Preparation and microstructural and thermal properties of a vulcanized Eucommia ulmoides gum modified asphalt

In this study, a vulcanized Eucommia ulmoides gum modified asphalt (VEUGMA) was prepared using a natural plant-based renewable rubber Eucommia ulmoides gum (EUG) as the matrix. The preparation process and microstructural and thermal properties of VEUGMA were investigated. The results showed that the optimum shearing time for preparing VEUGMA was 45 min, and the optimum development time was 120 min. Moreover, the EUG dosage follows a monotonically decreasing linear relationship with the optimum sulfur dosage. The VEUGMA exhibited a preferable corrugated network structure, and the vulcanization process of EUG in asphalt can be divided into three stages: slight crosslinking, deep crosslinking, and supreme crosslinking. The X-ray diffraction pattern displayed that only new diffraction peaks of ZnO appeared in the VEUGMA, and the EUG and asphalt exhibited better compatibility under the action of vulcanization aids. After EUG was vulcanized in asphalt, the aromatic ring hydrogen in the asphalt was replaced by aliphatic chains. The VEUGMA exhibited a lower glass transition temperature that suggests a better low-temperature crack resistance. Two maximum decomposition temperatures were noted in the thermal decomposition process of VEUGMA. Moreover, the main gases released were CO2, CO, CH4, SO2, NO2, and NO; of which, CO2 and CO exhibited the highest content, whereas the inferior emissions of SO2, NO2, and NO, can be ignored. The VEUGMA can effectively reduce the release of CO2 and CO but has no significant effect on the release of CH4. Further, VEUGMA demonstrated a smaller storage modulus (E'), loss modulus (E"), and loss factor (tan delta), which suggested better flexibility at low temperatures. Therefore, this work demonstrated the preferable modification effect achieved by adding 3.5 wt% EUG and 6 phr (parts per hundred parts of resin) sulfur to the matrix asphalt.