How open-stage melt crystallization affects tensile and shrinkage properties of 3D printed polypropylene

Melt crystallization of isotactic Polypropylene (PP) on open platform during 3D processing is critical and often challenging. Numerous factors that influ-ence the melt extrusion of PP directly influence its crystallization and hence impact the physico-mechanical properties of the printed parts. The present article represents a detailed investigation of the influence of 3D processing parameters on tensile and shrinkage properties of PP subject to respective melt-crystallization behaviors. Moreover, the article also demonstrated the best experimental conditions that can produce mechanically stronger parts (even stronger than compression molded specimens used for comparison) with mini-mum warping. Influence of print temperature, bed temperature, print layer thickness (when the layer thickness varies by a margin of four folds), print ori-entation (horizontal or vertical), and infill rates was found to be highly sensi-tive towards melt crystallization of the PP dumbbell (which was printed as a product) hence brought about the highest variation in tensile and shrinkage properties. A print head temperature of above 220 degrees C and a bed temperature of 60 degrees C produced stronger dumbbells when printed with a higher layer thickness (0.20 mm/0.25 mm) in horizontal conditions with a 100% infill rate. Such spec-imens possessed higher tensile strength, and elongation at break values than the compression molded sample.