Search

As a cost‐effective and environmentally friendly natural mineral, cryptocrystalline graphite (CG) is applied in rubber materials and its performance has been evaluated. In this work, the filler dispersion and mechanical and tribological properties of carboxylated acrylonitrile butadiene rubber (XNBR)/CG composites by different preparation methods were studied. XNBR/CG composites prepared by latex blending (XNBR/CG‐L) exhibited better mechanical and tribological performance, higher toughness, and lower heat build‐up than those prepared by mechanical blending (XNBR/CG‐M). These differences were ascribed to the filler dispersion degree, filler amount and dispersed size, and also filler–rubber interfacial interaction. Adding CG was conducive to improving the stability of the friction coefficient and reduced the wear rate via the formation of graphite lubricant and transfer films. The tribological performance of XNBR/CG‐L was superior to that of XNBR/CG‐M because of the improved tensile strength, tear resistance, and toughness as well as lower temperature rise. Scanning electron microscopy (SEM) and optical microscope observation showed a smoother worn surface, less and smaller wear debris of XNBR/CG‐L, and a more uniform transfer film on the steel counterpart surface. The relevant results provided new insight into the performance and structural design of CG/rubber composites. [ABSTRACT FROM AUTHOR]

Fluorographene (FG) with layer numbers of 3–4 was successfully prepared through facile microwave‐assisted liquid phase exfoliation of raw graphite fluoride (GrF). The raw GrF and the as‐prepared FG were then directly incorporated into polyamide 66 (PA66) by melt processing without using any surfactants. Microstructural, mechanical and tribological properties of the prepared PA66 composites were investigated. Various characterization results showed that both GrF and FG, as novel solid lubricants, can effectively improve the mechanical and anti‐wear performances of the PA66 matrix. It was also found that FG is better at improving mechanical properties and reducing the friction of PA66 than GrF at low concentrations owing to the large surface–volume ratio. The addition of 0.5 wt% FG into PA66 exhibits a ca 13% increase in tensile modulus, ca 5% increase in tensile strength, ca 18% reduction in coefficient of friction (COF) and ca 43% reduction in wear rate. However, at relatively high concentrations, such as 1.0 wt%, GrF shows a better reinforcement effect than FG owing to a uniform dispersion of GrF in the PA66 matrix. The addition of 1.0 wt% GrF into PA66 exhibits a ca 18% increase in tensile modulus, ca 5% increase in tensile strength, ca 37% reduction in COF and ca 46% reduction in wear rate. Wear tests also show that the excellent wear resistance of the PA66 composites is due to the improved mechanical properties and the lubrication of GrF and FG between the worn surfaces. Our current work demonstrates the tremendous potentials of fluorinated carbon materials for enhancing mechanical and anti‐wear properties of polymeric materials. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: Si3N4/Ag composites were firstly prepared through SPS technology, using Si3N4 and AgNO3 as raw materials. Utilizing the coordination bonding of Ag+ ions with nitrogen atoms of Si3N4, in situ generated Ag particles about 1 μm were tightly anchored on Si3N4 surface, thereby preventing the outflow of silver during sintering process. Meanwhile, smaller silver particles about 20 nm were located at the grain boundaries of Si3N4, which effectively improved the mechanical and tribological properties of Si3N4‐based composites. Finally, the Si3N4/Ag composites reinforced by Ag particles showed a friction coefficient of 0.48 ± 0.01, wear rate of 1.79 × 10−6 mm3 N−1 m−1 and fracture toughness of 7.05 ± 0.2 MPa m1/2, respectively. [ABSTRACT FROM AUTHOR]

A self‐assembling molecule, n‐octadecane phosphate, is successfully synthesized and used to modify the surface property of carbon nanofibers (CNFs). Both untreated CNFs (CNFs(u)) and treated CNFs (CNFs(t)) are incorporated in polyimide (PI) as filler to study the interfacial­property‐determined thermal, mechanical, and tribological properties of their corresponding nanocomposites. At room temperature, the mechanical properties of PI/CNFs(t) including elongation‐to‐break, tensile strength, bending strength, and impact strength are remarkably improved by 150%, 29.4%, 26.7%, and 183%, respectively, in comparison with the PI/CNFs(u) composites. At 150 °C, the enhancement of the elongation‐to‐break reaches 250%, while the tensile and flexural‐strength enhancement reduce to 2.8% and 20.4%. In addition, the tribological properties of PI/CNFs(t) composite are also improved due to the better interfacial interaction between the filler and the matrix. Microstructure analysis of the fracture surface directly reveals the better dispersion quality of CNFs(t) in PI and superior interfacial adhesion with the introduced assembling layer. [ABSTRACT FROM AUTHOR]