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Test summary
The ‘loop’ tack value of a pressure sensitive material is expressed as the force required to separate a loop of material at a specified speed after being brought into contact with a specified area of a standard surface
Test apparatus
Test plates made of float glass
Tensile tester with grips and suitable range loadcell
Cutting apparatus
Cleaning materials and solvents as detailed in the standard
Preparation
Cut strips from a representative sample 25 mm wide and minimum 175 mm long in the machine direction.
Clean the float glass plate as detailed in the standard using the materials and solvents specified
Test method
Representative samples of the material are cut to 25 mm width and formed into a loop with the adhesive facing outwards. The loop is lowered at 300 mm per minute onto a standard sized piece of float grass, then immediately pulled off while the maximum force recorded. The average of the peak force of at least 5 samples is calculated
The test strips should be conditioned at 23 ±2 °C and 50 ± 5%. RH for at least 4 hours.
Clean the float glass with the solvents and protocol detailed in the standard..
Clamp the float glass in the lower (fixed) grip of the tensile tester.
Form the sample into a loop with the adhesive on the outside. Clamp the ends of the loop for a distance of 10 mm into the upper (moving) grip of the tensile tester.
Set the tensile tester to descend at 300 mm per minute and bring the loop into contact with the glass plate.
When full contact over the glass plate has been achieved (25 mm x 25 mm), immediately reverse the direction of the tensile tester and pull upwards at 300 mm per minute until the loop is completely detached.
Record the maximum force necessary to completely separate the loop from the glass plate.
Report
‘Loop’ tack is expressed as the average value (ignoring the initial peak) and range for at least 5 samples in newtons