01/24/2025
By Danielle Fretwell

The Francis College of Engineering, Department of Plastics Engineering, invites you to attend a Doctoral Dissertation Proposal defense by Rebecca Olanrewaju on: "The Design and Processing of High-Performance Architected Blends via Shape Forming Elements"

Candidate Name: Rebecca Olanrewaju
Degree: Doctoral
Defense Date: Friday, February 7, 2025
Time: 11 a.m. - 1 p.m.
Location: Emerging Technologies and Innovation Center (ETIC), Room 445

Committee:
Advisor: David Kazmer, Professor, Plastics Engineering, University of Massachusetts Lowell

Committee Members*
1. Margaret Sobkowicz-Kline, Professor, Plastics Engineering, University of Massachusetts Lowell
2. Jay Park, Associate Professor, Plastics Engineering, University of Massachusetts Lowell
3. Thao (Vicky) Nguyen, Professor, Mechanical Engineering, Johns Hopkins University

Brief Abstract:
Polymer composites often consist of blends containing two or more polymers to enhance performance, and architected polymer composites represent a specialized subset engineered with tailored properties. Architected composites combine the advantages of their constituent materials to meet specific application requirements, including enhanced mechanical, electrical, and thermal properties. Traditional reinforcements like glass and carbon fibers improve performance but can increase viscosity, complicating processing and distribution, and contributing to wear and filler breakage. Melt processing, including using Schrenk’s Layer Multiplying Elements (LMEs) and Shape Forming Elements (SFEs), offers an alternative by manipulating microstructure and enabling precise material placement at high production rates. LMEs create layered structures by cutting, redistributing, and recombining polymer flows, while SFEs enable mechanical interlocking through complex cross-sectional designs.

Liquid crystalline polymers (LCPs) are promising candidates for architected blends due to their unique anisotropic properties, thermal stability, and low viscosity in the molten state. When blended with other high-performance polymers like polycarbonate (PC) and aromatic nylons, LCPs can act as both processing aids and reinforcements, forming fibrils during cooling that enhance mechanical properties along the direction of alignment. However, the immiscibility of LCPs with many polymers can lead to interfacial separation. This research aims to overcome these challenges by employing LMEs and SFEs to engineer immiscible blends with optimized orientation and crystallinity for improved strength and toughness.

There are several objectives in this research. The first objective is to characterize the mechanical properties of blends generated by LMEs, specifically various blend combinations of PC and LCP, with differing configurations of LMEs. The configurations of LMEs include no LMEs, 1 LME, and 2 LMEs stacked. The second objective is to investigate the ability of the SFEs to produce complex cross sections, with validation methods such as a piston-driven polymer clay extruder and ANSYS Polyflow, before moving to coextrusion with high-performance materials. The third objective is to design and validate a design and optimization methodology for developing generative shape-forming elements.