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Type FINAT Test Method no. 8

Resistance to shear from a standard surface T = 60°C

Scope
This test method measures the capability of an adhesive to withstand static forces applied in parallel way between the adhesive sample and the test plate. It gives an indication of the adhesive or cohesion failure.

Definition
Resistance to shear from a standard surface is defined as the time required for a standard area of a pressure sensitive adhesive material to slide from a standard flat surface in a direction parallel to the surface.

Test Equipment
• A rack to hold the test plate precisely 2° from the vertical (see fig.2).
• 1 kg weight.
• A standard FINAT Test roller.
• Test plate made of stainless steel.

Test Samples
These should be strips taken from a representative sample of material. The strips should be 25mm wide and have a minimum length of 175mm in the machine direction. The cuts should be sharp and straight. At least three strips should be taken from each material sample.

Test Conditions
60°C +/-2°C and 50 % RH +/-5% RH.
The test sample or test strips should be conditioned for not less than 4 hours before testing.

Procedure
Remove the protective paper from each strip and place the sample with the adhesive side down, onto a clean test plate applying light finger pressure, so that a square of pressure adhesive material (25mm x 25mm), is in intimate contact with the plate surface. Roll twice in each direction with the standard FINAT test roller at a speed of approximately 10 mm per second to obtain intimate contact between the adhesive mass and the surface. Any strips found by inspection to have air bubbles trapped between the adhesive mass and test plate should be discarded.

Place the test plate into the rack and hang up the 1 kg weight to the free end of the test strip (not less than 5 minutes and not more than 10 minutes after rolling). Record the time taken for the strips to part from the plate.

Results
Resistance to shear from a standard surface is expressed as the average time taken for the three strips to shear from the test plate.

Notes
The test plates must be thoroughly cleaned so that no trace of adhesive, grease, silicone or moisture is left on the surface.

Results
Peel test results
The peel adhesion test has the results in the figure 3.

A higher tack or peel strength can at first be appreciated however, it becomes a drawback when the underpacking foil has to be removing from the cylinder

Shear test results
The shear resistance test is the most important as it evaluates the performance of an underpacking adhesive foil. When the foil is on the cylinder the forces work on it in rotation direction (Fig. 4).

The test method, FINAT 8, is carried out at T = 60°C +/-2°C

The analysis of the stainless steel surface after the test has underlined the adhesive transfer of the sample H45-RB. The adhesive separates clearly from sample material, leaving an adhesive film on the test. The approximate extent of transfer should be quoted as percentage of 20% on the top side of the plate area of contact between foil and surface.

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Information reflect on this site is supplied in good faith & is based on our experience in the use of printing inks. Such information is just intended only as a guide and can not be taken as legally binding.