Loop Tack

Loop tack testing is a specialist method used to evaluate the initial tack, or quick stick, of pressure-sensitive adhesives (PSAs). It measures the peak force required to detach an adhesive from a standard substrate after only light contact under controlled conditions. Unlike peel or shear testing, which measure long-term adhesion or cohesive strength, loop tack testing focuses on immediate bonding performance.

This property is essential for applications where the adhesive must form a bond immediately, such as in packaging, labelling, medical tapes, and industrial adhesive tapes. In quality control, loop tack testing ensures products meet adhesion specifications, while in product development it helps engineers fine-tune formulations for optimal performance in real-world use.

Several international standards govern loop tack testing to ensure results are consistent and repeatable:

• ASTM D6195: Describes methods for loop tack measurement of PSAs using a constant-rate-of-extension tensile tester, including loop dimensions, test speed, and substrate type.
• PSTC 16: Developed by the Pressure Sensitive Tape Council, with guidance for tack testing adhesive tapes, specimen preparation, loop geometry, and speed.
• FINAT FTM 9: Common in the label industry, involving a loop of tape pressed lightly onto a standard plate then peeled away under controlled conditions.

While all measure initial tack, they differ in substrate specification, loop geometry, and environmental conditioning. ASTM D6195 is used across multiple sectors, PSTC 16 is tape-specific, and FINAT FTM 9 is often preferred in labelling and packaging.

Sample preparation

Cut adhesive strips to the required length and width stated in the chosen standard. Condition the samples at the specified temperature and humidity before testing.

Equipment setup

Mount the loop tack fixture to the tensile tester. Form a loop with the adhesive facing outward, ensuring it is free from twists or distortions.

Test execution

Lower the loop onto the test substrate, usually stainless steel or glass, at the specified rate until full contact is made. Immediately reverse the motion to peel the loop away, recording the maximum force during separation.

Data interpretation

The peak force is recorded as the loop tack value, normally in newtons per specified width (e.g. N/25 mm). Multiple specimens are tested to reduce variability.

• Low repeatability: Check fixture alignment and loop consistency.
• Unexpectedly low tack: Ensure the adhesive surface is clean and properly conditioned.
• Equipment drift: Calibrate load cells and check displacement settings.

Mecmesin loop tack testers are designed for precision, repeatability, and compliance with industry standards.

Key features:

• Precision load cells for accurate peak force measurement
• Motorised crossheads for constant test speeds
• Dedicated fixtures to maintain correct loop geometry
• Integrated calibration routines for force and displacement verification

Regular calibration and maintenance help ensure accuracy, including checking fixture alignment, cleaning substrates, and confirming compliance with the relevant standards.

• Packaging

  Checks resealable closures, tamper-evident labels, and PSA seals to ensure adequate instant tack for both production and consumer use.

• Labelling

  Verifies that labels adhere instantly to glass, plastic, or cardboard, which is crucial for high-speed production lines.

• Medical adhesives

  Tests tapes, dressings, and wearable sensor patches to ensure secure adhesion to skin without excessive application pressure.

• Industrial and consumer tapes

  Evaluates double-sided and mounting tapes for automotive trim, electronics assembly, and home improvement products where instant hold is important.

In R&D, loop tack data is used to compare formulations, optimise coating thickness, and assess the effect of additives on initial bond strength.

• Secure adhesive firmly in the fixture to prevent slippage
• Clean substrates between tests to remove residue
• Maintain consistent loop dimensions using fixture guides
• Control temperature and humidity to match the test standard

Following these practices improves repeatability and builds confidence in results for internal QA and compliance reporting.

If you require loop tack testing to meet quality, performance, or compliance requirements, Mecmesin can provide the right solution for your application. Our technical team can help you select equipment and fixtures that deliver accurate, repeatable, and standards-compliant results, whether for R&D or production quality control.