectr ic Strength, DC/DF, Surface & Volume Resistivity
6. Thermal: Differential Scanning Calorimetry (DSC),Thermogravimetric Analysis (TGA), Coefficient of ThermalExpansion (CTE), Dynamic Mechanical Analysis (DMA)
7. Flammability: UL 94VTM, Oxygen Index (OI)8.Accelerated Weathering: Xenon-arc & QUV exposure
9. Optical: Color, Gloss, Haze, Refractive Index, Yellowness Index
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What Is A Film? A film is defined as sheeting having a thickness less than or equal
to 250m (microns) which is equivalent to 0.010 (inches) which is
equivalent to 10mils (thousandth of an inch) which is equivalent to0.254mm (millimeters)
If a material is greater than 250m, it is considered a sheet.
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Test Specimen Preparation
ASTM D6287 Standard Practice for Cutting Film and SheetingTest Specimens this guide specifies techniques used for cuttingnarrow strips that will be used for tests like Tensile Properties of
Film.
Procedure A employs the use of a Hand Rotatable Drum Cutter
Procedure B employs the use of a Dual Blade Shear Cutter (used byIntertek PTL for producing Tensile specimens.
This method does not address preparation of all specimens for film testing.
The objective is to produce straight, clean, parallel edges free ofnicks or flaws
The most important part of film testing (or any testing for thatmatter) is in the specimen preparation. Poorly preparedspecimens will yield poor results that you do not have confidencein.
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Dual Blade Shear Cutter
SupportPlatform
Dual BladeCutters
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Various Die Cutters Used For
Producing Test Specimens
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Standard Laboratory Conditioning
Prior To Testing
ASTM D618 Conditioning Plastics For Testing
Six different procedures specified Methods A through F
Time, Temperature, Humidity, Immersion medium Procedure A Condition 40/23/50 is common for
most plastics and is the typical procedure forphysical and mechanical film testing
40+ hours / 23C 2C / 50% RH 10%
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Tensile Properties of Film Test Method: ASTM D882
Stress & Elongation
Crosshead Speed and Grip Separation are chosen based on elongation at break Elongation less than 20% Speed = 0.5 in/min Grip Separation = 5.0 in
Elongation 20% - 100% Speed = 2.0 in/min Grip Separation = 4.0 in
Elongation greater than 100% Speed = 20 in/min
Grip Separation = 2.0 in Strain can be measured using crosshead displacement or extensometers
Modulus of Elastici ty Standard gage length specified is 10 inch
Test speed of 1.0 in/min
Properties of Interest Stress at Yield
Elongation at Yield Stress at Break
Elongation at Break
Modulus of Elasticity
Tensile Energy to Break
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Tensile PropertiesResponse of a material to an axial deformation applied
at a constant rate of speed.
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Tensile PropertiesTensile Strength = Force/Cross Sectional Area
Tensile Strain = Change in Length/Original LengthElastic modulus = Change in Stress/Change in Strain in Elastic Region
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Tensile Properties of Film Specimen Preparation
Dual Blade Shear Cutter
SupportPlatform
Dual BladeCutters
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Razor Die
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Tensile Specimen In Test Grips
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Tensile Data :
The Stress/Strain Curve
Yield
Break
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Important Areas of the Stress/Strain Curve
Elastic and Plastic Regions
Linear Elastic Region - follows Hookes law for an elastic materialthe stress is proportional to the strain.
Plastic Region - area where permanent deformation occurs afterrelease of load.
Proportional limit
Greatest Stress a material is able to sustain with out deviation fromHookes law.
Elastic limit The greatest stress a material is able to withstand without permanent
deformation remaining after release of load.
Yield Point The first point on a stress strain curve that exhibits an increase in
strain without a corresponding increase in stress.
