The Nanjing University team successfully created asphalt like materials to overcome the problem of unsustainable asphalt sources

Asphalt is widely used in fields such as road repair, waterproof coatings, and waterproof rolls. According to statistics, the global demand for asphalt exceeds 100 million tons per year

Asphalt is widely used in fields such as road repair, waterproof coatings, and waterproof rolls. According to statistics, the global demand for asphalt exceeds 100 million tons per year. However, conventional asphalt is often extracted from petroleum or coal tar, which usually requires a heating step. The aromatic compounds contained in asphalt may escape during heating, which is very detrimental to the health of workers and surrounding populations. It can be said that this method is neither clean nor sustainable.

To solve the problem of unsustainable asphalt at its root, it is necessary to find an efficient, non-toxic, and low-cost method.

On the other hand, elemental sulfur is an industrial waste, whose supply far exceeds demand, causing the global problem of excessive sulfur. According to reports, there is still 60 million tons of sulfur left every year. Therefore, it is urgent to find a method to convert elemental sulfur waste into high value-added industrial products that can be consumed on a large scale.

Based on the above research background, how to convert waste elemental sulfur into asphalt industrial products with promising application prospects has been a question that Professor Li Chenghui and his team at Nanjing University have been pondering.

Figure | Li Chenghui (Source: Li Chenghui)

As a type of industrial waste, elemental sulfur is abundant and urgently needs to be consumed, while asphalt faces the challenge of unsustainable sources. Therefore, they have decided to find a way to turn waste into treasure to solve these problems.

After determining the research objectives, literature research will begin. How should we complete the conversion of elemental sulfur to asphalt like materials? Literature research has found that as a highly atomic economy reaction, the reverse sulfurization reaction has good feasibility.

The so-called reverse sulfurization reaction refers to a type of reaction using elemental sulfur as the raw material to generate sulfur rich polymers. This reaction can generate sulfur rich compounds by heating the ring opening of elemental sulfur to form double radicals, which react with unsaturated carbon carbon bonds to generate sulfur rich compounds, with a yield of nearly 100% and high atomic economy.

Therefore, they envision using this efficient reaction method to convert elemental sulfur into asphalt like materials. Through literature research, it has been found that aryl groups and liquid sulfur have good compatibility, and both phenolic hydroxyl groups and diene structures can effectively inhibit the polymerization of polysulfide chains.

On this basis, through extensive literature search and reactant screening, the team identified the other two reactants for the ternary reverse sulfurization reaction. Afterwards, it is necessary to adjust the proportion of ingredients and characterize the basic properties of the materials.

In the study, they used two low-cost and non-toxic biomass materials, eugenol and sorbic acid, to undergo ternary reverse sulfurization reaction copolymerization with elemental sulfur, thereby successfully obtaining asphalt like materials.

After fully understanding the properties of materials, they began to explore possible application scenarios for materials. It is reported that the asphalt like material obtained in this study not only exhibits rheological properties highly similar to that of asphalt 70, but also benefits from its viscous flow state and shear hardening properties at room temperature. The material can be used for fast self-healing waterproof sealing belts, impact protection devices, and non Newton fluid speed bumps.

Specifically, they used this type of asphalt material to prepare a waterproof sealing tape that can quickly self repair at room temperature. When cut by a blade, the above sealing strip can complete self repair without any external force. The commercial sealing strip cannot be repaired even when pressed to stop leakage. Therefore, this type of asphalt material exhibits a unique advantage of rapid self repair in waterproofing and sealing.

In addition, conventional solid speed bumps not only generate huge noise when vehicles pass by, but also cause severe bumps for passengers and drivers as the vehicle height increases, even at low speeds. Non Newtonian fluid speed bumps, due to their shear hardening properties, can exhibit a viscous flow state at low speeds and a solid state under high-speed impacts. Therefore, such speed bumps can ensure a smooth driving experience when driving at low speeds, while achieving the same deceleration effect as regular solid speed bumps when driving at high speeds.

However, existing non Newtonian fluid speed bumps typically contain shear thickened solid-liquid mixtures, which inevitably faces the problem of internal solid deposition. The asphalt like material involved in this work is a homogeneous viscous fluid, which does not have problems such as sedimentation or deterioration during long-term storage. Therefore, it has good application prospects in the field of non Newtonian fluid speed bumps.

Li Chenghui said, "When evaluating the deceleration effect of speed bumps, we involved a large number of experimental processes. Because we not only need to complete the construction of experimental facilities and testing equipment, but also confirm the safety of the experiment. Therefore, this test needs to be completed under real road conditions on campus. Not only should the road section be sealed, but also personnel should be arranged to guard each intersection to ensure that no accidents occur

Therefore, all members of the entire research group took action and completed a very large-scale experimental process in close cooperation.

(Source: AdvancedFunctionalMaterials)

In summary, they achieved the goal of "killing two birds with one stone" by converting elemental sulfur from waste into widely used asphalt like materials in a simple, efficient, low-cost, and non-toxic manner:

Recently, a related paper titled 'Bitumen LikePolymers Preparedvia InverseVulcanization with ShearStiffening and Self Healing Capabilities for Multifunctional Applications' was published in theAdvancedFunctionalMaterials[1] .

Hou Kexin, a doctoral student in chemistry at Nanjing University, and Zhao Peichen, a postdoctoral fellow, are co authors. Professor Li Chenghui from Nanjing University and Professor Zheng Pengfei from Nanjing Medical University Affiliated Children's Hospital serve as co correspondents.

| (Source: AdvancedFunctionalMaterials)

The method of converting elemental sulfur into asphalt like materials through reverse sulfurization reaction can fundamentally solve the problem of unsustainable asphalt sources and provide an effective solution for the large consumption of elemental sulfur waste. In addition, the paper mentions that the use of coordination bonds can further expand the application temperature of this type of asphalt material.

It is also reported that Li Chenghui has won the 2020 Thieme Chemistry Journals Award. The Thieme Chemistry Journals Award was established in 1999 and is presented annually to emerging researchers from around the world who are in the early stages of independent academic research careers, such as assistant professors and junior professors.

The winners are exclusively selected by the editorial board members of SYNTHESIS, SYNLETT, and SYNFACTS. This award continues to pay attention to promising young people engaged in chemical synthesis and catalysis or fields closely related to organic chemistry, with the aim of recognizing and encouraging the new generation of organic chemists.

The reason why Li Chenghui won the award is mainly based on his and his team's innovative achievements in organic dyes. Previously, the research group synthesized a new class of planar fused ring compounds using phthalonitrile as raw material. Compared to phthalocyanine, phthalocyanine compounds have the characteristics of good solubility, easy spectral regulation, and diverse coordination methods. Due to the unique properties and wide applications of phthalocyanine, it is believed that phthalocyanine will also shine brightly in the field of organic dyes and optoelectronic functional materials in the future, "he said.

In the future, he and his team will also carry out further optimization and practical applications for the performance of this type of asphalt material. The versatility and application value of asphalt like materials have been preliminarily proven, which also gives us confidence in their future practical applications

References:

1. Hou, K.X., Zhao, P.C., Duan, L., Fan, M., Zheng, P.,& Li, C.H. (2023). Bitumen LikePolymersPreparedvia InverseVulcanization with ShearStiffening and Self Healing Abilities for Multifunctional ApplicationsAdvancedFunctionalMaterials2306886

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