| Solid-state shear pulverization (SSSP) is an innovative, continuous, environmentally benign, and industrially scalable process used to make materials that cannot be made via conventional processing techniques, reduce material cost by eliminating processing steps, and/or produce materials with superior properties as a result of better break-up and dispersion of additives. The SSSP process employs a modified twin-screw extruder in which the barrels are cooled rather than heated. This allows for high shear and compressive forces on the material during operation, which results in repeated fragmentation and fusion steps in the solid state.;Technologically, this thesis provides the first in-depth study of the concept of specific energy in SSSP and how this variable can be tailored to optimize the end-properties while lowering costs for processing homopolymer, blend, or polymer composite systems. Furthermore, this thesis demonstrates the successful injection molding of SSSP-processed materials. An 80/20 wt% polypropylene (PP) and microcrystalline cellulose composite was manufactured with SSSP and injection molded into a bottle cap. These caps showed major benefits over neat PP such as increased stiffness and reduction in oxygen permeability. Finally, a description is provided of how SSSP can be used as a one-step solid-state compounding process that can add color, UV stabilizers, anti-statics, and other processing aids to polymer and uniformly and effectively disperses them in the polymer while pulverizing to a fine powder for roto-molding.;Scientifically, process-structure-property relationships are investigated in detail with several homopolymers. The SSSP process is used to disperse heterogeneous nucleation agents (naturally found in commercial pellets) in the polymer. This led to major structural changes such as an increase in crystallizability and crystallinity for poly(lactic acid) (PLA) and in rigid amorphous fraction (RAF) at constant crystallinity for Nylon 11 and poly(caprolactone) (PCL). These structural changes resulted in major property enhancements, and a quantitative understanding of how RAF affects oxygen permeability was achieved. |
