polymer film testing

7/28/2019 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.


7/99Oil, Chemicals and Agri (Caleb Brett Division) March 2007

Dual Blade Shear Cutter

SupportPlatform

Dual BladeCutters



Various Die Cutters Used For

Producing Test Specimens



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%



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



Tensile PropertiesResponse of a material to an axial deformation applied

at a constant rate of speed.



Tensile PropertiesTensile Strength = Force/Cross Sectional Area

Tensile Strain = Change in Length/Original LengthElastic modulus = Change in Stress/Change in Strain in Elastic Region



Tensile Properties of Film Specimen Preparation

Dual Blade Shear Cutter

SupportPlatform

Dual BladeCutters



Razor Die



Tensile Specimen In Test Grips



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


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


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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(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



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(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


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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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



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Air Oil


Dielectr ic Constant / Dissipation Factor


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Dielectr ic Constant / Dissipation Factor


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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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.



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Equipment

Electrodes

Differential Scanning Calorimetry
http://www.ptli.com/testlopedia/subs/quadtech_SV.asp


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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



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e e a Sca g Ca o e y



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g y

(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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p

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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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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