UV cured polysulfone based membranes for ultrafiltration

Membrane technology has acquired significant importance in a variety of applications such as water treatment, health sector and food industry. Nevertheless there is a growing demand of more functional and stable membranes. This thesis is focused on improving solvent stability of polysulfone based membranes without compromising the flux properties. Polysulfone (PSF) is a widely used membrane material for ultrafiltration process because PSF can be easily fabricated into highly porous structure via non–solvent induced phase separation (NIPS). Such a structure is imperative for ultrafiltration process as efficiency of filtration largely depends upon the size of pores and overall porosity of membrane. Generally membranes made of pristine PSF have good chemical and mechanical stability but get dissolved in many of organic solvents. Though previous attempts somehow attained solvent stability but membrane structure was deteriorated and so does the transport property. In order to increase the solvent stability, an approach based on UV induced acrylic functionalization of PSF is described in this thesis. A two-steps method of membrane fabrication, involving NIPS and UV curing, was established. At first the acrylic functionality was introduced on the backbone of polysulfone chain through synthesis of methacrylated polysulfone (PSF–DM) macro-monomer. The thin films of PSF-DM containing phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide (BAPO) photoinitiator cast on the glass plates were subjected to UV curing and NIPS processes to prepare the membranes. The reverse process i.e. NIPS followed by UV curing was also applied. The developed membranes were thoroughly characterized and the flux properties were evaluated in a dead–end filtration apparatus. The solvent stability was good in DMSO and acetone. Regardless of sequence of operations the average flux values were in the range of tight ultrafiltration. The sequence UV–NIPS resulted into more uniform and structurally stable membranes. The next approach was based on incorporating acrylic functionality in a way that a diacrylate monomer was added into pristine PSF solution in DMF and the membranes were fabricated following the previously established method i.e. UV curing followed by NIPS. For this purpose two structurally different di-acrylates, Bisphenol A ethoxylate diacrylate (BEDA) and Poly (ethylene glycol) diacrylate (PEGDA) were incorporated and in order to study the effect of concentration, different amounts of acrylic resins were investigated. The acrylic double bond conversions were studied through FTIR and ATR–FTIR. The viscoelastic properties were analyzed via dynamic mechanical thermal analysis (DMTA) and morphological properties were studied through field emission scanning electron microscopy (FESEM). The solvent stability was analyzed by immersing the membranes cutouts in a number of solvents for 120 hrs at room temperature. The flux properties were evaluated in a pressurized stirred cell apparatus and the rejection of 27 nm polystyrene particles was also collected. Almost all the formulations came up with excellent solvent stability in DMF, DMSO, THF, Acetone, Toluene and Ethyl Acetate. The 10 % BEDA functionalized PSF membrane exhibited the best flux properties, i.e. very close to that of pristine PSF, along with good rejection (>90 %) of 27 nm polystyrene particles. The UV cured acrylic functionalized PSF membranes were further applied to specific contaminant removal. The previously developed best UF membranes were coated with polydopamine (PDA) in order to combine the rejection of ultrafiltration membrane with the adsorption of contaminant by PDA layer. As BEDA cross-linked membranes were developed through UV curing followed by NIPS so the strategy of PDA coating was coupled with NIPS either as a separate action next to NIPS or in a more facile and advantageous one–step method where NIPS and PDA coating occurred at the same time. In order to study the increased adsorptive behavior of PDA coated membranes, methylene blue (MB) was taken as a model contaminant. The removal of MB was investigated both in batch and continuous filtration. The Zwitterionic behavior of PDA was effectively exploited and the coated membranes released MB in acidic condition thus regenerated for next adsorption. The cyclic stability of several adsorption and desorption cycles was studied. Above stated all three works discussed the development of UV cured membranes through NIPS In recent years, electrospun nano-fibrous membranes (ENMs’) have been employed as successful replacement of phase separation membranes because of high porosity thus much lower mass transfer resistance. We designed a reactive electrospinning setup where electrospinning was coupled with online UV irradiation. The same BEDA functionalized PSF formulation was taken as feed solution. All the parameters of electospinning and UV curing were thoroughly investigated, optimized and correlated so the optimum curing of acrylic monomer and production of nano fibers take place simultaneously. The electrospun mats were also prepared via offline curing method and compared with the counterparts. All the UV cured mats were fully characterized and solvent stability was assessed in the same way as reported before

