03/25/2022
By Sokny Long
The Francis College of Engineering, Department of Plastic Engineering, invites you to attend a doctoral dissertation defense by Masoumeh Pourali on “The effect of Crystallization Kinetics on Material Extrusion Additive Manufacturing of a Semicrystalline Hot Melt Adhesive.”
Ph.D. Candidate: Masoumeh Pourali
Defense Date: Wednesday, April 6, 2022
Time: 3 to 5 p.m. EST
Location: This will be an in person defense in ETIC 445, and also a virtual defense via Zoom. Those interested in attending should contact Masoumeh_Pourali@student.uml.edu and Amy_Peterson@uml.edu at least 24 hours prior to the defense to request access to the meeting.
Committee Chair (Advisor): Amy Peterson, Associate Professor, Department of Plastic Engineering, UMass Lowell
Committee Members:
- David O Kazmer, Professor, Department of Plastic Engineering, UMass Lowell
- Margaret Sobkowicz, Associate Professor, Department of Plastic Engineering, UMass Lowell
- Jay Park, Assistant Professor, Department of Plastic Engineering, UMass Lowell
- Charles Paul, Henkel Corporation
Brief Abstract:
Additive Manufacturing (AM) is an increasingly important aspect of modern manufacturing due to its advantages over traditional manufacturing techniques. AM enables manufacturing of parts with complex geometries without the need for assembling, tool design, and tool changes. However, narrow material range and poor part reliability limit further application of AM. Thermally-driven material extrusion (MatEx), which uses thermoplastics or thermoplastic-based composites as the feedstock, is the most common AM technique. Use of MatEx is limited by poor bonding strength between layers, anisotropic mechanical properties, limited material range, and residual stresses within parts. The MatEx process is thermally driven and the heat drives the bond development between layers. MatEx is more challenging in semicrystalline polymers due to the different amounts of shrinkage during cooling in semicrystalline and amorphous phases and residual stress build up below the crystallization temperature, which can cause warpage and delamination from the build plate. These challenges can be addressed with a fundamental understanding of the MatEx process and the effect of crystallization kinetics on heat transfer mechanisms.
This dissertation focuses on the printability of a semicrystalline hot melt adhesive, and the effect of glass fibers, and path length on weld strength and dimensional accuracy of prints. Additionally, the effect of crystallization kinetics on heat transfer during MatEx is studied by coupling the nonisothermal crystallization kinetics of the material with a heat transfer model. The model provides temperature profiles and relative crystallinity at any location within a part as a function of cooling time. Experimental results are used to examine the impact of toolpath on percent crystallinity and bond strength of prints and to validate the model. Combined, this work helps to explore processing-structure-properties-performance relations within MatEx of semicrystalline polymers. This will enable optimizing of print parameters and subsequent control of percent crystallinity and interlayer bonding and reduction in MatEx-related defects.
All interested students and faculty members are invited to attend the online defense via remote access.