Theses - PRISM: Polymer, Recycling, Industrial, Sustainability and Manufacturing Institutehttps://research.thea.ie/handle/20.500.12065/24492024-03-28T21:59:30Z2024-03-28T21:59:30ZThe development of smart 4D materials utilising smart temperature responsive polymersZhuo, Shuohttps://research.thea.ie/handle/20.500.12065/46882023-11-29T03:02:42Z2023-01-01T00:00:00ZThe development of smart 4D materials utilising smart temperature responsive polymers
Zhuo, Shuo
This study involved the preparation and optimisation of novel temperature-sensitive
hydrogel copolymer and terpolymer systems, and also the development and evaluation of
smart hydrogels with the potential for 4D printing and shape-shifting behaviours.
In this work, N-vinylcaprolactam (NVCL) was chosen as the base polymer. NVCL is a
temperature-responsive polymer which is often used for biomedical applications due to its
biocompatibility, solubility and non-toxic features. However, studies of the use of NVCL
for developing 4D material have been limited. This polymer was bonded with different
types and concentrations of photoinitiators, crosslinkers, and other polymers to obtain the
optimum ratio, with the most suitable properties and performance for 3D printing. UV
polymerisation, a process with similar mechanisms to Stereolithography (SLA) printing,
was first employed for the preparation of samples. The cured polymers were characterised
by the following techniques: The chemical structure of the hydrogels was confirmed using
Fourier transform infrared spectroscopy (FTIR). Four techniques were used to determine
the lower critical solution temperature (LCST) of the polymers in aqueous solution: i)
cloud point analysis, ii) UV-spectrometry, iii) differential scanning calorimetry and iv)
rheology. Pulsatile swelling studies were performed to investigate the effect of the
transition temperature, monomer feed ratio and crosslinker content on the swelling size
and quality. The mechanical properties of the polymers were detected by tensile tests.
Goniometry was used to probe the water absorption capacity of the samples. Results
indicated that the physically and chemically crosslinked NVCL based polymers exhibited
a tuneable LCST by modifying the contents with regard to the material composition and
concentration. The LCST could be raised to 54°C and was validated by four different
techniques. FTIR showed that the samples were successfully synthesised. After
incorporating with the monomer N, N-dimethylacrylamide (DMAAm), the mechanical properties improved. The copolymer P (70NVCL-30DMAAm) exhibited potential for the
next stages of 4D printing trials. It exhibited outstanding swelling capabilities and was
flexible to changes in size as the temperature increased or decreased.
By changing structures that can be converted in a pre-programmed manner in response
to a stimulus, 3D printed materials can be modified to impart flexibility and boost utility.
Four-dimensional (4D) printing is a relatively new concept that was initially reported in
2013. 4D printing refers to the idea that the shape or properties of a printed object can be
changed again when an external stimulus is applied. In this study, by using a modified P
(NVCL-DMAAm) candidate formulation, containing 2 wt% H-Nu 400IL, 2 wt%
PEGDMA, 30 wt% DMAAm and 70 wt% NVCL, 4D printing was achieved. The same
characterisation tests were applied to the 3D printed samples to compare the differences
in the properties of materials between samples prepared using SLA and those prepared
with UV chamber photopolymerisation.
Due to the superior properties of the shape memory polymers, a number of
scholars have used the material to produce 4D printed objects in multi-material 3D printers.
The printed objects are capable of demonstrating complex and magnificent changes when
stimulated. However, smart hydrogels are only able to expand/contract in water. In
addition, the printer used in this study was an inexpensive one and could only apply one
material at a time for printing. It is difficult to develop flexible shape-shifting behaviours
by using a single hydrogel material and a single material 3D printer. This study exploited
a new method to utilise bilayer structures and a UV chamber system to allow hydrogel based materials to exhibit controllable shape shifting behaviours (such as self-curving and
self-bending behaviours). Although other researchers have developed similar smart
structures, none have use a NVCL based polymers developed in a UV chamber system.