The Impact of Financial Leverage on Firm Performance in Fuel and Energy Sector, Pakistan

This research is finds the effect of financial leverage on firm performance of the fuel and energy sector in Pakistan. For this purpose 10 listed public limited firms out of 16 form fuel and energy sector listed at Karachi Stock Exchange (KSE). The main objective of the study is investigate the financial leverage has an effect on financial performance of the firm by taking evidence from listed fuel and energy companies of Pakistan. There is a positive relationship between the financial leverage and financial performance or not?  The main plan of this study is to examine the simplification that the firms get work with high profits may choice high leverage by using different statistical tools. Keywords: Financial leverage, Firm Performance, Financial ratio, Fuel and Energy Sector in Pakistan Paper type: Research pape

Total quality management and sustainability in the public service sector : the mediating effect of service innovation

Purpose This study aims to critically investigate the structural relationships between total quality management (TQM), service innovation and sustainability performance in the public service sector of the United Arab Emirates (UAE). Design/methodology/approach The study employed an online survey to collect data from 400 employees working in eight selected UAE public service sector organisations located in Abu Dhabi. The collected data were analysed using structural equation modelling (SEM) to empirically examine whether TQM practices improve service innovation and, subsequently, sustainability performance in the UAE's public service sector. Findings The results show that TQM has a significant impact on service innovation and sustainability performance in the UAE's public service sector. Additionally, service innovation partially mediates the relationship between TQM and sustainability performance. Practical implications The public service sector's TQM practices and service innovation in the UAE have a much greater impact on social and environmental sustainability than on economic sustainability performance. Adopting five dimensions of TQM (following the Abu Dhabi Award for Excellence in Government Performance [ADAEP] model) across the UAE's public organisations will enable government departments to deliver innovative services to its beneficiaries. Originality/value This study provides a substantial contribution by addressing the gaps in the literature. Very few studies have empirically investigated the possible association between TQM, service innovation and sustainability performance in public sector organisations, particularly in developing countries such as the UAE, where the increasing efforts in TQM practices are still in their emerging stages, mainly targeting innovative service offerings and sustainable performance.©2022 Emerald Publishing Limited. This manuscript version is made available under the Creative Commons Attribution–NonCommercial 4.0 International (CC BY–NC 4.0) license, https://creativecommons.org/licenses/by-nc/4.0/fi=vertaisarvioitu|en=peerReviewed

Determinants of corporate hedging policies and derivatives usage in risk management practices of non-financial firms

Derivatives are the major icon among risk management practices. Firms usually use derivatives to hedge their foreign exchange and interest rate risk. This study aims to examine the determinants’ of corporate hedging policies and derivative usage in risk management particularly with respect to Pakistan, as the political and economic conditions in Pakistan are highly volatile which intends the corporations to handle and mitigate their risk through channelizing the derivatives. Secondary data of 75 non financial firms listed in Karachi Stock Exchange was collected over the period 2007-2011 – to regress empirically – for achieving the aim of this study. Mann-Whitney U test was used to distinguish the derivative user and non user. Findings of this test characterize users as large size, higher growth opportunities, cash flow volatility, foreign exchange and interest rate exposure. Moreover this study finds that there is a significant relationship between the use of derivatives and foreign purchase, liquidity, firm growth and size. Our findings suggest that derivative users have competitive edge over the non user, as they get economies of scale and proper risk management through using these kinds of derivative instruments

Determinants of corporate hedging policies and derivatives usage in risk management practices of non-financial firms

