UV-cured fouling release acrylic coatings and protective coatings for clay bricks

The topic of this thesis is the protection of surface through UV cured polymeric coatings. In the first part coatings are designed to inhibit the adhesion of microorganisms on different substrate, while in the last chapter the coatings are developed to protect clay bricks from water. Degradation of surfaces caused by biofouling is a common issue in a variety of application, such as naval equipment, food industry and biomedical implants. In clay bricks, in addiction to biodegradation, the water causes other aesthetical and functional degradation phenomena, such as delamination, cracking, efflorescence, patina, black crusts. In this thesis was studied the growth of yeast in presence of different polymeric coatings prepared by UV curing. The approach followed was mainly based on the interfacial interactions between the surfaces and the microorganism. The experimental methods have been designed in order to control the physicochemical and mechanical properties of the surfaces. Interface interactions are governed by a variety of parameters, depending on the characteristic of both the substrate and the microorganism. Surface tension, hydration, wettability, roughness, topographies and elastic modulus and glass transition temperature are influent factors for polymeric materials. The microrganism selected for this works was a yeast isolated from garden soil and identified as Rhodotorula mucillaginosa. Rhodotorula species are ubiquitous, filmogenic, pigment yeasts. They are often called “pink yeast” because of the peculiar pink to orange coloration of the colonies. R. mucillaginosa and its adhesion properties are interesting in different application field. Selective and controlled proliferation of R. mucillaginosa could be useful in soil and wastewater bioremediation and industrial production of carotenoids. On the contrary, in biomedical application the biofilm formation in not desirable. Despite R. mucillaginosa generally is not harmful for human health, it is known as an emergent opportunistic pathogen able to infect immunosuppressed adults and newborns. Another important risk factor in infected patients is the presence of foreign bodies. Despite this, the Biosafety level of R. mucillaginosa is 1, this means that its manipulation in laboratory does not required special precautions. Coatings were prepared by UV-induced crosslinking processes. The UV curing or photopolymerization technique consists in the fast transformation of a liquid mixture of precursors into a solid crosslinked polymeric film. Low energy requirements, room temperature operation and solvent-free systems make UV curing an ecofriendly technology suitable for coatings industries. Monomers selected for the UV-curing process were characterized by acrylic end groups assuring fast and complete polymerization. For the protection of substrate against fouling, different monomers were selected in order to obtain coatings with different surface properties: 1. Hydrophobic monomers, i.e. perfluoropolyether diacrylates 2. Hydrophilic monomers, i.e. polyethilenglycol diacrylates. Hydrophobic coatings were based on perfuoropolyether (PFPE) diacrylic oligomer. It was studied the effect of surface tension, topography and elastic modulus on R. mucillagionosa adhesion and release. In Hydrophilic coatings were compared the effect of alkyl and poly(ethylene oxide) chain. The attention was focused on the effect of different chemical compositions, and thus different surface tension, on the induced morphology of R. mucillaginosa. Properties of acrylic coating have been checked by water absorption, contact angle measurement, profilometry and dynamic mechanical thermal analysis (DMTA). The interaction between the coatings and the yeast cells were examined through a simple in vitro test and correlated to the material properties of the polymers. The yeast test was designed to monitor the growth of R. mucillaginosa and the potential biofilm formation in presence of acrylic coatings. Biofilm release by a gentle washing was also evaluated. During the test, cell density was measure by UV visible spectroscopy. The growth morphology of the yeast on the coatings surface was observed by optical microscopy and FESEM. In addition, the effect of uncured monomers and the photoinitiator on the microorganism growth was studied. The coatings under investigation showed a different fouling behavior. The interaction between yeast cells and the coating surface appreciably change, mainly driven from the surface tension and the hydration of the materials. Different yeast morphologies were found. In the second part of the thesis are presented two hybrid coating as protective coating for clay bricks: a waterborne polyurethane coating and a perfluorinated (PFPE) coating. Masonry is susceptible from aesthetic and functional deterioration due to atmospheric agents, pollution and microorganism. The most diffuse degradations of facing bricks are lacunas, pulverization, delamination, cracking, presence of efflorescence, patina, black crusts and dissolution and leaching of mortar between brick courses. Water is known as an important factor of degradation; thus, hydrophobic coatings is an effective way to preserve bricks. The main characteristic required to this coating are hinder the liquid water absorption but maintain the water vapor transmission in the substrate. Protective coating for building porous materials are divided in two main categories: film formers and penetrants. The first coating presented in this thesis is a polyurethane based film formers coatings. It was prepared by combining two ecofriendly process: UV-curing of a waterborne diacrylic polyurethane and sol-gel reaction of a Tetraethoxysilane (TEOS). The perfluorinated coating is penetrants and was obtained by a sol-gel reaction of an α–ω-terminated triethoxysilane PFPE. Hybrid PFPE was obtaind using the sol-gel process in the presence of TEOS. Coated and uncoated facing bricks were compared by scanning electron microscopy, surface profilometry, water wettability and capillary rise tests. The hybrid coating acts as a moderate water repellent: interestingly no appreciable alteration of the aesthetical properties of the brick was observed, in particular no gloss and color change appeared after the treatment. Both the proposed coating could be applied on brick in the manufacturing process, or on existing brickwork

