High strain rate elastomeric polymers such as polyurea are light weight coating options to vastly enhance the blast and ballistic response of armor. While these explosion resistant coatings have been in use for over 15 years, their design is still largely trial and error. This reliance on trial and error is due to the complexity of the coupled high strain rate and high-pressure response, which itself has been tied to a multitude of dispersion and dissipation mechanisms. Polyurea is a phase-segmented material in which the hard domains are composed from stacked aggregates of hydrogen bonded rigid polymer components and the soft domains are primarily composed of initially unoriented flexible polymer chains. These features are best measured experimentally though x-ray scattering – wide angle x-ray scattering (WAXS) that reveals the crystalline structure and orientation of the aggregates and small angle x-ray scattering (SAXS) that reveals inter-domain spacing. Here we will present the microstructural evolution of polyurea P1000 and P650 under cyclic hydrostatic pressure loading. The PU samples were synthesized <i>via </i>condensation polymerization of a carbodiimide modified diisocyanate and an oligomeric diamine (Versalink P650 or P1000). Polymers synthesized using Versalink P650 (PU-P650) have a shorter soft segment length than those synthesized using Versalink P1000 (PU-P1000). Polymers were solvent cast and annealed first in the mold and then after specimen preparation. The x-ray scattering experiments were conducted at the Cornell High Energy Synchrotron Source with a diamond anvil cell used to apply the hydrostatic pressure. This behavior under hydrostatic pressure will be contrasted with the mechanisms observed under uniaxial tension. Aspects from the parallel multiscale modeling effort will be presented as well if time allows. This model is being used to help interpret experimental results and also as a tool to design enhanced version of polyurea.

Understanding and improving polyurea

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.