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 health care 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.
ASTM D1894 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.
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.
The ASTM D1894 test requires a universal test machine to be equipped with a coefficient of friction fixture, we recommend our GD1894-62, which is specifically engineered to meet the requirements of ASTM D1894 and other industry standards from TAPPI and ISO.
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.
When testing thin plastic film to ASTM D1894 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 ASTM D1894 requirements.
G62 series sleds and COF fixtures can be added to any universal test machine, using our test machine adapters. Our fixtures conform to ASTM D1894 standard requirements.
Our ASTM D1894 software module is ideal to report static and dynamic coefficients of friction.
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 (.01 lbs).