Poly(methyl methacrylate) (PMMA) was added to aluminum/poly(vinylidene fluoride) (Al/PVDF) energetic blends to enhance melt flow rate and adhesion in a fused deposition modeling (FDM) manufacturing scenario. Composites were successfully printed with up to 30 wt% nano-scale Al after PMMA addition. Melt flow rate increased with increasing PMMA content. This resulted in a partially fluorinated binder that can facilitate high solids loadings and can be easily printed with a standard FDM 3D printer. PMMA addition promoted nucleation of the electroactive β-phase PVDF, which suggests the potential to print piezoelectric, energetic composites. Thermal stability was assessed using differential scanning calorimetry and thermogravimetric analysis. Results verified that composite stability decreased with increasing PMMA and Al content, however, decomposition onset temperatures for all concentrations remained well above printing temperatures. Burn rates at higher Al loadings (e.g., fuel rich) showed a decreasing trend. Analysis of post burn soot revealed α-AlF₃ and amorphous carbon char as the primary reaction products. Combustion performance results indicate that although PMMA may serve as a heat sink, the reaction between Al and PVDF was not significantly affected by PMMA addition. These findings indicate that by changing PMMA concentrations, rheology, piezoelectric content, thermal properties and combustion performance can be altered to suit specific needs.

In the broader polymer field, the term ‘crystallinity’ is often used rather loosely. However, increasingly, it becomes critical to clearly distinguish between degree of crystallinity, which provides the fractional amount of crystalline phase in a polymer, and the crystalline quality, which describes the perfection of the crystalline moieties that may form in a polymer. The reason is that these different structural features dictate important properties of plastic materials, including the mechanical properties of commodity polymers and the behavior of macromolecular ferroelectrics; they also determine which photophysical processes occur in semiconducting polymers. Hence, rigor needs to be applied when establishing structure/processing/property interrelations; and it should become a general practice that specific functions are clearly attributed to the degree of crystallinity, the crystalline quality or a combination of the two. In this perspective, in memoriam of Professor Dick Jones, a long‐time member of IUPAC's Polymer Division, we discuss the challenges of identifying—and distinguishing between—these important structural characteristics when using commonly applied measuring techniques and/or theoretical approaches. This task is often elaborate, as small changes in the chemical nature of the polymer and/or processing conditions selected can have drastic effects on both the crystalline quality and the degree of crystallinity, an issue that combined with the general ambiguity of data obtained with methodologies used to characterize polymer structures, theoretically or experimentally based. © 2023 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Processing highly filled polymers (>50 vol%), whether with particle or short fiber additives, is needed for many applications, such as pharmaceuticals, ceramics, batteries, coatings, etc. Forming these materials into more complex geometries with graded properties is necessary to meet the growing demand for structures with increasingly specialized functions. However, there are many poorly understood processing effects that must be studied to enable the reliable forming of new structures and the qualification of said structures for new applications. Here, we highlight four challenges that impede the processing of highly filled polymers, with a stronger emphasis on additive manufacturing and extrusion processes. They are: (1) understanding process-induced porosity, (2) understanding the solid-liquid interface during the manufacturing process, (3) overcoming equipment limitations, and (4) appropriate use of in-situ monitoring and measurement. We anticipate that by highlighting these research gaps and identifying paths forward, the processing science necessary to form highly filled polymer will advance.