Based on the different ways of transformation, diverse demonstrators were developed In summary, by constantly modifying and improving the formulation of NVCL
solutions, a new ‘NVCL-based resin’ that can be used in an SLA 3D printer has been
successfully systhesised. In the presence of water, the 4D printed parts were able to switch
their sizes as the temperature rises and falls. In addition, by using bilayer structures, the
shape shifting behaviours have also been successfully developed for hydrogel-based
materials. This research not only opens up new applications for NVCL materials, but also
provides a simple and fast method for the preparation of 4D materials.
2023-01-01T00:00:00ZDeep Eutectic solvents and green reagent based process for polyethylene terephthalate depolymerisationAzeem, Muhammadhttps://research.thea.ie/handle/20.500.12065/46842023-11-29T03:02:54Z2023-09-01T00:00:00ZDeep Eutectic solvents and green reagent based process for polyethylene terephthalate depolymerisation
Azeem, Muhammad
Polyethylene terephthalate (PET) is a ubiquitous thermoplastic polymer which has
numerous industrial applications including textile, construction, and packaging
applications due to its versatile nature, transparency, strength, and barrier properties.
According to recent studies, the production of PET is increasing at a growth rate of 8% per
annum with of plastic waste rising to 8 million tons every year. It is therefore imperative to
develop sustainable and scalable plastics recycling methodologies to reduce plastic waste
accumulations stockpiles.
Recently enzymatic treatment methodologies have emerged as promising and
environment-friendly techniques for efficient PET depolymerisation. Higher selectivity of
desired monomers is achievable due to specific targeting enzymes. Considerable further
research and development is required to overcome the enzyme costs, sensitivity limitations
and long reaction times to become amenable to industrial-scale production. Chemical
recycling of PET has advantages over other recycling techniques due to increased
efficiency while utilising a wide range of PET waste products and converting them into
primary building blocks that could be used in repolymerisation to make virgin PET.
However, the usage of harsh solvents and longer reaction conditions restrict their large scale applications. Therefore, it is important to develop a most efficient and industrial
applicable PET depolymerisation techniques.
Deep eutectic solvents (DESs) are mixtures of different compounds with many applications
in organic, analytical, and polymer chemistry fields. Recently, DESs were proposed as
green catalysts in plastics chemical recycling and have shown remarkable potential as
catalysts in PET depolymerization reactions. Microwave (MW) technology has been
investigated as an efficient method for fast PET depolymerization reactions. The rapid
heating achievable via MW while utilising DESs as model catalysts has allowed significant
shortening of reaction times while delivering acceptable monomers conversion yields.
As there is insufficient knowledge in this area, this thesis aims to address PET waste pre treatments and depolymerisation reactions under new and instant MW technology coupled
with DESs. Three studies were carried out to investigate DESs based MW depolymerisation
technology and are detailed in the appended papers. As this research work explores the
ultra-green and sustainable depolymerisation methodologies for PET, Paper I
demonstrates combined ultra-green chemical and biocatalytic depolymerization of PET
using DES-based MW treatment followed by enzymatic hydrolysis. A green DES with a
triplet composition of choline chloride, glycerol, and urea was selected for PET
depolymerization under MW irradiation without the use of additional depolymerization
agents. Under the optimized conditions of 20 mL DES volume, 260 W MW power, and 3
min MW irradiation time, a significant increase in the carbonyl index and PET percentage
weight loss was observed. The combined MW-assisted DES depolymerization and
enzymatic hydrolysis of the treated PET residue using LCC variant ICCG resulted in a total
monomer conversion of ≈16% (w/w) in the form of terephthalic acid, mono-(2-
hydroxyethyl) terephthalate, and bis-(2-hydroxyethyl) terephthalate. Paper II illustrates
combined green and fast glycolysis-hydrolysis depolymerization of PET under MW with excellent efficiencies. In MW-assisted glycolysis of PET, the catalytic activity of two DES
based on (choline chloride-urea (DES 1)) and (choline chloride-thiourea (DES 2)) was
evaluated and compared. Optimised glycolysis conditions were determined using Box
Behnken Design (BBD) to attain maximum weight loss of PET, low crystallinity and
increased carbonyl index of residual PET.
