National Repository of Grey Literature 111 records found  beginprevious58 - 67nextend  jump to record: Search took 0.00 seconds. 
Compressibility of the powder mixture with calcium hydrogen phosphate dihydrate.
Brejchová, Veronika ; Řehula, Milan (advisor) ; Šklubalová, Zdeňka (referee)
Compaction process can be evaluated with the viscoelastic parameters and with compaction equations too. Viscoelastic paramaters are obtained from test of stress relaxation and force-displacement compression profile. The equation of compaction expreses the dependence of volume, density or height of pressed material on the pressure. With this parameters we are able to define various phases of compaction process, mechanism of this process and to characterize pressed material. This diploma thesis deals with the evalution model granulate, which was made from lactose monohydrate and corn starch with in the addition with calcium hydrogen phosphate dihydrate in the ratio from 10 % to 40 %. The samples were evaluated three-exponentional equation was created in the Department of pharmaceutical technology Faculty of Pharmacy in Hradec Králové. This equation is based on the equation of Cooper and Eaton, but it isn't based on real density and charakterizes individual parametrs. In this thesis, it was found that during the pre-compaction and elastic deformation phases, the parameters A1/A2 and E1/E2 are in decrease, while t1/t2 is in increase. In the phase of plastic deformation parameters A3 and E3 grow. It means that with decreasing reduction of volume, the enrergy is in decrease and the process is...
Compressibility of the powder mixture with microcrystalline cellulose.
Hrdinová, Petra ; Řehula, Milan (advisor) ; Ďoubal, Stanislav (referee)
Compressing process can be evaluated by the parameters that are acquired from the record of force-run, stress relaxation or compaction equation. Compac- tion equation expresses the dependency on height, volume or density compression moulded material by pressure. In these thesis is pressing process characterized by parameters of compaction equation. Original Heckel equation declared range of pressing pressures, which caused plastic deformation of materials. Simultaneously pressed material is characterized by rate constant, expressing the rate of reduction of material in the plastic deformation. In these thesis is used triple - exponential equation, which was created at the Department of Pharmaceutical Technology and which is based on Cooper-Eaton equation. In a comparison between the Cooper- Eaton equation, the triple-exponential equation is not based on genuine values of density and detailed interpretation of the meaning of individual parameters. These thesis evaluates the granulate produced from a mixture of lactose monohydrate and microcrystalline cellulose and starch in mixtures where the microcrystalline cellulose is added at the concentration of 10, 20, 30, 40 %. The work results showed that with increasing reduction of volume, at the same time increases the volume of energy consumption and...
Compressibility of different batches of the drug Simvastatin.
Havelková, Adéla ; Řehula, Milan (advisor) ; Ondrejček, Pavel (referee)
This thesis deals with the characterization of pressing energy using the force-displacement diagram. The theoretical part defines the substance - simvastatin - and excipients which could occur in unknown samples. Also energies of pressing process, methods of assessment of force-displacement diagram for different substances and factors which affect pressability and thus the pressing energy are described there. The aim of the experimental part of the thesis was to characterize the energy profile using force-displacement diagram of eight batches of preparation simvastatin and to find applicable method of assessment. Tablets were pressed from each batch of preparations using a T1-FRO 50 machine at three pressing forces 5, 10, and 15 kN. Obtained parameters E2, E3, Elis and Pl were evaluated using three methods: method of outlying values, method of analysis of average for one factor and method of analysis of average for two factors. The most suitable method for assessment of divergent values is the method of analysis of average for two factors thanks to its complex character. This method showed lower values of the parameters E1, E2, Elis and Pl for batches E, G and H which could be caused by larger particles and higher moisture of granulate.
