Microcellular injection molding of foamed engineering plastic parts with high dimensional accuracy

Yu‐Teng Feng, Haiying Zhan, Hao‐Yang Mi, Maxwell Fordjour Antwi‐Afari, Youfu Chen, Laifa Gu, Binbin Dong, Chuntai Liu, Changyu Shen

Research output: Contribution to journalArticlepeer-review


Polyformaldehyde (POM) and Polyamide 66 (PA66) are engineering plastics with excellent mechanical properties and thermal stability. Producing microcellular injection molded POM and PA66 parts with high dimensional accuracy would be beneficial to reduce material cost and product quality. In this research, foamed POM and PA66 gear parts were fabricated by using microcellular injection molding with supercritical nitrogen as the blowing agent. Compared to conventional injection molded parts (parts that foaming is not involved), the foamed POM and PA66 gear parts achieved 5% and 10% average weight reduction, respectively. The foamed parts displayed a lower shrinkage ratio when compared to the solid counterparts, which was attributed to the cell expansion that offset part of the inward shrinkage stress. Moreover, POM gear parts with a higher crystallinity degree presented more serious shrinkage ratio compared to the PA66 gear parts, which contributed to the denser polymer molecular chains arrangement. The shrinkage ratio in both directions of PA66 foamed gear parts depended on the injection volume, and the lowest shrinkage ratio of 0.043‰ was obtained at the injection volume of 74 mm, when the polymer reached the maximum foaming ratio. The findings from this study could provide practical guidance for preparing microcellular injection molded products with high dimensional accuracy.
Original languageEnglish
Article numbere54336
JournalJournal of Applied Polymer Science
Issue number35
Early online date30 Jun 2023
Publication statusPublished - 15 Sept 2023

Bibliographical note

Copyrigh © 2023 Wiley Periodicals LLC. This is the peer reviewed version of the following article: Feng, Y.-T., Zhan, H., Mi, H.-Y., Antwi-Afari, M. F., Chen, Y., Gu, L., Dong, B., Liu, C., Shen, C., J. Appl. Polym. Sci. 2023, e54336., which has been published in final form at https://doi.org/10.1002/app.54336. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.

Funding Information: The authors would like to acknowledge the financial support of the National Natural Science Foundation of China (52173049), the China 111 project (D18023), and the China Postdoctoral Science Foundation (2021M101797).


  • cell morphology
  • dimensional accuracy
  • microcellular injection molding
  • shrinkage ratio


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