Use Of Hollow Microspheres Research Articles

Shrinkage stress of thermal cured epoxy resin reduced by addition of functional hollow microspheres

The shrinkage stress of thermal cured epoxy resin developed during curing process can cause low film adhesion strength, low dimensional accuracy and even coating films warping which severely reduce service lifetime of the coating. Therefore, there is growing interest in developing effective means to reduce the shrinkage stress. In this paper, we report the use of hollow microspheres prepared from Pickering emulsion droplets in the thermal cured epoxy resin formulations and the shrinkage stress due to resin solidification is monitored in real time to reveal the effect of hollow microspheres upon shrinkage stress of the resin. Epoxy group functionalized silica nanoparticles from the Stöber method are used as Pickering emulsion stabilizer and the emulsion droplets are polymerized to obtain hollow microspheres with controllable mechanical properties and surface morphologies. Due to the reactivity of the hollow microspheres, they can be incorporated into the epoxy resin coatings and the shrinkage stress is thus reduced with the addition of hollow microspheres. It is revealed that the shrinkage stress is reduced from 195.79 kPa to 140. 40 kPa with the addition of 12 wt% hollow microspheres and polydisperse hollow microspheres are more effective in shrinkage stress reduction. As the modulus of the hollow microspheres is reduced and elasticity is increased, the shrinkage stress of the coating film is also reduced from 181. 37 kPa to 157.42 kPa which is not achieved by hollow glass microspheres. The hollow microspheres are well dispersed in the resin matrices which doesn't undermine the basic mechanical properties of the coating such as adhesion and surface hardness.

Hierarchical Porous Interlocked Polymeric Microcapsules: Sulfonic Acid Functionalization as Acid Catalysts

Owing to their unique structural and surface properties, mesoporous microspheres are widely applied in the catalytic field. Generally, increasing the surface area of the specific active phase of the catalyst is a good method, which can achieve a higher catalytic activity through the fabrication of the corresponding catalytic microspheres with the smaller size and hollow structure. However, one of the major challenges in the use of hollow microspheres (microcapsules) as catalysts is their chemical and structural stability. Herein, the grape-like hypercrosslinked polystyrene hierarchical porous interlocked microcapsule (HPIM-HCL-PS) is fabricated by SiO2 colloidal crystals templates, whose structure is the combination of open mouthed structure, mesoporous nanostructure and interlocked architecture. Numerous microcapsules assembling together and forming the roughly grape-like microcapsule aggregates can enhance the structural stability and recyclability of these microcapsules. After undergoing the sulfonation, the sulfonated HPIM-HCL-PS is served as recyclable acid catalyst for condensation reaction between benzaldehyde and ethylene glycol (TOF = 793 h−1), moreover, exhibits superior activity, selectivity and recyclability.

Preparation of Lightweight Porcelain Body by Mixing Shirasu-Balloon.

Lightweight porcelain has been developed by forming closed pores in the porcelain body through the use of hollow micro-spheres made from volcanic ash. These micro-spheres are called Shirasu-balloon. A green for lightweight porcelain was prepared by mixing the Shirasu-balloon with the green by hand. Experimental specimens were obtained by pressing the green, and drying and firing it at temperatures from 1160 to 1400°C for 2h in air. Bulk density, liner shrinkage, and flexural strength were measured, and the morphology and structure of the Shirasu-balloon in the porcelain bodies were observed using SEM. When the Shirasu-balloon was mixed with green of less than 10 mass%, the bulk density was reduced from 2.38 to 1.77 (×103kg·m-3) along the ideal value. The Shirasu-balloon was deformed and was shrunk over 13% by the addition of the Shirasu-balloon at more than 20mass%. The density reduction did not progress ideally beyond this point and approached the saturation value. When the mixing ratio was less than 10 mass%, the reduction of the flexural strength of the lightweight porcelain was slightly suppressed. This might be explained by the residual stress formed in the porcelain body.