Thermoplastic pavement striping has dominated the road marking industry for decades. It is extremely durable, long lasting and reflective. It is the product of choice for almost every municipality in the United States. Thermoplastic striping will outlast traditional DOT paint by years, making it a very cost effective road marking solution.
The purpose of this article is to explain how thermoplastic works and how it bonds to surfaces. By understanding how this product works it will help you in determining if thermoplastic will meet your needs and perform as expected. It will also help you to understand why the steps taken during installation are necessary.
By definition, thermoplastic is a plastic that when hot turns into a liquid and when cool hardens into a solid. It has a multitude of applications because of this characteristic. In general, the majority of preformed thermoplastics as well as regular thermoplastics are made up of Alkyd Resins, Polymers, Fillers, Glass Beads for reflectivity and Pigments for color. The main ingredient is the Alkyd Resin. The other ingredients add desirable characteristics to the product such as wear resistance, reflectivity and color.
For the most part, the bond that thermoplastic makes is a mechanical bond which simply means it grabs the surface and holds on much like a rock climber looks for crevices to grab while climbing. On certain surfaces an additional bond is achieved when the hot thermoplastic and the hot surface actually melt and mix together creating more of a cohesive bond. As stated before, the material becomes liquid when hot. When it is in this state it fills in every pore, crack and crevice of the surface that it is on. When it cools it is locked into place. In the sections below this will be covered in more detail.
PreMark is a top heat only product meaning that it is not necessary to preheat the surface to a predetermined temperature to install the product. Instead, you simply warm the surface to dry it, lay down your pieces and heat from the top. When it cools it is ready for traffic. With the PreMark product you can lay out all your pieces at one time and then apply heat. This makes applying the material easier when doing long runs.
Premark on Asphalt
On asphalt, Premark becomes a hot liquid when heated to around 300 degrees. Since the bitumen in asphalt has a similar melt point the two materials tend to melt together. Premark also conforms to every nook and crevice and creates a mechanical bond as well. (see diagram above)
Premark on Concrete or Cement
On cement a primer is used first. The primer is made up of an acrylic resin in a solvent carrier. When applied to porous cement it penetrates the surface and carries the acrylic with it. It dries quickly and leaves a layer of acrylic on both the surface and beneath the surface. Then the Premark is positioned and heated just like it would be on asphalt. The hot thermoplastic melts together with the acrylic to form a bond similar to the one you would get with the bitumen in asphalt. Additionally, the material fills all pores and crevices and creates a mechanical bond as well.
Note – Thermoplastic does not perform well on smooth, non porous concrete. To test, put a teaspoon of water on the surface. If it soaks in the thermoplastic should bond. If not it needs to be ground or scarified so that it is porous.