Mixed post-consumer recycled polyolefins as a property tuning material for virgin polypropylene

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Li, Yifan
Jiang, Shan
Vorst, Keith L.
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Curtzwiler, Greg
Assistant Professor
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Chemical and Biological Engineering

The function of the Department of Chemical and Biological Engineering has been to prepare students for the study and application of chemistry in industry. This focus has included preparation for employment in various industries as well as the development, design, and operation of equipment and processes within industry.Through the CBE Department, Iowa State University is nationally recognized for its initiatives in bioinformatics, biomaterials, bioproducts, metabolic/tissue engineering, multiphase computational fluid dynamics, advanced polymeric materials and nanostructured materials.

The Department of Chemical Engineering was founded in 1913 under the Department of Physics and Illuminating Engineering. From 1915 to 1931 it was jointly administered by the Divisions of Industrial Science and Engineering, and from 1931 onward it has been under the Division/College of Engineering. In 1928 it merged with Mining Engineering, and from 1973–1979 it merged with Nuclear Engineering. It became Chemical and Biological Engineering in 2005.

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1913 - present

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  • Department of Chemical Engineering (1913–1928)
  • Department of Chemical and Mining Engineering (1928–1957)
  • Department of Chemical Engineering (1957–1973, 1979–2005)
    • Department of Chemical and Biological Engineering (2005–present)

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Materials Science and Engineering

The Department of Materials Science and Engineering teaches the composition, microstructure, and processing of materials as well as their properties, uses, and performance. These fields of research utilize technologies in metals, ceramics, polymers, composites, and electronic materials.

The Department of Materials Science and Engineering was formed in 1975 from the merger of the Department of Ceramics Engineering and the Department of Metallurgical Engineering.

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Polyethylene and polypropylene are widely used packaging materials that are commonly present in the same waste-streams (e.g., beverage bottle enclosures, laminated flexible packaging). Since these immiscible plastics are difficult to separate with current recycling practices, it is critical to understand the influence of mixed polyolefin post-consumer recycled feedstock composition on key performance properties of recycled blends for widespread industrial adoption. This research comprehensively characterized the optical, thermal, mechanical, morphological, and gas barrier properties of melt blended virgin polypropylene/mixed post-consumer recycled polyolefin materials at different blend ratios. The results strongly indicate that polyolefin beverage container enclosures can be melt blended with virgin polypropylene to tune physical performance properties (74% increased yield stress, 49% increased strain at yield, 160% increased UV blocking, 30–40% gas transmission reduction) and simultaneously reduce environmental contamination. Most measured properties followed the Law of Mixtures which enables highly predictable and tunable properties via precision melt blending of post-consumer recycled and virgin plastic. We hypothesize that increased compatibilization of polyolefin amorphous regions from plastic oxidation and structural changes in the plastic crystalline domains directly influence plastic physical properties. These data fill current knowledge gaps that post-consumer materials can provide value beyond sustainability to justify innovative landfill diversion strategies and realize a more circular economy.
This accepted article is published as Curtzwiler, Greg W.*, Schweitzer, Matt., Jiang, Shan., Vorst, Keith. Mixed Post-Consumer Recycled Polyolefins as a Property Tuning Material for Virgin Polypropylene. Journal of Cleaner Production. 239 (2019) 117978. https://doi.org/10.1016/j.jclepro.2019.117978