Comparative studies of technological-to-structural relationships of rotomolded self-stabilizing composites with plant-waste functional fillers based on pistachio, walnut, and pecan shells

Abstract

Thermooxidative stability of polymers is a key process-related functionality required of materials manufactured by rotational molding. Applications of plant-derived fillers rich in antioxidants create prospects for the production of self-stabilizing composites, with the possibility of minimizing the use of synthetic additives. This study compares the impact of a one- or two-stage manufacturing processing procedure of high-density polyethylenebased (HDPE) composites filled with ground pistachio (PS), walnut (WS), and pecan (PES) shells (2–15 wt%) on the rheological, mechanical properties, and the structure of rotomolded products. The investigations were supplemented with an analysis of changes in the resistance of polyethylene composites to oxidation induced by the migration of low molecular weight compounds with antioxidant activity from plant-based fillers to the HDPE matrix. The reduced filler particle size in the case of no-shear and no-pressure RM technology constitutes a significant limitation to maintaining the functionality resulting from the plant-based chemical composition of the filler, resulting from agglomeration of the filler and limited interfacial interactions. Introducing fillers rich in antioxidants with different contents of non-bounded polyphenolic compounds and particle size distribution into the polyethylene matrix by preliminary melt mixing causes partial consumption of active compounds. However, the justification for using this procedure allows the production of materials with much more advanced me chanical properties and homogeneous structure than dry-blending, with still increased resistance to oxidation in the molten state. *