An Introduction to ISO 527-3

Tensile Testing of Thin Plastic Film

Written by Dan Caesar

ASTM D882

 

ISO 527-3 is an international standard used to determine the tensile properties of plastic film or sheeting. Plastic films and sheeting are a popular choice for packaging manufacturers and can be found protecting many everyday items from leftover food to consumer goods. It is critical that plastics manufacturers and packaging companies obtain an accurate mechanical profile of the plastic films they are producing to ensure that they meet the required specifications.

What Does it Measure?

Material properties to be reported for ISO 527-3 include

Tensile strength
Yield: stress and strain
Break: stress and strain

Related Standards

Film or sheeting is defined to be a plastic test specimen with a thickness less than 1 mm. Plastics with a thickness greater than 1 mm should be tested per ISO 527-2. The equivalent ASTM standard to ISO 527-3 is ASTM D882.

Recommended Testing Equipment

Because thin film specimens break at relatively low forces, ISO 527-3 testing is often performed on a single column universal testing machine. However, due to the fact that many thin film specimens exhibit high elongation at break, an extra height single column frame or possibly a dual column frame may be required in order to test until break. Instron's 3400 and 6800 Series include a variety of test frames suitable for thin film testing, with the 6800 Series offering many advanced features for those wishing to maximize repeatability and throughput.
ISO 527-3 test setup

ISO 527-2 Test Setup

1. Instron 34SC-1

2. Bluehill Universal Dashboard (2490-696)

3.2519-1kN Load Cell

4. 1 kN Pneumatic Side-Action Grips (2712-041) 

 

Gripping Solutions 

Due to the flexible, delicate nature of thin film specimens, specimen gripping can be a challenge. Pneumatic side action grips are an ideal solution because they provide an adjustable inlet air pressure to ensure that specimens can be clamped sufficiently throughout the test. When using pneumatic grips with the Smart-Close Air Kit, operators can define the inlet clamping pressure in the Bluehill Universal test method, replacing the need to manually change the pressure at the air supply’s regulator. The Smart-Close Air Kit not only promotes a safer use of pneumatic grips, but it can make testing more efficient and repeatable.

For those looking for a non-pneumatic solution for ISO 527-3 testing, Instron recommends self-tightening roller grips. Manually-tightened screw grips are not recommended for thin film testing, because the variability they add to the clamping pressure can negatively impact the repeatability of results and cause a higher frequency of improper gripping (jaw breaks or slippage). 

2712-041
1 kN Model | 2712-041
2613-007
1 kN Model | 2713-007

Strain Measurement

While ISO 527-3 does not require extensometry, the use of an extensometer always results in the most accurate strain measurement. Non-contacting video extensometry is the best solution for thin film testing, as typical clip-on extensometers weigh down the specimen causing premature failure. Instron's Advanced Video Extensometer (AVE2) can measure strain as accurately as a clip-on extensometer without physically contacting the specimen.

Results

Instron's Bluehill® Universal testing software makes it easy to report calculations in compliance with the standard. Customers who choose the Plastics method suite will receive a pre-configured test method for ISO 527-3 testing, complete with specific test parameters and calculations to help ensure compliance.

Throughput

For labs with high-volume testing needs, several modifications to the tensile machine setup can be made to speed up the testing process and increase throughput, up to and including fully automated test systems. Fully automated systems such as Instron's AT3 are designed to incorporate specimen measurement, specimen loading, testing, and removal, and are able to run for hours without operator interaction. These systems help to reduce variability due to human error and can be left running after a shift ends to continue getting results when operators go home.

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