In this closed MASc oral exam, Pardis Mehinrad will be discussing their research into Advancing Sustainable Packaging: The role of nanofibers in bioplastics
Abstract:
Packaging has become one of the fastest-growing industries worldwide.
Bio-based materials have emerged as one of the most interesting research
subjects in the packaging industry due to the environmental concerns
associated with materials derived from petrochemical sources, such as
resource depletion, recycling challenges, and biodegradation, resulting in
the development of eco-friendly materials. Synthetic polymers are extensively
employed in this industry mainly because of their outstanding mechanical
properties, effective barriers against oxygen and water, and ease of
processability. However, they present significant downsides, such as poor
degradability and challenges in recyclability. The challenges associated with
biopolymers include poor mechanical and barrier properties and high
production costs. To modify the properties of biopolymers, various methods
could be employed, such as reinforcing the polymer matrix with nanomaterials,
especially nanofibers.
The first goal of this project is to improve the process of preparing
nanofibers derived from hemp. By applying pre-treatments before fibers
undergo the refining process, we aim to reduce the number of steps required
for their refinement and investigate the role of pre-treatments on the
stability and diameter size of the nanofibers produced. This could save time,
energy, and cost and enhance the overall efficiency of the process, a
significant step forward for the industry. In this study, mechanical
treatment was applied for the fibrillation of hemp fibers. This method has
significant advantages over chemical treatment, particularly in terms of
reducing the amount of chemicals used, promoting a more sustainable and
cost-effective approach. In order to improve the efficiency of the
fibrillation process, some pre-treatments were applied. Among them, the one
using fiber hydration by placing the fiber inside the water for one hour, a
strong vacuum for 30 minutes, and a pressure cooker under high temperature
(≈ 120°C) and pressure (12 psi) for 10 minutes resulted in the smallest
reduction in fiber size after eight passes. Meanwhile, based on the stability
test, this sample exhibited the highest stability, remaining stable after
seven days.
Additionally, mechanical tests demonstrated that adding HNF to PBS films
increased tensile strength and modulus. However, decreased elongation at
break. Beeswax increased the film's elongation because of its plasticizing
effect and improved the compatibility and dispersion between PBS and HNF,
resulting in a more uniform composite and enhanced tensile strength.
Meanwhile, its plasticizing effect is expected to reduce the tensile modulus.
At low concentrations of SDS, it reduced the surface tension between PBS
and
HNF, leading to a better dispersion of the nanofibers throughout the PBS
matrix. This can help prevent premature failure at specific points and allow
for more stretching before breaking, increasing elongation. While, excess SDS
can make the film more susceptible to break under stress, potentially leading
to decreased elongation. Meanwhile, the initial addition of SDS enhanced the
composite's tensile strength mainly because of improved PBS-HNF adhesion and
better stress transfer from the polymer matrix to the fibers. The addition of
SDS over the optimal concentration resulted in phase separation, which could
be regarded as a weak point in the composite, thereby having an adverse
effect on the tensile strength. It was observed that by introducing SDS to
the formulation tensile modulus also decreased.
Supervisor: Professor Simon
Co-Supervisor: Professor Turbiani