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Flaw In Edge of Tensile Specimen
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Seal Strength
Test Method ASTM F88
Technique A: Unsupported Technique B: Supported 90 (By Hand)
Technique C: Supported 180
Force required to separate a sealprepared in a test strip
Useful for monitoring package integrity
Quality control and R & D
Strong seals to prevent a package frombeing opened
Sometimes the objective is to keep theforce to a minimum so a package canbe easily opened
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Slow Rate Puncture Probes
MIL-STD-3010B Method 2065 ASTM F1306
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Base Clamp and Puncture Probe
Clamp Opening
Penetration Probe
Film
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Slow Rate Puncture Graph
Layer 1 Maximum Load
Layer 2 Maximum Load
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High Speed Puncture Properties of Plastic Films Using
Load and Displacement Sensors
ASTM D7192
Specimen : 100 mm diameter or square (or 13mm greater than baseopening diameter used)
Preferred striker: 12.7mm
Support diameter: 76mm
Impact Velocity: 200 m/min (3.3 m/s)
Other support openings and velocities can be used
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Multi Axial Impact Data Generated
Maximum load required to penetrate or break a specimen Units: lbs or Newtons
Energy absorbed by the specimen Units: FT-lbs or J oules
Displacement of specimen during impact Units: inches or mm
Time of impact event Units: milli-seconds
Load - Time (or displacement)-Energy curves
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Multiaxial Impact Tester
Weighted Crosshead
Load CellElectric Eye
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Multiaxial Impact Clamping Mechanism
Specimen
Clamp
Tup / Dart / Impact Head
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Typical Load-Time-Energy Curve - Ductile Material
Maximum Load
Energy @ maximum loadTotal Energy
Load Curve
Energy Curve
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Impact Resistance of Plastic Film by
the Free-Falling Dart Method
Test Method ASTM D1709 Test method A: 38 mm (1.5") diameter dart dropped from 0.66 m (26")
Test method B: 51 mm (2") diameter dart dropped from 1.5 m (60")
Specimen Clamp = 125mm (5.0 ) diameter
Property of Interest: Impact failure weight in grams force
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Close Up Of Clamping Mechanism
ASTM D1709
Clamp
Specimen
Falling Dart
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Comparison of Mult iaxial Impact and Free-Falling Dart
Impact
Test is designed sothat dart penetratesthrough specimen.
Instrumented Test
Data genertaed
Load Energy
Displacement
Bruceton Staircasetechnique
Non-instrumented
Data generated Failure weight
Multiaxial Impact Free-Falling Dart
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Tear Testing
Elmendorf Tear (ASTM D1922)
Tear propagation
Graves Tear (ASTM D1004) Tear initiation
Trouser Tear (ASTM D1938)
Tear propagation
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Elmendorf Tear
Pendulum Tester Constant Radius Die & Specimen
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Elmendorf Tear
Test Method ASTM D1922
Pendulum Impact Tester
Three different specimen types Constant Radius (preferred for plastics)
Rectangular
Textile Specimen
Data Generated Tear Resistance in grams force
Specimen Types
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Graves Tear
Die & SpecimenGrips & Specimen
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Graves Tear
Test Method ASTM D1004
Tear Initiation
Performed on a universal tester 1.0 grip separation
2.0 in/min test speed
One specimen type 90 degree angle to create stress concentration
Data Generated Tear Resistance in Newtons
Maximum extension in Millimeters
Not applicable for specimens that fail in a brittle manner or extend morethan four inches during test
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Trouser Tear
Test Method ASTM D1938
Tear Propagation
Performed on a universal tester 2.0 grip separation
10 in/min test speed
One specimen type Trouser specimen with two tongues
Data Generated Tear Propagation in Newtons
Maximum extension in Millimeters
Not applicable for specimens that fail in a brittle manner
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A basic generic polymer identification of an unknown material can bedetermined by FTIR.
The first logical step in identifying an unknown polymer is to generate aninfrared scan of the unknown. The unknowns infrared spectral scan can thenbe analyzed to determine the base material of the unknown.
