Viscosity of beta-glucan in oat products

Selostus: Kauran beetaglukaanin viskositeetti kauratuotteissa

Reaction Kinetics and Viscosity Modelling in the Fusion Syntheses of Ca- and Ca/Mg-resinates

Rosin is a natural product from pine forests and it is used as a raw material in resinate syntheses. Resinates are polyvalent metal salts of rosin acids and especially Ca- and Ca/Mg- resinates find wide application in the printing ink industry. In this thesis, analytical methods were applied to increase general knowledge of resinate chemistry and the reaction kinetics was studied in order to model the non linear solution viscosity increase during resinate syntheses by the fusion method. Solution viscosity in toluene is an important quality factor for resinates to be used in printing inks. The concept of critical resinate concentration, c crit, was introduced to define an abrupt change in viscosity dependence on resinate concentration in the solution. The concept was then used to explain the non-inear solution viscosity increase during resinate syntheses. A semi empirical model with two estimated parameters was derived for the viscosity increase on the basis of apparent reaction kinetics. The model was used to control the viscosity and to predict the total reaction time of the resinate process. The kinetic data from the complex reaction media was obtained by acid value titration and by FTIR spectroscopic analyses using a conventional calibration method to measure the resinate concentration and the concentration of free rosin acids. A multivariate calibration method was successfully applied to make partial least square (PLS) models for monitoring acid value and solution viscosity in both mid-infrared (MIR) and near infrared (NIR) regions during the syntheses. The calibration models can be used for on line resinate process monitoring. In kinetic studies, two main reaction steps were observed during the syntheses. First a fast irreversible resination reaction occurs at 235 °C and then a slow thermal decarboxylation of rosin acids starts to take place at 265 °C. Rosin oil is formed during the decarboxylation reaction step causing significant mass loss as the rosin oil evaporates from the system while the viscosity increases to the target level. The mass balance of the syntheses was determined based on the resinate concentration increase during the decarboxylation reaction step. A mechanistic study of the decarboxylation reaction was based on the observation that resinate molecules are partly solvated by rosin acids during the syntheses. Different decarboxylation mechanisms were proposed for the free and solvating rosin acids. The deduced kinetic model supported the analytical data of the syntheses in a wide resinate concentration region, over a wide range of viscosity values and at different reaction temperatures. In addition, the application of the kinetic model to the modified resinate syntheses gave a good fit. A novel synthesis method with the addition of decarboxylated rosin (i.e. rosin oil) to the reaction mixture was introduced. The conversion of rosin acid to resinate was increased to the level necessary to obtain the target viscosity for the product at 235 °C. Due to a lower reaction temperature than in traditional fusion synthesis at 265 °C, thermal decarboxylation is avoided. As a consequence, the mass yield of the resinate syntheses can be increased from ca. 70% to almost 100% by recycling the added rosin oil.

Crystallization characteristics of bioactive glasses

Bioactive glasses are excellent candidates for implant materials, because they can form a chemical bond to bone or guide bone growth, depending on the glass composition. Some compositions have even shown soft tissue attachment and antimicrobial effects. So far, most clinical applications are based on monoliths, plates and particulates of different grain sizes. There is a growing interest in special products such as porous implants sintered from microspheres and fibers drawn from preforms or glass melts. The viscosity range at which these are formed coincides with the crystallization temperature range for most bioactive glasses, thus complicating the manufacturing process. In this work, the crystallization tendency and its kinetics for a series of glasses with their compositions within the range of bioactivity were investigated. The factors affecting crystallization and how it is related to composition were studied by means of thermal analysis and hot stage microscopy. The crystal compositions formed during isothermal and non-isothermal heat treatments were analyzed with SEM-EDXA and X-ray diffraction analysis. The temperatures at which sintering and fiber drawing can take place without interfering with crystallization were determined and glass compositions which are suitable for these purposes were established. The bioactivity of glass fibers and partly crystallized glass plates was studied by soaking them in simulated body fluid (SBF). The thickness of silica, calcium and phosphate rich reaction layers on the glass surface after soaking was used as an indication of the bioactivity. The results indicated that the crystallization tendencies of the experimental glasses are strongly dependent on composition. The main factor affecting the crystallization was found to be the alkali oxide content: the higher the alkali oxide content the lower the crystallization temperature. The primary crystalline phase formed at low temperatures in these glasses was sodium calcium silicate. The crystals were found to form through internal nucleation, leading to bulk crystallization. These glasses had high bioactivity in vitro. Even when partially crystalline, they formed typical reaction layers, indicating bioactivity. In fact, sodium calcium silicate crystals were shown to transform in vitro into hydroxyapatite during soaking. However, crystallization should be avoided because it was shown to retard dissolution, bioactivity reactions and complicate fiber drawing process. Glass compositions having low alkali oxide content showed formation of wollastonite crystals on the surface, at about 300°C above the glass transition temperature. The wide range between glass transition and crystallization allowed viscous flow sintering of these compositions. These glasses also withstood the thermal treatments required for fiber drawing processing. Precipitation of calcium and phosphate on fibers of these glasses in SBF suggested that they were osteoconductive. Glasses showing bioactivity crystallize easily, making their hot working challenging. Undesired crystallization can be avoided by choosing suitable compositions and heat treatment parameters, allowing desired product forms to be attained. Small changes in the oxide composition of the glass can have large effects and therefore a thorough understanding of glass crystallization behavior is a necessity for a successful outcome, when designing and manufacturing implants containing bioactive glasses.

