Development of coffee-PLA composite for 3D printing and injection moulding

Abstract

The objective of the thesis was to manufacture a spent coffee grounds - polylactic acid composite. The plastic used as matrix was polylactic acid (PLA) and spent coffee grounds (SCGs) were used as filler material. The objective was to gradually raise the filler concentration as much as possible.

The project consisted of drying the coffee, mixing the composite with a laboratory mixer and then manufacturing filament with a filament extruder. The filament was used in 3D printing or granulated for injection moulding. Four different filler to matrix concentrations of 20 %, 30 %, 25 % and 50 % were prepared on a case-by-case basis.

The 3D printing quality of 25 % SCGs concentration with smaller than 0.50 mm particle size was compared against commercial PLA filament prints. Injection moulding was tested with a 50 % SCGs concentration with smaller than 1.0 mm particle size. The injection moulded parts were compared to pure PLA samples and the PLA manufacturers reference values with tensile tests.

The thesis was commissioned by the company Preloved Coffee Oy.