Tomsk chemists led by Prof. Pavel Postnikov and a research associate Olga Guselnikova have published a review of existing methods of polymer waste upcycling in Chemical Society Reviews (Q1; IF:46,2). The article summarizes latest achievements in functional upcycling of polymer waste and defines the notion of "functional upcycling" as such.
There is a number of common polymer recycling methods such as landfilling, incineration, mechanical processing, and chemical processing. The first three entail significant environmental hazards associated with the formation of microplastics or carbon dioxide emissions. Chemical processing can result in both monomers or basic units in a polymer chain and new chemically derived products. Despite their advantages, chemical methods are cost intensive.
Functional upcycling is the golden mean among the polymer waste recycling methods. The method makes it possible to produce a new high added-value material due to new properties without considerable chain destruction. The major advantage of this method is the retention of the original polymer properties. These effects are often achieved by using surface modification methods or polymer chain transformations.Chemists from Tomsk Polytechnic University have been working successfully on the development of novel paradigm-shifting approaches to the upcycling of polymer waste for more than five years. The main research focus is on smart technologies and materials for environment protection based on polymer waste, such as sorbents for water purification from anthropogenic pollutants, catalytic systems for photochemical degradation of ecotoxicants, and conductive materials.
Chemists have been studying how to obtain new polymer-based materials for a long time now. For example, transformation methods for commercially available polymers have spurred the creation of materials with controlled wettability that can quickly convert from hydrophobic (water-repelling) to hydrophilic (water-absorbing) ones, and vice versa. Articles covering this topic have been published in Advanced Materials Interfaces (Q2; IF:5,4) and ACS Applied Materials & Interfaces (Q1; IF:9,5). These technologies were also used by the authors to create a polymer hybrid material that can effectively remove contaminants from water surfaces (Separation and Purification Technology (Q1; IF:8,6).The idea of functional upcycling is that a significant effect can be achieved by minimal changes in surface structure of a material. Moreover, new hybrid materials can be obtained by combining a modified material with other materials. Combining two materials with different properties gives not just a material with a combination of these properties, but new properties, a new effect. In this way, we can control the process and achieve the desired properties,
Fundamental developments in polymer chemistry fitted well into upcycling of polymer wastes. Chemists from Tomsk Polytechnic University have created an easy-to-obtain sorbent based on waste medical face masks and disposable sheets (Journal of Environmental Chemical Engineering, (Q1; IF:7,7). For this purpose, a material was coated with a special metal-organic framework by a simple chemical method. As a result, they synthesized a new material, a superhydrophobic oleophilic fabric that absorbs oils, diesel, dyes, and other pollutants.
For instance, a PET-based composite with an metal-organic framework on its surface can be used to sorb hazardous insecticides (Applied Materials Today (Q1, IF:8,3). A simple addition of special plasmon-active nanoparticles to this system creates a hybrid material that can not only absorb but also degrade pesticides when exposed to sunlight (Chemical Engineering Journal (Q1, IF:15,1).However, polyethylene terephthalate (PET) has become our key finding. This is a basic polymer used to make plastic bottles. The terephthalic acid in its composition is a basic component required to obtain such a class of compounds as organometallic frameworks. These are porous organic compounds composed of organic ligands and metal ions. They have a number of useful properties, preconditioning their functioning as, for example, sorbents or catalysts. We grow metal-organic frameworks on the surface of PET polymers, whereby PET itself is a source of ligand for the frameworks. It was found that these methods could be used to synthesize novel hybrid materials with unique properties,
Recently, the researchers from the Research School of Chemistry and Applied Biomedical Sciences have proposed an advanced method of functional PET upcycling to create conductive materials (Journal of Materials Chemistry A (Q1, IF:11,9). They created a metal-organic framework on PET surface, which was further exposed to laser light to transform it into a graphene-like material. It can conduct electricity and effectively absorb sunlight, thus triggering the photothermal effect by solar energy.
More recently, researchers from the TPU research laboratory Non-Valent Interaction in Materials Chemistry have developed a method to obtain unique sorbents using non-valent interactions to separate hazardous chlorine-containing substances from similar structures under a megagrant from the Russian Ministry of Science and Higher Education (ACS Materials Letters (Q1,IF:11,4).
"Functional upcycling is an alternative to the chemical method of polymer recycling. In addition, it is a more economically feasible recycling technology. By using cheap raw materials and agents, we can get a value-added product. The upcycling method is potentially applicable in the production of electricity generators, polymer-based sorbents, sensor systems, and new conductive materials," summarizes Pavel Postnikov.