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.
Trips | Tips |
---|---|
Debonding |
|
Bubbles in line |
|
Flowing Line (i.e., no defined edge), line with excessive rounded edges |
|
Cracks in line |
|
Rough line surface or crumbly edges |
|
Smooth, shiny, glossy line |
|
Smooth line with slight dimples |
|
Cratered line |
|
Greenish yellow appearance |
|
Splattering |
|
Dingy or dull white color |
|
Lumps in line |
|