No description available.

No description available.

The performance of polymeric diphenylmethane diisocyanate (PMDI) resin is known to be highly dependent on the wood species. This species dependence may be due to differences in: cure chemistry, interphase morphology, or both of these factors. This study addresses aspects of the cure chemistry and interphase morphology of wood/PMDI bondlines; specifically these effects are compared using two woods: yellow-poplar and southern pine. In this study, the cure chemistry of wood-PMDI system was analyzed with solid state NMR (SSNMR) using wood samples cured with doubly labeled (15N,13C) PMDI resin. The kinetics of PMDI cure in the presence of wood was analyzed with differential scanning calorimetry. Thermogravimetric analysis was used to analyze the effect of resin impregnation on the degradation patterns of wood. The wood-PMDI bond morphology was probed with dynamic and static (creep) mechanical analyses in both dry and plasticized conditions. The effect of resin on wood polymer relaxations was quantitatively analyzed by both the time-temperature superposition principle and the Kohlrausch-Williams-Watts equation. The presence of a small but statistically significant species effect was observed on both the cure chemistry and bond morphology of wood-PMDI system at low cure temperatures. The cure of PMDI resin was found to be significantly faster in pine relative to corresponding poplar samples. Resin impregnation showed a significant species dependent effect on the wood mechanical properties; the resinated pine samples showed increase in compliance while the corresponding poplar samples became stiffer. The in situ lignin relaxation was studied with both dynamic and static modes, using plasticized wood samples. Results showed that the lignin relaxation was slightly affected by resin impregnation in both woods, but the effect was relatively larger in pine. Static experiments of dry wood samples showed a significant reduction in the interchain interactions of wood polymers in pine samples, exclusively. Investigation of plasticized pine samples, which focuses on the in situ lignin relaxations, showed only minor changes with resin impregnation. This led us to hypothesize that the large changes observed in dry samples, were due to the in situ amorphous polysaccharides. The wood-PMDI interactions were significantly reduced upon acetylation of wood. This study also discusses three new and highly sensitive methods for the analysis of wood-resin interactions. / Ph. D.

Bakgrund: Aerob kapacitet är en viktig fysiologisk egenskap och kan mätas genom maximala- och submaximala tester. Ekblom-Bak testet (EB-testet) är ett submaximalt cykeltest medan Cooper 12 min test (CRT-12) är ett maximalt test, men dem båda uppskattar maximal syreupptagningsförmåga (VO2max) genom matematiska formler. Det finns fördelar med estimerade tester i idrottsvärlden, men tillförlitligheten varierar. Syftet var att undersöka validiteten av EB-testet och CRT-12 genom kriterievaliditet för ett urval av uthållighetsidrottare. Vidare syftar studien till att undersöka om det sker en eventuell över- eller underestimering av EB-testresultat och av CRT-12 testresultat. Metod: De rekryterade studiedeltagarna var åtta uthållighetsidrottare inom olika uthållighetsidrotter. Studien bestod av två testtillfällen. Vid första testtillfället genomfördes EB-test och ett VO2max test. Under andra testtillfället genomförde CRT-12. Uppmätt relativt syreupptag ställdes mot estimerade värden genom Bland-Altman analys och Interklass korrelation koefficient (ICC). Resultat: EB-testet hade måttlig överensstämmelse med ICC värde av 0,57. CRT-12 hade god överensstämmelse med ICC värde av 0,75. Både mätmetoderna överestimerade resultat vid jämförelse mot kriteriemetoden.  Konklusion: För studiens urval ansågs CRT-12 ge mer tillförlitliga resultat än EB-testet. För att kunna möjliggöra generalisering av resultatet behövs vidare forskning med en större urvalsgrupp av studiedeltagare. / Background: Aerobic capacity is a physiological component which can be measured through maximal- and submaximal tests. The Ekblom-Bak test (EB-test) is a submaximal cycle test whereas Cooper 12 min run test (CRT-12) is a maximal test, but they both estimate maximal oxygen consumption (VO2max) through mathematical formulas. There are advantages of estimated testing methods in the sports world, but reliability varies. The study aims to investigate the validity of the EB-test and the CRT-12 through criterion validity for a sample of endurance athletes. Further the study aims to investigate if there occurs an over- or under estimation of the EB-test results and of the CRT-12 results. Method: The recruited participants where eight endurance athletes from various sports. The study consisted of two test occasions. The first occasion consisted of the EB-test and the VO2max test. The second occasion consisted of the CRT-12. Measured relative oxygen consumption was opposed to the estimated values through a Bland-Altman plot and a interclass corelation coefficient (ICC). Results: The Ekblom-bak test was seen to have moderate agreement with an ICC of 0,57. The cooper 12 min run test was seen to have good agreement with an ICC of 0,75. Both tests overestimated the results when compared to the criterion method. Conclusion: For the population of the study, it was seen that CRT-12 is more reliable than the EB-test. To be able to generalise the results there is a need for further research with a larger study population.