Monosaccharides and disaccharides classification by Creep testing Mehod
Frýdlová, Dana ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
- EN The name of study: Monosaccharides and disaccharides classification by Creep testing Method Student: Mgr. Dana Frýdlová Tutor: Doc. RNDr. Milan Řehula, CSc. Consultant: Mgr. Roman Adámek Department of Pharmaceutical Technology, Faculty of Pharmacy in Hradec Kralove, Charles University in Prague, Czech Republic Background: The whole process of tablet compression is depended on viscoelastic properties of fillers. Terms plasticity and elasticity are not clearly defined. In this area, their interpretation results from a method which is applied. Aim: In this study the Creep test was used for classification of viscoelastic properties of following fillers: sorbitol, manitol, saccharose, Tabletose and anhydrous lactose. Methods: Measurement was realized by a special apparature T1 - FRO 50 (producer: Zwick GmbH and Co, Ulm, Germany) and the compaction process was recorded by a special software, which was connected to the compressing device. Obtained data were processed by Origin Professional 7.5 and Microsoft Excel. Results: Monosaccharides were found to be more plastic and more pressable than disaccharides. The most plastic material was mannitol. Disacharides were more elastic than monosaccharides. Tabletose was the most elastic material. Anhydric form of lactose was more plastic than its monohydric...
Influence of Skid Substances to Compression Equations Parameters
Linková, Markéta ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
Mgr.Markéta Linková The rigorous assignment Influence of Skid Substances to Compression Equations Parameters Abstract The rigorous assignment engages in impact of skid substances on parameters of compression equations. Parameters of compression equations are used for compressed material characteristic and for study of compression process mechanism. The mostly used compression equations are described in the theoretic part. Additionally are analyzed factors, which have influence to the parameters of compression equations. (For example: particles size, material type, compression speed) Target of experiment was to prove influence of skid substances to parameters of compression equations. As a skid substances has been used magnesi stearat and talc. Compression process is possible to evaluate through parameters AR, LT, E, EP. For calculation of polymers on cellulose basis the three - exponential equation has been used. For crystallic substances two - exponential equation has been used. Final results prove that both skid substances had same impact to parameters of compression equations.
Evaluation of Celluloses and Maize Starch by the Creep Test Method
Doležalová, Julie ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
Evaluation of Celluloses and Maize Starch by the Creep Test Method The aim of this work was to consider the appropriateness of using the creep test for evaluation of visco-elastic characteristics of pharmaceutical fillers and to compare these properties. Pharmaceutical powders involved in this assessment were powdered cellulose (Vitacel A 300), hydroxyethylcellulose (HEC, Natrosol 250), hydroxypropylcellulose (HPC, Klucel EF), hydroxypropylmethylcellulose (HPMC, K 100) and maize starch. The powders were compressed with a material-testing machine T1-FRO 50 by compression forces of 0,25; 0,5; 1; 2; 3; 4; 5; 7,5; 10 and 15 kN. Compression data for each tablet were then recorded by a software connected to the compressing machine. The recorded data, such as die displacement and time, were transferred into relation between creep compliance (J) and time. Obtained values were then used for calculating the parameters such as immediate elasticity (E1), retarded elasticity (E2), plasticity (P1) and factor of plasticity (FP). To summarize all results, we can say that hydroxypropylcellulose has the highest values of elasticity and the lowest values of plasticity among all tested powders. Conversely hydroxypropylmethylcellulose shows the lowest elasticity and powdered cellulose presents the most plastic...
The Viscoelasticity of Pharmaceutical Fillers for Direct Tabletting
Adámek, Roman ; Řehula, Milan (advisor) ; Rabišková, Miloslava (referee) ; Špaček, Vladimír (referee)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department of Pharmaceutical technology Candidate: Mgr. Roman Adámek Supervisor: Doc. RNDr. Milan Řehula, CSc. Title of Doctoral Thesis: Viscoelasticity of fillers for direct tablet compacting Keywords: stress relaxation, viscoelasticity, Maxwell-Wischert model, hydrogen bond, van der Waals bond Important property of pharmaceutical fillers is viscoelasticity which can be evaluated in many ways. The Stress relaxation test is a method when a punch of compacting machine stops precisely in a moment of reaching set up pressure and decreasing pressure in a tablet during time is recorded. This action is mathematically described by a three-exponential equation which facilitates to separate the Stress relaxation test in three simultaneously running actions. Each of these actions is described by the moduli of plasticity and elasticity which point out in detail on viscoelastic properties of measured materials. The Stress relaxation test was used for 20 pharmaceutical fillers by 11 compacting pressures. To infer clearer conclusions, tablet strength, Young's modul of elasticity and elastic potential energy were determined. With help of above mentioned compacting parameters conclusions of viscoelasticity and compacting properties of used...