Determination of slurry’s viscosity using case based reasoning approach

Case-based reasoning (CBR) is a recent approach to problem solving and learning that has got a lot of attention over the last years. In this work, the CBR methodology is used to reduce the time and amount of resources spent on carry out experiments to determine the viscosity of the new slurry. The aim of this work is: to develop a CBR system to support the decision making process about the type of slurries behavior, to collect a sufficient volume of qualitative data for case base, and to calculate the viscosity of the Newtonian slurries. Firstly in this paper, the literature review about the types of fluid flow, Newtonian and non-Newtonian slurries is presented. Some physical properties of the suspensions are also considered. The second part of the literature review provides an overview of the case-based reasoning field. Different models and stages of CBR cycles, benefits and disadvantages of this methodology are considered subsequently. Brief review of the CBS tools is also given in this work. Finally, some results of work and opportunities for system modernization are presented. To develop a decision support system for slurry viscosity determination, software application MS Office Excel was used. Designed system consists of three parts: workspace, the case base, and section for calculating the viscosity of Newtonian slurries. First and second sections are supposed to work with Newtonian and Bingham fluids. In the last section, apparent viscosity can be calculated for Newtonian slurries.

Lämpökynttilän palo-ominaisuuksiin vaikuttavien tekijöiden analytiikka: raaka-aineet, sydänlanka, rakenne ja olosuhteet

Työn tavoitteena oli tutkia lämpökynttilän palo-ominaisuuksiin vaikuttavia tekijöitä. Työn taustalla on yhteistyö suomalaisen kynttilävalmistajan kanssa. Kynttilävalmistajan lämpökynttilöissään käyttämän raaka-aineen hinnan noustessa, on valmistaja kiinnostunut käyttämään edullisempia raaka-aineita. Palamisen kriteerit saavuttavan kynttilän valmistaminen markkinoilla olevista uusista raaka-aineista on havaittu olevan haastavaa, ja vaatii edelleen kehitystyötä. Teoriaosassa käytiin läpi kynttilänvalmistusta yleisesti, RAL-laatustandardin asettamat kriteerit lämpökynttilälle, palamiseen vaikuttavia tekijöitä sekä työn kokeellisessa osassa käytettyjen analyysimenetelmien periaatteet. Työn kokeellisessa osassa tutkittiin erilaisten kynttiläraaka-aineiden koostumusta ja ominaisuuksia sekä sydänlankojen rakennetta. Lisäksi tutkittiin, miten sydänlangan sisältämien säikeiden määrä, eri raaka-aineiden seossuhteiden muutos sekä jäähdytyslämpötilan muutos vaikuttavat lämpökynttilän palo-ominaisuuksiin. Työssä myös selvitettiin muutaman markkinoilla olevan kynttilän raaka-ainekoostumus. Tutkimuksissa havaittiin, että vaadittavan liekin korkeuden saavuttamiseksi viskositeetti on yksi raaka-aineen tärkeimmistä ominaisuuksista. Raaka-aineen viskositeetin kasvaessa tarvitaan paksumpi sydänlanka. Raaka-aineen viskositeetin kasvaessa liekin korkeus ei aina pienene, koska liekin korkeuteen vaikuttaa myös langalle tehty kemiallinen käsittely. Mitä korkeampi kynttilän liekki on, sitä suurempi on raaka-aineen kulutus eli palovuo ja tällöin liekin korkeus vaikuttaa myös kynttilän paloaikaan. Kokeissa havaittiin, että liekin korkeuden ollessa vakio, palovuo oli korkein steariinilla. Steariinin jälkeen tulivat palmuvaha ja parafiini. Tällöin parafiinia tarvittiin vähemmän vastaavan paloajan saavuttamiseksi. Nopean jäähdytyksen havaittiin vaikuttavan palmuvahan palovuohon alentavasti, vaikka jäähdytystavalla ei ollut vaikutusta liekin korkeuteen.