Structure and mechanical properties of micro and macro balloons: An overview of test techniques

A recently developed technique for obtaining uniaxial compression properties of individual microballoons by using a nanoindentation instrument equipped with a flat-ended tip of cylindrical or square cross-section will be described. A variety of useful parameters can be extracted from load vs. displacement curves such as: failure load, strain to failure, fracture energy, and a pseudo-stiffness or spring constant of each microballoon tested. The technique allows for a comparison of compression properties between individual microballoons of varying size or morphology. Other techniques for compression of both individual and large numbers of microballoons simultaneously, will be compared to this new test procedure. Two novel tensile test techniques will be reviewed. Additionally, the utility of complimentary test methods—including quantitative microscopy, SEM, interferometry, and nanoindentation—for characterizing the structure and properties of microballoons will be discussed.