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2 Materials Science Poland

2 2024

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Mechanical properties and quantum mechanical simulations of natural rubber composites with cerium complexes under aging conditions

100%

Li Y. , Liu Y. , Hao W. , Liu Z. , Zhang W. , Hu Y. , Wu J.

2024

tom Vol. 42, No. 1

158--170

Enhancing the service life of natural rubber (NR) products, including antioxidants, is crucial to prevent rubber degradation and enhance its oxidation resistance. Phenolic antioxidant 2246 and cerium complex of p-amino salicylic acid (PAS-Ce) are utilized as NR antioxidants. Numerous studies have qualitatively analyzed the antioxidant mechanisms of these compounds. Building upon this perspective, this study quantitatively assessed the protective mechanisms of these antioxidants by combining experimental data with molecular simulations. Additionally, it compared their impacts on the thermal oxidative aging performance of NR. The findings revealed that the PAS-Ce/NR system exhibited the highest mechanical performance retention following multiple days of thermal-oxidative aging. Analyzing the PAS-Ce/NR system through ATR-FTIR and DTA techniques demonstrated that it had the lowest C=O content after thermal-oxidative aging. Furthermore, calculating the activation energy required for thermal-oxidative aging decomposition using the Kissinger and FWO methods indicated that PAS-Ce/NR had the highest activation energy, suggesting superior inhibitory effects against thermal-oxidative aging. Quantum mechanical simulations also illustrated that the dissociation energy of the O-H bond in antioxidants 2246 and PAS-Ce was lower than that of the C-H bond in NR. However, PAS-Ce exhibited a quicker capture of radical species, effectively delaying the oxidation reaction rate of NR molecular chains and thus more efficiently inhibiting the aging process. These insights contribute significantly to comprehending the antioxidative mechanisms in NR aging.

Enhancing mechanical properties of PVC composites through surface composite modified calcium sulfate whiskers

84%

Zhang Y.-M. , Wu J. , Lu Q. , Qin S.-C. , Liu Z.-G. , Hu Y.-H. , Li J.-F. , Yang D.-H.

2024

tom Vol. 42, No. 3

55--71

To enhance the high-value utilization of industrial wastewater, this study used ammonium sulfate wastewater discharged from a rare earth plant as a raw material for producing anhydrous calcium sulfate whiskers (CSWs) through a hydrothermal method. Subsequently, the whiskers underwent modification using a C18H36O2–titanate coupling agent. The modification mechanism of CSW was investigated by comparing the surface contact angle before and after modification, along with characterization and analysis involving X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric-differential thermal analysis, and X-ray photoelectron spectroscopy. Finally, composite-modified calcium sulfate whiskers (CMCSWs) were incorporated into polyvinyl chloride (PVC) composites, and their mechanical properties were evaluated. The results indicated that at a modifier dosage of 15%, a modification time of 25 min, a modification temperature of 80°C, a stirring speed of 400 rpm, a drying temperature of 100°C, and a C18H36O2-to-titanate coupling agent compound ratio of 1:2, the contact angle reached 124.45°, and a nanoscale hydrophobic layer with a thickness of 15.63 nm was formed on the surface. Regarding PVC reinforcement, the tensile strength and elongation at the break of PVC composite with 15 parts of CMCSW added increased by 73 and 262%, respectively, compared to the material without CSW. This CSW serves as an innovative reinforcing agent for PVC composites. The study developed modified CSW with high hydrophobicity, offering theoretical insights for effectively modifying fiber-type whiskers and their reinforcement in PVC applications.