Fountain Rollers

Fountain rolls consist of a shaft or core of metal or other hard material covered with a rubber or elastomeric coating. The coating thickness may vary from a few thousandths of an inch to an inch or more. Many different rubbers are used in fountain roll coverings.

1. Neoprene - polymerized chloroprene (2-chloro-1,3-butadiene) crosslinked with sulfur.
   • A tough elastomer with good oil, chemical and water resistance and high resilience.
2. Nitrile or Buna N - Copolymer of butadiene and acrylonitrile.
   • Main attribute is oil resistance.
   • Good chemical and water resistance.
3. Ethylene Propylene Diene Monomer (EPDM) - Ethylene and propylene copolymer with small amount of a diene copolymerized for crosslinking purposes.
   • Because the backbone is chemically saturated, it has excellent chemical, heat and ozone resistance.
   • Resistant to polar solvents such as ketones but not to oils.
4. Polyurethane - Backbone of a diol that has been reacted with diisocyanate to form urethane linkages.
   • Diol is usually a polyether or polyester resin.
   • Urethanes soften in high humidity and high temperature.
5. Natural Rubber - Polyisoprene crosslinked with sulfur.
   • Poor oil, ozone and heat resistance.

When an elastomer is deformed, it doesn't completely return to its original configuration.

• The amount of residual deformation is known as “set”. This is usually expressed as a percentage. Resilience is the ratio of returned to impressed energy.
• The term “rebound” is often used in this context. Hardness is measured by plastometer, densimeter or durometer.
• The Plastometer is the most accurate because there is no hand actuation. The weight of one kilogram depresses a steel ball, 1/8" in diameter, into the rubber.
• The scale records the depth of depression in units of 10 microns (10-3 cm). The Adams Densimeter is a hand actuated instrument which uses a rounded impresser pin projecting through the bottom of the meter and connected to the scale pointer.
• Higher densimeter readings indicate softer rubber and are roughly half the plastometer readings. The Shore durometer is similar except that higher numbers indicate greater hardness.
• Since hardness is usually measured by an indentation, the thickness of the rubber can effect the hardness reading.