BURA Collection:
http://bura.brunel.ac.uk/handle/2438/180
2024-03-15T10:05:33ZDevelopment of sustainable core systems for vacuum insulation panels in building applications
http://bura.brunel.ac.uk/handle/2438/28483
Title: Development of sustainable core systems for vacuum insulation panels in building applications
Authors: Neiva Coutinho Marshall Corker, Jorge
Abstract: Vacuum Insulation Panels (VIPs) are a remarkable state-of-the-art thermal insulation solution with
promising building applications. However, current market products still pose several significant
challenges, including the usage of highly embodied carbon footprint and costly materials, i.e. fumed
silica (FS), mostly necessary to cope with long-term performance. The ultimate goal of this study has
been to assess the possibility of entirely or, at least, partly replacing the conventional FS VIP cores
with cheaper and more environmentally friendly alternatives, such as, among others, a fine perlite
powder (PEa) and industrial residues in the likes of inorganic aluminium anodising sludge (ALW) and
renewable organic cork powders (CP). The fundamental study includes understanding the primary
heat transfer mechanisms involved throughout comprehensive experimental and modelling
campaigns. The designs comprise sole and hybrid core solutions with a straightforward mechanical
blending technique, wherein the proposed mixed materials are combined with different weight
ratios of fumed silica (25%, 50% and 75%). The study also encompasses a thorough raw material
characterisation and comprehensive investigation of novel core designs involving the structure,
density, porosity and extinction coefficient determination. Thermal conductivity is measured by both
steady-state and transient methods, and its correlation with density is explored, while monitoring
the effect of internal gas pressure changes within the VIP cores served as a key indicator for both
pristine and long-term proficiency considerations. Accelerated ageing tests conducted in controlled
harsh temperature and moisture conditions facilitate an insightful evaluation of the performance of
different core designs over time. Numerical models are introduced to evaluate and predict the
thermal efficiency of novel solutions and quantify the contribution of each mechanism participating
in the heat transfer process of the different cores.
Effective centre-of-panel thermal conductivities of the pure alternative solutions are close to
10 mW路m-1路K-1, or even below, at fully evacuated pristine conditions. However, within the 1 to
10 mbar range, the solid-gas coupling effects start to become significant and soon dominant over gas
conduction, as the inner pressure rises in these cores due to moisture and air permeation through
the envelope. A likely rapid decline in performance over time, foreseen by their estimated extremely
low 饾洸/ values, is corroborated by accelerated ageing tests indicating that, without using dedicated
getters and desiccants or superior barrier envelopes, neither the pure PE or the CP alternative core
systems envisaged is particularly suitable for standard long-term building insulation applications
following the current established practices, and the pure ALW core design may struggle to
technically compete with a single FS core. However, all pure core systems may find possible
utilisations in less demanding markets. On the other hand, while presenting lambda values within the range of 5.4路mW路m-1路K-1 to 7.0 mW路m-1路K-1 when fully evacuated, several PEa/FS, ALW/FS and
CP/FS hybrid compositions are revealed to be far more promising towards the construction industry
adoption due to their ease of production, low density, excellent superinsulation thermal
performance and acceptable service lifetime likelihood. Moreover, utilising either cheaper materials
or, even better, recycled ones driven from both industrial inorganic wastes and renewable organic
residues, as the hybrid core designs in this study, would undoubtedly enhance the potential benefits
of these alternative solutions.
Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London2023-01-01T00:00:00ZMethods to measure and enhance the circularity of wastewater resources
http://bura.brunel.ac.uk/handle/2438/28101
Title: Methods to measure and enhance the circularity of wastewater resources
Authors: Renfrew, David C.
Abstract: The need for an alternative to the linear economy and a practical method to operationalise
sustainable development has led to a surge in popularity of the circular economy (CE) concept.
