Lightweight polypropylene/stainless-steel fiber composite foams with low percolation for efficient electromagnetic interference shielding

Aboutaleb Ameli, Mohammadreza Nofar, Sai Wang, Chul B. Park*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

301 Citations (Scopus)

Abstract

Lightweight polypropylene/stainless-steel fiber (PP-SSF) composites with 15-35% density reduction were fabricated using foam injection molding. The electrical percolation threshold, through-plane electrical conductivity, and electromagnetic interference (EMI) shielding effectiveness (SE) of the PP-SSF composite foams were characterized and compared against the solid counterparts. With 3 wt % CO2 dissolved in PP as a temporary plasticizer and lubricant, the fiber breakage was significantly decreased during injection molding, and well-dispersed fibers with unprecedentedly large aspect ratios of over 100 were achieved. The percolation threshold was dramatically decreased from 0.85 to 0.21 vol %, accounting for 75% reduction, which is highly superior, compared to 28% reduction of the previous PP-carbon fiber composite foam.1 Unlike the case of carbon fiber,1 SSFs were much longer than the cell size, and the percolation threshold reduction of PP-SSF composite foams was thus primarily governed by the decreased fiber breakage instead of fiber orientation. The specific EMI SE was also significantly enhanced. A maximum specific EMI SE of 75 dB·g-1·cm3 was achieved in PP-1.1 vol % SSF composite foams, which was much higher than that of the solid counterpart. Also, the relationships between the microstructure and properties were discussed. The mechanism of EMI shielding enhancement was also studied.

Original languageEnglish
Pages (from-to)11091-11100
Number of pages10
JournalACS applied materials & interfaces
Volume6
Issue number14
DOIs
Publication statusPublished - 23 Jul 2014
Externally publishedYes

Keywords

  • electrical properties
  • electromagnetic interference shielding
  • foam
  • percolation
  • polymer-matrix composites

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