Thermomechanical investigations of polyurea microspheres

Polyurea is a thermoset elastomer with a wide range of implementations in industrial and biomechanical applications. In the past two decades, bulk polyurea was heavily investigated under different environmental, operating, and loading conditions. The further exploitation of the superior thermomechanical properties of polyurea necessitates the exploration of smaller length scales, e.g., microscales and nanoscales. Thus, the objective of this research was to fabricate cross-linked polyurea microspheres, which was hypothesized to inherit some of the properties of the bulk polyurea. While the production yield was found to be low, the resulting polyurea microspheres exhibit the hallmark characteristics of their bulk counterpart. The microspheres, fabricated by a modified precipitation polymerization process, were examined with a scanning electron microscope showing the microspheres to have a highly textured surface morphology and an average diameter of 2.4 +/- 2.9 mu m. Using FTIR spectroscopy and a thermogravimetric analyzer, the microspheres were found to have inherited the overall chemical structure and hygrothermal properties of bulk polyurea. Using an atomic force microscope, the elastic modulus of the microspheres was found to be 114.75 +/- 40.71 MPa, four times stiffer than that of bulk polyurea. With such disparity of the elastic modulus, the polyurea microspheres can be used as a reinforcement phase in future polymer-polymer composites.

Automated summary

Cross-linked polyurea microspheres were successfully fabricated, exhibiting similar characteristics to bulk polyurea including highly textured surface morphology and superior mechanical properties. Analysis showed that the microspheres inherited the overall chemical structure and hygrothermal properties of bulk polyurea, with an elastic modulus four times stiffer than that of bulk polyurea.