We are often asked what the "True" thickness of polyethylene (plastic sheeting) means. The plastic sheeting (engineered films) industry is somewhat unique in that lots of terms get used. "True" means that a film that says it is 6 mils in thickness will measure at that thickness of 6 mils by a micrometer. People in this industry understand that most films are +/-10%, so in the case of 6 mil, a 5.4 mil is commonly accepted as 6 mils. When films are reinforced, meaning they have strings running through the film, then the film is often measured at the thickest point, where the reinforcement crosses. Some of these films are as low as 3 mil between the reinforcement grid, yet are sold all day long as a 6 mil film.
There are films that are "true" 6 mil films. One of our films is called, PolyScrim 6. This reinforced film measures at 6 mils. Another example of a "true" 6 mil film is, Anti-Static Fire Retardant 6 mil. It's important to note that plastic sheeting can be made to a multitude of thicknesses to suit the application's needs. For example, plastic sheeting liners (geomembranes) that are used in landfills need to be really strong- and thus call for a thicker plastic than a job that isn't is rugged.
If we look at the terminology behind the thickness of plastic sheeting, it starts with the Greek alphabet. The Greek letter µ when by itself stands for micron. This term has recently been superseded by micrometer or µm. The thickness of plastic (plastic gauge) is expressed in microns. 1 micron = 0.0254 mm =1 millimeter = 1 mil = 1µm.
If you consider the application for the plastic film, now not only does the thickness comes into play but the additives that are added to make the film perform for its intended use. For example, often people need plastic that is fire retardant- so a 6 mil film won't do the job, unless it is certified as fire retardant. The same goes with whether a film will be in the sun. Without UV inhibitors, a regular piece of plastic won't hold up over time to the sun regardless of the thickness.
There are so many things that go into making an engineered plastic film. Feel free to call us anytime to learn more. Thank you- 866.597.9298