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Preparation and characterization of unsaturated bio-polyester resins
Žůrek, Michal ; Petrůj, Jaroslav (referee) ; Figalla, Silvestr (advisor)
The theoretical part of this work is devoted to the selection of suitable components for synthesis of a branched oligoester and their structural arrangement. Further, oligomers of lactic acid esterified with crotonic acid branched by erythritol or pentaerythritol are discussed. Crosslinking of prepared oligoesters is accomplished by free radical mechanism using vinyl acetate as reactive diluent and 2,2'-azo-bis-isobutyronitrile as initiator. Resin was cured by vinyl acetate in different mass ratios. Results show that there in an optimal ratio for curing between oligoester and reactive diluent. Using less vinyl acetate results in insufficient crosslink density or, on the contrary, using considerable excess of vinyl acetate causes rapid polymerization, that also results in lower density of crosslinking. The crosslink density was determined indirectly by extraction of the soluble part to acetone after curing and drying of the product.
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Butyl Rubber Modified Using Expanded Graphite
Žůrek, Michal ; Petruš, Josef (referee) ; Kučera, František (advisor)
This work deals with the influence of expanded graphite (EG) as a reinforcing filler on the mechanical and tribological properties of vulcanizates of butyl rubber blends. Tensile strength, elongation at break, moduli (M100, M200, M300 a M500), and Young's modulus of elasticity of the prepared vulcanizates were studied by the tensile test method. In addition to the tensile test results, the dispersion of EG particles was studied on scanning electron microscopy (SEM) images of the fracture surfaces of the prepared vulcanizates. The filler-matrix interaction was evaluated using the Kraus model for filled rubber and the results were subsequently compared with SEM images of the EG particle-matrix interface on the fracture surfaces of the vulcanizates. The effect of EG on the properties of the vulcanizates was compared with the effect of common rubber blacks (N220 and N772). It was found that an important factor affecting the mechanical properties of filled vulcanizates is the dispersion of filler particles. EG dosage higher than 5 phr promotes the agglomeration of filler particles in the butyl rubber matrix, which negatively affects the mechanical properties of the blend. Vulcanizates filled only with EG have lower tensile strength than those filled with N220 or N772 blacks. By choosing an appropriate ratio of EG to blacks, higher mechanical strength was achieved than with the use of only one filler.
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Preparation and characterization of unsaturated bio-polyester resins
Žůrek, Michal ; Petrůj, Jaroslav (referee) ; Figalla, Silvestr (advisor)
The theoretical part of this work is devoted to the selection of suitable components for synthesis of a branched oligoester and their structural arrangement. Further, oligomers of lactic acid esterified with crotonic acid branched by erythritol or pentaerythritol are discussed. Crosslinking of prepared oligoesters is accomplished by free radical mechanism using vinyl acetate as reactive diluent and 2,2'-azo-bis-isobutyronitrile as initiator. Resin was cured by vinyl acetate in different mass ratios. Results show that there in an optimal ratio for curing between oligoester and reactive diluent. Using less vinyl acetate results in insufficient crosslink density or, on the contrary, using considerable excess of vinyl acetate causes rapid polymerization, that also results in lower density of crosslinking. The crosslink density was determined indirectly by extraction of the soluble part to acetone after curing and drying of the product.
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Návrh obnovy krovové konstrukce kostela
Žůrek, Michal
The main aim of this thesis is to evaluate current situation and propose renovation of the wooden roof structure of the baroque Dominican church of the Holy Cross in Znojmo. Disrepair historic truss structure over the church is the main impetus for the creation of technical documentation. Truss structure assessment was based on sensory and instrumental methods. The technical documentation of the existing structures (including drawings) was created in the first part. In the next phase, the research evaluates damage of the timber parts of construction and determination of their causes.In the third stage, redevelopment arrangements of damaged parts of the construction are proposed. This proposal will serve as a basis for their restoration.A large part of the work consists of drawings, supplemented with a 3D model of the truss structure.
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