Preparation of Polypropylene Composites with Pyrolyzed Carbon Fibers Using an Internal Mixer
The use of pyrolyzed carbon fibers (pCFs) in the secondary raw material market is growing, but potential applications for pCFs are limited by their wool-like appearance. Common solutions are further processing into fiber mats or shredding and adding the fibers during compounding in twin-screw extrud...
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MDPI AG
2024-11-01
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| author | Dennis Müller Matthias Bruchmüller Florian Puch |
| author_facet | Dennis Müller Matthias Bruchmüller Florian Puch |
| author_sort | Dennis Müller |
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| description | The use of pyrolyzed carbon fibers (pCFs) in the secondary raw material market is growing, but potential applications for pCFs are limited by their wool-like appearance. Common solutions are further processing into fiber mats or shredding and adding the fibers during compounding in twin-screw extruders (TSEs). In the latter process, the initial fiber length is usually reduced to less than 1 mm during compounding and further reduced during injection molding. Hence, this paper presents an alternative compounding approach by investigating if internal mixers (IMs) are suitable for retaining pCFs after compounding longer. First, the influence of the mixing sequence for adding pCFs to the mixing process of the resulting fiber length was investigated. Second, a design of experiments was carried out using a laboratory IM, considering the process parameters of rotational speed, mixing time, coupling agent content, initial fiber length, and chamber filling level. Third, the results obtained were scaled up and applied to a production-scale IM. Important findings are that the melting of the matrix polymer should occur before fibers are added. This results in fiber contents of 20 wt.%. To achieve higher fiber contents, small amounts of carbon fiber must be added during the melting process. The process parameters investigated had no significant influence on the resulting fiber length. Compounding with IM is suitable for an initial fiber length of up to 24 mm. A composite with carbon fibers from industrial offcuts (rCFs) prepared by TSE compounding was used to compare the mechanical properties of the injection-molded samples due to the non-availability of composites with pyrolyzed fibers. Compounding resulted in an improvement in the weight-average fiber length from 226 µm (TSE) to 540 µm (IM). However, this fiber length could not be preserved during injection molding, resulting in similar mechanical properties of both, the pCF composites prepared by an IM and the commercially available rCF composites. |
| format | Article |
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| institution | Kabale University |
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| publishDate | 2024-11-01 |
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| spelling | doaj-art-461c8f1864f141dbb868c0f620c8e0d42024-12-27T14:50:08ZengMDPI AGRecycling2313-43212024-11-019611510.3390/recycling9060115Preparation of Polypropylene Composites with Pyrolyzed Carbon Fibers Using an Internal MixerDennis Müller0Matthias Bruchmüller1Florian Puch2Plastics Technology Group, Faculty of Mechanical Engineering and Thuringian Center of Innovation in Mobility, Technische Universität Ilmenau, 98693 Ilmenau, GermanyPlastics Technology Group, Faculty of Mechanical Engineering and Thuringian Center of Innovation in Mobility, Technische Universität Ilmenau, 98693 Ilmenau, GermanyPlastics Technology Group, Faculty of Mechanical Engineering and Thuringian Center of Innovation in Mobility, Technische Universität Ilmenau, 98693 Ilmenau, GermanyThe use of pyrolyzed carbon fibers (pCFs) in the secondary raw material market is growing, but potential applications for pCFs are limited by their wool-like appearance. Common solutions are further processing into fiber mats or shredding and adding the fibers during compounding in twin-screw extruders (TSEs). In the latter process, the initial fiber length is usually reduced to less than 1 mm during compounding and further reduced during injection molding. Hence, this paper presents an alternative compounding approach by investigating if internal mixers (IMs) are suitable for retaining pCFs after compounding longer. First, the influence of the mixing sequence for adding pCFs to the mixing process of the resulting fiber length was investigated. Second, a design of experiments was carried out using a laboratory IM, considering the process parameters of rotational speed, mixing time, coupling agent content, initial fiber length, and chamber filling level. Third, the results obtained were scaled up and applied to a production-scale IM. Important findings are that the melting of the matrix polymer should occur before fibers are added. This results in fiber contents of 20 wt.%. To achieve higher fiber contents, small amounts of carbon fiber must be added during the melting process. The process parameters investigated had no significant influence on the resulting fiber length. Compounding with IM is suitable for an initial fiber length of up to 24 mm. A composite with carbon fibers from industrial offcuts (rCFs) prepared by TSE compounding was used to compare the mechanical properties of the injection-molded samples due to the non-availability of composites with pyrolyzed fibers. Compounding resulted in an improvement in the weight-average fiber length from 226 µm (TSE) to 540 µm (IM). However, this fiber length could not be preserved during injection molding, resulting in similar mechanical properties of both, the pCF composites prepared by an IM and the commercially available rCF composites.https://www.mdpi.com/2313-4321/9/6/115carbon fiber-reinforced thermoplasticpyrolyzed carbon fiberIMfiber attritionrecycled carbon fiberrecycling |
| spellingShingle | Dennis Müller Matthias Bruchmüller Florian Puch Preparation of Polypropylene Composites with Pyrolyzed Carbon Fibers Using an Internal Mixer Recycling carbon fiber-reinforced thermoplastic pyrolyzed carbon fiber IM fiber attrition recycled carbon fiber recycling |
| title | Preparation of Polypropylene Composites with Pyrolyzed Carbon Fibers Using an Internal Mixer |
| title_full | Preparation of Polypropylene Composites with Pyrolyzed Carbon Fibers Using an Internal Mixer |
| title_fullStr | Preparation of Polypropylene Composites with Pyrolyzed Carbon Fibers Using an Internal Mixer |
| title_full_unstemmed | Preparation of Polypropylene Composites with Pyrolyzed Carbon Fibers Using an Internal Mixer |
| title_short | Preparation of Polypropylene Composites with Pyrolyzed Carbon Fibers Using an Internal Mixer |
| title_sort | preparation of polypropylene composites with pyrolyzed carbon fibers using an internal mixer |
| topic | carbon fiber-reinforced thermoplastic pyrolyzed carbon fiber IM fiber attrition recycled carbon fiber recycling |
| url | https://www.mdpi.com/2313-4321/9/6/115 |
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