Tensile testing for plastic according to ISO 527-2

ISO 527-2 is an international standard for determining the tensile properties of reinforced and non-reinforced plastics. Although it provides similar results with ASTM D638, ISO 527-2 is not considered to be technically equivalent due to differences in sample size and test requirements.

Tensile testing is always considered an important step in the material strength test, in order to determine the maximum force that a specimen can withstand. While some major manufacturers test both ASTM D638 and ISO 527-2, most of our customers show preference for one or another based on the geographic location of surname. For example, in North America, manufacturers often use ASTM D638 for testing, while in Europe and Asia mainly use ISO 527-2, while customers in China use both. the two criteria above.

The following is a plastic tensile test method according to ISO 527-2

ISO 527-2 is carried out on universal compressors by applying tensile force to the sample and measuring the various properties of the sample material under stress. The test is carried out with a tensile speed ranging from 1 to 500 mm / min until the test piece is damaged (yield or breakage).

So, what does ISO 527-2 measure?

Although ISO 527-2 measures many different tensile properties, the following are most common:

  • Tensile strength: force can be applied to a material before it melts or breaks.
  • Pull module: how much material can be deformed to meet stress before being melted? A module is a measure of material hardness.
  • Elongation – increase in the length of the dimensions measured against the original dimensions. Greater elongation indicates greater flexibility of the material.
  • Poisson’s ratio – a measurement of the relationship between the length of a material and the thickness of the material over the stretching process.

Is ISO 527-2 the right method for you?

There are many different testing methods for plastic materials. ISO 527-2 is used to test hard and semi-rigid plastics whether they are cast, extruded or machined or even reinforced plastics (except those reinforced with fibers). When testing films and sheets with a thickness of less than 1 mm, ISO 527-3 should be used. These methods can be found in the Bluehill® Universal Application Module, which contains preconfigured modal patterns for the most commonly used ISO and ASTM standards.

Find out which Instron machines are suitable for this tensile test method

Most of the ISO 527-2 tests are performed by universal tractors. The 5 kN or 10 kN systems are the most common, particularly for machined resins or composites with greater stiffness the 30 or 50 kN system is suitable.

Instron offers 2 series for universal tensile testing systems: frames, clamps, force sensors and extensometers that meet the exact requirements of ISO 527-2 testing standards. However, customers who require higher testing often prefer the Instron 5900 system with pneumatic clamps for higher test efficiency and accurate specifications.

Plastic tensile test jaws

Because the test process exposes the sample to strong forces, it is important that the samples are kept safe inside the machine. Pneumatic grips with serrated grips are usually the best type to hold hard plastic. Pneumatic clamps maintain their clamping force with air pressure, remain constant even when the test piece deforms during the test and its thickness varies significantly. For forces above 10 kN, usually found only with reinforced materials, wedge-type clamps should be used.

Choose the appropriate extensometer

In laboratories with high throughput requirements, an automatic extensometer can eliminate manual labor time and also provide a more suitable position on a large number of test pieces, increasing repeat value. AutoX750 automatically attaches to the test piece without interference from the test operator.

The extensometer (AVE 2) is a non-contact extender that uses the camera to monitor the deformation of the sample during the test. If tested against other standards, such as ASTM D638 or ISO 178, the automatic extensometer also provides the flexibility of using different gauge lengths with a single device.

Requirements on test samples

There are 6 sample sizes that can be tested to ISO 527-2. Preferred samples are dumb-bell-shaped 1A (injection molding) and 1B (machining). Despite the difference in length between the two types of samples, they share a nominal length of 10 mm and a width of 4 mm.

The appropriate gauge length for Type 1A specimens is 75 mm, which is a change from the standard introduced in 2012. Until 2012, the appropriate gauge length for 1A types was 50 mm, which is still acceptable. received for quality control testing or specified.

In the case of restricted materials, many laboratories will use specimens of size dependent on type 1BA, 1BB, 5A or 5B. In these cases, it may be technically difficult to measure the module because of the small length of the ruler and the short test time. Results obtained from small specimens cannot be compared with results obtained from type 1 specimens.

Video on testing plastic scissors according to ASTM D638 and ISO 527 (Click to see details)

This post is also available in: Tiếng Việt

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