The study on the mechanical properties of PU/MF double shell self-healing microcapsules

The self-healing microcapsules can be buried in the coating to improve the anticorrosive ability.In this paper,self-healing microcapsules of polyurea(PU)/melamine resin(MF)double shell were prepared by in-situ polymerization and interfacial polymerization with isocyanate as the core material.Scanning electron microscope was used to observe the microcapsule morphology.The structures of microcapsules prepared with different chain extenders were characterized by Fourier transform infrared spectroscopy.The micromanipulation system was used to loading–holding,loading–unloading and loading to rupture individual microcapsules,so as to explore the mechanical properties of microcapsules.The Young’s modulus corresponding to microcapsules was calculated by mathematical model fitting.The self-healing properties of microcapsule coating were characterized by optical microscope.The experimental results showed that the microcapsule shell prepared under optimized conditions had a complete morphology and good mechanical properties.The microcapsule was in the elastic deformation stage under small deformation,and the plastic deformation stage under large deformation.The Young’s modulus range of microcapsules was 9.29–14.51 MPa,and the corresponding Young’s modulus could be prepared by adjusting the process.The surface crack of the coating containing microcapsule could heal itself after48 h in a humid environment.

Effect of surfactant on zeta potential and rheology behavior of methylene bis (thiocyanate) suspension concentrate

Methylene bis(thiocyanate)(MBT) is insoluble in water, so suspension concentrate(SC) of MBT is extremely relied on surfactants. In this paper, SC of MBT was prepared with wet-grinding technology, and the effect of surfactants,such as Morwet D425(D425) and Morwet EFW(EFW)(two kinds of dispersant), on the Zeta potential and rheology behavior of MBT SC were investigated. The results showed that the Zeta potential absolute value of MBT SC increased with the increasing content of D425, and it decreased with the increasing content of EFW at acidic solution(pH = 4.5). In the combination system of D425 and EFW, Zeta potential of MBT SC decreased first and then increased with the increasing content of EFW. The relationship between shear rate(γ) and viscosity(η) was studied according to Herschel–Bulkley model: η = η0+ k/γ, and the relationship between shear rate(γ) and shear force(τ) was investigated according to:τ = τ0+Kγ~n. It was revealed that the mixed fluid belonged to Yield Pseudoplastic Fluid.

Performance analysis and optimization of free cooling strategies for a liquid-cooled data center

The increasing power density of IT electronics and the enormous energy consumption of data centers lead to the urgent demand for efficient cooling technology.Due to its efficiency and safety,liquid-cooled heat sink technology may gradually replace air-cooled technology over time.With the ambient or higher water supply temperature,the liquid-cooled technology shortens the operating time of the chiller and improves its coefficient of performance,while the pump power consumption may increase for satisfying the constant cooling capacity.Therefore,it is significant to study the optimal water supply temperature to achieve energy-efficient operation of data centers.A virtual 30.1 kW data center is considered as the case,the liquid-cooled system is constructed with a combination of innovative manifold microchannel heat sink with oblique fins and indirect evaporative cooling technology to minimize energy consumption.A hybrid thermal management model integrating the heat dissipation model and the power consumption model is established by TRNSYS and FLUENT software.To the highest chip-safe operating temperature premise,the energy performance is analyzed under various water supply temperatures in Guangzhou.The result shows that only 21.5-hour mechanical cooling is needed with the 30℃server inlet temperature throughout the year.And the minimized power consumption occurs with the constant 29℃server inlet temperature.Moreover,the temperature adaptive control strategy(TACS)is adopted to test the cooling system power consumption under different regulation frequencies,and the by-week TACS can achieve another 11.5%energy saving than the minimum power consumption of the constant temperature control strategy.