Airless tires are essential for enhancing the safety,reliability,and convenience of maintenance of electric bicycles.Polyurethane(PU)is considered a promising candidate for such applications owing to its versatile pro...Airless tires are essential for enhancing the safety,reliability,and convenience of maintenance of electric bicycles.Polyurethane(PU)is considered a promising candidate for such applications owing to its versatile properties.However,their use is limited by insufficient heat resistance and excessive dynamic heat generation under cyclic loading.In this study,star-shaped trifunctional polypropylene glycerol(PPG3)was incorporated into conventional poly(tetramethylene glycol)(PTMG)and 4,4'-methylenediphenyl diisocyanate(MDI)-based systems to construct microporous star-shaped casting polyurethanes(SCPU),with water serving as a green foaming agent.Unlike conventional small-molecule trifunctional crosslinkers that create junctions within hard segment domains,PPG3 introduces long flexible arms between the hard segments,anchoring the crosslinking points at its molecular core.The large steric hindrance of PPG3 effectively suppresses soft segment crystallization and lowers the degree of microphase separation,whereas the crosslinked network restricts chain mobility,thereby reducing dynamic heat generation.These structural features also enhance the heat resistance,yielding a softening temperature of 183℃,which is 30.9%higher than that of polyurethane without PPG3.When applied to airless tires by casting SCPU into rubber treads,the fabricated hybrid airless tires achieved a rolling distance of over 3000 km under a load of 65 kg at 25km/h without structural failure,satisfying practical performance requirements.This strategy offers a simple,solvent-free,and environmentally friendly process,underscoring the potential of SCPU for scalable production of high-performance airless tires.展开更多
This paper presents experimental and numerical studies on spray painting processes by using airless spray guns for ship painting. A computational fluid dynamics code was applied to calculate the flow field and the dro...This paper presents experimental and numerical studies on spray painting processes by using airless spray guns for ship painting. A computational fluid dynamics code was applied to calculate the flow field and the droplet trajectories. Droplet size distributions and droplet velocities as necessary inlet characteristics for the simulations were experimentally obtained using a Spraytec Fraunhofer type particle sizer and laser-Doppler anemometry. Effects of shoreline winds and painting distance on the transfer efficiency and on the paint film thickness distributions on the target were numerically studied.展开更多
Airless spray painting, widely adopted for its efficiency and cost-effectiveness, generates a significant amount of airborne paint particles that contribute to air pollution and pose health risks to workers and nearby...Airless spray painting, widely adopted for its efficiency and cost-effectiveness, generates a significant amount of airborne paint particles that contribute to air pollution and pose health risks to workers and nearby residents. In this study, a paint particle dispersion reduction device (PPDRD) utilizing an axial cyclone separator and a high efficiency particulate air (HEPA) filter was designed and evaluated to minimize the dispersion of paint particles during airless spray applications. The cyclone separator captured larger paint particles through centrifugal force, while the HEPA filter effectively removed smaller particles that escaped the cyclone separator. Computational fluid dynamics (CFD) simulations were conducted to optimize key design parameters, including the number and height of guide vanes and suction flow rate. Lab-scale and field experiments demonstrated that the PPDRD significantly reduced airborne paint particles, with respirable particles (4 μm or smaller) decreasing by 50–80 % depending on particle size, while maintaining coating quality. These findings indicate that the PPDRD effectively mitigates the inhalation risks associated with hazardous paint aerosols, providing a practical solution for improving workplace safety and environmental compliance. This technology is expected to be widely applicable in exterior building painting, shipbuilding, and the automotive industry.展开更多
基金financially supported by the National Natural Science Foundation of China(No.52303063)Hubei Provincial Department of Education Guided Scientific Research Project(No.B2024056)。
文摘Airless tires are essential for enhancing the safety,reliability,and convenience of maintenance of electric bicycles.Polyurethane(PU)is considered a promising candidate for such applications owing to its versatile properties.However,their use is limited by insufficient heat resistance and excessive dynamic heat generation under cyclic loading.In this study,star-shaped trifunctional polypropylene glycerol(PPG3)was incorporated into conventional poly(tetramethylene glycol)(PTMG)and 4,4'-methylenediphenyl diisocyanate(MDI)-based systems to construct microporous star-shaped casting polyurethanes(SCPU),with water serving as a green foaming agent.Unlike conventional small-molecule trifunctional crosslinkers that create junctions within hard segment domains,PPG3 introduces long flexible arms between the hard segments,anchoring the crosslinking points at its molecular core.The large steric hindrance of PPG3 effectively suppresses soft segment crystallization and lowers the degree of microphase separation,whereas the crosslinked network restricts chain mobility,thereby reducing dynamic heat generation.These structural features also enhance the heat resistance,yielding a softening temperature of 183℃,which is 30.9%higher than that of polyurethane without PPG3.When applied to airless tires by casting SCPU into rubber treads,the fabricated hybrid airless tires achieved a rolling distance of over 3000 km under a load of 65 kg at 25km/h without structural failure,satisfying practical performance requirements.This strategy offers a simple,solvent-free,and environmentally friendly process,underscoring the potential of SCPU for scalable production of high-performance airless tires.
文摘This paper presents experimental and numerical studies on spray painting processes by using airless spray guns for ship painting. A computational fluid dynamics code was applied to calculate the flow field and the droplet trajectories. Droplet size distributions and droplet velocities as necessary inlet characteristics for the simulations were experimentally obtained using a Spraytec Fraunhofer type particle sizer and laser-Doppler anemometry. Effects of shoreline winds and painting distance on the transfer efficiency and on the paint film thickness distributions on the target were numerically studied.
基金the“Reduction Management Program of Fine Dust Blind-Spots”and supported by the Ministry of Environment as part of the Korea Environmental Industry and Technology Institute(grant No.2020003060010)supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(grant No.RS-2024-00346834).
文摘Airless spray painting, widely adopted for its efficiency and cost-effectiveness, generates a significant amount of airborne paint particles that contribute to air pollution and pose health risks to workers and nearby residents. In this study, a paint particle dispersion reduction device (PPDRD) utilizing an axial cyclone separator and a high efficiency particulate air (HEPA) filter was designed and evaluated to minimize the dispersion of paint particles during airless spray applications. The cyclone separator captured larger paint particles through centrifugal force, while the HEPA filter effectively removed smaller particles that escaped the cyclone separator. Computational fluid dynamics (CFD) simulations were conducted to optimize key design parameters, including the number and height of guide vanes and suction flow rate. Lab-scale and field experiments demonstrated that the PPDRD significantly reduced airborne paint particles, with respirable particles (4 μm or smaller) decreasing by 50–80 % depending on particle size, while maintaining coating quality. These findings indicate that the PPDRD effectively mitigates the inhalation risks associated with hazardous paint aerosols, providing a practical solution for improving workplace safety and environmental compliance. This technology is expected to be widely applicable in exterior building painting, shipbuilding, and the automotive industry.
