Influence of Multiple Recycling Cycles on the Mechanical, Rheological and Thermal Behaviour of a Commercial Cellulose...

In this study, the commercial biobased cellulose-acetate-based blend ARBOBLEND^® 4655V was analysed with regard to its property changes after multiple mechanical recycling at three different processing temperatures (170 °C, 190 °C, and 210 °C). The results demonstrate that the material properties evolve in a distinct manner across the recycling cycles, depending on the processing temperature. While no relevant changes in the zero-shear viscosity, rheologically indicated average molecular weight, or thermal and mechanical properties were observed at 170 °C, moderate changes were observed at 190 °C, in particular an increase in the zero-shear viscosity and rheological indications of an increased average molecular weight, a broadening of the molecular weight distribution, and a change in crystallisation behaviour over the recycling passes. At 210 °C, a marked reduction in the zero-shear, rheological indications of a decreased average molecular weight, and a narrowing of the molecular weight distribution were observed. These rheology-based structural changes had an effect on the mechanical properties, such as the impact strength, the elongation at break, and the elongation at ultimate tensile stress, which were found to decrease with an increasing number of recycling passes. The study suggests that the processing temperature exerts a significant influence on the recycling behaviour of the cellulose-acetate-based blend ARBOBLEND^® 4655V. It is evident that even minor fluctuations in temperature can result in substantial changes to the physical, thermal, and mechanical properties of biopolymers. The findings underline the necessity of conducting recycling-related investigations with the processing temperature as a critical factor, particularly for temperature-sensitive materials such as cellulose-acetate-based compounds.