Glossary of Self Adhesive Terms
By Denise Nathan
CAST FILMS – Cast films are top sheets that are produced by the casting method. PVC ingredients are mixed using solvents into a liquid that is poured onto a casting sheet. The sheet moves through a series of ovens where the solvents are evaporated to produce the final top sheet. The adhesive and backing paper is then added.
CALENDERED FILMS- Calendered films are top sheets that are produced by the calendaring method. PVC ingredients are mixed using temperature into a dough like lump and then pass through a series of rollers to achieve the desired thickness. The adhesive and backing paper is then added.
POLYMERIC PVC – In order to make PVC soft, additives called plasticizers are added. Polymeric refers to the type of plasticizer. Polymeric (“poly” meaning many) are linked molecular chains. Because they are linked they tend to offer more stable and durable PVC constructions. Polymeric films are more intermediate to high grade films.
MONOMERIC PVC- In order to make PVC soft, additives called plasticizers are added. Monomeric refers to the type of plasticizer. Monomeric (“mono” meaning one) are single molecules. Because of their singular nature they tend to be more unstable and migrate out of the film more readily then polymeric plasticizers causing a faster deterioration of the film. As such monomeric PVCs are usually shorter to intermediate term films.
REMOVABLE ADHESIVE- The industry definition of removable is an adhesive that when removed will leave less than 30% glue residue however good quality removable adhesives can leave no to minimal glue.
PERMANENT ADHESIVE- Permanent adhesives have higher adhesion values. They are designed for more demanding long term applications.
SEMI PERMANENT ADHESIVE- offer adhesion values between removable and permanent and are ideal for applications requiring more adhesive strength but also removability characteristics.
BUBBLE FREE ADHESIVE- special adhesives with adhesive free channels that allow air to escape from under the film during application. They help to decrease labour time and ensure a bubble free appearance to applied graphics. They are easier for less skilled applicators to apply on flat surfaces but still require skilled application techniques for more complex applications like vehicle wraps.
TACK – refers to the initial bonding of an adhesive to the substrate (High tack, Low Tack). Tack is not necessarily an indication of long term adhesion. i.e. an adhesive can be low tack initially to make application easier, then increase in value over time to give strong bonding during the life of the graphic.
ADHESION- refers to the stickability of the adhesive to the substrate .Adhesives generally take 24 to 48 hours to cure so adhesion values are measured after this time. Adhesion values are generally lower with removable adhesives and higher with permanent adhesives.
COHESION- refers to the internal strength of the adhesive and the ability of the adhesive to stay together. Highly cohesive adhesives are useful in removability ensuring the adhesive stays together on removal. They can also control shrinkage levels of the top sheet by holding the vinyl in place.
SURFACE ENERGY – all substrates have a surface energy value. These are measured in dynes. The lower the dyne value the more difficult it is for an adhesive to stick.
Denise Nathan is Marketing Manager - MACtac in Oceania