Optimising MMA-based traffic paints

For this purpose, in the first step, the effect of initiator, benzoyl peroxide (BPO) content on the polymerisation of MMA-based traffic paints was evaluated. No-pick-up time, pendulum hardness, tensile strength and colour difference (ΔEw) before and after exposure to the accelerated weathering conditions (AWC) of the samples containing various BPO wt% (0.5, 1.0, 1.5 and 2.0) were determined.

Mixture experimental design
In the second step, the MMA-based paint formulation was optimised using mixture experimental design (MED). The amounts of MMA resin, chlorinated paraffin wax (plasticiser) and silica fillers with different average particle sizes were considered as the variables in the paint formulations. Viscosity, reflectance, color difference (ΔEw) before and after exposure to AWC, skid resistance, and dirt pick-up property were selected as the practical properties and responses in the MED.

The results showed that the BPO initiator in low level of usage did not sufficiently affect the curing rate of the paint samples. In addition, high level of BPO led to decrease in mechanical properties of the paint, due to the presence of plasticiser and non-reacted BPO compounds within the polymeric network. The results also confirmed the MED as an operative method to optimise MMA-based pavement marking paints for purpose of balancing between skid resistance and dirt pick-up properties.