Mit der Entwicklung und Einführung ökologischer Bauweise im Neubau sowie neuen Baustoffsystemen in Sandwichbauweise wird es zunehmend erforderlich, neue effektive Befestigungsvarianten zu entwickeln, die eine dauerhafte Fixierung auch unter sicherheitstechnischen Bestimmungen sowie aus Garantie- bzw. haftungsrechtlichen Gründen ermöglichen. Die aus der Praxis bisher bekannten chemischen Befestigungssysteme (Zweikomponentenverbundmörtel, Verbundankerpatronen) weisen hinsichtlich der Applikation unter bautechnischen Bedingungen noch einige Nachteile auf. Dazu gehören vor allem längere Aushärtungszeiten zur Realisierung der abschließenden Verbundfestigkeit, Inhomogenitäten im Verbund, der Einsatz toxischer Verbindungen und eine Limitierung der Applikationsmöglichkeiten in horizontalen und Überkopf-Einsatzbereichen sowie Hohlkammersystemen. Alle zuvor genannten Punkte haben bis jetzt die Nutzung solcher Verbundwerkstoffe als universale Anwendungsmöglichkeit verhindert. Ein neues chemisches Befestigungssystem, welches aus Novolak gehärteten mit Hexamethylentetramin (Hexa) und anorganischen Füllstoff besteht, wurde für Applikationen in Beton entwickelt. Das Bindemittel härtet bei der Temperaturzuführung aus. Die unkatalysierte Befestigungsmasse zeigt bei einer Temperatur zwischen 150-300 °C eine hohe Reaktivität. Die Vorteile dieses Systems sind die unbegrenzte Lagerfähigkeit der vorgemischten härtbaren Masse sowie die Gewährleistung einer homogenen Netzwerkstruktur im gesamten Verbund und sie ist frei von giftigen und flüchtigen Substanzen. Auf den Einsatz toxischer Substanzen wurde verzichtet. In dieser Arbeit wurde die Gesamtkinetik der Reaktion während des Aushärtungsprozesses dieser Polymerkomposite untersucht. Die DSC- (nicht-isothermen, isothermen) und MDSC-Untersuchungen haben sich als ein sicheres Verfahren zur Qualitätskontrolle des Aushärtezustands der Befestigungssysteme herausgestellt. Parallel zur nicht-isothermischen und isothermischen DSC wurden Leitfähigkeitsmessungen durchgeführt, um den Endpunkt der Aushärtungsreaktion zu bestimmen. / The development and introduction of ecological construction methods and the use of sandwich materials make it necessary to develop new fixing systems and technologies. Dealing with the application in concrete and other substrates commercial chemical fixing systems show some disadvantages up to date. Especially the rather long curing time in order to realize the final bond strength, inhomogenities in the composite, the partial use of toxic substances and application limits of such systems in horizontal direction as well as hollow section materials has so far prevented the use of such composites for all-purpose applications. A new chemical fixing system, which consists of hexamethylene tetramine (hexa) cured novolac and inorganic filler, was developed for application in concrete. It is applied by a thermo-curing procedure. The uncatalyzed curable mixture has a high reactivity at temperature between 150-300 °C. Compared with commercial chemical fixing systems, the premixed curable mass has many benefits. First it has a unique storage stability and second, it is free of toxic and volatile substances. Another important aspect is, it is self-foaming. In this study was investigated the overall kinetics of the reaction during the curing process of these polymer composites. An appropriate method for this experiment proved to be the DSC in isothermal and non-isothermal mode and MDSC. This turned out to be a safe quality control technique for these systems. Parallel to the non-isothermal and isothermal DSC conductivity measurements have been performed to determine the end point of the curing reaction.

