Polypropylene waste significantly contributes to environmental pollution due to its low biodegradability. Numerous experiments have shown that laser irradiation of polymers can lead to the conversion of laser-induced graphene (LIG). In this paper, the LIG formation process in polypropylene (PP), polydimethylsiloxane (PDMS), and polypropylene/polydimethylsiloxane (PP/PDMS) systems in a vacuum environment was simulated using molecular dynamics. The LIG yields and carbon network sizes of the systems in oxygen and vacuum environments at different temperatures were analyzed to determine the optimal temperature for upgrading PP to LIG. It was observed in all three systems that the LIG structure was formed. The structure was composed not only of six-membered carbon rings, but also of five-membered and seven-membered rings, resulting in out-of-plane fluctuations and bending. A vacuum environment and high temperature promote LIG formation with high yield, large size, and minimal defects. The current study provides theoretical guidance for optimizing the laser graphene process for PP assisted with PDMS in a vacuum environment and helps to understand the mechanism underlying the conversion from polyolefins to graphene under CO2 laser at the atomic level.

This study aims to develop the designs and patterns of yoga tops that are better adjusted to suit females in their 30s and 40s. After conducting a comparative analysis of three different popular yoga garments, one yoga top currently on the market was selected. Subsequently, a fit evaluation was conducted on Trail 1-garment α, which was developed body analysis performed based on selected yoga top C, followed by the production of the Trial 2 garment after making adjustments according to the comparative observation results. Based on these results, garment C with the longest top length was evaluated as the best. The results of the evaluation of appearance and fit conducted of Trial 1-garment α compared to those of C showed that Trial 1-garment α was superior in both evaluations. Trial 2-garment β was produced after making improvements on Trial 1-garment α and then placed under identical comparative evaluation condition as Trial 1-garment α. Results showed a significant improvement compared to Trial 1-garment α, and the Trial 2 garment with an additional arm pattern was shown to be superior in shoulder strap width stability, shoulder strap pressure, chest stability, degree of waist pressure, waist comfort, general fitting, and supportiveness.

In this study, nitric acid oxidation with varied treatment temperature and time was conducted on the surfaces of polyacrylonitrile- based ultrahigh modulus carbon fibers. Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and surface tension/dynamic contact angle instruments were used to investigate changes in surface topography and chemical functionality before and after surface treatment. Results showed that the nitric acid oxidation of ultrahigh modulus carbon fibers resulted in decreases in the values of the crystallite thickness Lc and graphitization degree. Meanwhile, increased treating temperature and time made the decreases more obviously. The surfaces of ultrahigh modulus carbon fibers became much more activity and functionality after surface oxidation, e.g., the total surface energy of oxidized samples at 80 °C for 1 h increased by 27.7% compared with untreated fibers. Effects of surface nitric acid oxidation on the mechanical properties of ultrahigh modulus carbon fibers and its reinforced epoxy composites were also researched. Significant decreases happened to the tensile modulus of fibers due to decreased Lc value after the nitric acid oxidation. However, surface treatment had little effect on the tensile strength even as the treating temperature and processing time increased. The highest interfacial shear strength of ultrahigh modulus carbon fibers/epoxy composites increased by 25.7% after the nitric acid oxidation. In the final, surface oxidative mechanism of ultrahigh modulus carbon fibers in the nitric acid oxidation was studied. Different trends of the tensile strength and tensile modulus of fibers in the nitric acid oxidation resulted from the typical skin–core structure.