Overcoming the achilles' heel of processing of polymer nanocomposites: Achieving well-dispersed polymer-graphite, polymer-carbon nanotube, polymer-carbon nanofiber, and polymer-graphene nanocomposites with major property enhancements by solid-state shear pulverization

Polymer nanocomposites consisting of polypropylene (PP) and low levels of as-received graphite (ARG) or carbon nanotubes (CNT) were prepared via a continuous and industrially scalable process called solid-state shear pulverization (SSSP). This novel polymer processing technique exposes polymers to high shear and compressive forces near ambient temperature, which allows for fragmentaion and fusion steps in the solid-state. We found that SSSP processing leads to excellent exfoliation and dispersion of ARG and debundling and dispersion of CNT in the PP matrix. This excellent dispersion is accompanied by major property enhancements. For example, a 97.5/2.5 wt% PP/ARG nanocomposite made by SSSP exhibits a 100% increase in tensile modulus and a 50 % increase in tensile strength relative to neat PP while retaining most of the net PP elongation at break. Similar mechanical property enhancements are achieved with 99/1 wt% PP/carbon nanotube nanocomposites.