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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
381

Analyzing components of barrier coatings in different fractions during a repulping process.

Särnholm, Evelina January 2021 (has links)
During paper manufacturing, coating and adhesives are added to paper and cardboard to improve quality and durability. When the paper is later recycled or becoming new paper, the coatings may pollute the water used in the recycling process. Thus, it is important to know in which fraction these coatings finish during the process. In this study, laboratory made samples that mimic the repulping and paper making process is used. The different fractions of the processes were analyzed for a clay as well as a polymer coating. Metal content from clay coating is analyzed using inductively coupled plasma-mass spectrometry and microwave plasma-atomic emission spectrometry. For analyzing polymer coating, gas chromatography-mass spectrometry was used. From the result of the analysis the Reject sample, which was collected with a bigger mesh sieve in a repulping system, contained the highest amount of both clay and polymer coating. The other sample fractions from the repulping process and paper making process, did not contain as high mass content of either clay nor polymer coating.
382

Chemické modifikace polypropylénových povrchů / Chemical modifications of polypropylene surfaces

Pospíšek, Marek January 2014 (has links)
Diploma thesis is focused on modification and characterization of polypropylene (PP) products surfaces by the chemical way. In theoretical part of thesis are summarized the current knowledge of this topic including characterization methods. Polypropylene surfaces were modified by acrylic monomers (acrylic acid, acrylic acid with 20 mol% content of sodium acrylate and acryl amide). Modified surfaces were characterized by infrared spectroscopy with ATR technique. The comparative parameter was carbonyl index determined from absorption peaks of functional methyl groups (2950 cm-1 ) and functional carbonyl groups (1700-1750 cm-1) of FTIR-ATR spectra. Determination of effect of initiator concentration on the modification process was done for acetophenone and benzophenone. There were determined the time dependence of carbonyl index for time from 0 to 600 s of mentioned monomers. In the same condition were modified test specimens designed for preparation of adhesive joints. Joints were bonded by cyanoacrylate adhesive that provide reaction with surface of polyacrylic acid. There were founded conditions of modification that provided strength of adhesive joints higher than strength of original PP. There were identified changes of surface roughness by using of confocal microscopy.
383

Steric Stabilization of Polylactide particles achieved by Covalent 'grafting-from' with Hydrophilic Polymers

Nugroho, Robertus Wahyu Nayan January 2013 (has links)
Despite numerous advantages of using particles in a wide range of applications, they have one drawback that is their tendency to agglomerate. One way to overcome this problem is to sterically  stabilize the particles by introducing polymeric  chains covalently attached to the surface. Surface modification by covalently attaching polymer chains to the particle surface can be achieved by e.g. a ‘grafting-from’ technique under UV irradiation. In this thesis, polylactide (PLA) particles were surface modified, under UV irradiation, with the hydrophilic monomers: acrylamide (AAm), acrylic acid (AA), and maleic anhydride (MAH). The developed ‘grafting-from’ technique was shown to be nondestructive method for surface modification of PLA particles of two different geometries. The change in surface chemistry of the PLA particles was confirmed by FTIR and XPS, indicating the success of the surface grafting technique. Force interaction between two surface grafted PLA substrates was measured by colloidal probe AFM in different salt concentrations. In order to understand the repulsive force, the AFM force profiles were compared to the DLVO theory and AdG model. Long range repulsive interactions were mainly observed when hydrophilic polymers were covalently attached to the surface of PLA particles, leading to steric interaction. Attractive force dominated the interaction when neat PLA particle was approaching each other, resulting in particle aggregation, even though short range repulsion was observed at small separation distance, i.e. approximately 10 nm. Attractive interaction was also observed when neat PLA was approaching to PAA-grafted PLA substrate. This attractive interaction was much greater than force interaction between two neat PLA substrates.  The surface grafted particles can be used in biomedical application where secondary interactions are important to overcome particle agglomeration such as particle-based drug delivery. / <p>QC 20130529</p>
384

