17)Zero and calibrate the tensile machine. Set the cross head speed to 100mm/minute, The jaw gap to approximately 3cm and the load range to 20 kg. Zero and calibrate the chart recorder, and set the chart speed directly proportional to the cross head speed. 18) Clamp in approximately 20mm of rubber into the jaws both upper and lower. The sample must be clamped in such a manner that the bond line can be observed by the operator ad the peeling progresses. 19) Continue testing until all but the last 1cm has been separated. INTERPREATION OF TEST RESULTS: The peel strength is measured utilizing only “peaks” and “plateaus” on the stress-strain plots from the chart recorder. A peak is defined as any point on the plot at which the load decreases immediately proceeding and following this point (see figure A). A plateau is defined as an location on the plot where the load neither increases o decreases for distance of 5mm or more ( See Figure B). Disregard the readings over the initial 1cm of the sample and the final 1cm of the sample. For each test sample, determine the average of the three minimum peaks and/or plateaus (L) In addition, the mode of failure should be noted follows: AF = Failure at the adhesive/ substrate interface of the adhesive/ primer interface. CF = Cohesive failure of the adhesive ( failure within the adhesive or between the two layers of adhesive). PF = Failure at the primer/ Substrate interface. SF= Failure of the substrate, Including the location of the failure within the substrate. If identified, the reason for bond failure should also be reported. For example, insufficient activation temperature (IT), Inadequate pressing (IP) , under application of adhesive (UA) or primer (UP), etc. CALCULATIONS: Peel strength (kg/cm)= L Retained peel strength = Average peel strength after Hydrolysis average peer strength before Report: The average of the five peel strength samples to the nearest 0.1kg/cm
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