Protecting Solar Film

Just an old article I wrote seven years ago. Thought you might like. From the Glass Smart blog.

Extending the Life of Solar Film

Solar film is Poly (Ethylene Terephthalate), otherwise known as PET, or polyester. Mylar, Decron, and Recron are trade names. It is applied to window glass for the purpose of blocking different portions of solar radiation. Such as heat energy, visible light, or ultraviolet which fades carpets and fabrics. It has been known to last up to 25 years. The warranties can be from 5 to 15 years. The residential and commercial films start out as three sheets. One sheet is removed before application. This reveals a dry PVA adhesive. Which is sprayed with water for activation. The window is then sprayed with water and the film applied. The two sheets which are applied to the window have a metallic/ceramic deposition in between. This is the part that selectively blocks radiation. There are no dyes that will fade over time. Further there is a protective acrylic hard coat applied to the exterior of the film to guard against abrasion during cleaning. Although it is still suggested that a soft applicator with soapy water and a squeegee be used.

Solar Film is between .001 and .010 inch thick depending on the product. The manufacturers suggest not using abrasives for good reason. But this is not the only way film can be damaged. We all have seen what happens when a simple piece of scotch tape is used on film. It leaves a kind of shadow that will not “come off”. Some have also seen how the entire sheet of film can turn cloudy. This is because the PET molecules have been changed in some way. Which demonstrates how easy it is to chemically damage film. In fact it is possible to change the nature and arrangement of the PET molecules mechanically, chemically, thermally, and by radiation. To put it very simply there are many different things that can happen to the PET polymers. They can be broken in pieces, have their side groups sheared off, shriveled up, stiffened up, stuck together, have other molecules stuck to them, crystallized, and just plain rearranged into bunches. Certain chemicals can start a change that can become a chain reaction. Other conditions like heat can perpetuate the reaction. Some of the chemicals that will degrade PET are sulfuric acid, toluene, xylene, butyl alcohol, isopropanol, ammonia, dibutyl ether, and chlorinated water. The higher the concentration and temperature the stronger and quicker the reaction will be. Even water at a high enough temperature will split the PET polymer in half. Keeping this simple fact in mind I personally would not want to clean film in the hot sun. Always make sure it is cool.
If we simply do not use the wrong chemicals to remove paint, wood stain, or some other deposit from solar film we should be good. Just use a mild soapy water and a squeegee for routine cleaning under cool conditions. As for ultraviolet radiation this is quite another matter. Remember that solar film is usually applied to the inside of windows. This is for the purpose of blocking UV from getting to fabrics. Glass will block a certain amount of UV but obviously not all or we wouldn’t need to use the film. The perfect answer would be to find some type of a wipe on coating for the outside of windows to block or reflect even a portion of UV. Along with everything else mentioned in this article this too would help to extend the life of solar film.

Written by Henry Grover jr.
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