Multivariate Modeling of Mechanical Properties for Hot Runner Molded Bioplastics and a Recycled Polypropylene Blend

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The generation of submicron structures on plastic part surfaces can be used to modify their wetting properties allowing the creation of superhydrophobic surfaces. The modified wetting behavior can allow functionalities such as fluid collection or transport, which are critical for microfluidics. Consistent manufacturing is achieved through surface replication and process characterization. In this work, submicron structures were generated on steel mold inserts using ultrafast femtosecond laser and then replicated by micro injection molding on polypropylene and polylactic acid. Samples with Laser-Induced Periodic Surface Structures (LIPSS) were fabricated using a femtosecond laser and characterized to investigate the effects of mold temperature, texture orientation, and material selection on the dynamic contact angle. The dynamic wetting functionality of the surfaces was investigated by analysis of the advancing and receding contact angles. The hysteresis obtained from the dynamic measurements provides information about the fluid/texture interaction dynamics. The experimental results show that the effects of mold temperature and drop orientation are only significant for the advancing contact angles. The large contact angle hysteresis suggests a parahydrophobic wetting behavior for the manufactured plastic parts.

Section: Methodsmentioning

confidence: 99%

Section: Polymer and Manufacturing Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Dynamic wetting characteristics of submicron‐structured injection molded parts

Krantz

Caiado

Piccolo

et al. 2022

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“…Hot runner systems add significant cost but lower material usage and cycle time through the avoidance of molding in the cold runner system. [45,46] To support the cost and sustainability analysis, a valve gated hot runner design to make tensile bars was also considered. The hot runner mold (design shown at right in Figure 2) was designed to produce two 9.6 g tensile specimens in every molding cycle.…”

Section: Injection Moldingmentioning

confidence: 99%

Strategic cost and sustainability analyses of injection molding and material extrusion additive manufacturing

Kazmer

Peterson

Masato

et al. 2023

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Economic and environmental costs are assessed for four different plastics manufacturing processes, including cold and hot runner molding as well as stock and upgraded material extrusion three dimensional (3D) printers. A larger stock 3D printer was found to provide a melting capacity of 14.4 ml/h, while a smaller printer with an upgraded extruder had a melting capacity of 36 ml/h. 3D printing at these maximum melting capacities resulted in specific energy consumption (SEC) of 16.5 and 5.28 kWh/kg, respectively, with the latter value being less than 50% of the lowest values reported in the literature. Even so, analysis of these respective processes found them to be only 2.9% and 3.8% efficient relative to their theoretical minimum energy requirements. By comparison, cold and hot runner molding with an all‐electric machine had SEC of 1.28 and 0.929 kWh/kg, respectively, with efficiencies of 9.9% and 13.6% relative to the theoretical minima. Breakeven analysis considering the cost and carbon footprint of mold tooling found injection molding was preferable at a production quantity of around 70,000 units. Parametric analysis of model inputs indicates that the breakeven quantities are robust with respect to carbon tax incentives but highly dependent on mold costs, labor costs, and part size. Dimensional and mechanical properties of the molded and 3D printed specimens are also characterized and discussed.

“…In this context, the manufacturing process selection should consider cost and sustainability, [ 3 ] and the use of secondary feedstocks. [ 4 ]…”

Section: Introductionmentioning

confidence: 99%

Thermoformability analysis of TPO sheets blended with postindustrial secondary feedstock

Masato

Licata

Gao

et al. 2023

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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.