For vertical applications, the adhesive's viscosity determines its sag resistance - how much it will sag or run under the force of gravity before curing.
To understand the value of ASTM D1876, one must first understand the mechanics of peel resistance. Unlike tensile testing, which pulls bonded materials directly apart in a linear direction, peel testing involves a much more complex stress distribution. When an adhesive bond is peeled, the stress is concentrated at the interface line where separation occurs. This stress is not uniform; it involves a combination of tensile and shear forces, often accompanied by bending moments in the adherends.
How to calculate and report the apparent viscosity.
The primary goal of ASTM D1876 is to measure the force required to progressively separate a bonded joint. It provides critical data for:
The viscosity of adhesives affects their performance in several key areas:
