Plastics have become widely used materials in everyday life due to their special properties such as durability, easy processing, lightweight nature, and low cost of production. However, because of their stable and nonbiodegradable nature, postconsumer plastics become an issue to the environment. The growing amounts of waste are generated, as plastic products are commonly used only once before disposal. The alternatives of practical techniques for solid waste management are redesign, reprocessing, and recycling. Thus, even recycling is not the most profitable technique for the treatment of plastic waste, and it should be constantly developed. The recycling of plastic waste helps to conserve natural resources due to polymeric materials being made from oil and gas. There are four main recycling methods: reuse, mechanical recycling, chemical recycling, and energy recovery. Mechanical recycling turns polymeric waste into new polymer products when energy recovery process releases the energy contained within plastics through combustion and chemical recycling converts waste polymers into feedstock for chemicals/monomers/fuels production. Nowadays chemical recycling of plastic waste is the most noteworthy polymer recovery technique. The manuscript presents a literature review on chemical recycling methods of various polymers, such as polyethylene (PE; low-density PE [LDPE] or high-density PE [HDPE]), polypropylene, or mixture of these polymers, poly(ethylene terephthalate), polycarbonate, and polyurethane. We describe the effect of the reaction parameters on obtained products, used catalysts and agents, and used equipment for specific methods of chemical recycling. In this way, the state of the art of the chemical recycling methods of several polymers is presented.

Commercially available polyurethanes are synthesized by the polyaddition of diisocyanates with polyols and low molecular weight chain extenders. A new approach to polyurethanes synthesis is realized via non-isocyanate routes. Negative impacts of petroleum-based chemicals on the environment and human health as well as gradual reduction of fuel-based resources, which leads to an increase in their prices, are an incentive to looking for bio-based components derived from renewable resources for the polyurethanes synthesis. The purpose of the presented review is a critical summary of the possibilities of using renewable natural resources as green intermediates to obtain non-isocyanate polyurethanes by polyaddition of bis(cyclic carbonate)s and di- or polyamines. The possibility of using carbon dioxide, plant oils, fatty acids and biomass-derived platform chemicals in non-isocyanate polyurethane synthesis is exhaustively commented.

The manuscript presents the latest data on the market of isocyanates, methods for producing their eco-friendly substitutes and the toxicity of the phosgene used in isocyanate production.