Rheo-NMR velocimetry was used to study shear banding of a 6 wt.% cetylpyridinium chloride (CPCl) worm-like micelle solution under shear startup conditions with and without pre-shear. 1D velocity profiles across the fluid gap of a concentric cylinder Couette shear cell were measured every 1 s following shear startup for four different applied shear rates within the stress plateau. Fitting of the velocity profiles allowed calculation of the shear banding characteristics (shear rates in the high and low shear band, the interface position and apparent slip at the inner rotating wall) as the flow transitioned from transient to steady state regimes. Characteristic timescales to reach steady state were obtained and found to be similar for all shear banding characteristics. Timescales decreased with increasing applied shear rate. Large temporal fluctuations with time were also observed and Fourier transform of the time and velocity autocorrelation functions quantified the fluctuation frequencies. Frequencies corresponded to the elastically driven hydrodynamic instabilities, i.e. vortices, that are known to occur in the unstable high shear band and were dependent upon both applied shear rate and the pre-shear protocol.
The adhesive properties of a self-prepared bio-based epoxy resin with native cellulose nanocrystals (CNCs) are evaluated in this article. The porosity of actual CNCs is high. The most promising finding is the acquisition of high tensile modulus. The addition of CNC composites significantly increased the tensile modulus at lower wt.%, and the maximum crystallinity of CNCs was obtained. Bearing in mind the advantages of CNCs, scanning electron microscopy (SEM) showed a uniform distribution of concentrated CNCs. Clusters were formed at higher CNCs ratios, and the composite matrix content with high CNCs produced good expansion, low crystallinity, and increased elongation. Our analysis showed that the original CNCs were more evenly distributed in the self-prepared bio-based epoxy resin, which enhanced transformation, supported by improved dispersion of native CNCs. The presence of native CNCs greatly improved and enhanced the bonding performance of the bio-based epoxy resin in the interface area. Enhancing the mechanical properties of native CNCs has broad application prospects in environmental areas. This suggests that the widespread use of native CNCs in environmental engineering applications is feasible, especially in terms of adhesives properties.
To obtain uniform and controllable material removal on hard and brittle materials, a novel processing technology with functionally graded lapping and polishing plate (FG-LPP) was proposed. Taking application of particles/rubber composites and adjustable contact stress of workpiece as key point, the abrasive particles and rubber were mixed with different mass ratios; then the FG-LPP was formed with characteristics of required quasi-continuous distribution of Young’s modulus in the radial direction by two-step processing technique. The properties of Young’s modulus, loss factor, and glass transition temperature of different particles/rubber composites were tested and calculated. Through comparison and analysis, silicon carbide (SiC)/chloroprene rubber (CR) composites are the suitable application object of FG-LPP. Moreover, by laser particle size analyzer, scanning electron microscope, and X-ray diffraction, the size distribution of abrasive particles, micromorphology of particles/rubber composites and their phase composition were tested respectively to better reveal the structure and properties. The test results indicate that under the action of ZnO and MgO, CR undergoes a vulcanization reaction gently and forms a spatial three-dimensional structure. Thus, it helps to increase the intermolecular distance and weaken the intermolecular forces because the NO is easy to enter the CR molecules, which improves the intermiscibility between SiC and CR.