Abstract
In this work, biochar (BC) derived from spent coffee grounds has been incorporated into high density polyethylene (PE) through melt mixing. The influence of the filler content on the rheological and thermal behavior of the obtained composites was assessed. In particular, a rheological study was performed systematically using different flow fields, including linear and nonlinear dynamic shear flow, revealing that the dynamics of PE macromolecules in the composite materials are slowed down because of the confinement of the polymer chains onto the filler surface and/or within the BC porous structure. Oscillatory amplitude sweep tests indicated that composites show weak strain overshoot behavior in the nonlinear regime: This finding clearly proves the formation of weak structural complexes, which cause a retardation of the macromolecular chains dynamics. Furthermore, the embedded BC particles were able to improve the thermo-oxidative stability of PE-based composites, remarkably increasing the PE decomposition temperatures.
Highlights
Increasing attention towards environmental safety and the consequent rising demand for new eco-friendly products, has stimulated the interest of both academic and industrial research to investigate renewable and bio-based materials, with the aim to develop a more sustainable manufacturing approach [1,2,3]
In this work, biochar (BC) derived from spent coffee grounds has been incorporated into high density polyethylene (PE) through melt mixing
Oscillatory amplitude sweep tests indicated that composites show weak strain overshoot behavior in the nonlinear regime: This finding clearly proves the formation of weak structural complexes, which cause a retardation of the macromolecular chains dynamics
Summary
Increasing attention towards environmental safety and the consequent rising demand for new eco-friendly products, has stimulated the interest of both academic and industrial research to investigate renewable and bio-based materials, with the aim to develop a more sustainable manufacturing approach [1,2,3]. It has attracted considerable attention due to its intriguing characteristics: First, BC possesses high thermal and chemical stability, excellent electric conductivity, and a great surface area compared to natural fibers [28,29], notwithstanding its lower aspect ratio and poorer mechanical properties with respect to traditionally used fillers; besides, suitable pyrolysis conditions lead to uniform carbon-based and porous structures, potentially containing abundant functional groups, which could interact with polymer functionalities when BC is embedded into the host matrix [30]. The present study is aimed at studying the effect of BC particles derived from waste coffee grounds on the structure–properties relationships of PE-based composites For this purpose, different amounts of BC, ranging from 1 to 7.5 wt%, were embedded within the polymer matrix through melt mixing, and the morphology, rheological, and thermal behavior of the resulting composite systems were thoroughly investigated.
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