SPE Library

The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.

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Conference Proceedings

3D Characterization And Mechanical Analysis Of Polyethylene Foams Processed In Rapid Rotational Foam Molding

P. Karimipour-Fard | W. Y. Pao | R. Pop-Iliev | G. Rizvi, May 2018

Rapid Rotational Foam Molding (RRFM) products are integral cellular composites that consist of a solid skin which encapsulates a foamed core. This paper focuses on characterizing the morphologies in 3D and identifying the key mechanical properties of respective integral-skin polyethylene (PE) cellular structures produced in RRFM by making use of Micro-CT Scanner. Two types of PE grades were used to produce the foamed core, whereas a PE and a PP grade were used to produce the surrounding solid skin layer. The effects of varying relevant processing parameters such as: foam filling directions, processing temperatures and skin temperatures on the quality of the obtained foams were studied. In addition, the correlations between the resulting cellular structures, cell size distributions, and cell densities have been assessed. Finally, simultaneous stress-strain behavior and 3D structure changes were monitored with in-situ compression testing. The experimental results revealed that foam layers adjacent to the integral skin solid layer demonstrate a higher cell density compared to those located in the core, which affects the compressive strength of the material by 0.2 MPa. It was also observed that higher processing and skin temperatures cause increase in cell size, and conversely, decrease in cell density. Mechanical analysis results indicated that cellular structures near the skin have higher compressive strength, and in general, the manufactured LLDPE foam exhibited higher mechanical properties than the sHDPE foam. Compression tests revealed that foam cell size decreases through compression, while cell density was not specifically affected with increased strain.

3D Printing Feedstock From Recycled Materials

Nicole Zander, May 2018

United States Army warfighters in theater are often faced with the challenge of broken, damaged, or missing parts necessary to maintain the safety and productivity required. Waste plastics can be utilized to improve the self-reliance of warfighters on forward operating bases by cutting costs and decreasing the demand for the frequent resupplying of parts by the supply chain. In addition, the use of waste materials in additive manufacturing in the private sector would reduce cost and increase sustainability, providing a high-value output for used plastics. Experimentation is conducted to turn waste plastics into filament that can be used in fused deposition modeling. The effect of extrusion temperature and number of extrusion cycles on polymer viscosity and crystallinity are explored. The effect of blends and fillers to impart additional functionality are also examined. Tensile specimens were tested and compared to die-cut and injection molded parts. Parts printed from recycled polyethylene terephthalate had the highest tensile strength of all recycled plastics evaluated (35.1 ± 8 MPa), and were comparable to parts printed from commercial polycarbonate-ABS filament. Elongation to failure of all recycled plastics was similar to their injection molded counterpart. In addition, select military parts were printed with recycled filament and compared to original parts. This research demonstrates some of the first work on the feasibility of using recycled plastic in additive manufacturing.