Thermoplastic Marking — Surface Preparation

The temperature of the thermoplastic material is a very important factor in the performance of the thermoplastic-roadway surface bond. Suitable application temperatures range from 400–450°F, with 420°F as the recommended temperature for most applications. For proper bonding, the following conditions must exist:
  • The pavement surface must be free of dirt, dust, and other contaminants.
  • The pavement surface must be free of poorly adhered existing markings, glass beads, and curing compound.
  • The pavement surface must be free of moisture.
  • Pavement and air temperatures must be at least 50°F and 55°F, respectively, to ensure proper rate of cooling.
It must be emphasized that a clean and dry pavement surface is critical for thermoplastic materials to achieve proper bonding with the pavement surface. If primers are used, they must be given proper cure time (until tacky) prior to applying the marking material. Special pavement heating devices are now available that are effective for removing pavement surface moisture and elevating the pavement surface temperature, allowing for better thermoplastic bonding.
Table 2-7 describes problems and solutions associated with the application of thermoplastic markings.
Table 2-7. Tips and Trips for Thermoplastic Application
Trips
Tips
Debonding
  • Unclean road surface
  • Low temperatures
  • Moisture in pavement
  • Defective material
  • Marking speed too fast
Bubbles in line
  • Moisture in pavement
  • Overheated material
Flowing Line (i.e., no defined edge), line with excessive rounded edges
  • Material too hot
Cracks in line
  • Temperature stress from overheating
  • Low temperatures
  • Material applied too thin
Rough line surface or crumbly edges
  • Material temperature too low
  • Material has been scorched
  • Moisture in pavement
Smooth, shiny, glossy line
  • No or insufficient glass beads or beads too deeply embedded
Smooth line with slight dimples
  • Glass beads too low
  • Bead gun too close to application shoe
Cratered line
  • Glass beads have popped out
  • Material is too cool or bead gun located too far back
Greenish yellow appearance
  • Material has been scorched
  • Material reheated too many times or inadequate cleaning of application pots
Splattering
  • Material too hot or too cold
Dingy or dull white color
  • Material has been scorched
  • Material reheated too many times or inadequate cleaning of application pots
  • Yellow thermoplastic not completely removed before white was added to the application pots
Lumps in line
  • Material is either overheated or underheated
  • Charred material has been overheated where unblended pigments and fillers have been underheated