There are two main applications of adhesives used in window films.
The first is the laminating adhesive. This is used to laminate the layers of polyester film together. The second type are the mounting adhesives used to apply the film to the surface of the glass. These fall under three main categories:
- Pressure Sensitive Adhesives (PS)
- Detackified PS Adhesives (DPS)
- Water Activated Adhesives (Dry Adhesives)
All film installations follow a similar pattern of installation. After cleaning the glass, the protective liner is removed from the film, the adhesive and glass are sprayed with a soapy water solution. The film is positioned on the glass, excess water is squeegeed out and the film is cut to size.
The main difference between pressure sensitive and dry adhesives is how they bond with the glass. PS adhesives form a mechanical bond with the surface of the glass based on the pressure between the film and the glass. When damaged film is removed, usually both the film and most of the glue can be removed together. Water activated adhesives on the other hand, form a chemical or molecular bond with glass. This chemical reaction makes for a very strong bond and generally has a greater longevity versus PS and DPS adhesives. However, should the film become damaged, and needs to be replaced, its removal can be difficult.With more widely used toughened glass these days, which is more prone to scratching than other types of glass, we tend to favour the use of PS adhesives.
PS versus DPS adhesives
Regular PS and DPS use the same adhesive formulation. PS is tacky when the release liner is removed. DPS has a protective gel coating protecting the PS, so when the liner is removed, the adhesive surface is not sticky. When the soapy water solution is sprayed on the film, the gel dissolves, the installer can position the film, before using the squeegee to remove the water and bond the film to the glass.
The main advantage of using a non-tacky adhesive is in the reduced of risk in trapping contaminants between the glass and film. On DA and DPS adhesives, any contamination is usually easier to remove or flush out
Difference between solar and safety film adhesives
A solar film adhesive system is designed to ensure that the window film stays adhered to the glass. As the film itself is very lightweight, it does not require a great deal of adhesive strength (peel strength) to keep this film sticking to the glass. Flat glass films can utilise any adhesive system. Automotive films require an instant bond, only offered by a PS adhesive, due to the nature of curved glass and the film wanting to lift off the contours. Dry adhesives take some days to develop their bond, especially during the cooler part of the year.
Safety films are designed in such a manner that in the event of glass breakage, the glass itself remains adhered to the thicker safety film. Due to the vast weight of the glass, the amount of adhesion required demands a much stronger bond. To achieve this, safety films normally have a very thick layer of PS mounting adhesive.
The strength of the adhesive is measured by its peel strength, which is tested according to internationally recognised standards. All films we use have passed these tests and can be certified to comply with building regulation standards in New Zealand.
Safety films versus anti-graffiti film
In essence, the film is the same, but the purpose of the anti-graffiti is to prevent damage to the glass. The adhesive peel-strength is much less for easier removal and replacement of the damaged film.
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