Bubble inflation method for dispersing nanoparticles in polymers

A bubble inflation method for dispersing nanoparticles in polymers and its application in epoxy/nano-SiO₂ composite preparation were presented. The method injected nanopartciles into polymer melt (solution) by compressed gas in terms of particle-gas jet. Then, the particle-gas jet turned into particle included gas bubbles embedded in the melt (solution). Nanoparticles were dispersed in polymers with the stretching effect induced by bubble inflation in polymer melt (solution). Theoretical analysis and numerical simulation were carried out to enhance understanding of the dispersion mechanism. The effects of viscous drag caused by ultrahigh stretch and cohesive force of interaction, which comprised of short-range van der Waals attractive force and Born repulsive force, were considered in the analysis. According to theoretical analysis, when the bubble expands, the stretch rate of the epoxy resin solution on the bubble wall can reach 10⁵ s^-1. The viscous drag caused by ultrahigh stretch can destroy nanoparticles agglomerate and disperse nanoparticles in polymers uniformly. The epoxy/nano-SiO₂ composite prepared by the proposed method was investigated with transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The result showed that the size of SiO₂ dispersed in epoxy resin was about 15-30 nm, and glass transition temperature was 18°C higher than that of the epoxy/SiO₂ composite obtained by high speed stirring.