Characterization of Compaction Process According to New Equation Parameters of Compaction
Rysl, Tomáš ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee) ; Rabišková, Miloslava (referee)
Charles University in Prague, Faculty of Pharmacy in Hradec Králové Department: Department of galenic pharmacy Candidate: Mgr. Tomáš Rysl Supervisor: doc. RNDr. Milan Řehula CSc. Title of Doctoral Thesis: Characterization of compaction process according to new equation parameteres of compaction. The thessis deals with comparation of excipients used for production of tablets using new equations of tablet compaction. A lot of mathematical interpretations exist for determination of excipient behaviour during compaction process of tablet production. Obtained parameters of them express more or less possible behaviour of these excipients during compaction. The new mathematical interpretation was proposed for crystallic and polymeric materials. It seems to be very exact method to express compation process very correctly. 40 materials was evaluated according to this new proposed equation of compaction. Zwick/Roell Z050 was used to obtain this equation. Different behaviour of polymeric and crystallic materials has been found out. Behaviour of crystallic materials is interpreted by 2 phases, expressed by biexpoinencial equation. Behaviour of polymeric materials is interpreted by 3 phases, expressed by triexponencial equation. According to obtained paramateres, excipients have been described in term of...
Determining the compression behaviour of fillers and magnesium stearate
Szwedová, Lenka ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
1 Abstract The energy of tablets compaction is obtained from the force-distance record. The aim of this work was to determine accumulated energy in a tablets (plastic energy), to determine energy released from a tablet after compaction (elastic energy) and summation of these two energies. Mixtures of magnesium stearate 0%, 0,5% and 1% were prepared in a blending cube. The T1 - FRO 50 compacting machine was used for compacting tablets (weight of each tablets was 500 mg). Compacting forces were 5, 10 and 15 kN. In the first procedure the compaction was ceased after reaching the maximal compaction force, in the second procedure the upper punch was stopped when the maximal compaction force was reached and during 180 s dwell time of decreasing compacting force was recorded while the tablet height was kept constant. The results show that increasing concentration of lubricant leads to a decrease of accumalated energy in a tablet and on the contrary it leads to an increase of energy released from a tablet. The 180 s dwell time with a tablet height kept constant increases plastic energy because of forming more bonds. Microcrystalline cellulose is characterized by higher plastic and lower elastic energy than lactose monohydrate.
Determining the compression behaviour of microcrystalline cellulose and magnesium stearate
Smékalová, Petra ; Řehula, Milan (advisor) ; Špaček, Vladimír (referee)
This thesis deals with the characterisation of a specific compression process by monitoring the viscoelastic properties of pressed material. The theoretical part of the thesis describes the substances - microcrystalline cellulose and magnesium stearate. It also describes methods for the assessment of tablet viscoelasticity using the force-displacement diagram and factors influencing the viscoelasticity of tablets. The aim of the experimental part of the work is to characterise the viscoelastic properties of microcrystalline cellulose as well as a mixture of microcrystalline cellulose and magnesium stearate lubricant of various lubricant concentrations using the force-displacement diagram and calculation of tablet relaxation. Tablets were pressed from a mixture of aggregates of microcrystalline cellulose and magnesium stearate lubricant using a T1-FRO 50 machine at 11 molding pressures in the range of 1,9 -113,0 MPa with lubricant concentration in the range of 0 % - 2,50 %. The height and diameter of each tablet were measured immediately after pressing and the measurements were repeated 24 hours later. Measurements determined viscoelastic parameters E1, E2, E3, Elis, and P1, and the volumes of the tablets, both at time 0 and after 24 hours. The result of the study was to determine the effect of...

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