Current Progress in Biopolymer-Based Bionanocomposites and Hybrid Materials

In recent years, the development of biopolymers based on constituents obtained from natural resources has been gaining considerable attention. The utilization of biopolymers to engineer advanced bionanocomposites and hybrid materials is the focus of increasing scientific activity, explained by growing environmental concerns and interest in the novel features and multiple functionalities of these macromolecules.In this Special Issue, we aim to present the current state of the art in research pertaining to biopolymer-based bionanocomposites and hybrid materials, and their advanced applications. Contributions on the processing of biopolymers and bionanocomposites, the use of diverse biopolymer sources such as polysaccharides, the reinforcement of nanosized materials with biopolymers, and applications of these biopolymers, bionanocomposites, and biohybrid materials will constitute the backbone of this Special Issue

Various Aspects of Silicon Polymer Chemistry

This special issue of Molecules is dedicated to Professor Julian Chojnowski on the occasion of his 85th birthday for his outstanding achievements in the field of organosilicon chemistry. This issue contains one review and eleven original articles written by eminent experts on various aspects of silicon polymer chemistry, which reflect the tireless passion of Professor Chojnowski to the development of organosilicon chemistry

Design of advanced materials and nano delivery approaches for enhancing activity against Methicillin resistant Staphylococcus aureus.

Doctoral Degree. University of KwaZulu-Natal, Durban.Infectious diseases, including bacterial infections, continue to be a significant cause of morbidity and mortality globally, antimicrobial resistance has further made them fatal. Limitations of conventional dosage forms have been found to be one of the contributing factors to antimicrobial resistance. Novel nano delivery systems are showing potential to combat antimicrobial resistance. The search for novel materials for efficient delivery of antibiotics is an active research area. The aim of the study was to design and synthesize advanced materials and explore nano-based strategies for preparations of novel drug delivery systems to treat SA and MRSA infections. In this study two novel materials; a linear polymer dendrimer hybrid star polymer (3-mPEA) comprising of a generation one poly (ester-amine) dendrimer (G1-PEA) and copolymer of methoxy poly (ethylene glycol)-b-poly(ε-caprolactone) (mPEG-b-PCL) and oleic acid based quaternary lipid (QL) were synthesized and characterized and Poloxamer 188 (P188) material available in the market were employed to formulate three nano drug delivery systems for efficient and targeted delivery of antibiotics. The synthesized materials and the drug delivery system were found to be biosafe after exhibiting cell viability above 75% in all the cell lines tested on using MTT assay. The formulated nano based systems were evaluated for sizes, polydispersity indices (PDI), zeta potential (ZP), surface morphology, drug release, in vitro and in vivo antibacterial activity. Nanovesicles were formulated from 3-mPEA and they had sizes, PDI, ZP and entrapment efficiency of 52.48 ± 2.6 nm, 0.103 ± 0.047, -7.3 ± 1.3 mV and 76.49 ± 2.4%. respectively. QL lipid was employed to formulate vancomycin (VCM) loaded liposomes with Oleic acid based ‘On’ and ‘Off’” pH responsive switches for infection site and intracellular bacteria targeting. They were found to have the size of 98.88 ± 01.92 at pH 7.4. and exhibited surface charge switching from negative at pH 7.4 to positive charge accompanied by faster drug release at pH 6.0. Fusidic acid nanosuspension (FA-NS) with size, PDI and ZP of 265 ± 2.25 nm, 0.158 ± 0.026 and -16.9 ± 0.794 mV respectively was formulated from P188. The drug release profile from both the nanovesicles and liposomes was found to have sustained release. In vitro antibacterial activity for the nanovesicles, FA-NS and liposomes showed 8, 6 and 4-fold better activity at pH 7.4, while the liposome being a pH responsive antibacterial system at pH 6 showed 8- and 16- fold better activity against both Methicillin susceptible (MSSA) and resistant Staphylococcus aureus (MRSA) respectively when compared with the bare drugs. An in vivo BALB/c mice, skin infection model revealed that treatment with VCM-loaded nanovesicles, liposomes and FA-Ns significantly reduced the MRSA burden compared to bare drugs and untreated groups. There was a 20, 6.33 and 76-fold reduction in the MRSA load in mice skin treated with nanovesicles, liposomes and FA-NS respectively compared to those treated with bare VCM and fusidic acid. In summary, synthesized material showed to be biosafe and potential for the development of nano-based drug delivery systems of antibiotics against bacterial infections. The data from this study has resulted in one book chapter and 3 first authored and 3 co-authored research publications

