Microstructure and Properties of Polytetrafluoroethylene Composites Modified by Carbon Materials and Aramid Fibers

Abstract

Polytetrafluoroethylene (PTFE) is polymerized by tetrafluoroethylene, which has high corrosion resistance, self-lubrication and high temperature resistance. However, due to the large expansion coefficient, high temperature will gradually weaken the intermolecular bonding force of PTFE, which will lead to the enhancement of permeation absorption and the limitation of the application range of fluoroplastics. In order to improve the performance of PTFE, the modified polytetrafluoroethylene, filled by carbon materials and aramid fiber with different scales, is prepared through the compression and sintering. Moreover, the mechanical properties and wear resistance of the prepared composite materials are tested. In addition, the influence of different types of filler materials and contents on the properties of PTFE is studied. According to the experiment results, the addition of carbon fibers with different scales reduces the tensile and impact properties of the composite materials, but the elastic modulus and wear resistance are significantly improved. Among them, the wear rate of 7 μm carbon fiber modified PTFE has decreased by 70%, and the elastic modulus has increased by 70%. The addition of aramid fiber filler significantly reduces the tensile and impact properties of the composite, but its elastic modulus and wear resistance are significantly improved. Among them, the wear rate of the modified composite material with 3% alumina particles and 5% aramid pulp decreased by 68%, and the elastic modulus increased by 206%.

Experimental and Analytical Investigations on Tribological Properties of PTFE/AP Composites

“…The interfacial friction temperature of pure PTFE samples rises higher, and the increase in carbon and fluorine contents proves that the interfacial reaction intensifies. In comparison (Table 2), it has been found that both friction coefficient and wear rate of PPTA/AP composites obtained in this study are similar or lower than those according to previous investigations [13,19,33].…”

“…(Mpa) COF Wear Rate (10 −14 m 3 /N•m) PTFE + 20%glass fiber [7] 19.3 0.19 1.1 PTFE + 20% Carbon fibers (D = 7 μm) [13] 18.99 0.418 0.021 PTFE + 20% Basalt fibers (D = 9 μm) [13] 15.68 0.211 0.124 PTFE + 20% Serpentine + 10% UHMWPE fibers [18] 0.316 0.12 In comparison (Table 2), it has been found that both friction coefficient and wear rate of PPTA/AP composites obtained in this study are similar or lower than those according to previous investigations [13,19,33]. PTFE + 20%glass fiber [7] 19.3 0.19 1.1 PTFE + 20% Carbon fibers (D = 7 µm) [13] 18.99 0.418 0.021 PTFE + 20% Basalt fibers (D = 9 µm) [13] 15.68 0.211 0.124 PTFE + 20% Serpentine + 10% UHMWPE fibers [18] 0.316 0.12 PTFE + 3% Aramid fibers (D = 12 µm) [19] 0.703 0.82 PTFE + 2% Carbon fibers (D = 7 µm) [33] 18.74 0.174 60.4 PTFE + 2% Carbon fibers (D= 200 nm) [33] 21.87 0.151 58.2 PTFE + 2% Multiwalled carbon nanotube [33] 11.19 0.159 18.3 PTFE + 15% Potassium titanate whiskers [34] 23.7 0.15 0.12 PTFE + 15% Carbon fibers (D = 9 µm) [34] 20.18 0.121 0.23…”

“…The absorption peak at 2927 cm −1 represents the stretching vibration peak of saturated C-H bond. C=C stretching vibration peak at 1633 cm −1 , C-H asymmetric stretching vibration peak at 1212 cm −1 and 1153 cm −1 , and C-F bond at 639 cm −1 and 503 cm −1 are typical PTFE peaks [33]. The stretching vibration peak of amide A band from the N-H bond is represented at 3340 cm −1 in Figure 7b.…”

Mechanical Behavior and Morphological Study of Polytetrafluoroethylene (PTFE) Composites under Static and Cyclic Loading Condition

“…The average length of the lamellas was about 1 µm, and the thickness of the single crystals was about 0.01 µm. The lamellar structure of PTFE composites has already been described in the literature [ 23 ]. Cyclic loading changes the crystallographic structure of composites compared to static compression.…”

“…The higher the filler content, the more space for fibril nucleation. Due to the previously described chemical structure of PTFE, which practically prevents the formation of chemical bonds with other compounds, it can be said that the resulting microfibrils counteract PTFE against tearing [ 23 ]. This essence is confirmed by mechanical tests which show that with the increase of the filler, the ability of composites to plastic deformation decreases.…”