Observations of Short- and Long-Term Mechanical Properties of Glass Fiber Reinforced Polypropylenes with Post-Consumer Recycled Materials

Byunghyun Kang, Donguk Kim, Joo Seong Sohn, Nocheol Park, Kwangjoo Kim, Hyeong Jun Kim, Youngdeog Koh, Byoung Ho Choi

Research output: Contribution to journalArticlepeer-review


In this study, the change in the mechanical properties of glass fiber-reinforced thermoplastic (GFRTP) according to the recycled material content was evaluated. The recycled material was polypropylene, with short glass fiber reinforcement, dry blended with virgin polypropylene and additional glass fiber, and injected into its final shape. It is known that during the recycling process, the length of the glass fibers decreases, which leads to the deterioration of the mechanical properties. Therefore, to compensate for the fiber length shortening, long glass fibers were introduced, and changes of the length distribution of the glass fiber and mechanical properties were investigated. Variation of key short- and long-term mechanical properties by introducing long fibers was measured and investigated by performing tensile test, Izod impact test, essential work of fracture (EWF) test, and fatigue test. Most of the mechanical properties showed a linear relationship with the long glass fiber content, but the percent elongation at break and the resistance to the crack initiation were significantly improved immediately after the long fiber was introduced. In addition, the distribution of fiber length was measured and analyzed, and it was found that significant fiber breakage occurred during the injection process and the recycling process including the chopping of recycled material. Finally, through the observation of fracture surfaces, it was validated that the ductile-to-brittle fracture mechanism transition was mainly caused by the poor compatibility between virgin and recycled materials.

Original languageEnglish
Pages (from-to)523-535
Number of pages13
JournalInternational Journal of Precision Engineering and Manufacturing - Green Technology
Issue number2
Publication statusPublished - 2024 Mar

Bibliographical note

Publisher Copyright:
© The Author(s), under exclusive licence to Korean Society for Precision Engineering 2023.


  • Fatigue properties
  • Glass fiber
  • Mechanical properties
  • Polymer recycling
  • Thermoplastic composite

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • General Materials Science
  • Mechanical Engineering
  • Industrial and Manufacturing Engineering
  • Management of Technology and Innovation


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