Novel polyurethane/graphene nanocomposite coatings

A series of graphene based conductive and anticorrosion coatings were developed in this project. Multi layer coating consists of EPD pristine graphene coating, PU/graphene primer and PU/graphene topcoat was developed. A simple mechanical chemical approach was suggested to fabricate graphene with low cost and high efficiency. XRD was used to characterize the exfoliation efficiency of graphite. TEM was used to examine the size of the graphene sheets. SEM was used to characterize the surface morphology of the coatings. The particle size of all the carbon materials used was characterised by Malvern particle sizer. FTIR and XPS were used to characterize the chemical composition of the graphene powder and the coatings fabricated. MDSC and FTIR were used to monitor the cure dynamic of PU. [Continues.]</div

Nano- and Microcomposites for Electrical Engineering Applications

In a dedicated Special Issue, the journal Polymers has compiled papers on the current trends and research directions within the preparation, characterization and application of polymer-based composite materials in electrical engineering applications. In recent times, this type of material has evolved to become one of the most thoroughly investigated materials, stimulated by the demand for the resource-efficient assembly of generators, transformers, communication devices, etc. Novel composites are to be used as insulating materials with high thermal conductivity and excellent temperature stability, through which premature ageing and degradation of devices shall be avoided or at least reduced. This Special Issue comprises twelve contributions by internationally renowned researchers; to mention Petru V. Nothinger (University Politehnica of Bucharest), Alun S. Vaughan (University of Southampton), Stanislaw M. Gubanski (Chalmers University of Technology), Michael Muhr (Graz University of Technology), Johan J. Smit (TU Delft), and Ulf W. Gedde (KTH Royal Institute of Technology) as prominent examples. The state-of-the-art research and technology of the area ‘micro- and nanocomposites for electrical engineering applications’ has been summarized in three review articles, while the current research trends and the development and characterization of novel materials have been described in eight original research articles. Stimulated by the vivid current interest in this topic, this Special Issue of Polymers has additionally been compiled in a book version

Advances in Membrane Technologies

Membrane technologies are currently the most effective and sustainable methods utilized in diversified water filtration, wastewater treatment, as well as industrial and sustainable energy applications. This book covers essential subsections of membrane separation and bioseparation processes from the perspectives of technical innovation, novelty, and sustainability. The book offers a comprehensive overview of the latest improvements and concerns with respect to membrane fouling remediation techniques, issues of bioincompatibility for biomedical applications, and various subareas of membrane separation processes, which will be an efficient resource for engineers

Transparent, Lightweight, High Performance Polymer Films and Their Composites.

