Thermoplastic materials are classified by TxDOT as a Type I pavement marking material, with material specifications falling under and tested using Test Method . Thermoplastic materials consist of four general components: binder, pigment, glass beads, and filler material (usually calcium carbonate, sand, or both). Thermoplastic materials are classified into two basic categories based on the type of binder: hydrocarbon and alkyd. Hydrocarbon thermoplastic is made from petroleum-derived resins, while alkyd thermoplastics are made from wood-derived resins. Alkyd thermoplastics are currently the standard thermoplastic allowed for use by TxDOT as a pavement marking material under DMS 8220. Hydrocarbon thermoplastics are currently only allowed for use by TxDOT through a special provision to DMS 8220. A side-by-side comparison of the two types of thermoplastic materials is shown in Table 2-6.

The ability for thermoplastic materials to bond to the roadway surface is based on the thermal properties of the thermoplastic binder and the roadway surface along with the porosity of the surface. Thermoplastic is well suited for use on asphalt surfaces because the thermoplastic develops a thermal bond with the asphalt via heat fusion. When applied to hydraulic cement concrete surfaces, bond formation occurs by the liquid thermoplastic seeping into the pores of the concrete and forming a mechanical lock to the concrete surface. Primers are recommended prior to thermoplastic application on all hydraulic cement concrete surfaces and asphalt surfaces that are more than two years old, heavily oxidized, or have exposed aggregates.