Sustainable Thermoplastic Elastomers: Valorization of Waste Tires, Recycled HDPE, and Recycled EVA

Jose Suarez Loor¹Miguel Carrasco Cordero¹Miriam Lazo^1,2Angie Mendoza López^1,2Estephany Adrian^1,2Joan Vera Villalobos³Andrés Rigail Cedeño^1,2,4*

• ¹Escuela Superior Politecnica del Litoral Facultad de Ingenieria en Mecanica y Ciencias de la Produccion, Guayaquil, Ecuador
• ²Escuela Superior Politecnica del Litoral Laboratorio de Procesamiento de Plásticos, Guayaquil, Ecuador
• ³Escuela Superior Politecnica del Litoral Facultad de Ciencias Naturales y Matematicas, Guayaquil, Ecuador
• ⁴Escuela Superior Politecnica del Litoral Centro de Investigación y Desarrollo en Nanotecnología, Guayaquil, Ecuador

The present study focused on the comprehensive investigation of the properties of thermoplastic elastomeric composites (TPE) containing 70% by weight of ground tire rubber (GTR) and a range of 15 to 30% by weight of recycled polyethylene (rHDPE). To improve the properties of these composites, different percentages of recycled nylon fibers (rPA) and recycled ethylene vinyl acetate (rEVA) were incorporated as reinforcing and compatibilizing agent, respectively. It was found that composites containing 5% and 10% by weight of rEVA exhibited higher plastic deformation capacity (7.3%), lower stiffness, and higher impact strength (247.92 J/m). These results were attributed to lower interfacial tension between GTR and rHDPE, which allowed the rHDPE to be encapsulated in the GTR matrix, thus favoring these mechanical properties. A detailed scanning electron microscopy (SEM) analysis revealed that the considerable particle size of the GTR used had a negative impact by causing premature tearing of the TPEs and limited deformability. Furthermore, it was confirmed that incorporating rPA into the composites adversely affected the mechanical, physical, and processability properties. This was due to difficulties in the homogeneous dispersion of rPA fibers within the GTR matrix. Also, when analyzing the processability of the composites, a slight increase in processing torque was observed in the composites with rEVA, which was attributed to a slight crosslinking of these composites. In contrast, thermogravimetric tests did not evidence a significant variation in degradation temperatures; however, they showed that the processing temperature should be kept below 380°C. Taken together, these results underscore the considerable potential of the developed composites. These materials show high promise as they were made exclusively from 100% recycled raw materials, eliminating the need for pretreatment.