View the article online for updates and enhancements. Abstract. Polypropylene (PP) is usually added to bitumen to improve its mechanical properties, however, both of them have different chemical properties. To achieve best mechanical properties of the mixture, coupling agent such as lignin is importantly required. Lignin is an amorphous biopolymer, has bipolar characteristic due to its distinct chemical function which has carbonyl, carboxyl, hydroxyl and phenol chemical function. Otherwise, bitumen and PP have polar and nonpolar characteristic, respectively. In the previous research, it is found that lignin is potential to be used as coupling agent. In order to confirm the potential of lignin as a coupling agent, there are various compounds of lignin on PP-bitumen mixtures used in this research. This experiment consists of several stages, ranging from sample preparation, characterization of raw materials, mixing, and characterization of the PP-Modified Bitumen. This experiment used hot melt mixing to mix lignin, PP, and bitumen. The result of this experimental was analyzed by using FTIR and FESEM. The addition of lignin make Polymer Modified Bitumen (PMB) getting better mixing and increase mechanical properties. Furthermore, FESEM characterization indicated that the addition of lignin gave better mixing of PP-Bitumen. FTIR showed a new chemical structure due to the addition of lignin. From this experiment, the addition of lignin can improve mixing between PP and Bitumen. So, we can use lignin as coupling agent.

Summary Polyethylene (PE) and Polypropylene (PP) are already well‐known as a type of packaging materials and resulting on abundant amount of wastes. On the other hand, fabrication of papers always has lignin as one of the by‐products. These materials are potential to be combined with asphalt to create asphalt composite which will have better mechanical properties and higher water resistant compared with ordinary asphalt. This research focuses on preliminary observation on the effect of lignin, PE and PP addition in asphalt composite. Addition of 0.1% lignin into PP increases the penetration depth more significantly than PE. The increase of penetration depth is up to 350% in PP, and only 100% in PE. On the other hand, lignin addition into PP and PE have the same effect on the ductility. Lignin addition to both polymers increase the ductility up to 200%. In term of stability, PP‐Asphalt is better as it shows only 8% ductility reduction after 0.5% lignin addition, while PE‐Asphalt ductility is reduced up to 56.5%. The same trend also occured for hardness where PP‐Asphalt shows reduction of 14% and PE‐Asphalt is reduced by 32%.