Tato práce se zabývá studiem termooxidační stability kompozitů polymethylmethakrylátu (PMMA) plněného mikro a nanočásticemi siliky. V připravených vzorcích byly použity různé objemové zlomky a různé velikosti částic siliky. Studium stability bylo prováděno pomocí termogravimetrie, která umožňuje simulovat podmínky termooxidační degradace. Indukční perioda byla stanovena za použití různých rychlostí ohřevu a aplikací izokonverzních metod. Závislosti teplot degradací na rychlostech ohřevu sloužily pro určení parametrů odvozených ze čtyř různých teplotních funkcí, které dovolují předpověď stability materiálu (indukční periody) při zvoleném rozsahu teplot. Zjištěné výsledky ukazují, že větší částice siliky snižuji stabilitu PMMA, zatímco nanočástice v nízkých koncentracích ji nijak neovlivňují.

Akrylbaserat bencement är den gyllene standarden vid ryggförstärkningsförfaranden. Modifiering av akrylbencement med linolsyra har resulterat i attraktiva egenskaper vilka möjliggör lättare hantering för kirurger och minskar efterföljande komplikationer såsom närliggande ryggradsfrakturer. Även om de attraktiva egenskaperna hos linolsyramodifierat bencement är kända är ännu förståelsen för hur linolsyra påverkar egenskaperna outforskade. Som en komponent i bencement måste linolsyra steriliseras innan den används i bencement. Det finns emellertid oro för att autoklavsterilisering av linolsyra orsakar nedbrytning. Dessutom är det oklart vad som händer med linolsyra i härdat bencement över tid. I detta examensarbete utvärderades steriliserad och osteriliserad linolsyra. Linolsyra blandades med olika komponenter som finns i bencementet såsom aktivator, initiator, monomer och inhibitor, i närvaro och frånvaro av lösningsmedel. De efterföljande förändringarna studerades genom 1H NMR och UV-VIS. Resultaten visade att linolsyra bryts ned av sterilisering och oxidation. Oxidationen av linolsyra berodde på sterilisering, temperatur, lösningsmedel och mängden syrexponering. Det bekräftades genom 1H NMR och UV-VIS att linolsyra reagerade (steriliserad och osteriliserad) med aktivatorn, initiatorn och monomeren. Dessa reaktioner kan minska tillgängligheten av komponenterna för in situ-polymerisation av monomeren, och därmed förändra bencementens egenskaper, vilket i sin tur bidrar till lättare hantering under förstärkningsförfarandet och reducerar intilliggande ryggradsfrakturer efter operation. / Acrylic bone cement is the gold standard in vertebral augmentation procedures. Modification of acrylic bone cement using linoleic acid has resulted in attractive properties that enable convenient handling by surgeons and reduce follow-up complications such as adjacent vertebral fractures. Even though the attractive properties of linoleic acid-modified bone cement are acknowledged, the understanding of how it imparts those properties remain unexplored. As a component in bone cement, linoleic acid needs to be sterilized before its use in bone cement. However, there are apprehensions whether autoclave sterilization of linoleic acid causes degradation. In addition, it is unclear what happens with linoleic acid in hardened bone cement over time.  In this thesis, sterilized and unsterilized linoleic acid were evaluated alone and treated with different components of the bone cement such as activator, initiator, monomer, and inhibitor, in the presence and absence of solvent, and the ensuing changes were monitored through 1H NMR and UV-VIS. The results showed that linoleic acid degraded due to sterilization and oxidation. The oxidation of linoleic acid depended on sterilization, temperature, solvent, and the amount of oxygen exposure. As confirmed through 1H NMR and UV-VIS, linoleic acid (sterilized and unsterilized) reacted with the activator, initiator, and monomer. These reactions could reduce the availability of the components for the in-situ polymerization of the monomer, thus altering the properties of the bone cement including convenient handling during the operation and reduced adjacent vertebral fractures post the operation.

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Natural weathering and wear of structural materials in service nearly always generate surface roughness, and follow the Central Limit Theorem prediction for surface topology. This study couples experimental and statistical theory, and FEM to extend knowledge of life of materials from initial service surface conditions through surface damage accumulation. Statistical moments and other parameters were correlated with fracture locations probability (H/N), versus auto correlation length, and depth. As the surface grows to a full Gaussian, H/N increases its dependence on profile’s Average and RMS Roughness, and derived parameters. This dependence shows an asymptotic limit behavior that approaches agreeably Griffith’s crack criterion, though with multiple pit locations. Importantly, a Transitional Region was observed, below which the probable location of fracture is uncorrelated to the parameters studied. This is because introduced roughness is insufficient to compete with impurities, internal and external manufacturing flaws, and scratches, due to handling and machining, on the samples.

"NIST's Fire Dynamics Simulator (FDS) is a powerful tool for simulating the gas phase fire environment of scenarios involving realistic geometries. If the fire engineer is interested in simulating fire spread processes, FDS provides possible tools involving simulation of the decomposition of the condensed phase: gas burners and simplified pyrolysis models. Continuing to develop understanding of the capability and proper use of FDS related to fire spread will provide the practicing fire engineer with valuable information. In this work three simulations are conducted to evaluate FDS V.4's capabilities for predicting upward flame spread. The FDS predictions are compared with empirical correlations and experimental data for upward flame spread on a 5 m PMMA panel. A simplified flame spread model is also applied to assess the FDS simulation results. Capabilities and limitations of FDS V.4 for upward flame spread predictions are addressed, and recommendations for improvements of FDS and practical use of FDS for fire spread are presented."