Mechanical Properties Of Provisional Restorative Materials

Shimizu Oliva, Graciela, 1976- January 2010 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / A provisional restoration must fulfill biologic, mechanical, and esthetic requirements. These prostheses should provide comfort, pulp protection, positional stability, occlusal function, hygiene access, esthetics, strength and retention. Methyl-methacrylate acrylic has assumed many appli¬cations in the field of restorative dentistry. However, the material still has deficiencies, such as polymerization shrinkage, pulpal damage associated with exothermic polymerization and susceptibility to fracture. Bis-GMA composites, Bis-acryl composites and visible light-cured urethane dimethacrylate resins have been developed to address these issues. The purpose of this study was to compare the mechanical properties of provisional restorations made from composite resins (Protemp Plus, Luxatemp Solar, Radica, Protemp Crown) to those made of the traditional methacrylate resins (Jet, Snap, High Impact). Six groups of samples, two groups from methacrylate and four groups from composite based materials, were fabricated. Samples from each group were evaluated for microhardness (n=10), flexural strength and flexural modulus (n=20) according to ISO 4049, and fracture toughness (n=20) according to ISO 13586. From each of the six groups, ten samples were tested for flexural strength, flexural modulus and fracture toughness and 5 samples were tested for microhardness. These tests were done after storing at 37°C in a distilled water solution for 7 days followed by thermal cycling (2500 cycles, 5-55°C, 45 s. dwell). Identical sets of samples from each group were used as controls; these were tested after storing for 24 hours in dry conditions. The results were analyzed by two-way ANOVA with material type and aging conditions as the two main variables. Significance level was set at p=0.05. For flexural strength and flexural modules, the higher values were obtained for Radica. Protemp plus (7 days) and Radica (24h) had the highest fracture toughness value. Protemp crown showed the highest surface hardness. The mechanical properties of composite resin were superior.
385

The Effect of Surface Treatment on The Adhesive Strength of Chairside Hard Liners to Dental Polymers Used for The Conventional, Additive, and Subtractive Fabrication of Complete Dentures.

Aldosari, Abdullah Mohammed January 2022 (has links)
No description available.
386

Life Cycle Assessment within Arkema’s portfolio: Carbon Footprint of Acrylics / Livscykelanalys inom Arkemas portfölj: Akrylers koldioxidavtryck

Faye, Alizé January 2023 (has links)
Livscykelanalys är en metod som utformades och utvecklades för att kvantifiera miljöpåverkan från produkter och tjänster för mer än trettio år sedan. Sedan dess har den kontinuerligt förbättrats och blivit mer och mer robust. Som tillverkare av kemiska produkter och monomerer använder Arkema livscykelanalys för att mäta sina produkters miljöpåverkan. Detta görs för att förstå enskilda produkters fotavtryck samt företagets övergripande miljöpåverkan. För att göra detta används ISO-normerna 14040 och 14044. Dessa normer anger generiska ramar för LCA-beräkningar men är inte specifika för den kemiska industrin. Med tanke på att metodologiska svårigheter kan uppstå inom den kemiska sektorn har många riktlinjer och rekommendationer publicerats på senare tid. I denna uppsats studeras och jämförs några av dessa riktlinjer. Tillämpningen av dessa metoder utförs på två produkter inom Arkemas portfölj: akrylsyra och etylakrylat, som är byggstenar för många polymerer. Resultaten av utvärderingen visar på områden där förbättringar kan göras. För de studerade produkterna är råvarorna de största bidragande orsakerna. Därför kan det vara fördelaktigt att övergå från petroleumbaserade material till biobaserade. Att välja den minst miljöpåverkande produktionsvägen är också ett sätt att aktivt minska produkternas koldioxidavtryck. / Life Cycle Assessment is a methodology that has been designed and developed to quantify the environmental impacts of products and services more than thirty years ago. Since then, it has been in continuous improvement and becomes more and more robust. As a producer of chemical products and monomers, Arkema uses Life Cycle Assessment to measure the environmental impact of its products. This is done to understand the footprints of individual products as well as the company's overall environmental impact. To do so, the ISO norms 14040 and 14044 are used. These norms set generic frames for LCA calculation but are not specific to the chemical industry. Considering that methodological difficulties can arise in the chemical sector, many guidelines and recommendations are being published recently. In this thesis, some of those guidelines are studied and compared. The application of these methodologies is performed on two products within Arkema’s portfolio: acrylic acid and ethyl acrylate, which are building blocks for many polymers. The results of the assessment reveal areas where improvements can be made. For the products studied, the main contributors are the raw materials. Therefore, transitioning from petroleum-based materials to biobased ones could be beneficial. Additionally, selecting the least impactful production route is also a way to actively reduce the carbon footprint of the products.
387