DES volume of 4 mL, 5.5–6 mL of ethylene glycol, and 0.5 min MW irradiation time
resulted in a prominent rise in PET weight loss and carbonyl index of residual PET. DES 2
showed an improved catalytic activity than that of DES 1 which is associated to its stronger
interaction with EG and PET polymer chains during the course of the reaction. Residual
PET obtained post glycolysis reaction was further depolymerized using MW assisted
hydrolysis in the presence of weakly basic Na2CO3 and EG. Within 3-minute, the proposed
sequential depolymerization technologies facilitated ≈99% conversion of PET to
terephthalic acid (TPA), monohydroxyethyl terephthalate (MHET), and bis (2-
hydroxyethyl) terephthalate (BHET) monomers produced at a yield of 62.79–80.66%,
17.22–34.79% and 0.54–0.59% respectively.
Paper III explains a highly efficient 2-step microwave-based (MW) degradation of PET.
Initially, a MW-assisted pre-treatment was evaluated using glycerol as a non-toxic reagent
for the conversion of PET into a modified form that makes it easily depolymerized. Box
Behnken Design was employed to determine the optimised pre-treatment conditions
attaining maximum PET weight loss and favourable crystallinity and carbonyl indices for
the residual PET. Glycerol of 12 ml volume and 3 min of 182W MW irradiation resulted
in 11% PET weight loss at onset temperature of degradation and gave rise to carbonyl index
up to 4.22 and 33% crystallinity of residual PET. MW assisted hydrolysis of the pre-treated
PET was then performed in the presence of sodium bicarbonate and ethylene glycol as
depolymerizing agents. Within 3 min, the proposed depolymerisation methodology
provided 99.9% conversion of PET into 79.1% terephthalic acid (TPA), 17.6%
monohydroxyethyl terephthalate (MHET), and 1.8% bis (2-hydroxyethyl) terephthalate
(BHET). The obtained TPA was separated from the monomers mixtures and its purification
was evaluated via different characterization techniques against a standard TPA. A purity of
95%, 82.4 APHA colour value, 645.3 mgKOH/g acid number and acceptable heavy metal
content indicated that the purified TPA can be repolymerized as virgin PET. Hence, MW assisted DES technology is validated as an efficient process for boosting the
depolymerisation of PET in an ultrafast and eco-friendly manner
2023-09-01T00:00:00ZA versatile monitoring technique for real-time protein activity tracking within cellular and biomimetic scaffold environmentsRodriguez Barroso, Laura Gabrielahttps://research.thea.ie/handle/20.500.12065/46832023-11-25T03:02:02Z2023-07-12T00:00:00ZA versatile monitoring technique for real-time protein activity tracking within cellular and biomimetic scaffold environments
Rodriguez Barroso, Laura Gabriela
High biological noise is intrinsic within biological systems, and this poses critical challenges
to the in-situ detection and measurement of biomolecular and protein activities important to
advancing approaches to disease and injury treatment. These challenges arise due to possible
non-specific binding of other molecules in the analyte’s surrounding medium. Currently the
techniques available to characterize protein behaviours in living biological systems are highly
elaborate and are generally greatly hindered by the high background noise. Here we present a
versatile and straight forward technique for monitoring proteins and protein interactions within
cells and other complex environments, based on a novel nano-bio-technology method. Highly
sensitive gold edge coated triangular silver nanoplates (AuTSNP), which are highly responsive
to molecular interactions on their surfaces, are used to probe protein behaviours within complex
cellular and tissue regeneration environments, as well as recognize antibody-antigen (Ab-Ag)
interactions within dynamic biological surroundings. The extracellular domains within tissues
involve macromolecules vital for the provision of structural support to surrounding cells and
signalling cues for the modulation of diverse cellular processes. Tissue scaffolds are designed
to mimic the extracellular architecture and functions. In this work, monitoring of the dynamic
behaviour of a critical extracellular protein, Fibronectin (Fn), within the presence of bone tissue
regeneration scaffolds and living cells is reported. The optical response of Fn functionalised
AuTSNP, is used to distinguish between compact and extended conformations of the protein
and indicating Fn unfolding and fibril formation on incubation within cells.
