Emily Cranston

The full abstract for this thesis is available in the body of the thesis, and will be available when the embargo expires.

View record

Bio-based materials are promising alternatives to less sustainable materials (i.e., petroleum-based chemicals), however, very few have been commercialized in advanced material roles. In addition to formulation development, new processing methods must be established to allow bio-based materials to make the leap from lab-scale to industrial-scale processing. In this work, we investigated the use of cellulose nanocrystals (CNCs) in the microencapsulation of oils. First, drying techniques including freeze drying, spray freeze drying, and spray drying were compared for producing corn oil-filled powders stabilized by CNCs, methyl cellulose (MC) and tannic acid. All three techniques produced dry oil powders with high encapsulated oil content (>90%). The oil powders could be redispersed in water to reform an emulsion and could be stored dry for weeks (in the fridge) without oil leakage. The three drying techniques imparted different surface morphologies that were linked to powder redispersibility and oil release properties. Spray freeze dried powders displayed the most tunable oil release when tested on a hydrophobic substrate. It was demonstrated that spray drying could be used to encapsulate a variety of oils that have different interfacial tensions and volatilities, including jojoba, lavender, and tea tree oil. Next, a dry jet wet spinning apparatus was designed and fabricated to use the same CNC and oil encapsulation system to produce oil-filled fibres. Coaxial extrusion provided a continuous spinning process whereby an external CNC-MC “shell” and internal oil “core” led to fibres with discrete oil-filled beads measuring ca. 2 mm in width along the fibre. The spun fibres were stable under ambient conditions, relatively flexible, and exhibited interesting optical properties. The encapsulated oil could be released by shearing or by re-wetting the fibres. Both the oil-filled powders and fibres were prepared using scalable processing techniques, employed plant-based and industrially-produced “building blocks”, worked with commercially-relevant oils, and will hopefully contribute to the development of environmentally sustainable emulsions, powders, and fibres for food, cosmetic, biomedical, pharmaceutical, agricultural and construction applications.

View record