Objetivo: O objetivo deste estudo foi avaliar clínica e hitologicamente a reação do material de preenchimento em dois sítios diferentes. Método: Vinte e duas femêas de ratos Wistar (Rattus novergicus) foram submetidas a aplicação de PMMA testando duas técnicas: subcutânea e transmuscular. Passados 3 meses do ato cirúrgico os ratos foram eutanasiados e as áreas injetadas foram excisadas, submetidas a técnica de inclusão em parafina e coloração por hematoxilina e eosina. As lâminas foram analisadas observando-se a resposta local à injeção do corpo estranho quanto ao grau de inflamação. Resultados: Foi encontrada diferença significativamente estatística entre os sítios muscular e subdérmico quanto a formação de granuloma (p<0,05), sendo que o grupo subdérmico obteve melhores resultados. Conclusão: A aplicação de materiais de preenchimento, que provoca maior trauma e sangramento nos tecidos, é a casusa de reações adversas. / Objective: The objective of this study was to evaluate clinical and hitopathology the reaction of the fill material at two different sites. Method: Twenty-two female Wistar rats (Rattus norvegicus) submitted the application of PMMA testing two techniques: subcutaneous and trans. After 3 months of surgery, the rats were euthanized and the injected areas were excised, subjected to paraffin embedding technique and stained with hematoxylin and eosin. The slides were analyzed by observing the local response to injection of foreign body in the degree of inflammation. Results: We found statistically significant differences between sites and subdermal muscle as granuloma formation (p <0.05), and the subdermal group achieved better results. Conclusion: The application of filling materials, which causes more injury and bleeding in the tissues, is Casusa of adverse reactions.

In this study, the nanocomposite of graphene and PMMA at the different volume fractions was investigated by molecular dynamics and dissipative particle dynamics simulations. The MD simulation can be performed to simulate the nanocomposite system at different weight fractions to obtain the different repulsive parameters. After obtaining the repulsive parameters, the DPD simulation can be utilized to study the equilibrium phase of graphene and PMMA nanocomposite. From our result, all equilibrium phases at different volume fractions are cluster. However, it is difficult to enhance the property for nanocomposite material due to the aggregated graphene (cluster). Hence, we change the interaction repulsive parameters to stand for the different degrees of functionalized graphene. When the interaction repulsive parameter is smaller than 80, the equilibrium phase is dispersion. In addition, the different number of functionalized garphene bead per graphene was studied, and results show that the equilibrium phase is dispersion when all graphene beads per graphene are functionalized.

The thermal conductivity of PMMA films with thicknesses from 5 to 50 nanometers and layered over a treated silicon substrate is explored numerically by the application of the reverse non-equilibrium molecular dynamics (NEMD) technique and the development of a coarse-grained model for PMMA, which allows for the simulation time of hundreds of nanoseconds required for the study of large polymer systems. The results showed a constant average thermal conductivity of 0.135 W/m_K for films thickness ranging from 15 to 50 nm, while films under 15 nm in thickness showed a reduction of 30% in their conductivity. It was also observed that polymer samples with a degree of polymerization equal to 25% of the entanglement length had 50% less thermal conductivity than films made of longer chains. The temperature profiles through the films thickness were as predicted by the Fourier equation of heat transfer. The relative agreement between the thermal conductivity from experiments (0.212 W/m_K for bulk PMMA) and the results from this investigation shows that with the proper interpretation of results, the coarse-grained NEMD is a useful technique to study transport coefficients in systems at larger nano scales.

The existing researches on interface properties between heterology materials mainly focus on semiconductor-metal and dielectric materials, but little on organic-inorganic ones. In recent years, the nanometer scale phenomena of interfaces between organic-inorganic is gaining a lot of attentions and becoming new frontier regions of nano-related research. Since gold exhibits excellent optical, electrical and mechanical properties, which can be applied to nano-optics, mechanics and electronics. Therefore this study aims to investigate the deformation behavior of nanaoindentation using molecular dynamics simulation and nanoindentation experiments. The nano-effect of mechanical properties between the interface of gold and heterologous Polymethyl Methacrylate (PMMA) with different side groups; i.e., Isotactic-PMMA, Syndiotactic-PMMA and Atactic-PMMA, are explored, respectively. The molecular structures of those side groups of the different PMMAs are identified and characterized. Those PMMA isomer thin films are prepared using spin-coater to deposit the different side groups of PMMA upon Au thin film. Sputter technique is used to form gold thin film with different thickness. The morphology on the surface of samples is characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The indenter equipment is applied to realize the interface mechanical properties. The time-dependent properties of viscoelastic materials in nanoscale are measured using continuous stiffness measurement (CSM) nanoindentation technique. The effects of displacement rates on the hardness and modulus behavior of PMMA-based are investigated by nanoindentation. The mechanical properties are correlated with the side groups of the PMMA. The hardness of the PMMA-based increases with the raising displacement rate of the Berkovich tip. On the other hand, the modulus of the variation PMMA-based with the varied displacement rate of the Berkovich tip is not significant. The nanoindentation test shows different constituents in nanocomposite systems with a stronger material properties of the interface region than the matrix in each material.