Research results on 3D printed fluoropolymers are scarce since the filaments were introduced commercially only in the last several years to enable fused filament fabrication (FFF) of structural components for more demanding service conditions, where chemical, UV or fire resistance, high purity, sterilizability or biocompatibility are critical such as in biomedical industry. This experimental study reports on additive manufacturing and quasi-static mechanical testing of polyvinylidene fluoride (PVDF) and in-vitro cytocompatible polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) specimens that were 3D printed with different infill patterns at 75% density (linear, cubic, cross, concentric, octet, zigzag, triangular). Recommendations are provided for addressing issues related to weak adhesion and obtrusive warping, which occur in open-chamber FFF printer due to semi-crystalline and hydrophobic nature of PVDF-based thermoplastics. The measured tensile and flexural stress-strain curves are analyzed to determine the influence of strut-based infills on the strength and elastic performance by including comparisons in ratios between strength, modulus of elasticity and weight of the specimens. The concentric pattern demonstrates the highest tensile strength, while the cross and triangular lattices - the lowest one. In three-point bending, the linear pattern delivers the lowest strength, while the rest exhibit comparable mechanical properties. The results are conducive to the design of 3D printable PVDF homopolymer and copolymer load-bearing structures serving as lightweight high-performance components in biomedical applications.
Keywords: 3D printing; Biocompatible fluoropolymer; Partial infill; Specialty thermoplastic; Specific strength; Strut lattices.
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