Confused About Vinyl?
Monomeric Vs Polymeric - What's the difference?
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 70 to 80 micron thick and are prone to shrinkage. They are also quite stiff and hard on blade wear. 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.
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 60 to 80 microns 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 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.
The liquified 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 50 to 60 micron 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.
What is the difference between solvent and water based acrylic adhesives?
Acrylic is the most popular type of adhesive used in the sign industry due to its affinity for bonding to vinyl films. This bond helps the adhesive remain attached to the film during installation and removal.
Acrylic adhesives are divided into two categories: water based and solvent based. There is no indication that a water or solvent based provides a better bond to film. Water or solvent adhesives are the carriers for the solids in the coating process and are removed during the curing process. Water based adhesives produce less emission when cured and are generally faster to run when coating. Solvent based adhesives run slower when coating due to the time it takes to cure, making them generally more expensive. There is often a stigma attached to water based adhesives, but over time their construction and performance has greatly improved.
The performance of a film (shrink, aging, sheer, peel) is formula dependent, not technology dependent (water based vs. acrylic based). There is not a general statement that says water based adhesive is better than acrylic based adhesive or vice versa. To determine a performance difference you would need to compare a particular construction of water based adhesive to a particular construction of solvent based adhesive in a given application. The most important aspect of an adhesive, are its physical properties designed for the intended application and is it consistent in coating and quality?
Solvent based adhesives may provide greater performance over the life of the film. Water based adhesives may show lower resistance to shrink, aging, sheer and peel, but this usually occurs towards the end of their designed life.