Nowadays we meet polymers everywhere. If we exclude a small cave next to a water spring we find the presence of polymers literally in every household. Do you want to make thermal insulation, to distribute water or gas, to paint, do you have cosmetics in your bathroom, have you invested in electronics or computer equipment? As far as you can see everywhere you stumble over polymers. Do you drive a car, do you take a shopping basket, is your food packaged and what about your food? Do you go fishing, do you practise sport activities? In the present world, you are absolutely surrounded – practically absorbed – by polymer products. Don't you feel well? Medicine does not represent an exception.
Naturally, everybody implicitly expects the corresponding quality of polymer products. We do not want to throw a body lotion away after three days as it already subjected to degradation, we do not want to squeeze water out of a toothpaste tube. We expect the efficiency of face masks with nanofibrous mats, we require the efficiency of car dampers driving along uneven roads.
No polymer processing can be successfully handled without knowledge of flow properties of entry polymer components. Let us take as an example above mentioned body lotion. Apart from its stability we also demand easy spreading, in other words, consistency not approaching to water or honey. Therefore, it is also inevitable to set a proper ratio of entry components.
This optimisation is carried out applying so-called rheological measurements by means of which we are able to set a correspondent viscosity. Flow (rheological, rhéin – to flow, logos – science) characteristics are measured using rotational and capillary rheometers providing an application of various geometries. Measured material respecting its consistency is placed (a) between parallel circles – a measurement of a type plate-plate, (b) between a circle and moderate cone – a measurement of a type cone-plate, (c) between concentric cylinders or (d) extruded from a capillary die.
Research at the Institute of Hydrodynamics
The institutional research has two principal aims:
1) To set a correct procedure in preparation of studied materials, to propose adequate rheological measurements and corresponding data processing. An analysis of poly(isobutylene) used for the production of tyres characteristic by its flexibility, elasticity and ductility will be carried out in a completely different way than e.g. purely viscous materials non-accumulating any supplied energy. We also pay attention to the behaviour of polymeric materials in an electric or magnetic field.
2) To propose relationships describing flow behaviour of individual rheological characteristics with an emphasis to widely used shear viscosity. In this point, it is not possible to concentrate only to the numerical approximation of individual curves for individual measurements but a proposed relation (so-called constitutive equation) should be valid for wider ranges of varied parameters. An emphasis is paid especially e.g. to varying molecular weight (also for a reason that its value declared by the manufacturers is quite often non-negligibly different from reality corresponding to the individual batches) and to percentage participation of individual components. In the case of a proposal and usage of empirical relations, the optimal procedure is to derive so-called master curve independent of any adjustable parameter and providing immediately a required quantity (e.g. shear viscosity) after the entry data are input.
Filip, P., Hausnerová, B., Hnátková, E. (2020). Continuous rheological description of highly filled polymer melts for material extrusion. Applied Materials Today. 20(September), 100754.
Filip, P., Hausnerová, B., Barretta, C. (2019). Master flow curves as a tool to modelling Ceramic Injection Molding. Ceramics International. 45(6), 7468-7471.
Sanétrník, D., Hausnerová, B., Filip, P., Hnátková, E. (2018). Influence of capillary die geometry on wall slip of highly filled powder injection molding compounds. Powder Technology. 325, 615–619.
Zelenková, J., Pivokonský, R., Filip, P., (2017). Two ways to examine differential constitutive equations: initiated on steady or initiated on unsteady (LAOS) shear characteristics. Polymers 9(6), 205.
Pivokonský, R., Filip, P., Zelenková, J., (2016). Flexibility of three differential constitutive models evaluated by large amplitude oscillatory shear and Fourier transform rheology. Polymer 104(8), 171-178.
Pivokonský, R., Filip, P., Zelenková, J., (2015). The role of the Gordon-Schowalter derivative term in the constitutive models - improved flexibility of the modified XPP model. Colloid and Polymer Science 293(4), 1227-1236.
Pivokonský, R., Filip, P., Zelenková, J., (2015). Visualization of elongation measurements using an SER universal testing platform. Applied Rheology 25(1).