Standard Test Method for Static and Kinetic Coefficients of Friction of Plastic Film and Sheeting - PDF

ASTM D1894 Coefficient of Friction Test

ASTM D1894 measures the static and kinetic coefficients of friction (COF) of plastic film and sheeting, sliding against itself or another surface. A weighted sled covered with one specimen is pulled across a second specimen fixed to a flat plane. The force to start the sled moving gives static COF; the average force to keep it sliding gives kinetic COF. Packaging converters use it to set how film runs on form-fill-seal machines, stacks and unwinds.

Sled, Plane and Specimens

• Sled: 63.5 mm (2.5 in) square, total mass 200 ± 5 g, giving a 1.96 N normal force; the underside is covered with about 3.2 mm of sponge rubber so the film sits flat

• Sled specimen: about 120 mm square, wrapped around the sled and taped on top, with the test face out

• Plane specimen: about 250 × 130 mm, fixed flat to the plane with no wrinkles

• Plane: smooth, flat and at least 150 × 300 mm; either the sled is pulled across a fixed plane, or the plane moves under a held sled

• Condition at 23 °C and 50% RH for at least 40 h; handle film by the edges so oils from fingers do not change the result

Test Procedure

• Place the sled gently on the plane specimen without sliding it

• Connect the sled to the load cell with a nylon line or rigid link, running parallel to the plane through a low-friction pulley

• Pull at 150 ± 30 mm/min (6 in/min)

• The first peak is the static force; average the force over the next 130 mm of travel for the kinetic force

• Test at least 3 pairs and report film side (treated/untreated, inside/outside) and direction

Calculations

Static COF μs = As ÷ B

Kinetic COF μk = Ak ÷ B

As is the initial peak force, Ak the average sliding force and B the sled weight (1.96 N for a 200 g sled).

Example: the force peaks at 0.55 N and averages 0.39 N while sliding. μs = 0.55 ÷ 1.96 = 0.28; μk = 0.39 ÷ 1.96 = 0.20.

Equipment

• Universal testing machine with a very low-capacity load cell (5–10 N) so a 0.5 N signal is read accurately

• COF sled and plane fixture: 200 g sled, horizontal plane and pulley that attach to the machine base

• Film cutting template for sled and plane specimens

Related Standards

• ISO 8295 – coefficient of friction of plastic film and sheeting

• TAPPI T549 – COF of paper and board (horizontal plane)

• ASTM D3330 – peel adhesion of pressure-sensitive tape

• ASTM D882 – tensile properties of thin plastic sheeting

ASTM D1894 FAQ

What sled does ASTM D1894 use?

A 63.5 mm (2.5 in) square sled with a total mass of 200 g, covered with about 3.2 mm of sponge rubber, so the normal force is 1.96 N.

What test speed does D1894 use?

150 ± 30 mm/min (6 in/min).

How are static and kinetic COF calculated?

Static COF = initial peak force ÷ sled weight. Kinetic COF = average sliding force ÷ sled weight.

What load cell do I need for COF testing?

Friction forces with a 200 g sled are usually under 1 N, so use a 5 N or 10 N load cell to keep the reading in its accurate range.