Measurement Unit
Centimeter-gram-second units for force per unit length quantify the force acting along a liquid interface or solid surface. In packaging converting operations, dynes per centimeter measures the surface energy of polymer films and paperboard substrates. Equating one dyne per centimeter to one millinewton per meter aligns CGS measurements with standard SI units.
The measurement applies strictly to surface tension phenomena and does not describe bulk shear strength or tensile modulus.
Surface Energy
Corona discharge treatment increases polyolefin film reactivity by generating polar functional groups on the non-porous substrate. Untreated polypropylene film typically exhibits a surface energy around thirty-one dynes per centimeter. Commercial printing inks require film surface energy to exceed forty dynes per centimeter for proper wetting and adhesion.
Wetting Limit
Spreading behavior occurs when liquid surface tension falls below the critical surface energy of the solid substrate. Test fluids formulated in increments of two dynes per centimeter identify the wetting threshold of treated films. When the fluid surface tension matches substrate surface energy, the liquid wets the surface without bead formation.
Excessive surface energy decay during prolonged film storage drops values below required operational limits. Low surface values force converters to retreat substrates prior to extrusion lamination.
