Polylactic Acid based Blends and Composites for Material Extrusion 3D Printing: Formulation, Characterization, and Processing

In this PhD thesis, the objective was to develop polylactic acid/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends and their composites containing cellulose nanocrystals (CNCs), suitable for material extrusion 3D printing. In the first part, epoxidized canola oil (ECO), was utilized as a compatibilizer for PLA/PBAT blends at different weight ratios to produce toughened materials suitable for 3D printing applications. The incorporation of ECO into PLA/PBAT blends resulted in significant improvements in the compatibility, leading to significant increases in impact strength of 62% and 106% for blends containing 20 and 30 wt% PBAT, respectively, compared to their non-compatibilized counterparts. The blend (70/30) was further evaluated for 3D printing suitability. The addition of ECO was found to facilitate fusion between adjacent deposited strands and to reduce the size and number of voids, resulting in a substantial improvement in interlayer adhesion and tensile ductility. In the second part of this research, a simple and sustainable hydrophobic modification of cellulose nanocrystals (CNCs) using ECO was investigated to improve their compatibility with PLA. After modification, the hydrophobicity of the CNCs was significantly enhanced, as evidenced by their loss of colloidal stability in water and an increase in water contact angle from 33° to 73°. The modified CNCs also exhibited improved dispersion and distribution within the PLA matrix, regardless of the processing method used (solvent casting or melt compounding). More importantly, CNC-g-ECO demonstrated enhanced thermal stability and completely mitigated discoloration and thermal aging, which are common issues in CNC-based composites. Finally, this thesis investigated the effects of CNC treatment on the morphology, properties, and material extrusion behavior of PLA/PBAT/CNC composites. Although the addition of non-modified CNCs to 70/30 PLA/PBAT blends resulted in some improvements in mechanical properties, their poor dispersion and preferential localization within the PBAT phase remained major limitations. In contrast, the incorporation of CNC-g-ECO led to more pronounced improvements in mechanical properties in certain cases. Notably, the addition of both unmodified CNCs and CNC-g-ECO enhanced the printability of PLA/PBAT blends by improving interlayer fusion, reducing the size and number of voids, and yielding significant improvements in tensile properties.

Department dc:contributor.department

Chemical Engineering

Year dc:date.issued

2026

Author dc:creator

• Wahbi, Mohamed

Advisors dc:contributor.supervisor

• Kontopoulou, Marianna
• De France, Kevin

• Polymer
• Composites
• Polylactic acid
• Cellulose nanocrystals
• Polymer blends
• 3D printing
• Compatibilization
• Functionalization

Statement dc:rights

• Attribution-NonCommercial 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc/4.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1974/36191

OAI identifier oai:identifier

oai:queensu.scholaris.ca:1974/36191