Preparation of fluorescent calcium carbonate and visualization of its dispersion states in polypropylene

The dispersion states of fillers in the polymer matrix is an important factor to determine the properties of the polymer composites. Mastering the dispersion structure of inorganic minerals such as calcium carbonate in the polymer matrix is of great significance for the design of high performant polymer composites. Currently, due to the limitations of conventional electron microscope imaging capabilities, it is difficult to understand the internal dispersion structure of fillers in polymer composites comprehensively, regionally and stereoscopically. Here, we successfully embed the rare earth complex into the silica of the calcium carbonate surface to realize the fluorescent labeling of the calcium carbonate fillers. The fluorescent calcium carbonate exhibited broad excitation band ranging from 220 nm to 440 nm and showed bright red under ultraviolet light (365 nm). The two-dimensional dispersion states of the fillers at different depths in the polymer composite were obtained by the fluorescent imaging ability of laser scanning confocal microscope; these two-dimensional confocal images were further three-dimensionally reconstructed through Avizo Fire VSG software, and the spatial distribution of fillers in polymer composite was obtained without damage. This characterization method provides a new noninvasive method for studying the dispersion structure of fillers in polymers.