WS₂ inorganic nanotubes (WS₂-NT) have been incorporated into Polylactic Acid (PLA) by melt mixing to create a bio-degradable, mechanically reinforced nanocomposite filament. The filament was then processed by Fused Filament Fabrication (FFF) 3D-printer, and the morphology and characteristics before and after printing were compared. We found that addition of WS₂-NT to PLA by extrusion mixing increases the elastic modulus, yield strength and strain-at-failure by 20%, 23% and 35%, respectively. Moreover, we found that the printing process itself improves the dispersion of WS₂-NT within the PLA filament, and does not require changing of the printing parameters compared to pure PLA. The results demonstrate the advantage of WS₂-NT as reinforcement specifically in 3D-printable polymers, over more traditional nano-reinforcements such as graphene and carbon nanotubes. WS₂-NT based 3D-printable nanocomposites can be used for variety of applications from custom-made biodegradable scaffold of soft implants such as cartilage-based organs and biodegradable soft stents to the more general easy-to-apply nano-reinforced polymers.

The composition–processing–property relationship of imine containing reversible covalent bond containing polymers (RCBPs) was studied using an innovative (regarding this type of polymer) combination of characterization methods. This combination led, for the first time, to a classification of the various chemical reactions occurring during the processing of imine based RCBP, affecting their final chemical structure and properties. RCBPs, based on PIs (polyimines), were synthesized from polyethyleneimine (PEI) and terephthalaldehyde (TPA) in the presence of ethanol. The chemical composition and derived thermal and mechanical properties were investigated. Material characterization using ATR-IR, ¹³C-solid state NMR, swell tests, and a novel illustrative model based on the Flory–Rehner equation led to the conclusion that at least 80% of the secondary amine groups reacted to form a cross-linking network, along with 100% of the primary amines, and that during 20 min compression molding at 220 °C under 2.7 MPa, a post-curing reaction occurs. ¹³C-SSNMR and ATR-IR indicated that the chemical structure is determined not only by the reactants but also by the elevated temperature processing conditions. During heating, three mechanisms affect the final composition–transimination, reduction (back into amine groups) and oxidation (to oxaziridine and amide groups which are almost negligible). The reduction/oxidation processes were found to dominate the mechanical properties. The vitrification temperature (T_v), which is characteristic of RCBPs, is dependent on the thermal history, with a higher T_v resulting from longer compression molding times. The mechanical properties are affected by the processing temperatures, changing from high-performance to very low strength. Under specific processing conditions, the imine cross-linking bonds are reduced/oxidized, which causes the formation of more polar but lower energy bond cross-linking, resulting in lower tensile strength and a change in the hydrophobicity of the polymer, which may be used in future applications.