Date of Thesis

Spring 2023

Description

Solid-state shear pulverization (SSSP) is a continuous and scalable processing technique that imposes mechanochemical changes in polymer-based materials. It has been shown to impart beneficial properties onto homopolymers or create copolymers and composites through continuous fragmentation and fusion. The unique technology employs cold temperature to keep the polymer in the solid state. This thesis investigates industrial polymer processing in the context of real-world applications. This thesis analyzes SSSP using an organized methodology called systematic innovation (SI). SI facilitates problem solving by assisting engineers in conducting root cause analysis around a material and studying the physical setup of the equipment.

This thesis conducts a side-by side comparison of ten polymers and their processability by SSSP for the first time in its 30+ year history. The polymers are analyzed before and after processing to determine what innate characteristics allow them to engage with the SSSP screws in a beneficial fashion from a processing-structure-property standpoint. A follow-up study with a graphite filler is conducted to analyze the dispersion levels across the ten polymers. SSSP is by no means a universal process, but the study reveals that tough, semicrystalline polymers with a high heat capacity and thermal diffusivity engage well with the SSSP screws.

This thesis takes a deeper dive into what parameters and covariants impart beneficial properties onto polystyrene. A design of experiments is conducted with 20 trial runs to correlate the parameters and covariants of SSSP process to the resulting properties of the material. The study confirmed many hypotheses around the covariants specific mechanical energy (Ep) and screw temperature (Tscrew) while providing meaningful statistical trends.

This thesis ends with a major investigation into polylactic acid, a bio-based and biodegradable polymer, as a realistic replacement for real world injection molded products. The study focuses on crystalline enhancement with SSSP while maintaining optical clarity needed in plastic labware products. The SSSP process is also used to disperse 0–5% cellulose nanofibers into the PLA to increase stiffness. Loading just 2.0 wt% of CNF into PLA maintains stiffness without the need for fast cooling or long annealing times. These studies lead to a continued effort to innovate the polymer processing industry for sustainable polymer use.

Keywords

solid-state shear pulverization, systematic innovation, polymer processing, polylactic acid, design of experiments, nanocomposites

Access Type

Masters Thesis

Degree Type

Master of Science in Chemical Engineering

Major

Chemical Engineering

First Advisor

Katsuyuki Wakabayashi

Comments

As per our discussion with Eloise Stevens (and the Graduate Studies Office), this is the late submission of the Master's thesis that has been redacted to remove confidential information relevant to the industrial collaborator.

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