ISO 8295 Coefficient of Friction of Plastic Film Testing

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ISO 8295 Coefficient of Friction of Plastic Film Testing

Plastic film and sheeting has many different applications. It is used to create a wide range of products including trash bags, construction liners, and I.V. bags. and is most common in the packaging industry. Food films are often used to wrap fresh produce to maintain freshness by preventing moisture loss and non-food films are primarily found in flexible packaging options like shrink wrapped packages and bags. Plastic films are becoming an increasingly popular product in the healthcare industry as they can be used to dress wounds or protect sensitive skin from irritation from adhesives or tape. To ensure that these films perform as expected for the end user, their frictional properties must be characterized and controlled.

What is ISO 8295?

ISO 8295 defines the procedures and equipment requirements needed to measure coefficients of starting (static) and sliding (dynamic or kinetic) friction of plastic film and sheeting when sliding over itself or other substances.

ISO 8295 Scope

The coefficients of friction are related to the slip properties of plastic films that are of wide interest in packaging applications. These methods yield empirical data for ensuring quality control in film production applications. Correlation of test results with actual performance can usually be established.

ISO 8295 Test Method

The ISO 8295 test requires a universal test machine to be equipped with a coefficient of friction fixture, we recommend our GISO8295-62, which is specifically engineered to meet the requirements of ISO 8295 and other industry standards from TAPPI and ASTM.

The film being tested is secured on the fixtures flat plate which is mounted in the universal test machine. A sled of specified weight is wrapped in a foam material defined by the standard, and included with the fixture. When the test machine crosshead moves upward in a tensile load mode, special low friction bearings convert the motion into a dragging motion of the COF sled over the film being tested. Force is measured by our test machine controller which includes a software module that converts the measurements into static and kinetic coefficients of friction. Test reports and data are available as an output to the process.

What Is the Test Procedure for Plastic Film & Sheeting per ISO 8295?

  1. Start the test with a speed of 150 mm/min (5.9 in/min)
  2. Record the initial peak force for static friction
  3. Record the average force during sliding motion over 127 mm (5 in) of travel

ISO 8295 Test Specimens

  • Test specimen for the plane is typically 127 mm (5 in) wide by 254 mm (10 in) long and attached to the base plane
  • Test specimen for the sled is typically 114 mm (4.5 in) square and attached to the sled for thin films
  • Test specimen for the sled is typically 63 mm (2.5 in) square and attached to the sled for films greater than 0.254 mm (0.01 in) thick.

What Are the ISO 8295 Test Machine Requirements?

When testing thin plastic film to ISO 8295 it is important to use a universal test machine with a high data capture rate, that can be captured with our high speed controller. Test events can happen quickly, so a machine with a low data capture rate may miss key peaks and troughs in the data, leading to an inaccurate average strength value.

Our test machines meet or exceed the ISO 8295 requirements.

ISO 8295 Fixtures

G62 series sleds and COF fixtures can be added to any universal test machine, using our test machine adapters. Our fixtures conform to ISO 8295 standard requirements.

Our ISO 8295 software module is ideal to report static and dynamic coefficients of friction. 

Important Considerations When Testing According to ISO 8295

Uniform Test Speed

The frictional properties of plastic film and sheeting depend on the uniformity of the rate of motion between the two surfaces. The measurement of the static coefficient of friction is highly dependent on the rate of loading and on the amount of blocking occurring between the loaded sled and the platform due to variation in time before motion is initiated.

Accurate Force Measurement

Our test machine controller can accurately measure forces down to 1% of the test machine load cell's capacity, with load cells full scale rating being matched to application requirements. Forces beneath the lower limits of load cells can be measured, but may be outside 1% accuracy. A 50 N (11 lbs) load cell is relatively inexpensive and would result in an accuracy of 0.5 N (0.1 lbs). A 5 N (1.1 lbs) cell would have an accuracy of 0.05 N (0.01 lbs).

Important ISO 8295 Calculations

  • Friction - resistance to relative motion between two bodies in contact.
  • Coeffıcient of friction - the ratio of the force required to move one surface over another to the total force applied normal to those surfaces.
  • Kinetic coeffıcient of friction - the ratio of the force required to move one surface over another to the total force applied normal to those surfaces, once that motion is in progress.
  • Static coeffıcient of friction - the ratio of the force required to move one surface over another to the total force applied normal to those surfaces, at the instant motion starts.
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