Influence of mixing speed and post-curing duration on the tensile performance of recycled coffee waste filled bio-based SLA photopolymer composites
Abstract
Incorporating environmentally friendly materials into additive manufacturing (AM) is driving research toward sustainable, biologically derived photopolymers filled with natural waste. While such composites offer promising ecological benefits, the critical influence of processing parameters on their mechanical integrity remains a significant research gap. This study evaluates the tensile properties of a bio-based stereolithography (SLA) resin filled with 1 wt% recycled coffee waste. To isolate the effects of processing variables, specimens were prepared at varying mixing shear rates and post-cured for different ultraviole (UV) exposure durations. Testing according to ASTM D-638 standard indicated that both mixing rate and curing time significantly dictated mechanical performance. Increased post-curing duration enhanced tensile strength by improving the cross-linking density of the polymer network. Furthermore, fracture surface analysis revealed that optimal mixing provided homogeneous filler dispersion while excessive shear rates resulted in inconsistent strength values driven by microbubble entrapment, localized viscosity changes, and subsequent interfacial debonding or particle pull-out. These results demonstrate that optimizing processing variables to maintain microstructural integrity is far more critical for the performance of sustainable SLA composites than merely adjusting filler content, thereby establishing a robust structure-property relationship.
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URN: https://sloi.org/urn:sl:tjoee111404
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