Using vitrimers to improve the mechanical properties and the processability of recycled polymers

The polymer materials have invaded all areas of our lives due to their versatility, lightweight, and low-cost. However, the mechanical recycling of plastic waste is still facing challenges such as chain degradation, immiscibility of blends, and limited applicability. In the last decade, the incorporation of dynamic bonds within polymer chains has emerged as the solution to improve the recycling of a wide variety of polymers while preserving their mechanical properties. The present study compares the flow properties of two linear polystyrene samples in which different fractions of vitrimer are added. To achieve this, the linear viscoelastic response and transient shear viscosity of each sample are obtained using a rotational rheometer. Additionally, the elongational viscosity is measured using a filament stretching rheometer. The results confirm that dynamic covalent bonds contribute to delaying chain relaxation. However, the concentrations of vitrimer additives studied are insufficient to create a percolated network. It also emerged that the vitrimers had an influence on strain hardening during uniaxial elongation. Furthermore, the study highlights the importance of considering micro-phase separation and self-assembly when designing vitrimer blends. Finally, this work contributes to the limited resources on the non-linear rheological study of entangled polymeric systems and vitrimer blends in the literature. It expands the understanding of the flow behaviour of these materials and provides valuable insights for future research in this field.