Derivatives are the major icon among risk management practices. Firms usually use derivatives to hedge their foreign exchange and interest rate risk. This study aims to examine the determinants’ of corporate hedging policies and derivative usage in risk management particularly with respect to Pakistan, as the political and economic conditions in Pakistan are highly volatile which intends the corporations to handle and mitigate their risk through channelizing the derivatives. Secondary data of 75 non financial firms listed in Karachi Stock Exchange was collected over the period 2007-2011 – to regress empirically – for achieving the aim of this study. Mann-Whitney U test was used to distinguish the derivative user and non user. Findings of this test characterize users as large size, higher growth opportunities, cash flow volatility, foreign exchange and interest rate exposure. Moreover this study finds that there is a significant relationship between the use of derivatives and foreign purchase, liquidity, firm growth and size. Our findings suggest that derivative users have competitive edge over the non user, as they get economies of scale and proper risk management through using these kinds of derivative instruments

Managing project scope creep in construction industry

Purpose Project scope creep is a nightmare and nearly intolerable task. Most project managers struggle to curtail the expanse and degree of scope creep. This study examines different likely project scope creep factors associated with the construction industry projects. Design/methodology/approach After many brainstorming sessions with construction stakeholders, several project scope creep factors were identified. Then, a detailed survey was executed in big construction projects of the United Arab Emirates (UAE). The data were analyzed using exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). Findings The results derived and validated five conspicuous factors leading to project scope creep. Respectively, the highest and the lowest impact on project scope appears to be imposed by tasks/specifications and complexity/uncertainty. Practical implications It offers crucial support to the project stakeholders in scrutinizing different factors that stand as hurdles to project success and allows them to seek remedies to resolve them. Originality/value It is among the first study in the region that identifies and validates the factors that hinder construction project success.©2022 Emerald Publishing Limited. This manuscript version is made available under the Creative Commons Attribution–NonCommercial 4.0 International (CC BY–NC 4.0) license, https://creativecommons.org/licenses/by-nc/4.0/fi=vertaisarvioitu|en=peerReviewed

Green supply chain management in manufacturing firms: A resource-based viewpoint

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Greening of supply chain to drive performance through logical integration of supply chain resources

Sustainability has always been a concern of humankind in one form or the other. Still, it has come into sharper focus after the promulgation of the sustainable development goals in 2015 and the disruptive forces unleashed by the COVID‐19 pandemic. Supply chain management is an aspect of business operations wherein the need for sustainability has been felt more keenly. The academic and business understanding of various nuances of incorporating sustainability, particularly environmental concerns in the supply chain, is still evolving. Our study seeks to enrich the growing literature in the area by proposing to uncover a novel, logical sequence of intangible supply chain resources that can amplify the impact of green supply chain management practices (GSCMPs) on business performance. We use the dual‐theoretical lens of a resource‐based view and stakeholder theories to conceptualize the sequential mediational role of supply chain visibility, resilience, and robustness between GSCMP and performance. Analyzing data collected from 318 individuals working in the manufacturing sector in the United Kingdom, we found a positive direct association of GSCMP with performance and the serial mediational role of visibility and robustness between the two. The findings of our study are pertinent for theorists as well as managers

Solvent-stable UV-cured acrylic polysulfone membranes

A systematic investigation of the effect of the presence of acrylate resin on polysulfone-based membranes was performed with the aim of obtaining chemically stable crosslinked membranes without affecting their flux performances. The membranes were prepared via UV curing of the polymer dope followed by a non-solvent-induced phase separation process. Two different acrylic monomers were investigated and their amount was varied in the polymer dope, to study the influence of concentration on final results. High crosslinking degrees were achieved by irradiating the solution for one minute. Morphological investigations of the active surface and of the cross-sections of the fabricated membranes showed that the typical porosity of ultrafiltration membranes was obtained starting from solutions containing a low amount of crosslinker (10 wt%), which is consistent with the water flux values which were comparable to that of the pristine polysulfone membrane. High concentrations of crosslinker resin in the initial polymer dope produced denser membranes with lower permeability. High rejection of 27 nm particles (>90%) was measured for all samples having measurable flux. The addition of the crosslinker allowed one to obtain stability in various solvents without affecting the flux and rejection performance of the porous membranes. © 2016 Society of Chemical Industry.Peer Reviewe