PhD ThesisThis thesis aims to develop novel polymeric material with an excellent balance in high optical transparency and mechanical properties. More particularly, the current thesis reports the processing and characterization of highly oriented transparent polyethylene films and their use in laminated composites. First, highly transparent high-density polyethylene (HDPE) films with high modulus and tensile strength were developed by regulating solid-state drawing conditions without the need of additives. The effects of drawing parameters like drawing temperature and draw ratio on optical and mechanical properties as well as morphology of these solid-state drawn HDPE films were methodically investigated. It was found that a fairly broad processing window can be utilized to tailor the required balance in optical and mechanical performance. Subsequently, the production of these ultra-drawn transparent HDPE films was carried out using a scalable and continuous cast-film extrusion and drawing process. High optical transparency of around 91 % was achieved even in the far field. A maximum modulus of ~ 33 GPa and tensile strength of ~ 900 MPa of these solid-state drawn HDPE films was attained without compromising optical transparency, which is an order of magnitude higher than mechanical properties of conventional transparent plastics such as polycarbonate (PC) and poly(methyl methacrylate) (PMMA). The influence of extrusion draw down and two-step drawing on optical and mechanical behaviours was also explored. Finally, these highly oriented transparent HDPE films were used as the reinforcing phase in high performance transparent composite laminates. The far field light transmittance of Abstract 6 4-layer HDPE-reinforced laminates with either a unidirectional (UD) or bidirectional (BD) lay-up sandwiched between glass or PC skins, was maintained at around 85 %. The fabricated transparent composite laminates were shown to have not only a high tensile strength but also a high energy absorption capability, outperforming existing transparent glazing materials such as laminated glass or PC

A novel hydrophobic ZRO2-SIO2 based heterogeneous acid catalyst for the esterification of glycerol with oleic acid

The low market value of glycerol has led to extensive investigations on glycerol conversion to value-added derivatives. This work focuses on industrially important catalytic esterification of glycerol with oleic acid due to the high commercial value of the resulting products. In this work, a novel heterogeneous acid catalyst featuring hydrophobic surface was developed on ZrO2-SiO2 support as water tolerant solid acid catalyst is vital for biphasic esterification reactions producing water. The synthesized catalyst (ZrO2-SiO2-Me&Et-PhSO3H) was prepared through silication and surface modification using trimethoxymethylsilane (TMMS) and 2-(4-chlorosulfonylphenyl) ethyltrimethoxysilane. The surface morphology, physiochemical and textural properties, acidity and hydrophobicity were characterized. The mechanism of the catalyst surface modification is thereof proposed according to comprehensive characterization results. A novel technique to control acidity and hydrophobicity level of the designed catalyst is disclosed in this work. The acidity and hydrophobicity of the catalyst were tuned by controlling the amount of surface modification agents. It was found that the hydrophobicity of the catalyst decreased as its acidity increased. ZrO2-SiO2-Me&Et-PhSO3H_70 catalyst with 70 mol% of TMMS and 0.62 mmol/g acidity is the optimal catalyst for glycerol esterification with oleic acid. Furthermore, the role of hydrophobicity in catalytic reaction was investigated herein. It was found that at constant catalyst acidity, the more hydrophobic catalyst showed better yield. The conversion using the designed catalyst (ZrO2-SiO2-Me&EtPhSO3H_70) is 88.2% with 53.5% glycerol monooleate selectivity and 40.0% glycerol dioleate selectivity (combined 94% selectivity of glycerol monooleate and dioleate) at equimolar oleic acid-to-glycerol ratio, 160 oC, reaction temperature, 5 wt% catalyst concentration with respect to weight of oleic acid, solvent-less reaction conditions and 8 h reaction time. This work reveals that the hydrophobicity and the pore volume of the designed catalyst significantly affect the product selectivity. In addition, the performance of the hydrophobic designed ZrO2-SiO2-Me&Et-PhSO3H_70 catalyst was used to benchmark with catalytic activity of sulfated zirconia (SO42-/ZrO2) and commercial catalysts (Amberlyst 15 and Aquivion). The correlation results showed that the average pore volume (pore size) influenced the product selectivity when ZrO2-SiO2-Me&Et-PhSO3H_70 catalyst was compared to three SO42-/ZrO2 catalysts that were developed from different zirconium precursors. Whereby, the higher pore volume catalyst is favourable to glycerol dioleate production at identical reaction conditions. It can be concluded that pore volume and size can be used to control the product selectivity. In addition, this study also revealed that hydrophobicity characteristic facilitated initial reaction rate effectively