Polymer Biomaterial Constructs For Regenerative Medicine and Functional Biological Systems

Meng, Linghui 26 June 2012 (has links)
No description available.
388

Förster resonance energy transfer confirms the bacterial-induced conformational transition in highly-branched poly(N-isopropyl acrylamide with vancomycin end groups on binding to Staphylococcus aureus

Sarker, P., Swindells, K., Douglas, C.W.I., MacNeil, S., Rimmer, Stephen, Swanson, L. 13 June 2014 (has links)
No / We describe a series of experiments designed to investigate the conformational transition that highly-branched polymers with ligands undergo when interacting with bacteria, a process that may provide a new sensing mechanism for bacterial detection. Fluorescent highly-branched poly(N-isopropyl acrylamide)s (HB-PNIPAM) were prepared by sequential self-condensing radical copolymerizations, using anthrylmethyl methacrylate (AMMA) and fluorescein-O-acrylate (FA) as fluorescent comonomers and 4-vinylbenzyl pyrrole carbodithioate as a branch forming monomer. Differences in reactivity necessitated to first copolymerize AMMA then react with FA in a separate sequential monomer feed step. Modifications of the chain ends produced vancomycin-functional derivatives (HB-PNIPAM-Van). The AMMA and FA labels allow probing of the conformational behaviour of the polymers in solution via Forster resonance energy transfer experiments. It was shown that interaction of this polymer's end groups with Staphylococcus aureus induced a macromolecular collapse. The data thus provide conclusive evidence for a conformational transition that is driven by binding to a bacterium.
389

pH Dependence of Acrylate-Derivative Polyelectrolyte Properties

Swift, Thomas 05 July 2018 (has links)
Yes / There are many polymers formed of acrylate monomers in existence. Here we interrogate four commonly-used examples and study how their solution properties are pH dependent, or how their state of ionisation can affect their solution properties. Poly(acrylic acid) and poly(methacrylic acid) are both polyelectrolytes, with ionisable functional groups that make them stimuli responsive, changing their hydrodynamic volume. Poly(acrylamide) is a mass-produced material used in a variety of industrial applications, often with an anionic and cationic co-monomer, which dictates both its efficacy and impact on the environment. Poly(N-isopropyl acrylamide) is a thermally responsive material with applications in smart bioengineering. In solution, these materials can interact with each other due to competing hydrogen bonding interactions. However, this interpolymer complexation is dependent on both the ionisation, and the conformational state, of the polymers involved. This review focuses on the results from fluorescence tagging and turbidimetric techniques.
390

Μελέτη αλληλεπιδράσεων ιόντων Cu2+ με συμπολυμερή του ακρυλικού οξέος σε υδατικό διάλυμα / Study of the interactions between Cu2 + ion with acrylic acid copolymers in aqueous media

