ASTM D882 Tensile Testing of Thin Film & Sheet Plastics

ASTM D882 is a widely used testing standard for tensile properties of thin plastic sheet films. It is commonly used for in-line quality control. Thin plastic films and sheeting are surprisingly durable, making them an excellent choice for packaging. Not only are they strong enough to withstand shipping or transportation, but also provides an effective barrier against moisture, oxygen, light, and bacteria.

Many everyday items are wrapped in thin plastic films and sheeting before being shipped to consumers. From leftover food to consumer goods, any package you send out is potentially at risk of damage.

Why ASTM D882?

ASTM D882 is a common method of examining the mechanical properties of thin plastic films of less than 1 mm (0.040 in). In this test, a sample of film is mounted between two grips that are 250 mm (10 in) apart at the beginning of the test (gage length) distance which are then pulled by applying a tensile load. The elongation (or extension) produced in the sample is registered as the load increases.

If your plastic samples are thicker than 1 mm (0.04 in) you should consider ASTM D638.

How to Perform a Tensile Plastic Test per ASTM D882?

ASTM D882 stretches a specimen until it fails. Plastic films and sheeting are typically highly elastic, and this means that you are to test at a high crosshead speeds, based on the criteria in the standard. In order to calculate the required crosshead speed, multiply the starting length of the specimen (distance between grips) by the starting strain rate in mm/mm per min. Also, note that thin film specimens are usually not kept flat and not pulled tight when loaded into grips for testing. Apply a preload to ensure results are accurate and repeatable. Preloads remove slack in the specimen prior to taking measurements during testing.

Important Considerations for ASTM D882 Specimens

If you're sampling isotropic material (materials whose properties have no directional preference) then you'll need five samples from each sample tested on one side only; meaning that if something's been suspected as being anisotropic (having different properties depending on which direction they're measured), ten samples should be taken: five short-axis ones, and five long-axis ones or longitudinal ones.

If your material behaves differently when observed from different directions (anisotropic materials) there needs to be enough variety in your tests so that any difference might still show up in far fewer trials.

What Are the Important ASTM D882 Calculations?

Tensile tests of flexible films help measure strength, stiffness, and resistance to stretching. Test reports include:

• Modulus of elasticity
• Strain at break
• Tensile strength
• Yield strength
• Yield strain