Preparation of expandable flake-graphites with different particle sizes and their flame-retardant application for polypropylene

Nhung Hac Thi, Thi Thu Hien Nguyen, Truong Cong Doanh, Do Thi Mai Huong, Tien Dat Doan, Ho Thi Oanh, Nguyen Duc Tuyen, Mai Ha Hoang
Author affiliations


  • Nhung Hac Thi Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam
  • Thi Thu Hien Nguyen Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam
  • Truong Cong Doanh Hanoi University of Industry, 298 Cau Dien, Bac Tu Liem, Ha Noi, Viet Nam
  • Do Thi Mai Huong University of Fire Prevention and Fighting, 243 Khuat Duy Tien, Thanh Xuan, Ha Noi, Viet Nam
  • Tien Dat Doan Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam
  • Ho Thi Oanh Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam
  • Nguyen Duc Tuyen Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam
  • Mai Ha Hoang Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Ha Noi, Viet Nam



Graphite, flake-graphite, flame retardant , polypropylene


Bisulfate intercalated graphites with different particle sizes were prepared by a chemically oxidative method using natural flaky graphites as raw materials. The morphology and structure of the expandable graphites were confirmed by Fourier transform infrared spectroscopy, X-ray diffraction patterns, and scanning electron microscope. The effect of the particle size on the expanded volume was also investigated. Expandable graphite with +100 mesh particle size (EG100) showed the highest expanded volume of 225 mL/g. Moreover, a combination of expandable graphite, red phosphorus (RP), and melamine cyanurate (MC) into a polypropylene (PP) matrix exhibited a synergistic flame retardant effect. The composite loading EG100, RP, and MC with a mass ratio of 1:1:1 and a total filler content of 18 wt.% achieved a UL94 V-0 rating and a limiting oxygen index (LOI) of 28.9 %. The effect of particle size of expandable graphite on the mechanical properties was also evaluated.


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How to Cite

N. Hac Thi, “Preparation of expandable flake-graphites with different particle sizes and their flame-retardant application for polypropylene”, Vietnam J. Sci. Technol., vol. 62, no. 1, pp. 78–91, Feb. 2024.