Developing a sustainable grease from jojoba oil with plant waste based nanoadditives for enhancement of rolling bearing performance.

This paper presents a novel grease from jojoba oil and activated carbon nanoparticles (ACNPs) extracted from banana peel waste. The raw jojoba oil and ACNPs are first characterized for structural properties. Samples of jojoba grease blended with 0.5 and 1.5 wt. % ACNPs are prepared and tested for physicochemical and tribological properties as compared to plain jojoba grease. Adding ACNPs to jojoba grease improves corrosion resistance from grade 2c to 1a while increasing the dropping point from 100 to 109 °C. ACNPs enhanced the viscosity of jojoba oil by up to 33% for testing temperature range of 40-100 °C. The load-carrying capacity of jojoba grease is increased by about 60% when blended with 1.5 wt.% ACNPs. The same blending decreased both the coefficient of friction and the wear scar diameter by 38% and 24%, respectively. A customized test rig is used to test the effectiveness of the grease samples in rolling bearing lubrication in terms of vibration levels and power consumption. The novel jojoba grease proved to show exceptional reductions power consumption reaching 25%. The vibration spectra show the absence of resonant peaks at high frequencies suggesting the capability of jojoba grease to form a stable full film lubrication.

Electrospraying of Bio-Based Chitosan Microcapsules Using Novel Mixed Cross-Linker: Experimental and Response Surface Methodology Optimization.

Chitosan microcapsules draw attention due to their biodegradability, biocompatibility, antibacterial behavior, low cost, easy processing, and the capability to be used for different applications. This study utilized the electrospraying technique for the chitosan microcapsules formulation. As a novel cross-linking agent, a mixture of oxalic acid and sodium phosphate dibasic was utilized as a collecting solution for the first time in the electrospraying of chitosan microcapsules. Scanning Electron Microscopy (SEM) was utilized to optimize the spherical morphology and size of the experimentally obtained microcapsules. The different parameters, including chitosan concentration, applied voltage, flow rate, and tip-to-collector (TTC) distance, affecting the microcapsules' size, sphericity, yield, and combined effects were optimized using Surface Responses Methodology (RSM). The Analysis of Variance (ANOVA) was utilized to obtain the impact of each parameter on the process responses. Accordingly, the results illustrated the significant impact of the voltage parameter, with the highest F-values and least p-values, on the capsule size, sphericity, and yield. The predicted optimum conditions were determined as 5 wt% chitosan concentration, 7 mL/h flow rate, 22 kV, and 8 cm TTC distance. The predicted responses at the optimized conditions are 389 µm, 0.72, and 80.6% for the capsule size, sphericity, and yield, respectively. While the validation of the model prediction was conducted experimentally, the obtained results were 369.2 ± 23.5 µm, 0.75 ± 0.04, and 87.3 ± 11.4%, respectively. The optimization process was successfully examined for the chitosan microcapsules manufacturing.

Monothetic Analysis and Response Surface Methodology Optimization of Calcium Alginate Microcapsules Characteristics.

Owing to bio-polymer's low-cost, environmental friendliness and mechanically stable nature, calcium alginate microcapsules have attracted much interest for their applications in numerous fields. Among the common production methods, the Electrospraying technique has shown a great potential due to smaller shape capsule production and ease of control of independent affecting parameters. Although one factor at a time (OFAT) can predict the trends of parameter effect on size and sphericity, it is inefficient in explaining the complex parameter interaction of the electrospray process. In the current study, the effects of the main parameters affecting on size and sphericity of the microcapsules using OFAT were optimized to attain calcium alginate microcapsules with an average diameter below 100 µm. Furthermore, we propose a statistical model employing the Surface Responses Methodology (RSM) and Central Composite Design (CDD) to generate a quadratic order linear regression model for the microcapsule diameter and sphericity coefficient. Experimentally, microcapsules with a size of 92.586 µm and sphericity coefficient of 0.771 were predicted and obtained from an alginate concentration of 2.013 w/v, with a flowrate of 0.560 mL/h, a needle size of 27 G and a 2.024 w/v calcium chloride concentration as optimum parameters. The optimization processes were successfully aligned towards formation of the spherical microcapsules with smaller average diameter of less than 100 µm, owing to the applied high voltage that reached up to 21 kV.