Face films: Vinyl in general, can be manufactured in one of two ways – by calendering or by casting.
The molten resin is squeezed between a series of rollers to produce a film of vinyl.
Due to the mechanical method of manufacture, the PVC has a built in memory and will attempt to return to its original form, which may result in film shrinkage.
PVC in its ‘natural’ form is a rigid material, so additives known as plasticisers have to be added to soften the film and make it useable. Other additives are included to stabilise against the effects of heat, UV and to add colour etc.
Currently, there are two types of plasticisers used, these divide the calendered vinyl’s into two distinct groups – Monomeric and Polymeric. Both types of Calendered films perform slightly differently in one direction than the other, i.e. in machine direction and cross machine direction.
- Monomeric PVC’s
In this case, the plasticisers used are short-chain; which means that they do not bind into the film particularly efficiently, thus having a tendency to migrate out of the film and leave it brittle.
These films are generally 70µ to 80µ thick and are prone to shrinkage and are also quite stiff.
Generally, the films have an expected outdoor life of 3-5 years for black and white and 2-3 years for colours.
They are available in a range of matt and gloss finishes and are economically priced.
They are suitable for most internal applications and selective short term external applications.
The films are barely conformable over contours and are recommended for flat-sided applications only.
- Polymeric PVC’s
These are sometimes known as stabilised films or extended life films. The plasticisers used are long-chain, which allows them to bind into the film more efficiently, thus reducing the migratory effect.
These films are generally 60µ to 80µ thick and are less prone to shrinkage, typically 50% less than the monomeric range.
They feel softer and in general have an outdoor life expectancy of 7-8 years for black and white, 5-7 years for colours and 3 years for Metallics.
These films are primarily available in a gloss finish, although translucent and matt finishes are also obtainable.
They are suitable for most external applications, but conformability over complex contours is somewhat limited.
The liquefied resin is coated onto a highly polished substrate, i.e. casting paper, to produce a thin film of vinyl.
Due to the lack of mechanical force being used, cast films do not have the same memory as calendered vinyl; consequently shrinkage is minimal, typically 50% less than polymeric films.
Cast films are generally 50µ to 60µ thick and are very soft to handle.
They have a typical outdoor life expectancy of 10 years for black and white, 7 years for colours and 5 years for metallics.
The films are primarily available in a high gloss finish and are the ultimate in terms of conformability over complex contours, i.e. rivets, corrugations etc.
All the ingredients used in the production of cast vinyl are of the best quality, consequently performance in terms of temperature ranges, colourfastness etc. is generally better than that of calendered films.
Cast films perform equally well in both directions, i.e. in machine and cross machine direction.
In the signage market, manufacturers generally standardise on acrylic adhesives for external, permanent applications and the adhesives are formulated to be compatible with the life expectancy of the face film being used. These acrylic adhesives are either solvent based acrylics or emulsion/water based acrylics.
- Solvent based adhesives are our general preference. While more costly to produce they are more forgiving at low application temperatures and do not whiten when applied wet and cold. They also have excellent temperature resistance in service and are very durable externally.
- Aqueous or emulsion based adhesives are lower in cost but the adhesive can milk when applied wet and cold, the application temperature range is narrower and they are less durable longer-term when used externally.