Microencapsulation of phase change materials(Micro PCMs) has been paid special attention because of their extensive applications in saving and releasing energy. Micro PCMs containing paraffin with a melting point of ...Microencapsulation of phase change materials(Micro PCMs) has been paid special attention because of their extensive applications in saving and releasing energy. Micro PCMs containing paraffin with a melting point of 55 ℃ in polystyrene-divinylbenzene(P(St-DVB)) were prepared by suspension-like polymerization. The characterization of microcapsules by FTIR, DSC and TG proved that paraffin had been successfully encapsulated and the proportion of encapsulated paraffin was 49.8%—58.5%. The effects of polyvinylpyrrolidone(PVP) with different molecular weights serving as the suspension stabilizer were investigated in detail. The results illustrated that the type of PVP had a significant influence on the particle size of Micro PCMs. The average diameter of Micro PCMs decreased with an increasing molecular weight of PVP. Moreover, the crosslinker-postaddition method was adopted in this study to improve the morphology of P(St-DVB) Micro PCMs. SEM images showed that when the DVB was added at the 2nd hour of polymerization the morphology of obtained P(St-DVB) Micro PCMs exhibited good sphericity since it could avoid the influence of cross-linker agent during the nucleation period.展开更多
In order to use micro ultrasonic bonding technique to package polymer microfluidic chips, an auxiliary microstructure named micro energy director is designed and fabricated. The hot embossing process for PMMA （ polym...In order to use micro ultrasonic bonding technique to package polymer microfluidic chips, an auxiliary microstructure named micro energy director is designed and fabricated. The hot embossing process for PMMA （ polymethyl methacrylate） substrates with both concave micro channel and convex micro energy director for ultrasonic bonding is studied. The embossing processes with different embossing temperatures are simulated using Finite Element Method （FEM）. The optimized parameters are： the embossing temperature of 135 ℃ , holding time of 200 s, and the embossing pressure of 1.65 MPa. The experimental results show that the replication error between experiments and simulations is less than 2% and the replication accuracy of the microstrueture is more than 96%. The study offers a method for quick optimizing parameters for hot embossing both concave and convex microstructures.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 20973022 and 11472048)the State Key Laboratory of Catalytic Materials and Reaction Engineering (RIPP, SINOPEC)
文摘Microencapsulation of phase change materials(Micro PCMs) has been paid special attention because of their extensive applications in saving and releasing energy. Micro PCMs containing paraffin with a melting point of 55 ℃ in polystyrene-divinylbenzene(P(St-DVB)) were prepared by suspension-like polymerization. The characterization of microcapsules by FTIR, DSC and TG proved that paraffin had been successfully encapsulated and the proportion of encapsulated paraffin was 49.8%—58.5%. The effects of polyvinylpyrrolidone(PVP) with different molecular weights serving as the suspension stabilizer were investigated in detail. The results illustrated that the type of PVP had a significant influence on the particle size of Micro PCMs. The average diameter of Micro PCMs decreased with an increasing molecular weight of PVP. Moreover, the crosslinker-postaddition method was adopted in this study to improve the morphology of P(St-DVB) Micro PCMs. SEM images showed that when the DVB was added at the 2nd hour of polymerization the morphology of obtained P(St-DVB) Micro PCMs exhibited good sphericity since it could avoid the influence of cross-linker agent during the nucleation period.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50975037)the State Key Development Program for Basic Research of China(Grant No.2011CB013105).
文摘In order to use micro ultrasonic bonding technique to package polymer microfluidic chips, an auxiliary microstructure named micro energy director is designed and fabricated. The hot embossing process for PMMA （ polymethyl methacrylate） substrates with both concave micro channel and convex micro energy director for ultrasonic bonding is studied. The embossing processes with different embossing temperatures are simulated using Finite Element Method （FEM）. The optimized parameters are： the embossing temperature of 135 ℃ , holding time of 200 s, and the embossing pressure of 1.65 MPa. The experimental results show that the replication error between experiments and simulations is less than 2% and the replication accuracy of the microstrueture is more than 96%. The study offers a method for quick optimizing parameters for hot embossing both concave and convex microstructures.
