Technology transforms our lives; even if most of the time it is difficult to appreciate the technology used to produce apparently simple materials. For example, up to 230 layers are used in some window film to create its advanced properties. Advanced technology makes window film highly durable, quality products. Quality window film complements and enhances the benefits of glazing.
Window film during the coating and laminating process undergoes quality control inspections as shown in this equipment that utilises laser inspection technology.
It is important to ensure that the product selected comes from a high quality, world-class manufacturer because film construction, the materials and process controls used by the manufacturer strongly affect quality and durability. For example, manufacturers will be concerned about constituents such as:
- UV Protection: Adding UV protection to the adhesive and to the polyester film enhances durability.
- Location of colours: The colour in a film may be provided by different constituent parts and in different locations within the construction. Such variations can provide a variety of effects both in performance and in durability and it is worth checking with the manufacturer of any particular film on how the film is made, how it will perform and how long it may be expected to last.
- Coating uniformity: Metallized coatings must be uniform. To do so, manufacturers carefully control coating processes – for example, many sputtered coatings can be controlled to within 1% of the performance specification. Non-uniform coatings not only look bad but often do not have the properties claimed.
Window film manufacturers take advantage of modern technologies to make high quality products by carrying out certain important production processes in ultra-clean environments. A clean room controls and limits the number and size of airborne particles. Particles of ≥ 0.010 mm (i.e. 10 microns – 100 times smaller than the full stop at the end of this sentence) are filtered out. A Class 10 000 clean room has no more than 10 000 of these size particles per cubic metre of air compared with the millions of larger-sized particles per cubic metre of air in our normal environment. Adhesives used in window film are also filtered to eliminate foreign particles of more than a few microns. Machine operators also wear cleaned overalls and hair nets.
Quality Control Testing
Window film manufacturers test their products for a wide variety of properties to monitor and control
the properties and quality of the finished product, for example:
- Adhesion to glass
- Tear strength
- Tensile strength
- Metallization variation
- Lamination strength
- Scratch resistance
- Solar-optical properties such as solar energy rejection, glare reduction, visible light transmission and UV resistance. In addition, good quality, high performance window film is manufactured with three essential attributes:
The film layer(s) used are of high strength and are made from optically clear polyester.
Laminating adhesives to strongly bond individual film layers together and provide good optical properties.
The adhesive bonding the film to the glass with the correct coat weight on safety / security film in order to keep broken glass pieces together in event of glass breakage.
Resistance to Weathering Testing
Window film manufacturers routinely test window film products for resistance to weathering. Over the years, window film manufacturers have developed a very good understanding of weathering testing as their products are constantly exposed to the rays from the sun through the glass. Weathering resistance is essential for window film because they are continuously exposed to the sun. Sunlight contains damaging Ultra-Violet radiation; less well known is the fact that visible light and Infra-Red energy from the sun can also damage materials – so window film must resist both the degradation and the daily cycles of heating and cooling caused by solar energy. Accelerated weathering simulates high levels of solar energy (including UV), humidity, etc. found in hot and humid locations where degradation of the film is expected to be the worst. Testing is also done in ‘real world’ conditions in hot-humid and hot-dry locations. Only when the manufacturer is satisfied that the window film has the required durability is the product launched onto the market.
Window films have progressed rapidly over the last decade and have long since gained their reputation for extended lifetime, good scratch resistance and high performance. Warranties may vary in their criteria of coverage depending on the film type and its function, its geographical location and the film's construction. Usual warranties can cover between two and fifteen years. The most important thing to look for is that it is a warranty from the manufacturer themselves.