Stabilization of an Aqueous Bio-Based Wax Nano-Emulsion through Encapsulation.

The emulsification of biowaxes in an aqueous environment is important to broaden their application range and make them suitable for incorporation in water-based systems. The study here presented proposes a method for emulsification of carnauba wax by an in-situ imidization reaction of ammonolysed styrene (maleic anhydride), resulting in the encapsulation of the wax into stabilized organic nanoparticles. A parameter study is presented on the influences of wax concentrations (30 to 80 wt.-%) and variation in reaction conditions (degree of imidization) on the stability and morphology of the nanoparticles. Similar studies are done for encapsulation and emulsification of paraffin wax as a reference material. An analytical analysis with Raman spectroscopy and infrared spectroscopy indicated different reactivity of the waxes towards encapsulation, with the bio-based carnauba wax showing better compatibility with the formation of imidized styrene (maleic anhydride) nanoparticles. The latter can be ascribed to the higher functionality of the carnauba wax inducing more interactions with the organic nanoparticle phase compared to paraffin wax. In parallel, the thermal and mechanical stability of nanoparticles with encapsulated carnauba wax is higher than paraffin wax, as studied by differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical analysis. In conclusion, a stable aqueous emulsion with a maximum of 70 wt.-% encapsulated carnauba wax was obtained, being distributed as a droplet phase in 200 nm organic nanoparticles.

Comparative Screening of the Structural and Thermomechanical Properties of FDM Filaments Comprising Thermoplastics Loaded with Cellulose, Carbon and Glass Fibers.

Additive manufacturing (AM) has been rapidly growing for a decade in both consumer and industrial products. Fused deposition modeling (FDM), one of the most widely used additive manufacturing methods, owes its popularity to cost effectiveness in material and equipment investment. Current efforts are aimed toward high load-bearing capacity at low material costs. However, the mechanical reliability of end-products derived from these compositions and their dependence on microstructural effects, have remained as major limitations. This is mainly owing to the unknown mechanics of the materials, including the reinforcing or filler components and their interphase/interface compatibility. For this reason, here we investigate the most relevant commercial polymeric materials used in composite filaments, associated phases and the characterization protocols that can guide component selection, screening and troubleshooting. We first present thermal analyses (thermogravimetric, TGA and differential scanning calorimetry, DSC) in relation to the constituent fractions and identify the type of polymer for uses in filaments production. The influence of various fillers is unveiled in terms of the crystallization behavior of derived 3D-printed parts. To understand the microstructural effects on the material strength, we carry out a series of tensile experiments on 3-D printed dog-bone shaped specimens following ISO standards. Simultaneously, real-time thermal energy dissipation and damage analyses are applied by using infrared measurements at fast frame rates (200 Hz) and high thermal resolution (50 mK). The failure regions of each specimen are examined via optical, scanning and transmission electron microscopies. The results are used to reveal new insights into the size, morphology and distribution of the constituents and interphases of polymer filaments for FDM. The present study represents advancement in the field of composite filament fabrication, with potential impact in the market of additive manufacturing.