Novel Polyurethane Elastomer Modified by Hybrid Shell Nano-/Microcapsules for Unique Self-Lubricating Behavior

Abstract

Self-lubricating microcapsules containing liquid paraffin as the core material were successfully synthesized with polyurethane (PU)/silica (SiO2) as the hybrid shell material using a sol–gel process and an interfacial polymerization method. The self-lubricating microcapsules were adopted as the filling matrix, which was compounded with the PU elastomer through an in situ polymerization method to improve the self-lubricity of the PU elastomer. The self-lubricating properties of the PU composites with different mass fractions of microcapsules have been characterized by a plastic sliding friction and wear tester. The particle size of spherical microcapsules is about 540 nm and it can effectively reduce the friction coefficient and wear of PU materials. When the concentration of self-lubricating microcapsules is 1.2 wt %, the PU composite has the lowest average friction coefficient of 0.301. The friction coefficient and wear of composite materials reduce by 64.8 and 66.7% compared to those of pure PU elastomers. Meanwhile, the PU composites show better thermal stability and mechanical properties. The thermal decomposition temperature, tensile strength, and elongation at break increased by 4.6, 69.1, and 30.8%, respectively, which extended the service life of the PU elastomer in special fields. Finally, the friction and wear mechanism of the PU composites was discussed with scanning electron microscopy images. It was confirmed that by virtue of the flexible structure of the microcapsule shell material and the release of core materials, the friction and wear mechanism of PU composites changes from severe fatigue wear and adhesive wear to slight adhesive wear.

Synthesis and self‐healing investigation of waterborne polyurethane based on reversible covalent bond

“…In addition, the peak at 7.86 ppm related to the hydrogen protons of CH═N is observed. 18 Meanwhile, in the 13 C NMR spectroscopy of the PA diol (Figure S3), the peaks at 144 ppm (C═N), 126 ppm (C C of benzene ring) and 167 ppm (C═O) could be found, respectively. These results indicated that PA diol had been successfully synthesized.…”

“…The 1 H NMR and 13 C NMR spectra were acquired on a German-Swiss Bruker DRX-400 superconducting 1 H NMR and 13 C NMR spectrometer with d 6 -DMSO as the solvent at 25 C. Element content was determinate by element tester (elementar varioel cube).…”

“…The chemical structure of PA diol was verified by 1 H NMR spectroscopy, 13 C NMR spectroscopy and FTIR spectra. The 1 H NMR spectroscopy of the PA diol is observed in Figure S2.…”

“…33,34 In addition, element content of PA diol presents the coexistence of N, C, H, and O without any other elements of impurity, and the actual content of organic elements in PA was close to the ratio designed in theory (Table S2). Based on the above structural characterization analysis ( 1 H NMR, 13 C NMR, FTIR and elemental analysis), PA diol was successfully prepared.…”

“…10,11 When the polymer material is damaged, the healing agents in the microcontainer will be released to the damaged site, and hence to repair the fracture. 12,13 Although this approach can exhibit self-healing capability, it inevitably has some defects such as irreversibility, complex operation and poor compatibility. Intrinsic self-healing is conferred by reversible reaction from dynamic non-covalent bond or covalent bond.…”