Texturing can be used to functionalize the surface of plastic parts and, in particular, to modify the interaction with fluids. Wetting functionalization can be used for microfluidics, medical devices, scaffolds, and more. In this research, hierarchical textures were generated on steel mold inserts using femtosecond laser ablation to transfer on plastic parts surface via injection molding. Different textures were designed to study the effects of various hierarchical geometries on the wetting behavior. The textures are designed to create wetting functionalization while avoiding high aspect ratio features, which are complex to replicate and difficult to manufacture at scale. Nano-scale ripples were generated over the micro-scale texture by creating laser-induced periodic surface structures. The textured molds were then replicated by micro-injection molding using polypropylene and poly(methyl methacrylate). The static wetting behavior was investigated on steel inserts and molded parts and compared to the theoretical values obtained from the Cassie–Baxter and Wenzel models. The experimental results showed correlations between texture design, injection molding replication, and wetting properties. The wetting behavior on the polypropylene parts followed the Cassie–Baxter model, while for PMMA, a composite wetting state of Cassie–Baxter and Wenzel was observed.

Production scrap is a significant cost for automotive thermoforming due to the expensive resin costs and large part sizes. Manufacturers strive to regrind and reprocess sheet cutouts from production runs, however, the utilization of a secondary feedstock can be limited by its impact on the sheet processing behavior. To mitigate the economic impact of production scrap, the thermoformability of a blend needs to be predicted at the material development stage. In this work, a test mold is designed to assess the thermoformability of blended TPO sheets. The mold design is developed to evaluate the effects of different geometries. Regrind content is introduced in the blend before extrusion to compare the sheet properties to those of a virgin material configuration. The statistical analysis of the thermoforming experiments shows that the sheet thickness reduction is affected by the draw ratio and sheet temperature. Multivariate regression modeling allows for predicting the thermoformed part thickness as a function of the sheet configuration, draw ratio, and processing conditions. However, the introduction of regrind content, below 50%, did not affect thermoformability. The stretchability of the sheets was also characterized by uniaxial tensile testing and dynamic mechanical analysis, confirming the absence of negligible differences when regrind content is introduced in the blend.

Polylactic acid (PLA) is a bio-based biodegradable polymer and is considered to be an environmentally friendly alternative to petroleum-based polymers for various applications. Neat PLA requires an extended period at elevated temperatures to attain its maximum crystallinity, which can be mitigated by the addition of nucleating agents. Orotic acid is a natural heterocyclic nucleating agent in PLA. The effect of orotic acid on the crystallization behavior of a commercial, high-purity PLA was studied in detail. A differential scanning calorimetry (DSC) technique was utilized for this purpose. A new protocol for the quantitative characterization of crystallization kinetics from DSC data was developed. It was found that the total crystallinity increased from 26% to 63% at 80 °C with 1% content of orotic acid. Meanwhile, the crystallization rate of PLA-OA blends increased by ~10 times as compared to neat PLA. The addition of orotic acid also reduced the incubation time by >17% under quiescent conditions. Injection molding experiments showed that highly crystallized (>50%) PLA samples could be fabricated with a 1% addition of orotic acid. The required mold temperature was reduced from the 120 °C recommended by the supplier to 80 °C.