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ASTM D3811
Tape Roll Unwind Test

Unwind roller fixture for ASTM D3811 tape testing
Standard Test Method for Unwind Force of Pressure-Sensitive Tapes - PDF

 

ASTM D3811/D3811M is the standard test method for unwind force of pressure-sensitive tapes. It measures the force needed to pull tape off its own roll at a low, constant rate, which is what an operator or a tape dispenser feels. Unwind force depends on the release coating on the tape back, the adhesive, roll age and temperature, so it is a key quality-control and specification check for packaging, masking, electrical, medical and industrial tapes.

Note that unwind force changes with unwind speed, and at high speeds the trend can reverse. D3811 is a low-rate method; it should not be used to compare tapes that will be unwound at high machine speeds.

ASTM D3811 Equipment

  • A universal testing machine with a low-capacity load cell (typically 10–100 N) and constant-rate crosshead

  • A tape unwind fixture: a free-turning mandrel or spindle that fits the roll core and is held in the lower grip, so the roll turns with minimal friction

  • A grip or clamp for the free tape end on the moving crosshead

  • Optional environmental chamber for tapes tested hot or cold; otherwise test at standard lab conditions (23 °C, 50 % RH)

ASTM D3811 Procedure

  • Condition full rolls at standard laboratory conditions before testing

  • Unwind and discard the outer few wraps so the test starts on fresh tape

  • Mount the roll on the free-turning mandrel below the moving grip

  • Attach the free end to the upper grip so the tape leaves the roll tangentially and runs straight up to the grip

  • Unwind at the constant rate given in the standard or your specification (300 mm/min, 12 in/min, is common) and record force over a set length of tape

  • Test at least three rolls and report the average force, with the peak and minimum if required

Results and Worked Example

Unwind force is reported as average force per unit tape width: unwind force = average force / tape width.

Example: a 48 mm wide packaging tape gives an average unwind force of 6.7 N over the measured length. Unwind force = 6.7 / 48 = 0.140 N/mm, or 3.5 N per 25 mm width (6.7 × 25 / 48). Three rolls giving 3.5, 3.3 and 3.7 N/25 mm average 3.5 N/25 mm. Compare the result with the minimum and maximum in the tape specification: too high and the tape is hard to dispense or delaminates; too low and the roll can telescope or unwind on its own.

Related Tape Test Standards

  • ASTM D3330 – peel adhesion of pressure-sensitive tape

  • ASTM D6195 – loop tack

  • ASTM D3759 – tensile strength and elongation of tape

  • ASTM D3654 – shear adhesion (holding power)

  • PSTC-8 – Pressure Sensitive Tape Council unwind adhesion method

ASTM D3811 FAQ

What does ASTM D3811 measure?

The force needed to unwind pressure-sensitive tape from its roll at a low constant rate, reported as average force per unit width.

How is the roll held?

On a free-turning mandrel in the lower grip, with the free end clamped in the moving upper grip so the tape leaves the roll tangentially.

Why does unwind speed matter?

Unwind force varies with rate, and the trend can reverse at high speeds, so D3811 results apply only to low-rate unwinding.

What units are reported?

Newtons per millimetre or per 25 mm width (or ounces or pounds per inch). Confirm the exact rate, tape length and reporting details against your copy of ASTM D3811.

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