3 challenges in plastics testing: melt flow, heat deflection temperature, & impact

The 3 Challenges in Plastics Testing

Melt Flow, HDT & Impact

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Agenda Overview

• Testing Standard • Changes and Trends in Key Standards

• Melt Flow

• HDT & Vicat Tests

• Challenges • Factors that Influence Results and Solutions

• Melt Flow

• HDT & Vicat Tests

• Impact

• Increasing Lab Efficiency and Throughput • HDT & Vicat Tests

• Impact

3

Melt Flow Index

Polymer

Melt

Extrudate

MFI = MFR = Fluidity = Inverse of Viscosity

Ability of material melt to flow under pressure

• ISO 1133

• ASTM D1238


ISO 1133-1,2

• Latest Revision in 2011

• Reference for most local standards on melt flow tests worldwide

• Similar to ASTM D1238, but differs in technical content

What’s Changed?

Testing Standards Reviewed – Melt Flow


2005 2011

TEMPERATURE

ACCURACY

TEMPERATURE

VERIFICATION /

CALIBRATION

PISTON

GEOMETRY

Max absolute deviation,

defined for all materials and

as a function of different

temperature ranges

One simple procedure

required for all applications

Head diameter defined by

difference from barrel

diameter, sharp lower edge

Evolution of ISO 1133

Max absolute deviation + relative

distribution along the barrel (for

sensitive materials) over the entire

temperature range

More complex procedure added

for sensitive materials (part 2)

Absolute tolerance on head

diameter, rounded lower edge

= Significant


Temperature Tolerance Specified by 2011 Revision of Standard

Temperature Tolerances ISO 1133-1:

• Maximum deviation at 10 mm above die surface:

± 1°C (all temperatures)

• Maximum deviation between 10 - 70 mm above

die surface : ± 2°C to ± 3°C (depending on

temperature)

• No maximum relative distribution specified

Temperature Tolerances ISO 1133-2:

For all temperatures, between 0 - 70 mm above

die surface:

• Maximum deviation from set temperature: ±

1°C

• Maximum relative distribution of the

temperature: ± 0.3°C


TEMPERATURE

ACCURACY

TEMPERATURE

VERIFICATION /

CALIBRATION

PISTON

GEOMETRY

RESULTS

METHOD

EFFICIENCY

PRODUCT Changes

How Will These Changes Impact You?


Heat Deflection Temperature Test

• A stress is applied on a sample in a 3-point bending mode while

temperature is raised at uniform rate

HDT value for the material

under test


Vicat Softening Temperature

• A standard indenter penetrates into the surface of a plastic test specimen

when the temperature is raised at a uniform rate

VST value for the material

under test


Testing Standards Reviewed – HDT & Vicat

• ISO 75-1,2

• ISO 75-3

• ASTM D648

• JIS K7207

• ISO 306

• ASTM D1525

• JIS K7206


ISO 75-1,2

• The most common plastics Heat Deflection Temperature (HDT)

standard worldwide

• Latest revision in 2013

• Not technically equivalent to ASTM D648

What’s Changed?


ISO 75-1, 2

Both flatwise with 64 mm

span or edgewise with 100

mm span

Only one mercury-in-glass

thermometer

Between 20 - 23°C

SPECIMEN

POSITION AND

SPAN

INITIAL

TEMPERATURE

TEMPERATURE-

MEASURING

HEATING

EQUIPMENT

Practically only oil bath

were available

Any suitably calibrated

temperature-measuring device is

allowed

(A device for each station is

recommended)

64 mm span no longer allowed for

edgewise tests

Liquid bath, fluidized bed or an air-

oven systems

Below 27°C

ISO 75:1974 (1st edition)

1987

(2nd edition) 2004 2013

1993/Split Part 1, 2 and (3) = Significant

C:/Users/GoshgaRi/Documents/APPLICATIONS/plastics/data rate calculation sheet Iso527.xlsx



HEATING

EQUIPMENT

SPECIMEN POSITION

AND SPAN

TEMPERATURE

MEASURING

INITIAL

TEMPERATURE

RESULTS

METHOD

EFFICIENCY

PRODUCT

Changes


ISO 306

• The most common plastics Vicat Softening Temperature (VST)

standard worldwide

• Latest revision in 2013

• Equivalent to ASTM D1525

What’s Changed?


ISO 306

Mercury-in-glass

thermometer

Between 20 - 23°C Initial

Temperature

Temperature-

measuring

Heating

Equipment

Practically only oil bath

were available

Load applied after

preconditioning

(5 minutes) phase

Test

Procedure

Any suitably calibrated

temperature-measuring device.

One per station, as close as

possible to both the indenting tip

and specimen

Liquid bath, direct-contact or

fluidized bed systems

Below 25°C

Load applied before

pre-conditioning (5 minutes) phase

1974

(1st edition) 1987 1994 2004 2013

= Significant





HEATING

EQUIPMENT

TEST PROCEDURE

TEMPERATURE

MEASURING

INITIAL

TEMPERATURE

RESULTS

METHOD

EFFICIENCY

PRODUCT

Changes


Other Standards

• ASTM D648

• 2000, 2001, 2004, 2006 and 2007 (latest)

• No significant changes observed

• Current ballot to incorporate fluidized bed as

alternative heat transfer medium

• ASTM D1525

• 1987, 2000, 2006, 2007, 2009 (latest)

• From 2009 it is including fluidized powder as heat

transfer medium

• Technically equivalent to ISO 306


Why are my results

inconsistent or

incorrect?

What influences results?


