Application of mixture experimental design to optimize formulation and performance of thermoplastic road markings
The influence offormulation components on the physical, mechanical and optical properties of hot melt thermoplastic road markings was studied. To minimize the number of experiments, mixture method was used as an effective tool for experimentaldesign. Binder (rosin ester and hydrocarbon based resins), pigment (TiO2), filler (talc) and plasticizer (long oil alkyd resin and dibutyl phthalate) were taken into consideration as the key factors at different levels. A range offormulations were prepared by melt blending of variables and other required components. Softening point temperature (Tsp) and its changes (ΔTsp), Taber abrasion resistance, color difference (ΔE) before and after exposure to the accelerated weathering conditions and heat stability test, were chosen as the key responses. A window of optimum end-use properties of thermoplastic road marking formulations was narrowed down within the range of desired responses in quadratic model using DX v.7.1.3 program.
The results showed that the optimized formulations were very close to those from the regression analysis, and the mixture experimental design was an effectual method to optimize the composition of a thermoplastic road marking formulation with respect to its properties. The precision of the model was evaluated by preparing two samples in the optimized window and comparing the predicted and actual properties. The results showed a good agreement between the proposed model and experimental measurements.