The following cannot be determined (with confidence) by FTIR analysis:the polymer manufacturer, the specific type of nylon or polyester, whether apolyethylene is high density or low density, whether an acetal is copolymer orhomopolymer, or the identification of specific additives or colorants used.Further analytical techniques are necessary for these situations.
A skilled FTIR analyst is needed to examine the computer selectedspectral matches to ensure that sample identifications are both accurateand complete.
Material Identification by FTIR
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FTIR: Fourier Transform Infrared Spectrometer for Material ID
FTIR Equipment
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This photo shows the top of the FTIR. Thesample would be placed where you can seethe circle.
An anvil, located in the center of the open
gate, is used to compress non-liquidsamples against a diamond ATR top plate.
The top plate is located inside the light greycircle centered under the open gate.
Close-up of FTIR
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Sample
ATR Crystal
IR Light From SourceIR Light To Detector
Simplistic Attenuated Total Reflectance Process
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A spectral scan of a reference material can be generated and storedin a spectral search database.
A stored reference scan will allow all future material spectra to becompared back to the same earlier scan. The objective is to look formaterial differences.
Differences noted in a newly generated spectral scan could indicatea change in processing or a possible contamination of the polymer.
Quality Control
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FTIR spectral subtractions can be used to look for contamination in
polymers. The amount of contamination that can be detecteddepends on the polymers involved.
Contamination involving polymers with very different infraredspectra can be detected at a level of about 1-2%.
Contamination involving polymers with similar infrared spectra maynot show up at even the 10% level.
Polymer Contamination
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Computer programs are very helpful for comparing unknown spectralscans to those of known materials, but computer selected matches canbe misleading.
Small spectral databases, polymer blends, fillers, certain types of
additives, and sample contamination can cause computerized searchprograms to suggest inappropriate matches.
Limitations of Computerized Searches
Fil Thi k ( k G )
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Film Thickness (a.k.a. Gage)
Drop Dial Gauge ASTM D6988 Apparatus A
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Techniques For Measuring Film Dimensions
ASTM D6988 - Standard Guide for Determination of Thickness of
Plastic Film Test Specimens Apparatus AManually Operated Thickness Gauge
Apparatus BAutomatically Operated Thickness Gauge
Apparatus CManually Operated Thickness Gauge with Linear OpticalEncoder
Apparatus DAutomatically Operated Thickness Gauge with Digital DisplayASTM D5947 - Standard Test Methods for Physical Dimensions
of Solid Plastics Specimens
This is an actual test method unlike ASTM D6988 which is a guide.
References four different types of measuring devices that can be used.
References five different test methods that can be used.
Film test methods typically refer to ASTM D5947 stating which technique is tobe used for measuring the test specimens for that particular test. For
example: ASTM D882 (Tensile Properties of Films) requires Method C of
ASTM D5947 to be used for measuring thickness of tensile strips.
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Common Units of Thickness Measurements For Films
Micron (m) = one millionth of a meter
Inch (in. or )
Mil (one thousandth of an inch)
Millimeter (mm)
1m = 0.000039in = 0.039mil = 0.001mm
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C ffi i t f F i ti
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Coefficient of Friction
Stationary Substrate
Moving Sled
Pulley
Monofilament
C ffi i t f F i ti
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Condition of surfaces
Dust Grease
Fingerprints
Slip Agents Blooming Action
Direction of pull
Machine direction Transverse direction
Foam Pad Density (0.25 g/cm3)
Pressure to compress (12.5 psi at 25% compression)
Level base
Technique Consistency between technicians
Consistency during test
Total weight of sled 200 5 grams
Coefficient of Friction
(Important Considerations)
C ffi i t f F i ti C l l ti
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Coefficient of Friction Calculations
Static Coefficient of Friction = Initial force to initiate sledmovement divided by sled weight.
Kinetic Coefficient of Friction = Mean force over five inchdistance divided by sled weight.
