Adhesion is reported as the force required to separate a sample per specimen width. Conversions for different reported adhesion units are shown in the table below. The typical width of strips is one inch. If adhesion is high, strips with a one-half inch width can be used. Variables for adhesion testing include testing speed, configuration, aging time, structure, and size of sample. It is important that results only be compared for samples with one variable change unless a designed multivariable experiment is being performed.
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Unit Conversions for Adhesion Testing |
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1 U.S. pound/inch |
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= 4.45 N/25.4 mm |
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= 268 g/15 mm |
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= 0.175 N/mm |
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= 179 g/cm |
The graph below shows the adhesion after several days. Adhesion initially increases as a function of time. Therefore, it is important to compare samples that have been aged for the same amount of time. Samples can be initiated right away but it is recommended to wait at least 72 hours before determining adhesion strength.