Study on Rheological Properties of Bituminous Binders and Mixtures Containing Waste Printed Circuit Boards (PCBs) and SBR Compound Modified Bitumen

Abstract

Improper handling of waste printed circuit boards (PCBs) can cause serious pollution to the water and soil environments. In order to explore a new method of recycling waste PCBs, this study investigated the effect of PCBs and butadiene styrene rubber (SBR) on the rheological properties of neat bitumen. The dynamic shear rheological (DSR) test was used to study the effect of different PCB contents on the high-temperature rheological properties of SBR-modified bitumen. Fluorescence microscopy and Fourier-transform infrared spectroscopy were used to study the microstructure change law and modification mechanism of PCB and SBR composite modified bitumen. Finally, the feasibility of the bitumen properties was verified through a test of the bituminous mixture properties. The DSR test results showed that the addition of PCBs improves the elastic recovery modulus, dynamic shear modulus, and rutting factor of SBR-modified bitumen, indicating that the high-temperature properties were improved. Infrared spectroscopy analysis revealed that a new absorption peak was generated in the infrared spectrum of the compound bitumen after the addition of PCBs, and the intensity of the original absorption peak also changed, indicating that PCBs and SBR-modified bitumen were mainly physically blended and accompanied by a weak chemical reaction. It was further found that the absorption peak of the unsaturated C=C double bond was significantly enhanced, and the increase in the content of the unsaturated bond C=C in the main chain of the polymer significantly increases the stiffness of the bitumen. Macroscopically, the high-temperature rutting resistance was improved to a certain extent. The fluorescence diagram shows that when PCBs do not exceed 10%, the PCBs can form a homogeneous structure and be dispersed in SBR-modified bitumen. The road test of PCBs and SBR composite modified bituminous mixtures showed that PCBs can significantly improve the rutting resistance and water stability of SBR-modified bitumen at high temperatures at the recommended optimum content. The crack resistance at low temperatures is weakened but still meets actual engineering requirements. The correlation analysis between the properties of bitumen and bituminous mixtures is carried out based on grey correlation theory. The results show that the index of modified bitumen has a very good guiding effect on the bituminous mixture properties. The development of PCBs and SBR composite-modified bitumen provides a new practical method for recycling waste PCBs.

Performance Evaluation of an Asphalt Mix Containing Non-Metallic Fractions of Recycled Printed Circuit Boards

“…In recent years, several researchers have directed their attention towards repurposing NMFs in the form of asphalt mix materials, aiming to tackle the mounting quantities of these fractions. In the field of road construction materials, a significant portion of past studies has centered around exploring the application of what is known as the 'wet process' in which the NMF is introduced as an asphalt binder modifier [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. In the wet process, NMF is blended with neat asphalt binder at a precise temperature and duration, utilizing a mechanical mixing machine to induce a reaction, aiming to achieve a homogeneous asphalt binder as the desired outcome.…”

High Value-Added Reutilization of Waste-Printed Circuit Boards Non-Metallic Components in Sustainable Polymer Composites

“…Until now, the researchers have searched for many feasible techniques for recycling WPCB non-metallic materials, such as chemical recycling (pyrolysis, depolymerization) and mechanical recycling. Among these techniques, the mechanical treatment of PCBs is considered to be a more straightforward and effective process, and as-obtained WPCB non-metallic powder could be further applied in construction products, modified asphalt, and polymer composites [24][25][26][27]. In particular, over the past few decades, scientists and engineers have dedicated great efforts to developing ecofriendly polymer composites by incorporating WPCB non-metals into various polymer matrixes, including thermosetting resin (e.g., epoxy resins, unsaturated polyester resin, phenolic resin, etc.…”

Recycling Non-Metallic Powder of Waste Printed Circuit Boards to Improve the Performance of Asphalt Material

“…Yu et al [20] tested modified asphalt with various PCB powder amounts; they discovered that adding PCBs improved the high-temperature performance, low-temperature performance, and temperature sensitivity of the asphalt material, but had a negative influence on the fatigue life. According to Meng et al [21], the performance test of PCBs and styrenebutadiene rubber (SBR) composite-modified bituminous mix demonstrated that PCBs may greatly increase the rutting resistance and water stability of SBR-modified bitumen at high temperatures at the specified optimum concentration. At low temperatures, the crack resistance is diminished, yet it still meets the engineering criteria.…”