Standard Test Methods for Loop Tack of Pressure Sensitive Adhesives - PDF

 

ASTM D6195 describes standardized test methods for measuring the loop tack (initial grab or stickiness) of pressure-sensitive adhesives (PSAs).
Loop tack refers to the adhesive’s ability to form a bond quickly when lightly pressed onto a surface without significant pressure or dwell time — an important property for tapes, labels, and decals.

This article explains the purpose of ASTM D6195, the required equipment, the general testing procedure, and related ASTM standards often used alongside it.

Purpose of ASTM D6195

The primary objectives of ASTM D6195 are to:

• Quantify the initial adhesive force developed by a PSA upon brief contact with a surface.

• Compare different adhesive formulations or manufacturing batches for quality control.

• Predict how easily an adhesive product will bond during application (e.g., how "tacky" it feels).

• Assist in product development and specification for high-performance PSA products.

Loop tack testing is particularly critical for labels, medical tapes, graphic films, and consumer tapes where immediate adhesion is needed.

Equipment Required for ASTM D6195 Testing

Testing to ASTM D6195 requires the following equipment:

• Universal Testing Machine (UTM):

  • Equipped with a suitable load cell (typically measuring forces in the 0.1 to 10 Newton range depending on tape type).

  • Capable of constant-rate extension (CRE) testing, typically at 300 mm/min (12 in/min) crosshead speed.

• Loop Tack Fixture:

  • A mandrel or bar to form a loop in the PSA sample.

  • Designed to bring the adhesive loop into contact with the substrate under controlled conditions.

• Substrate Panel:

  • A standardized test surface, usually a smooth surface such as stainless steel or a defined standard panel (e.g., glass or aluminum).

• Specimen Preparation Tools:

  • Scissors or cutting tools to prepare uniform strips of adhesive tape or sheet.

• Environmental Conditioning Equipment (optional):

  • For conditioning specimens to specific temperature and humidity requirements before testing.

Specimens

• Samples typically consist of tape or sheet material cut into strips (commonly 1 inch wide × 6 inches long).

• The adhesive must be free of dust, wrinkles, or contamination before testing.

• Standard conditioning is performed at 23°C (73°F) and 50% relative humidity for at least 24 hours, unless otherwise specified.

General Test Procedure for ASTM D6195

1. Sample Preparation:

   • Cut uniform strips of tape.

   • Form each strip into a loop with the adhesive side facing outward.

2. Mounting the Loop:

   • Attach the non-adhesive ends of the loop to the grips of the universal testing machine.

3. Testing:

   • Bring the loop into light contact with the standardized substrate.

   • The substrate remains stationary while the loop descends onto it and then is immediately pulled away.

4. Force Measurement:

   • Record the maximum force required to detach the loop from the substrate.

5. Repeat Testing:

   • Test at least five specimens per tape type to calculate an average tack value.

Results and Reporting

An ASTM D6195 test report should include:

• Adhesive type, product name, and manufacturing lot number.

• Dimensions of the test specimens.

• Description of the substrate used.

• Environmental conditions (temperature, humidity).

• Crosshead speed and loop configuration.

• Maximum tack force for each specimen.

• Average, minimum, and maximum tack force values.

• Observations regarding adhesive behavior (stringiness, transfer, lifting patterns).

A higher loop tack force generally indicates a higher "grab" strength, important for quick-stick applications.

Related ASTM and Similar Standards

Several other ASTM standards are related to adhesive strength and performance, complementing ASTM D6195:

• ASTM D3330 – Standard Test Method for Peel Adhesion of Pressure-Sensitive Tape:
  Measures the force required to peel tape from a flat surface at a specified angle.

• ASTM D3759 – Standard Test Method for Breaking Strength and Elongation of Pressure-Sensitive Tapes:
  Measures the tensile strength and stretch properties of PSA tapes.

• ASTM D3654 – Standard Test Method for Shear Adhesion of Pressure-Sensitive Tapes:
  Measures how well a PSA tape resists a sustained shear force.

• ASTM D3811 – Standard Test Method for Unwind Force of Pressure-Sensitive Tapes:
  Measures the force required to unwind tape from a roll, affecting application performance.

• PSTC 6 – Pressure Sensitive Tape Council Method for Loop Tack Testing:
  An industry-specific method similar to ASTM D6195, often cited in commercial specifications.

• ASTM F88 – Standard Test Method for Seal Strength of Flexible Barrier Materials:
  Although focused on flexible seals, this method also involves peel and adhesion forces related to initial tack.

Applications of ASTM D6195 Testing

Typical applications for loop tack testing include:

• Product labels (shipping, retail, ID labeling)

• Medical adhesive tapes (bandages, surgical tapes)

• Graphic films (vehicle wraps, signage)

• Consumer office tapes (sticky notes, masking tapes)

• Industrial assembly tapes (temporary bonding applications)

Manufacturers use loop tack testing to fine-tune adhesive formulas, ensuring the right balance between ease of application and adhesive strength.

Conclusion

ASTM D6195 provides a standardized and reliable method for measuring the loop tack of pressure-sensitive adhesives.
It ensures that PSA products perform properly in applications where immediate adhesion is critical.
ASTM D6195 is often used alongside standards like ASTM D3330, ASTM D3759, and ASTM D3654 to form a full mechanical profile of adhesive performance.