Page 277 - Training 2019

INTRODUCTION:

So what is surface tension? It is the ability of a liquid or fluid (inks, coatings, adhesives) in contact with a solid substrate
(metallised film, plastic film, polymers) to determine printability, coating laydown, and heat sealability of the treated
substrate, thereby assuring good adhesion quality.

WHY DO WE TEST THE SURFACE TENSION IN PRINTING?

So why do we need to test for surface tension in printing? Printers and converters who work with fast moving webs must
test the surface tension to avoid problems such as on - the - shelf delamination or ink lift off, before the job is finished and
shipped to the customer. It indicates whether a coating will wet and spread over, or retract from a solid substrate. Surface
tension is expressed as a force per unit of width – as dynes/cm or MN/m which is newton per meter and commonly
referred to as a dyne solution or dyne pen. The surface tension of inks and coatings must be lower than the wetting
tension of the substrate to attain good print, adhesive bendability or ink laydown.

Thus we test surface tension:
To know if a substrate is able to be printed on.
To know the cleanness of a metallic substrate (eg oil on rolled foil).
To know if the substrate has been treated (corona or flame treatment).
To quantify and measure actual treatment level on a substrate.
To check for back treatment on a substrate.

WEAK SURFACE ENERGY

The fluid will have a minimum contact with the substrate e.g. plastic film.

HIGH SURFACE ENERGY

The fluid will have a good contact with the substrate ensuring good wettability.

CORONA TREATMENT

This is the most common method of increasing surface energy on substrates to promote adhesion when printing, coating or
laminating. Corona treatment systems apply a high voltage, high frequency electrical discharge to the substrate.

See attached sketch

Proper Dyne Testing: How, Why, and When to Perform

Table of Contents
• Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
• Dyne Testing Options . . . . . . . . . . . . . . . . . . . . . . .2
• Suggested Treat Levels . . . . . . . . . . . . . . . . . . . . . 3

SURFACE TENSION TRAINING MANUAL 2
Updated - 24 June 2019