Optimisation of Polymer Addition Using the Plackett-Burman Experiment Plan

Abstract

At the present time, the utilization of waste polymer materials belongs to one of the most important challenges where global economies have to tackle. This article concerned the modification of petroleum road bitumen with waste polymer. The bitumen modification process with the use of polymeric materials was carried out considering a number of other quantitative factors, such as: mixing time, mixing speed, bitumen temperature and qualitative factors such as: waste polymer content, type of grain size, type of neat bitumen and type of waste polymer. Two kinds of waste polymers (PET, PP) were used in the research, which served as a modifier. Two petroleum bitumens were used: 20/30 (hard) and 70/100 (soft). Based on the divalent Plackett-Burman experiment plan, the number of variables and the number of combinations of mixtures were determined, which were required to determine the final response surface model. The following features were tested as the output variables: penetration, softening point, Fraass breaking point, dynamic viscosity 60oC, 90oC, 135oC, deformation energy and maximum elongation. The use of the experimental design methodology allowed to identify the factors that had the greatest impact on the bitumen modification process. The assessment of the significance of the parameters also allowed to identify a significant model allowing to find the optimal bitumen and waste polymer composition. Based on the test results, it was shown that the consistency of the modified bitumen was influenced by the type of bitumen, its amount, mixing speed and mixing time. With regard to the softening point, the type of polymer was also an important factor. Ultimately, the optimization process allowed for the determination of such a combination of both qualitative and quantitative input factors, which resulted in bitumen showing higher utility than input 20/30 and 70/100 bitumens. Moreover, it was found that the increase in mixing time did not result in an excessive increase in bitumen stiffness caused by the mixing process. Thus, the low-temperature properties left unchanged significantly