Europe鈥檚 CE Action Plan establishes the importance of circular wastewater treatment and
resource utilisation, however, a lack of standardised CE definitions and assessment methods
are hindering this transition. Therefore, the first step of this research reviewed the indicatorbased
decision support systems (DSS) developed for wastewater treatment plant (WWTPs). It
found that technology selection DSS aims are ill-defined and the scope of indicators used for
process optimisation is narrow, meaning the sector is far from standardised assessments and
decision making. This led to the development of a structured approach that generates shared
CE strategies at a regional level, by adapting a multi-criteria analysis tool to select resource
recovery technologies. A UK wastewater sector example demonstrated the approach鈥檚
decision-making capabilities, identifying five priority resources and quantifying the expected
benefits in terms of nutrient recovery. However, it was concluded that a holistic assessment is
required for further analysis of impacts to circularity and sustainability when implementing the
selected technologies. Reviewing circularity assessments, and definitions of waste, showed a
paradox exists when applied to WWTPs, as wastewater, regardless of its production, is nonvirgin
so is currently considered a circular input. To overcome this, the CE principle of resource
traceability was combined with their degree of environmental harm, to define the circularity of
water, carbon, nitrogen, and phosphorus. This method showed how actions of water users
impact upstream and downstream circularity of a conventional WWTP. Following this, it was
seen that material circularity is commonly used as a proxy for environmental performance,
revealing a large disconnect between circularity and sustainability during assessments.
Therefore, the assessment method was expanded to investigate how changes to physical
resource circularity directly impacts value creation. By defining several principles from
sustainability science literature, a method that systematically selects resource, action, and
sustainability indicators using participatory approaches was developed. Additionally, it showed
how appropriate benchmarks are defined for direct quantification of impacts to resource
circularity and sustainable value creation. This was validated by comparing extended aeration
and novel photobioreactor (PBR) WWTPs, highlighting multi-dimensional benefits of the PBR
compared with the conventional process. Lastly, it is believed the developed method can act as
the basis for standardising the holistic circularity assessment of wastewater resources.
Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London2023-01-01T00:00:00Z3D printing biopolymer: A comprehensively experimental study of interfacial bonding performance
http://bura.brunel.ac.uk/handle/2438/27469
Title: 3D printing biopolymer: A comprehensively experimental study of interfacial bonding performance
Authors: Wang, Yuxuan
Abstract: Additive manufacturing (AM) technologies have experienced a substantial growth in recent decades. AM technologies are able to fabricate and build complicated customised geometry composites without extra tools and execute multi-materials manufacturing that conventional manufacturing methods cannot offer. Polymeric material applied in AM has become the mainstream, but industrialisation still faces many challenges. Currently, bio-based polymers have also been highly demanded due to the sustainability requirements. The combination of AM and bio-based polymeric material shows significant potential in a wide range of applications.
This study has presented a comprehensive investigation programme focusing on the interface formulation, structure, bonding and performance of 3D printed biopolymeric materials. The experimental analysis firstly investigated the interfacial bonding performance of various bio-based polymeric materials in detail, then several material combinations and modifications have been investigated in order to enhance the printability and performance of AM biopolymeric materials. The formation mechanisms, failure modes and micromechanical performance of interlaminar bonding were comprehensively studied throughout the work programme. The printing performance was determined by the density profile, mechanical properties testing and micromechanical properties across the thickness and over cross-section area for all the materials studied. Thermal properties have also been carried out in order to determine the miscibility of the copolymers.
The optimised printing parameters and the effect of postprocess of Polylactide (PLA) polymer have been generated following this programme, up to 24% higher in tensile strength when the printing temperature is 220 藲C compared to the 200 藲C. Impressive mechanical strength obtained but severe anisotropy property and brittleness have also existed. The reduction of tensile strain in y-axis specimens compared to the x-axis has improved from 62% to 22% and competitive mechanical properties have also been achieved by the addition of PHBV biopolymer into the PLA, up to 86% increase in tensile strain has been achieved. Lastly, innovatively bio-based printing materials, such as Polylactide (PLA)/Polybutylene Succinate (PBS) and Polylactide (PLA)/Polybutylene Succinate (PBS)/Polyethylene glycol (PEG), have been investigated and up to 80% increase in ductility has been achieved in PLA/PBS/PEG blends. While the limited improvement has been achieved in the PHBV modifications and some challenges emerged and remained for further development, such as the anisotropy, brittleness, processability and geometric accuracy, a promising path is provided by this study to extend further research and commercial applications of bio-based polymers for additive manufacturing.
Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London2023-01-01T00:00:00ZShape stabilisation of cellulose-poly(ethylene glycol) phase change composites for building construction
http://bura.brunel.ac.uk/handle/2438/27359
Title: Shape stabilisation of cellulose-poly(ethylene glycol) phase change composites for building construction
Authors: Sivanathan, Amende
Abstract: In this thesis a series of unique formulations were developed and investigated for the stabilisation of PEG using cellulose fibre (CF) as the supporting material by implementing the highly feasible tricarboxylic acid (TCA) crosslinking reaction using deionised water as solvent. This resulted in producing a series of shape stabilised TCA crosslinked composite PCMs of different chemical compositions. The TCA crosslinked composite PCMs were characterised by FTIR, XRD, SEM, DSC, TGA and POM analysis.
FTIR results confirmed the formation of a crosslinked structure, and the presence of weak intermolecular forces of attraction between the unreacted PEG particles and CF. Hence, leakage problem of solid-liquid PEG PCM was successfully overcome in the current study; and therefore, PEG was able to retain its original solid state during the phase transition process. Microwave (MW) irradiation had no major effects on the final structure of TCA composite PCM, but it appeared to have reduced the moisture content significantly since the intensity of peak appearing at 3450 cm-1 corresponding to the presence of OH groups had reduced significantly which may indicate moisture loss or changes in the polarity strength of the O-H group.
XRD results indicated that the crystallinity of pristine PEG had changed drastically after TCA crosslinking reaction. The major two crystalline peaks appearing at 2胃 = 19.10 and 23.23掳 disappeared after chemical crosslinking reaction; thus, broad humps existed in the composite PCMs indicating the presence of amorphous structures which was attributed to the incorporation of amorphous polymer (e.g., CF). The crystallinity index (CI) value of PEG8000 was 52.94% while TCA composite PCMs had CI value in the range 8.92 to 45.3%. The crystallinity of the resulting composite PCMs were dictated by the PEG content, PEG/CF ratio and PEG/CA ratio. Ten minutes MW radiation exposure was observed to enhance the crystallinity of TCA composite PCM with blend ratio of 4.0:1:7.5 from 35.65 to 47.96% (e.g., 34.53% increase) but twenty minutes MW radiation exposure reduced it from 35.65 to 32.32% (e.g., 9.34% decrease) which was attributed to destruction of PEG crystal lattice structure by the thermal effect of MW radiation.
DSC results showed that pristine PEG8000 had a very high latent heat capacity of 181.5 J/g which was attributed to the fact that PEG was comprised of simple linear polymer chains. This indicated that pristine PEG8000 are susceptible to crystallisation; thus, could easily form crystals. After TCA crosslinking reaction the latent heat capacity of PEG had reduced significantly. Thus, TCA crosslinked composite PCMs had latent heat capacity in the range 18.19 to 58.08 J/g which was attributed to the reduced flexibility of the PEG chain during the crystallisation process. The phase transition temperature of PEG changed after TCA crosslinking reaction which was due to the changes in the thickness of the crystal lamellae. TGA results showed that the thermal stability of PEG had increased after TCA crosslinking reaction attributed to the formation of the crosslinked structure.
POM images indicated major changes in the spherulitic crystal structure of PEG after chemical crosslinking reaction due to the formation of the TCA crosslinked structure. Hence, the crystal structure became less prominent, and its size was observed to have reduced significantly attributed to the formation of crystal defects during chemical crosslinking reaction.
SEM images indicated the possibility of enhancing the structural integrity; thus, the homogeneity of the resulting composite PCMs using MW radiation exposure for ten minutes MW radiation exposure was observed to produce composite PCMs with compact structure and even topography; however, results suggested that twenty minutes MW radiation exposure was undesirable since cracks were observed to have formed due to severe moisture loss by the thermal effect of MW radiation.
Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London2023-01-01T00:00:00Z