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Static COF
S f E
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Surface Energy
Test method ASTM D5946 Uses a Contact Angle Goniometer for measuring water droplet angle
Adhesion of various materials to film Inks
Paints
Clear Coats
Film surfaces are often treated to increase adhesion properties.
Wetting out versus beading up Wetting out - the spreading of a liquid over a surface Contact angle can be related to a films ability to accept and retain inks, coating,
adhesives, etc.
Important Considerations Static Charge
Specimens should not be handled in the measurement area Water Quality
Cleanliness of glass substrate
Droplet angle measurement interpretation
Goniometer For Measuring Contact Angle
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Goniometer For Measuring Contact Angle
Test Strip
SyringeMagnifier
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Specific Gra it and Densit
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Specific Gravity is the ratio of the weight of a givenvolume of sample to that of an equal volume of water ata specific temperature.
Temperature normally 23.0C
Specific Gravity =Dry Wt / (Dry Wt Wet Wt)
Dry Wt = Apparent Weight in Air
Wet Wt = Apparent Weight in Water
Density (g/cm3) = Specific Gravity x 0.9976
Specific Gravity and Density
Dry Weight Measurement
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Dry Weight Measurement
Wet Weight Measurement
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Wet Weight Measurement
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Water Vapor Transmission
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Water Vapor Transmission
(ASTM E96)
Water Vapor Transmission (Test Method ASTM E96) Manual weight technique
Procedure A Desiccant method at 23C
Procedure B Water method at 23C
Procedure BW Inverted Water method at 23C
Procedure C Desiccant method at 32C
Procedure D Water method at 32C
Procedure E Desiccant method at 38C
Water Vapor Permeance the time rate of water vapor tramsmission
through unit area of material. The average permeability is expressed asfollows: Average Permeability (g/Pasm)
Water Vapor Transmission rate the steady water vapor flow in unit timethrough unit area of a material. The Water Vapor Transmission is expressedas follows: Water Vapor Transmission (g/hrm)
ASTM E96 Test Dish Assembly
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ASTM E96 Test Dish Assembly
Test Dish
Gasket /Seal
Specimen
Water Vapor Transmission
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Water Vapor Transmission
(ASTM F1249) Dry chamber separated from wet chamber by the barrier material
Dry chamber and the wet chamber make up a diffusion cell in which thetest film is sealed.
Water vapor diffusing through the film mixes with the gas in the drychamber
Carried to a pressure-modulated infrared sensor. Sensor measures the fraction of infrared energy absorbed to produce
electrical signal.
The amplitude is compared to a calibration film of known water vaportransmission rate.
Information is then used to calculate the rate at which moisture istransmitted through the material being tested.
Oxygen Transmission Rate
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Oxygen Transmission Rate
Test Method: ASTM D3985
Oxygen gas transmission rate is determined after the sample hasequilibrated in a dry test environment.
Specimen is mounted in apparatus and acts as a sealed semi-barrier
One chamber purged by nitrogen and the other contains oxygen.
As oxygen gas permeates through the film, the nitrogen carrier gas ittransports it to the detector.
Electrical current is generated which allows for measurement ofoxygen flowing into the detector per unit time.
Oxygen permeance (PO2) = mol/(m2sPa) Oxygen transmission rate (O2GTR) = mol/(m2s)
Equipment for measuring gas permeation rates
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slide provided by
Equipment for measuring gas permeation rates
Flow thru technology
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Flow thru technology
To the detector
Test film
Test gas
Carrier gas
To vent
Test film
Diffusion cell
slide provided by
Testing a formed bag
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Package
mounting
fixture
( BAG )
Entire assembly in either the
atmosphere or controlledenvironment
slide provided by
Testing a formed bag
Blocking Load of Plastic Films
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Blocking Load of Plastic Films
Test Method ASTM D3354
Blocking = unwanted adhesion Force required to separate two pieces of film blocked together
Procedure A: Modified Balance Technique Utilizes a two-pan balance and water titrator
Procedure B: Universal Tester / Load Cell Technique Technique used by Intertek PTL
5.0mm/min
4 x 4 aluminum blocks to wrap film around
Properties of Interest
Load in grams
Blocking Apparatus
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Blocking Apparatus
(ASTM D3354 Procedure B)
Load Cell
Mounting Blocks
Film Specimens
Electrical Properties of Film
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Electrical Properties of Film
Dielectric Strength
Dielectric Constant / Dissipation Factor Volume Resistivity and Surface Resistivity
Dielectr ic Strength
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Dielectr ic Strength
Test Method: ASTM D149 Alternating current with a frequency of 60Hz
Opposing Electrodes 0.25, 1.0 and 2.0 diameter are common.
