Comparison of the properties of biogenic wine by-products stabilized biocomposites compounded with a miniaturized single-screw extruder and a co-rotating twin-screw extruder

Abstract

Bioplastics research is currently challenged by high material prices and limited availability of biopolymers. For state-of-the-art compounding using a twin-screw extruder, even on lab-scale, large quantities of material are required. Poly(3-hydroxy-buthyrate) and its copolymers such as PHBV are promising biopolymers but are prone to degradation. The stabilizers used must also be biobased to ensure the sustainability of the material. In this study, a new material-saving process for the compounding of biocomposites was evaluated to investigate the potential of biogenic by-products from the winemaking industry to improve the stability of biopolyesters. Formulations based on PHBV powder and two different varieties of pulverized wine grape pomace with filler contents up to 10 wt.-% were prepared. The materials were processed on a modified miniaturized single-screw extruder with an L/D ratio of 15 equipped with a mixing screw and compared to a lab-scale twin-screw extruder with an L/D ratio of 44. Both extruders have screw diameters of 20 mm. Thermal and rheological properties of the compounded material were determined using standard polymer analyzing techniques such as GPC, MFR, DSC, TGA and OIT. The mixing quality of both extruder types was evaluated by light microscopy imaging. The results show that a miniaturized single-screw extruder represents an efficient alternative for research purposes, but minor differences in the dominant degradation mechanisms during processing must be considered for data evaluation. Especially for small quantities and frequent material changes, the miniaturized single-screw extruder is a beneficial option, reducing the limits of bioplastics research and contributing to its progress. Thermal analysis revealed that the wine-derived biogenic by-products act as antioxidant stabilizers preventing thermo-oxidative degradation of PHBV, representing sustainable biobased alternatives to synthetic stabilizers.

Mehr zum Titel