Abrasion Resistance: The ability to withstand wear in a service environment
Adhesion: The bond of the covering to the core body.
Coefficient of Friction (COF): A measure of the force required to make two materials slide against each other. Teflon against steel slides easily, and therefore has a low COF. Most elastomer compounds resist sliding against steel and have a relatively high COF.
Crown: The difference in diameter between the center of a roller covering and reference points at or near the end of the face.
Deflection: The bending, or degree of bending, of a cylinder or roller when pressure is applied to its journals or bearing surfaces.
Dual Durometer: Roller that fuses two materials of different physical properties into one uniform roller. The most common is the combination of a rigid material, for strength, with a soft or flexible material, for function.
Dynamic Balance: Uniform distribution of mass within a rotating roller body, so the centrifugal forces set up are self compensating and produce no external vibrations.
Hardness: The resistance to indentation that is typically expressed in a numerical value by a durometer or Rockwell gauge, i.e., Shore A, durometer gauge.
Hydrolytic Stability: The degree of resistance to reversion urethane compounds exhibit when exposed to moisture and humidity.
Hysteresis: The amount of mechanical stress that is converted to (heat build-up) heat by an elastomeric compound. Low hysteresis roll coverings are required for high speed and/or high pressure applications.
Modulus: The resistance of a covering to extension or deformation.
Nip: The contact area or width of the contact area between two rollers.
PLI: A measure of the force applied to a roller. A 100″ long roller being used at 100 PLI (pounds per lineal inch), has 10,000 pounds of force being applied.
Release: The ability of a material to not stick to what it contacts. Silicone and some hardcoats are widely used in rollers due to their good release properties. This is not the same as coefficient of friction or COF.
Resilience: The recovery or rebound of an elastomer to impressed energy.
Set: Occurs when the covering is deformed and does not totally recover.
Solvent Resistance: The resistance to swell or deterioration from solvent exposure.
Tensile Strength: The amount of energy required to rupture a test specimen.