2.0 is typical for film specimens.
Dielectric Breakdown Voltage the potential difference at which dielectric failureoccurs on a material located between two electrodes.
Dielectric Strength the voltage gradient at which dielectric failure of the insulating
material occurs. Method A: Short-time Test
Voltage increase at a rate to produce breakdown within 10 to 20 seconds.(Most common method)
500 Volts per second is a common rate
Method B: Step-by-Step Test
Voltage applied in steps and held at each step for a duration untilbreakdown occurs. Breakdown should occur in four to ten steps.
Method C: Slow Rate-of-Rise Test Typical rate of applied voltage is between 1 and 100 Volts per second.
Typical Film Set-up
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Typical Film Set up
(Dielectric Strength)
Voltage In
Electrodes
Specimen
Ground
Dielectr ic Strength
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Air Oil
Dielectr ic Strength
Dielectr ic Constant / Dissipation Factor
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Dielectr ic Constant / Dissipation Factor
Test Method ASTM D150
Dielectric Constant (Relative Permittivity) A measure of the ability of an insulator to store electrical energy
Specimen capacitance divided by the air capacitance using
the same electrode configuration
Dissipation Factor (Loss Index) Measures the inefficiency of an electrical insulating material.
The ratio of the power dissipated in the test material to the power applied
DC/DF Equipment
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DC/DF Equipment
Electrodes
Surface & Volume Resistivity
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Surface & Volume Resistivity
Test Method: ASTM D257 Surface Resistance - the resistance to leakage current along the
surface of an insulating material. Surface Resistivity the surface resistance multiplied by the ratio of specimen surface
dimensions which transforms the measured resistance to that obtained if the electrodes hadformed the opposite sides of a square.
Units = ohms (per square) or/square
Volume resistance - the resistance to leakage current through the body of an insulatingmaterial. Volume Resistivity the volume resistance multiplied by the ratio of specimen volume
dimensions which transforms the measured resistance to that resistance obtained if theelectrodes had formed the opposite sides of a cube.
Units = ohms-cm or-cm
The higher the surface/volume resistivity, the lower the leakage current and the lessconductive the material is.
Surface & Volume Resistivity
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Surface & Volume Resistivity
Equipment
Electrodes
Differential Scanning Calorimetry
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Test Method: ASTM D3418
Used for material identification, locate transitions, crystallinityTransition temperatures of polymers / properties of interest
Tm (melting point)
10C/min
Tg (glass transition temperature)
20C/min
Hm - the amount of energy in joules/gram a sample absorbs while melting
Tc - the temperature at which a polymer crystallizes upon heating
Hc - the amount of energy in joules/gram a sample releases while
crystallizing.
