Abstract
Currently, plastics and rubbers are broadly being used to produce a wide range of products for several applications like automotive, building and construction, material handling, packaging, toys, etc. However, their waste (materials after their end of life) do not degrade and remain for a long period of time in the environment. The increase of polymeric waste materials’ generation (plastics and rubbers) in the world led to the need to develop suitable methods to reuse these waste materials and decrease their negative effects by simple disposal into the environment. Combustion and landfilling as traditional methods of polymer waste elimination have several disadvantages such as the formation of dust, fumes, and toxic gases in the air, as well as pollution of underground water resources. From the point of energy consumption and environmental issues, polymer recycling is the most efficient way to manage these waste materials. In the case of rubber recycling, the waste rubber can go through size reduction, and the resulting powders can be melt blended with thermoplastic resins to produce thermoplastic elastomer (TPE) compounds. TPE are multi-functional polymeric materials combining the processability of thermoplastics and the elasticity of rubbers. However, these materials show poor mechanical performance as a result of the incompatibility and immiscibility of most polymer blends. Therefore, the main problem associated with TPE production from recycled materials via melt blending is the low affinity and interaction between the thermoplastic matrix and the crosslinked rubber. This leads to phase separation and weak adhesion between both phases. In this review, the latest developments related to recycled rubbers in TPE are presented, as well as the different compatibilisation methods used to improve the adhesion between waste rubbers and thermoplastic resins. Finally, a conclusion on the current situation is provided with openings for future works.
Highlights
Rubber, as an elastomeric material, has the ability of reversible deformation, which is significantly influenced by its chemical structure and molecular weight (MW).Ideally, rubber chains should return to their original shape after removing the applied force.The macromolecular chains of rubber are long and oriented without large substituents, which makes them capable of moving and rotating around chemical bonds at low temperatures because of their low glass transition temperature (Tg)
This review presents developments in surface modification and devulcanisation of ground tire rubber (GTR) and compatibilisation of thermoplastic elastomer (TPE) blends to improve the interfacial adhesion of GTR and thermoplastic matrix
TPE materials are categorized into thermoplastic olefin (TPO), thermoplastic natural rubber (TPNR), thermoplastic vulcanizate (TPV), thermoplastic polyurethane (TPU), styrene block copolymer (SBC), polyether block amide (PEBA), and copolyester (COPE) [30]
Summary
As an elastomeric material, has the ability of reversible deformation (between 100 up to 1000%), which is significantly influenced by its chemical structure and molecular weight (MW). Vulcanized rubber as an elastic, insoluble, and infusible thermoset material cannot be directly reprocessed. This is an important limitation for material recycling, especially after the end of life of a part. Stabilisers, anti-oxidants, and anti-ozonants are being used in rubber formulation to make tires extremely resistant to severe outdoor conditions (chemical reagents, high temperatures, radiations, and shear stress) during their lifetime [1,2,3]. Tires as the main application of rubber industries are complex materials containing several components suitable to operate in a wide range of environment. This paper reviews the progress of waste tire recycling focused on melt blending of ground tire rubber (GTR) with thermoplastic matrix. This review presents developments in surface modification and devulcanisation of GTR and compatibilisation of thermoplastic elastomer (TPE) blends to improve the interfacial adhesion of GTR and thermoplastic matrix
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