Abstract
Recently, great effort has been devoted to prepare various reinforce fillers to improve polymer performances, but ignoring the importance of raw polymer powders which are indispensable parts of hot-pressed polymer composites. Herein, we engineer raw polyimide (PI) powders with the assistance of polydopamine (PDA) in aqueous solutions. After the modification, polymer powders change from hydrophobic to hydrophilic, which makes it is possible to further modification of polymer powders in liquid phase. During the curing process of modified polymer powders, the partial dehydration of the catechol groups and crosslinking of PDA via C-O-C bonds are confirmed. Based on the features of PDA, a non-destructive mixing method is utilized to realize homogeneous dispersion of multi-walled carbon nanotubes (MWCNTs) in polymer matrix. In comparison with ball milling method, this way can preserve the integrated innate structure of MWCNTs effectively. Besides, by taking full advantage of the reducing and metal-coordination capability of PDA, Cu2+ is successfully loaded onto the surfaces of polymer powders. The related characterizations demonstrate that Cu2+in situ converts to metallic copper rather than copper oxide during the hot pressing process. The tribological properties of corresponding polymer composites are also studied. These results indicate that modifying polymer powders with PDA is multi-profit and presents practical application prospect.
Highlights
Polymer composites are among the most rapidly growing classes of materials that have been designed for various industrial applications because of their superior properties, such as easy manufacturability, low density, corrosion resistance, and excellent specific strength
Polymer powders changed from hydrophobic to hydrophilic
The analysis described above demonstrated that Cu2+ in situ converted to metallic copper rather than copper oxide during the hot pressing process and a well-dispersed state of reinforcing filler was obtained
Summary
Polymer composites are among the most rapidly growing classes of materials that have been designed for various industrial applications because of their superior properties, such as easy manufacturability, low density, corrosion resistance, and excellent specific strength. For the composites prepared by means of hot press molding technique, ball milling treatment of raw polymer powders, and reinforcing fillers is a common method to improve the dispersibility of nanoparticles, even though it may damage and chop the structure of nanoparticles to some extent [6]. Composites prepared by means of hot press molding technique generally relate to high curing temperature, for example it is 350 °C at least for PI. Under such condition, some metal ions will be oxidized to form corresponding metal oxides and well-dispersed nanoparticles can be realized. The tribological properties of PI composites prepared with modified polymer powders were further studied and the experimental results indicated the great application value of this method
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