g y
Differential Scanning Calorimetry
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e e a Sca g Ca o e y
Differential Scanning Calorimetry
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(Perkin Elmer DSC-7)
DSC Sample and Reference Heads
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Thermogravimetric Analysis
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Test Method: ASTM E1131
Measure resin content vs. filler content
g y
TGA Scan
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TGA Scan
Coefficient of Thermal Expansion
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p
Test Method: ASTM E831
Thermal Expansion by Thermal Mechanical Analyzer
Thermomechanical Analyzer
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y
Cooling/Heating Chamber
Specimen
Measurement Probe
Film Specimen in TMA Holder
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CTE Graph
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CTE Graph
Dynamic Mechanical Analysis (DMA)
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EnvironmentalChamber
Specimen Clamp
Test Specimen
Dynamic Mechanical Analysis - Tension
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Test Method ASTM D5024 (Tension)
Measure stiffness as a funct ion of temperature
Detect transitions l ike glass transition and other molecular movements
Quality Control
Failure Analysis
Application Specific Studies Shrink Wrap - Axial force changes with temperature
Properties of Interest Elastic or Storage modulus E1 - Elastic Component of the polymer. stiffness
Loss Modulus E11 - The viscous or dissipative component of the polymer.Energy lost to friction and internal motions
Tan Delta ratio of E11 to E1 relative degree of damping of the material. Howefficiently a material loses energy to molecular rearrangements and internal
friction
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DMA Plot Of A Nylon Polymer
-150.0 -100.0 -50.0 0.0 50.0 100.0 150.0 200.0 250.0
107
108
109
1010
0.0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
Temp [C]
G'(
)
[Pa]
G"(
)
[Pa]
tan_delta(
)
[]
Temp = 78C
Temp = -62C
G' Rubbery Plateau
Point A
Point B
Point C
Tg from E1 Curve
(half height)
Rubbery
Plateau
E1
E11
Flammability Testing
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Test Method: UL 94VTM (Very Thin Materials)
Vertical Burning Test
Specimens tested after conditioning at 23C/50% RH
Specimens tested after conditioning at 70C for 168 hours in an aircirculating oven
Test specimens are wrapped around a 12.7mm mandrel andclamped and hung vertically from one end.
20mm flame height
Flame applied 10mm below specimen for three seconds
Flame Ratings VTM-0
VTM-1
VTM-2
UL 94 VTM
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Specimen
Burner
Flaming
Oxygen Index Testing
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Test Method: ASTM D2863
Measures the minimum oxygen concentration to support candle-like
combustion
Accelerated Weathering
http://www.ptli.com/testlopedia/subs/Oxygen_Index2.htmhttp://www.ptli.com/testlopedia/subs/Oxygen_Index.htm -
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(Left) Q-Panel QUV/se Testerused for UV-A&B, Condensation
Exposure of Plastics, Paints and related coatings.
(Right)Atlas Electric Ci4000 Xenon Arc Weatherometerfor ASTMG155, SAE J 1960 SAE 1885.
Example of how the weather can effect a polymer
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The polymer on the left contains a UV Stabilizer. The
polymer on the right does not. Notice the severediscoloration, loss of gloss and degradation
Optical Testing
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Color (ASTM E308, ASTM D6290)
Ultra-Violet and Visible (UV/VIS) light absorption or transmission
Refractive Index (ASTM D542)
Gloss (ASTM D523)
Haze & Luminous Transmittance (ASTM D1003)
Yellowness Index (ASTM E313)
Case Study
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United States Postal Service USPS-T-3204
Outlines procedures for testing polywrap film used to enclose flat mail piecesthat are destined for automated sorting operations. Film Thickness (ASTM D374)
Thickness must be greater than 0.001
Tensile Modulus (ASTM D882) 1% Secant Modulus in MD must be greater than 40,000 psi
1% Secant Modulus in TD must be greater than 50,000 psi
Haze & Luminous Transmittance (ASTM D1003) Haze must be less than 70%
Coefficient of Friction (ASTM D1894) Film on Film must fall between 0.20 and 0.55
Film on Metal must be less than 0.45 Blocking Resistance (ASTM D3354)
Must be less than 15 grams of force
Static Electrification (ASTM D4470) Must be less than 2.0 kilovolts
Testlopedia
(Comprehensive Test Descriptions)
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Testlopedia, Free encyclopedia ofplastics tests on www.ptli.comIntertek PTLs index of plastics testing
facilitates:
Search by test type
View test equipment used at IntertekPTL
Determine appropriate scope & samplesize
(Comprehensive Test Descriptions)