Because of the thermal bonding characteristics between thermoplastic and asphalt, nearly all thermoplastic materials are well suited for application on new HMAC surfaces. This includes both hydrocarbon and alkyd thermoplastics. As HMAC surfaces wear and become more brittle through traffic exposure and oxidization, the use of a primer is suggested when applying thermoplastic directly to the pavement surface. Suitable minimum thickness of thermoplastic on new HMAC surfaces is 90 mils. Suitable restripe thickness on HMAC surfaces is 60 mils.

Not all thermoplastic materials have been shown to provide suitable durability on concrete surfaces. In other words, thermoplastics that are suitable on asphalt surfaces may not be suitable for concrete surfaces. Because the thermal bond is not available between thermoplastic materials and concrete surfaces, mechanical bonding is relied upon. For mechanical bonding to occur, the concrete surface must be porous enough to allow the liquid thermoplastic to seep into the pores and create a tight mechanical bond after cooling. This is often not the case with new concrete pavements, suggesting the use of primers. A major thermoplastic bonding failure on concrete is shown in Figure 2-11.

Certain thermoplastic products have been identified that provide suitable bonding with concrete either with or without a primer. Suitable minimum thickness of thermoplastic on new HCC surfaces is 90 mils. Suitable restripe thickness on HCC surfaces is 60 mils.

When thermoplastic markings are applied to coarse surfaces such as surface treatments, thickness plays a major role in the durability and retroreflective performance over time. As with all asphalt surfaces, suitable thermal bonding is achieved. However, much of the thermoplastic material seeps into the voids between the aggregates, leaving very little material on the top of the aggregates. This lack of material at the top of the aggregate leads to accelerated wear of the thermoplastic and premature bead loss. Research has shown that thermoplastic thicknesses of 100 mils or greater provide better performance than thinner applications on surface treatments. In most cases, a restripe thickness of 60 mils is suitable on surface treatments, although a greater thickness may sometimes be necessary.