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Impact Polypropylene Copolymers (IPCs) are extremely complex materials, consisting of a mixture of polypropylene homopolymer and copolymers having different comonomer (ethylene) contents and chemical composition distributions. IPC can only be effectively analysed by multidimensional analytical approaches. For this, initially, the individual components have to be separated according to any of their molecular characteristics, either by chemical composition distribution (CCD) or molar mass distribution (MMD), followed by further analysis of these separated fractions with conventional analytical techniques. The combination of preparative temperature rising elution fractionation (TREF) with several other analytical techniques have been reported for the thorough characterization of this material. However, even the combinations of these methods were of limited value due to the complex nature of this polymer. Therefore, novel analytical approaches are needed for a more detailed compositional analysis of IPCs. This work describes a number of multidimensional analytical techniques that are based on the combination of fractionation and hyphenated techniques. Firstly, preparative TREF was combined with high temperature size exclusion chromatography-FTIR (HT SEC-FTIR), HT SEC-HPer DSC (High Performance Differential Scanning Calorimetry) and high temperature two-dimensional liquid chromatography (HT 2D-LC) for the comprehensive analysis of a typical impact polypropylene copolymer and one of its midelution temperature TREF fractions. HT SEC-FTIR analysis provided information regarding the chemical composition and crystallinity as a function of molar mass. Thermal analysis of selected SEC fractions using a novel DSC method - High Speed or High Performance Differential Scanning Calorimetry (HPer DSC) - that allows measuring of minute amounts of material down to micrograms, yielded the melting and crystallization behaviour of these fractions which is related to the chemical heterogeneity of this complex copolymer. High temperature 2D-LC analysis provided the complete separation of this TREF fraction according to the chemical composition of each component along with its molar mass distribution. In a second step, the compositional characterization by advanced thermal analysis (HPer DSC, Flash DSC 1, and solution DSC) of the TREF-SEC fractions was extended to all semi-crystalline and higher temperature TREF fractions. By applying HPer DSC at scan rates of 5−200°C/min and Flash DSC 1 at scan rates of 10−1000°C/s, the metastability of one of the fractions was studied in detail. DSC measurements of TREF-SEC cross-fractions at high scan rates in p-xylene successfully connected reversely to the slow scan rate in TREF elution, if corrected for recrystallization. Finally, the exact chemical structure of all HT HPLC separated components was determined by coupling of HT HPLC with FTIR spectroscopy via an LCTransform interface. This novel approach revealed the capability of this hyphenated technique to determine the exact chemical composition of the individual components in the complex TREF fractions of IPCs. The HT HPLC–FTIR results confirmed the separation mechanism in HPLC using a solvent gradient of 1-decanol/TCB and a graphitic stationary phase at 160°C. FTIR analysis provided information on the ethylene and propylene contents of the fractions as well as on the ethylene and propylene crystallinities. / AFRIKAANSE OPSOMMING: Impak Polipropileen Kopolimere (IPKe) is uiters komplekse materiale, bestaande uit 'n mengsel van polipropileen homopolimeer en kopolimere met verskillende komonomeer (etileen) inhoud en chemiese samestelling verspreiding. IPKe kan slegs doeltreffend ontleed word deur multidimensionele analitiese benaderings te volg. Hiervoor moet die individuele komponente aanvanklik eers geskei word volgens enige van hul molekulêre eienskappe, hetsy deur die chemiese samestelling verspreiding (CSV) of molêre massa verspreiding (MMV), gevolg deur 'n verdere ontleding van hierdie geskeide fraksies met konvensionele analitiese tegnieke. Die kombinasie van voorbereidings temperatuur-verhogings eluasie fraksionering (TVEF) met verskeie ander analitiese tegnieke is gerapporteer vir die deeglike karakterisering van hierdie materiaal. Maar selfs die kombinasies van hierdie metodes was van beperkte waarde as gevolg van die komplekse aard van hierdie polimeer. Daarom word nuwe analitiese benaderings benodig vir 'n meer gedetailleerde komposisionele ontleding van IPKe. Hierdie studie beskryf 'n aantal multidimensionele analitiese tegnieke wat gebaseer is op die kombinasie van fraksionering en gekoppelde tegnieke. Eerstens is voorbereidings TVEF gekombineer met hoë temperatuur grootte-uitsluitingschromatografie-FTIR (HT GUC-FTIR), HT GUC-HPer DSK en hoë temperatuur twee-dimensionele