Τσοπελάκης, Φίλιππος 02 April 2014 (has links)
Στην εργασία αυτή προχωρήσαμε στη μελέτη της αλληλεπίδρασης των ιόντων δισθενούς χαλκού, Cu2+ με στατιστικά συμπολυμερή P(ANa-co-SSNa) του ακρυλικού οξέος, (ANa) με το στυρενοσουλφονικό οξύ (SSNa). Συντέθηκαν τα συμπολυμερή P(ANa50-co-SSNa) και P(AΝa80-co-SSNa) που περιέχουν 50 mol% και 80 mol% ακρυλικού οξέος αντίστοιχα. Τα συμπολυμερή αυτά χαρακτηρίστηκαν με φασματοσκοπία πυρηνικού μαγνητικού συντονισμού 1H NMR. Προχωρήσαμε στην φυσικοχημική μελέτη της αλληλεπίδρασης ιόντων δισθενούς χαλκού, Cu2+, με τα συμπολυμερή P(ANa50-co-SSNa) και P(AΝa80-co-SSNa) χρησιμοποιώντας διάφορες τεχνικές όπως η θολομετρία, η ιξωδομετρία και η φασματοσκοπία UV-vis. Τα πειράματα πραγματοποιήθηκαν σε υδατικά διαλύματα, στα οποία χρησιμοποιήθηκε ως διαλύτης τρισαπιονισμένο νερό, H2O-3D. Για λόγους σύγκρισης μελετήθηκαν επίσης τα αντίστοιχα ομοπολυμερή των μονομερών που αποτελούν τα συμπολυμερή P(ANa-co-SSNa). Έτσι, πραγματοποιήθηκε φυσικοχημική μελέτη της αλληλεπίδρασης των ιόντων Cu2+ με το πολυ(ακρυλικό νάτριο), PANa, και το πολυ(στυρενοσουλφονικό νάτριο), PSSNa, αντίστοιχα. Από την ιξωδομετρική μελέτη προέκυψε πως η εισαγωγή ιόντων χαλκού Cu2+ σε υδατικό διάλυμα πολυμερούς οδηγεί στην μείωση του ανηγμένου ιξώδους. Μάλιστα η μείωση αυτή είναι πιο δραστική καθώς αυξανεται η συγκέντρωση ιόντων Cu2+ στο διάλυμα. Αυτή η συμπεριφορά αποτελεί ένδειξη της συμπλοκοποίησης των ιόντων χαλκού, Cu2+, με τις ομάδες καρβοξυλίων του ακρυλικού οξέος (ΑΑ). Διαπιστώθηκε πως στα συμπολυμερή P(ANa-co-SSNa) τα Cu2+ συμπλοκοποιούνται με τα καρβοξύλια του ακρυλικού οξέος σε αναλογία ιόντων χαλκού προς ομάδες καρβοξυλίων ίση με 1:2. Όσον αφορά στην μελέτη με UV-vis, ενώ στην περίπτωση του ομοπολυμερούς PSSNa δεν υπάρχει κάποια ιδιαίτερη αλληλεπίδραση τύπου συμπλόκου ένταξης μεταξύ του πολυμερούς και των ιόντων του Cu2+, στην περίπτωση του συμπολυμερούς Ρ(ΑNa50-co-SSNa), παρατηρήθηκε μετατόπιση του σήματος των ιόντων Cu2+ (από τα 800 στα 745 nm) παρουσία του συμπολυμερούς. Αυτό είναι χαρακτηριστικό του σχηματισμού συμπλόκου ένταξης μεταξύ των ιόντων του Cu2+ και των ομάδων COO- του συμπολυμερούς. / In the present work we studied the interaction of bivalent copper ions Cu2+ with random copolymers P(ANa-co-SSNa) of acrylic acid (ANa) and styrenesulfonic acid (SSNa). Two copolymers, P(ANa50-co-SSNa) and P(AΝa80-co-SSNa) with 50 mol% and 80 mol% in acrylic acid, respectively, were synthesized and characterized by neutron magnetic resonance spectroscopy, 1H NMR. We proceeded in the physicochemical study of the interaction of bivalent copper ions, Cu2+, with P(ANa50-co-SSNa) and P(AΝa80-co-SSNa) copolymers using techniques like turbidimetry, viscometry and UV-vis spectroscopy. The experiments were performed in aqueous media using 3D water, H2O-3D. For reasons of comparison the respective homopolymers of sodium polyacrylate, PANa, and poly(styrene sulfonate), PSSNa, were also studied. From viscometry it was found that the introduction of copper ions in the polymer aqueous solutions leads to the decrease of the reduced viscosity. Moreover, this decrease is more pronounced as the concentration of Cu2+ increases in the solution. This behavior is indicative of the complexation between Cu2+ with the carboxylate groups of acrylic acid (ΑΑ). In the P(ANa-co-SSNa)/Cu2+ system, it was found that complexation occurs when the ratio of copper ions to carboxylates is equal to 1:2. UV-vis spectroscopy showed that, while in the case of PSSNa homopolymer there is not strong interaction with Cu2+, in the case of the Ρ(ΑNa50-co-SSNa) copolymer, the introduction of the polymer lead to a shift of the maximum absorbance of Cu2+ (from 800 to 745 nm). This was due to the complexation of Cu2+ with the COO- groups of the copolymer.

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