Poly(vinylidene fluoride) (PVDF) is a semicrystalline polymer that exhibits unique piezoelectric characteristics along with good chemical resistance and high thermal stability. Layer-based material extrusion (MEX) 3D printing of PVDF is desired to create complex structures with piezoelectric properties; however, the melt processing of PVDF typically directs the formation of the α crystalline allomorph, which does not contribute to the piezoelectric response. In this work, PVDF was compounded with poly(methyl methacrylate) (PMMA) and cyclopentyl-polyhedral oligomeric silsesquioxane (Cp-POSS) nanostructured additives in binary and ternary blends to improve MEX printability while maintaining piezoelectric performance. Overall crystallinity and β phase content were evaluated and quantified using a combination of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry (DSC). Enhancement of MEX printability was measured by quantifying the interlayer adhesion and warpage of printed parts. All blends studied contained a significant percentage of β allomorph, but it could be detected by ATR-FTIR only after the removal of a thin surface layer. Inclusion of 1% Cp-POSS and up to 10% PMMA in blends with PVDF improved interlayer adhesion (2.3-3.6x) and lowered warpage of MEX printed parts compared to neat PVDF. The blend of 1% Cp-POSS/1% PMMA/PVDF was demonstrated to significantly improve the quality of MEX printed parts while showing similar piezoelectric performance to that of neat PVDF (average piezoelectric coefficient 24 pC/N). MEX printing of PVDF blends directly into usable parts with significant piezoelectric performance while reducing the challenges of printing the semicrystalline polymer opens the potential for application in a number of high value sectors.

This work studies the effect of interlayer adhesion on mechanical performance of fluorinated thermoplastics produced by fused deposition modeling (FDM). Here, we study the anisotropic mechanical response of 3D-printed binary blends of poly (vinylidene fluoride) (PVDF) and poly (methyl methacrylate) (PMMA) with the isotropic mechanical response of these blends fabricated via injection molding. Various PVDF/PMMA filament compositions were produced by twin-screw extrusion and, subsequently, injection-molded or 3D printed into dog-bone shapes. Specimen mechanical and thermal properties were evaluated by mode I tensile testing and differential scanning calorimetry, respectively. Results show that higher PMMA concentration not only improved the tensile strength and decreased ductility but reduced PVDF crystallization. As expected, injection-molded samples revealed better mechanical properties compared to 3D printed specimens. Interestingly, 3D printed blends with lower PMMA content demonstrated better diffusion (adhesion) across interfaces than those with a higher amount of PMMA. The present study provides new findings that may be used to tune mechanical response in 3D printed fluorinated thermoplastics, particularly for energy applications.

Mismanaged plastic products should be designed to inherently reduce their environmental impacts by optimizing material efficiency and minimizing environmental persistence. Foaming biodegradable bioplastics (i.e., introducing microstructural pores into the material) was hypothesized to achieve this objective. To test this hypothesis, the marine biodegradation of novel cellulose diacetate (CDA) foams of varying relative density (ρ_foam/ρ_solid =0.09-1.00) was evaluated in a flow-through seawater mesocosm. After 36 weeks, the CDA foams (ρ_foam/ρ_solid =0.09) lost 65-70% of their mass, while equivalent polystyrene foams persisted with no change in mass. The degradation rates of the CDA foams were ~15 times that of solid CDA and the fastest of any plastic reported in the ocean. Material indices, value functions, and qualitative descriptors for circularity indicated that CDA foams could be the favorable choice of material for food-packaging applications with potential benefits to society worth hundreds of millions of dollars annually. Foaming of biodegradable bioplastics thus represents a promising strategy toward minimizing the environmental impacts of frequently mismanaged consumer plastics.

Cellulose diacetate (CDA), a bio-based material widely used in consumer products, is biodegradable in the coastal ocean. However, the effect of water temperature on biodegradation rates is unknown, limiting projections of lifetime across space and time. Here, we incubated CDA-based materials (film, foam, and straw), paper straws, polyethylene (PE) films, and polybutylene adipate terephthalate (PBAT) straws for 28 weeks at 10 and 20 °C in continuous-flow seawater mesocosms. The relative mass loss of the CDA film, foam, and straw increased by 20–25% from 10 to 20 ºC, and their degradation rates increased by 1.8- to 3.1-fold. Accordingly, model predictions of CDA-based article lifetimes in North American coastal waters were highly sensitive to differences in water temperature across latitude and seasonality. Paper straws also showed a notable temperature dependence, with degradation rates increasing 1.7-fold from 10 to 20 °C. PE films and PBAT straws showed no measurable degradation at either temperature, highlighting their persistence in the environment. Microbial communities implicated in CDA biodegradation were influenced by material type, temperature, and incubation time. Differential analysis revealed that ~93% (29/31) of the highly responsive microbial taxa implicated in the degradation of CDA were unique at 10 and 20 °C. These findings indicate that water temperature governs the lifetime of biodegradable materials, supporting its inclusion as a primary variable in experimental frameworks moving forward.