vloeistof chromatografie (HT 2D-VC) vir die omvattende ontleding van 'n tipiese impak polipropileen kopolimeer en een van sy mid-eluasie temperatuur TVEF fraksies. HT GUC-FTIR analiese het inligting verskaf met betrekking tot die chemiese samestelling en kristalliniteit as 'n funksie van molêre massa. Termiese analiese van geselekteerde GUC fraksies deur gebruik te maak van 'n nuwe-DSK metode - Hoë Spoed of Hoë Prestasie Differensïele skandeer kalorimetrie (HPer DSK) - wat die meting van klein hoeveelhede materiaal tot by mikrogram hoeveelhede toelaat, het die smelt en kristallisasie gedrag van hierdie fraksies bepaal wat verwant is aan die chemiese heterogeniteit van hierdie komplekse kopolimeer. Hoë temperatuur 2D-LC analiese het die volledige skeiding van hierdie TVEF fraksie volgens die chemiese samestelling van elke komponent saam met die molêre massa verspreiding moontlik gemaak. In 'n tweede stap, is die komposisionele karakterisering deur gevorderde termiese analiese (HPer DSK, Flash DSK 1 en oplossing DSK) van die TVEF-GUC fraksies uitgebrei na alle semi-kristallyne en hoër temperatuur TVEF fraksies. Deur die gebruik van HPer DSK, teen ’n skandeerspoed van 5-200°C / min, en Flash DSK 1, teen ’n skandeerspoed van 10-1000°C / s, is die meta-stabiliteit van een van die fraksies in detail bestudeer. DSK metings van TVEF-GUC kruis-fraksies by 'n hoë skandeeerspoed in p-xyleen het suksesvol omgekeerd verbind aan die stadige skandeerspoed in TVEF eluasie, wanneer gekorrigeer vir dekristallisatie. Ten slotte is die presiese chemiese struktuur van al die HT HPVC geskeide komponente bepaal deur die koppeling van HT HPVC met FTIR spektroskopie deur middel van 'n LC-transform-koppelvlak. Hierdie nuwe benadering het die vermoë van die gekoppelde tegniek om die presiese chemiese samestelling van die individuele komponente in die komplekse TVEF fraksies of IPKe te bepaal aan die lig gebring. Die HT HPVC-FTIR resultate het die skeidingsmeganisme in HPVC bevestig deur die gebruik van ’n oplosmiddelgradiënt van 1-dekanol/TCB en 'n graphitiese stasionêre fase by 160°C. FTIR analiese verskaf inligting in verband met die etileen en propileen inhoud van die fraksies sowel as die etileen en propileen krystalliniteit.

No description available.

The interactions which occur between both polar and non-polar fluid phases and surfaces of various carbon materials: Activated Carbon (AC), non-porous Carbon Black (CB) and Multiwall Carbon Nanotubes (MWCNTs)with different surface chemistry have been studied. These are currently of great interest as they govern the interfacial behaviour of carbons in a wide range of applications; separation adn composite technologies being two prime examples. Consequently, techniques for chemical modification of carbon surfaces ar also of interest. Surface oxygen functional groups have been introduced, or modified, using the following oxidation techniques: liquid-phase oxidation (both AC and CB), Fenton and Birch reduction treatment (MWCNTs) and in a more controlled manner using gas-phase ozone treatment (CB). The chemistry of all the resulting carbon surfaces were characterised using X-ray Photoelectron Spectroscopy (XPS), which gives a quick and direct quantitative measure of the external surface composition. This technique, which has not yet been extensively employed in detailed adsorption studies, is a promising alternative to Temperature Programmed Desorption (TPD) and Boehm titration method in the determination of oxygen and other surface groups. Physical effects of the various surface modifications have been studied using a variety of techniques appropriate for the material in question. Scanning Electron Microscopy (SEM) images show some deteriorating effects of the liquid-phase oxidations on the structure of both activated carbon and carbon black materials. Conversely, surface areas from nitrogen adsorption at 77oK, coupled witj immersion calorimetry data for toluene, show thet the physical structure of the carbon blacks is not modified by ozone treatment. This has allowed a detailed study of the effects of surface oxygen level (i.e. polarity) on vapour adsorption. Regarding the MWCNT materials, detailed High-Resolution Electron Microscopy (HRTEM) photographs show that the multi-wall structure of the nanotubes in not significantly disrupted during the introduction of active functional groups by the Fenton or Birch treatment and therefore keeping intact their mechanical properties which augurs well for their use as reinforcement in composite structures whilst also improving their dispersion properties in polar fluids. A systematic shift to higher adsorption values, due to the increasing specific interactions between the alcohol -OH groups and the surface oxygen groups, is observed in all the isotherms of alcohols from the CB series as the total surface oxygen concentration ([O]T) increases. Moreover, this effect was observed to be most significant for methanol confirming that the mechanism of adsorption is dominated by hydrogen bonding and therefore dependant on the surface concentration of oxygen sites; whereas it becomes less marked in the case of ethanol and isopropanol respectively due to the increasing non-specific, dispersion, interactions of the alkyl chain with the non-polar carbon surface. Overall correlations were observed between the surface oxygen concentration [O]T, the resulting enthalpy of immersion -^Hi values and the characteristic energy E of the Dubinin-Radushkevich-Kaganer (DRK) equation obtained for toluene and these alcohols and the influence of the carbon surface chemistry on the character of the adsorption isotherms is also discussed. This behaviour is also observed and much more pronounced in the case of water adsorption on other oxidised carbon materials (AC, CB and MWCNT) due to the higher polarity of water molecules. The water adsorption data were analysed using in particular the Dubinin-Serpinsky (DS) equation and also some of its recent variations such as Barton and D'Arcy & Watt equations. The DS2 and various Barton equations were found to fit best the AC and CB materials modified by liquid-phase oxidations and also for the CB 03 series with increasing level of oxidation while both D'Arcy & Watt equations gave the best fittings for the MWCNTs materials. It was also shown that the resulting parameters ao (for the DS equation) describing the surface concentration of primary polar adsorption sites and as the limiting water adsorption value were both linked to the surface oxygen level [O]T. Regarding interfacial bonding, the oxidised CB and MWCNT materials are expected to show an improved physicochemical wetting of their surfaces by various resin compunds

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Le développement de sondes moléculaires fluorescentes pour le suivi ex vivo de phénomènes biologiques (communication nerveuse, par exemple) est en plein essor. Dans cette optique, des dérivés fluorescents de cyclotrivératrylènes (CTV), cavitands propices à la complexation de petites molécules organiques, ont été synthétisés. La stratégie utilisée consiste à introduire des groupements électro-donneurs et électro-attracteurs conjugués sur chaque unité aromatique du CTV afin d’avoir des systèmes de type « push-pull ». L’extension de la conjugaison entre les groupements électro-attracteurs et électro-donneurs a été envisagée afin d’améliorer les propriétés spectroscopiques des sondes. Des réactions de couplage organométallique de Sonogashira, ainsi que des cycloadditions alcynes-azotures catalysées par le cuivre (CuAAc), ont été conduites sur le squelette CTV dans ce but. La caractérisation spectroscopique des différentes sondes fluorescentes développées a été réalisée en milieu organique et en conditions physiologiques, pour celles dont la solubilité le permettait. L’étude des propriétés de reconnaissance de ces dernières, pour des ammoniums d’intérêt biologique (tels que les neurotransmetteurs, acétylcholine, dopamine et dérivés) en conditions physiologiques, a également été menée par spectrofluorimétrie, ainsi que par d’autres techniques (RMN, calorimétrie). La formation d’assemblages moléculaires en milieu aqueux a également été mise en évidence (expériences de diffusion dynamique de la lumière, microscopie électronique en transmission), pour certaines sondes lors de ce travail. / The development of fluorescent probes for the ex vivo detection of biological phenomena (neuronal communication, for example) presents a growing interest. In this context, fluorescent cyclotriveratrylene (CTV) derivatives have been developed, as these cavitands are known to complex small organic molecules. The strategy used to get interesting spectroscopic properties, was to introduce conjugated electron-donating and electron-withdrawing groups on each aromatic unit of the CTV (leading to “push-pull” systems). To improve the spectroscopic properties of the probes, the conjugation between the electron-donating and the electron-withdrawing groups was extended. Hence, the Sonogashira organometalic coupling reaction and the copper catalyzed cycloaddition directly on CTV skeleton were used. The spectroscopic characterization of the new fluorescent probes synthesized was done, in organic solvent but also in physiological conditions when the solubility permits it. The recognition studies for biological ammoniums, such as neurotransmitters (acetylcholine, dopamine, and derivatives) were performed in physiological conditions by spectrofluorimetry but also other methods (like MNR or micro-calorimetry). The formation of molecular assemblies was also observed (by dynamic light scattering and transmission electron microscopy) during this work with some of the probes.