CAD-CAM Vinyl's

Vinyl's can generally be manufactured in one of two ways, i.e. 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 P.V.C. has a built in memory and will attempt to return to its original form, which in turn may lead to film shrinkage.  P.V.C. in its 'natural' form is a rigid material, so additives known as plasticisers have been added to soften the film and make it usable.  Other additives have to be included to stabilise against the effects of heat and UV and to add colour, etc.  There are two different types of plasticisers currently used which sub-divide the calendered vinyl's into distinct groups.  Monomeric and Polymeric.  Both types of calendered films perform slightly different in one direction than the other, i.e. in machine direction and cross machine direction.

In this case the plasticisers used are short-chain, which means that they do not bind into the film particularly efficiently and have a tendency to migrate out of the film itself, leaving the film brittle.  These films are generally 80-100 micron thick and are prone to shrinkage.  They are also quite stiff and hard on blade wear.  Generally they have an expected outdoor life of 3 years for black and white and 2 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.  They are barely conformable over contours and are recommended for flat-sided applications only.

These are sometimes also known as stabilised films or extended life films.  The plasticisers used are long-chain which allows them to bind into the film more efficiently, reducing the migratory effect.  These films are generally 60-80 microns thick and are far less prone to shrinkage then the monomeric range, typically 50% less.  They feel softer and generally have an outdoor life expectancy of 7 years for black and white, 5 years for colours and 3 years for metallic colours.  Available mainly in gloss finish, although translucents and some matt finishes are available.  They are suitable for most external applications, but conformability over complex contours is still somewhat limited.

The liquefied resin is coated onto a highly polished substrate, such as 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's and the resulting shrinkage is minimal, typically 50% less than polymeric films.  These films are generally 50 - 60 micron thick, and have a very soft handle.  Generally they have expected outdoor life of 10 years for black and white, 7 years for colours and 5 years for metallic colours.  Available in mainly a high gloss finish, these films are the ultimate in terms of conformability over contours such as rivets, corrugations, etc.  Due to the film construction, these vinyl's can be cut and weeded in finer detail than the calendered films.  Generally all the ingredients used in the production of cast vinyl's are of the best quality and so the performance in terms of temperature ranges, colour fastness, etc is better than the 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 currently on only acrylic adhesives for external permanent applications and the adhesives are formulated to be compatible with the expected life of the face film being used.  There are two basic types of adhesive.

In this case a chemical solvent is used to thin the acrylic adhesive during the coating process and is then flashed off through the ovens.  These adhesives are very good for long-life external applications, offering good initial and final adhesion values and cope well with temperature extremes.

In this case the solvent used is water itself.  For environmental and economic reasons this system is currently becoming more commonplace.  This adhesive system is generally used on the shorter term vinyl's as initial and final adhesion values are generally not as high as those of the solvent systems, however they are improving.  The other disadvantage with water or an aqueous based adhesive is that the adhesive tends to go milky (whiten) when in contact with water.  For example when the vinyl is being applied wet.  This is due to water being retained in the adhesive, then re-emulsifying when wet.  This milkiness will disappear through time, but is unsightly on glass or any clear substrate.  This milking effect can be reduced or eliminated by the use of RAPIDTAC application fluid.  Aqueous based adhesives often show more resistance to solvent attack than the solvent based acrylics.  More care has to be taken with water or aqueous based adhesives when applying wet or the substrate is cold.

 

 

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