Moreover, successful detection of native Fn present in isolated Extracellular Matrix (ECM) by
using Anti-Fn antibody functionalised AuTSNP is performed. The excellent sensitivity and
straight forward application within complex cellular environments, poses AuTSNP as powerful
new tools to detect protein interactions and monitor essential protein activity. For this reason,
a potential COVID-19 detection platform is explored where SARS-CoV-2 Spike protein is
detected through a nanoplate-based system using its corresponding antibody, Anti-Spike. This
work is conducted within the presence of horse serum (HS) as complex environment where the
dynamic surroundings present a challenge for the straightforward detection of the Ab-Ag
complex binding, nonetheless, the research presented is a significant step towards the
development of new technologies for medical diagnosis and monitoring
2023-07-12T00:00:00ZIntegrating 3D printing and injection molding for mass customization: advancements in hybrid manufacturingGong, Kehttps://research.thea.ie/handle/20.500.12065/46802023-11-24T03:02:13Z2023-08-01T00:00:00ZIntegrating 3D printing and injection molding for mass customization: advancements in hybrid manufacturing
Gong, Ke
Additive manufacturing (AM) is renowned for its ability to create complex
geometries and customized products but is limited by low throughput. Conversely,
injection molding (IM) excels in high-volume production but struggles with costeffective
customization due to mold tooling constraints. This thesis investigates hybrid
manufacturing (HM), which combines the strengths of AM and IM, as a solution for
mass customization - the production of personalized products at costs comparable to
mass production. The focus is on integrating fused deposition modeling (FDM), a form
of AM, with IM to achieve mass customization. The study is divided into two main
sections: overmolding and overprinting.
In the overmolding section, FDM-fabricated preforms are integrated into the
mold cavity. The study examines how various parameters, such as infill density, joint
configuration, interface direction, and material choice, affect the mechanical
properties of the hybrid products. The results indicate anisotropic maximum tensile
strength between half-length (25.47 MPa in HL-FT 25 for Acrylonitrile Butadiene
Styrene (ABS) batches and 30.11 MPa in HL-FT 75 for Polylactic Acid (PLA) batches) and
half-thickness specimens (48 MPa in HT-FT 50 for ABS batches and 68.38 MPa for HTFC
75 in PLA batches) for single-material overmolding specimens. As for the dualmaterial
overmolding, a worse tensile performance (46.1 MPa in 75-FT-60) in
comparison to the half-thickness series for single-material ones can be found.
The overprinting section explores the integration of FDM components onto
injection-molded substrates. While this approach showed inferior tensile performance
(47.1 MPa in 25-70-220 batch for ABS pieces and 56.3 MPa in 50-70-210 batch for PLA
pieces) compared to pure IM and overmolding, it demonstrated potential benefits
including reduced manufacturing costs and enhanced design flexibility.
In conclusion, this thesis establishes a groundwork for future HM techniques that
demand higher design flexibility and fabrication efficiency. Overmolding and
iv
overprinting have demonstrated their potential in producing customized products at
lower costs. Future research could explore the integration of Stereolithography (SLA)
for creating tailored molds with thermosetting polymers, combining higher design
flexibility with cost efficiency.
2023-08-01T00:00:00Z