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

ASTM D1894 Friction Test Fixture – Universal Grip Data Sheet (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.