Factors That Influence Results MFI

Temperature Accuracy

Preparation of Sample

(Moisture)

Sample Compacting

Method Parameters

Temperature Stability

Choice of Procedure

Encoder Accuracy

Extrudate Cutting

Precision

Melt Density Value

Manual Operations within Test

Maintenance of Die & Piston

Cleaning Procedures

= Most common

Hyperlinks for Plastics Strategy/Big Customers.pptx




Manual vs. Automatic

• Controlled Compacting

• Better reproducibility and less scattering of results

• No physical effort required by operator

(reduces risk of injury)

• Post-test automatic purging

• Reduces total test time

• Operator is ready to run next test more quickly

• Cleaning

• Thorough cleaning extends life of equipment

and helps to maintain consistent results


Material

• Has the material been pre-conditioned according to procedure?

• Hygroscopic materials give unreliable test results if they are not dried

in consistent manner

• Moisture tends to generate bubbles and trigger degradation of sample

• Temperature and length of drying time must be consistent

• Is the melt density being used in the MFR calculations correct?

• Is the amount of material being tested consistent?

• Was the material compacted properly (or were there air bubbles)?


Factors That Influence Results HDT/Vicat

Temperature Accuracy

LVDT Measurement

Accuracy

Specimen Dimensions –

Wrong Weights (HDT)

Span (HDT)

Oil Not Properly Selected

System Cooling Between Tests

Pre-Conditioning

Material Residual into

the Bath

Stress Applied (HDT)

Method Parameters

Unstable Temperature Rate Control

Oil Degradation

= most common sources of issues


Oil Selection & Degradation

• Selection of the right oils helps obtain

more consistent results

• Oil that is intended for testing at higher

temperatures will be too viscous for

sufficient circulation at lower temps

• Extending the life of your oil:

• Nitrogen valve can be activated to prevent

oil contact with oxygen and prevent

premature degradation

• Specimen cages reduce oil degradation

due to materials into bath

• Bonus: saves operator time

How Much Time Can You Gain?

Increasing Laboratory Efficiency


Solutions to Improve Throughput

6 stations

system

Automation

Manual

3 stations

system

Co

st

Effectiveness

Water Chiller


Manual vs. Automated Test Time

6 stations

Automatic

Chiller

6.5 minutes

5 minutes

180 minutes

45 minutes

Preheating

cooling

Station preparation

up to specimens in bath

Test time

(example up to 300°C)

Ideal Setup

Total Cycle Time: 235 minutes

Total Cycle Time: 270 minutes

6 stations

Manual

tap water

cooled

180 minutes

5 minutes

9.5 minutes

75 minutes

Manual Setup

Cycle time

reduced by

about 30

minutes


Factors That Influence Results Impact

Specimen Notching Method

Micrometers - Dimensional

Measurement

Accuracy of Equipment

Hammer Capacity

Environmental Losses

Specimen Notching Speed

Hammer Design Frame Design

Method Parameters

Indirect Verification

Calipers – Dimensional

Measurement

Specimen Conditioning

= most common sources of issues


Bad Notch Affecting Impact Results?

• At what speed are you notching specimens?

• What is the depth of every pass?

• Are you using a linear notching knife?

• Is your knife profile within tolerance?

• When did you last change the notching knife?

40

30

20

10

0

0.25 0.5 1 2 4 8 16 32

PVC

Nylon

POM

ABS

PMMA

Notch Tip Radius (mm)

Impact

Str

ength

(kJ/m

2)

Good Notch

Bad Notch


Bad Notch Affecting Impact Results?

Linear

Cutter

Rotary

Cutter

0.224

0.235

0.221

0.26 0.26 0.26

0.19

0.2

0.21

0.22

0.23

0.24

0.25

0.26

0.27

0.28

0.29

0.3

0.31

0 1 2 3 4

No

tch

Ba

se

Ra

diu

s (

mm

)

Number of specimens

Notch Radius Tolerance = 0.25 +/- 0.05 mm Linear cutter

Rotary cutter


Specimen Conditioning

• Are you impacting the specimen within 5 seconds after taking it out of

the refrigerator/ Cryodispenser /cooling unit?

• Are you handling the specimen with conditioned tongs and gloves?


Izod Vice Clamping

• Some plastics are sensitive to clamping pressure

• Differences in clamping pressure between tests and/or

operators will reduce results repeatability

Manual

Tightening Tightening with a Lever

Pneumatic Tightening

Increasing Laboratory Efficiency

How Much Time Can You Gain?


Types of Setups

IDEAL TYPICAL

Motorized Impactor

• Integrated micrometer

• Automatic hammer release

• Automatic positioning of

hammer

Manual Impactor

• Non-integrated Micrometer

• Manual release of hammer

• Manual positioning of

hammer

https://itwconnect.sharepoint.com/sites/i2/CEAST/Marketing/Products photos/CEAST 9050_Manual model.jpg


1. Measure specimen

dimensions

2. Enter specimen

dimensions

3. Place specimen on

the vice

4. Close the safety door

5. Release hammer

manually

6. Brake the test

7. Open the safety door

8. Reposition the

hammer manually

1. Place specimen

under micrometer

(Dimensions are

automatically sent

to the machine)

2. Place specimen on

the vice

3. Close the safety

door

4. Release hammer

pneumatically with

a click (Hammer is

repositioned

automatically)

SPECIMEN

HANDLING AND

MEASUREMENT

INITIATION OF

TEST

PREPARATION

FOR NEXT TEST

INCREASED USER INTERACTION MINIMIZED USER INTERACTION

The Differences


Cycle Times

Minutes 1 2 3

50s 30s

15s

40s

20s

40s

Test Time with

Hammer Release/Reposition

Test Preparation Specimen

Measurement

IDEAL

SETUP

TYPICAL

SETUP

> 32%

FASTER! Total Cycle Time: 75 seconds

Total Cycle Time: 110 seconds


Thank you for your time!

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3 challenges in plastics testing: melt flow, heat deflection temperature, & impact

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