Tomas Sedlacek

On the development and characterisation of crosslinked sodium alginate/gelatine hydrogels.

Sodium alginate (SA) and gelatine (G) based hydrogels with various SA/G ratios, crosslinked with calcium ions (Ca(2+)) and glutaraldehyde (GTA), respectively, were developed. Scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), and dynamic mechanical analysis (DMA) were applied to determine their physicochemical characterization. The swelling studies, conducted in phosphate-buffered saline with a pH ranging from 1 to 11 at 37 °C, were utilized for an evaluation of their absorption ability. FTIR spectra of the Ca(2+) crosslinked SA/G hydrogels revealed a small shift in symmetric stretching carboxyl groups, indicating an ionic binding between the Ca(2+) ions and the SA. Increasing the G content in hydrogels crosslinked with GTA significantly changed the shapes of the amide I and II bands in the FTIR spectra, thus confirming the G-GTA crosslink formation. After crosslinking, a DMA study proved the enhanced viscoelastic properties and improved thermal stability of the prepared samples. The obtained data indicated that Ca(2+) crosslinked hydrogels with a SA/G 50/50 ratio provide a good balance of swelling and viscoelastic properties, making them applicable as a potential nontoxic wound dressing material capable of adequately assuring a moist environment, elasticity and mechanical strength for comfortable wound healing.

On PVT and Rheological Measurements of Polymer Melts

Abstract The relation between PVT and rheological measurements of several polymer melts including polyethylenes, polypropylene, polystyrene, poly(methyl methacrylate), and polycarbonate has been taken into investigation. Pressure-temperature dependent viscosities, determined on rotational and backpressure-modified capillary rheometers, were fitted through the Carreau-Yasuda model. PVT data was analyzed by the help of the Simha-Somcynsky equation of state (SS EOS). The thermodynamical parameters of the SS EOS were connected to constant-stress viscosity (experimental) and zero-shear viscosity (extrapolated). The Doolittle relationship was modified into the form of η = exp(C1 ln(h′h)). The relation was employed and tested for the data evaluation. It proved to be a good tool for linearization of PVT and rheological data.

Pressure and Temperature Dependence of LDPE Viscosity and Free Volume: The Effect of Molecular Structure

Abstract Temperature and pressure dependencies of shear and elongational viscosities were examined using rotational and capillary rheometers. Two different batches of the same polymer grade have shown that the molecular structure diversion significantly influences the magnitudes of pressure coefficients, which vary more than the temperature coefficients. The pressure effect on viscosity notably depends on the amount of long-chain branching in polymer. Further, the paper shows that pVT data analysis via the Simha-Somcynsky equation of state can be employed to reveal differences in temperature and pressure viscosity dependencies through the free volume fraction.

On Pressure Affected Shear Viscosity of Poly(Lactic) Acid

Evaluation of pressure coefficient of polymer melt viscosity has become important parameter taken into account for flow behavior prediction in polymer processing simulation software. In this paper, the pressure coefficient of biodegradable polymers, poly(lactic) acid (PLA), was investigated. A capillary rheometer equipped with back pressure device controlling pressure in polymer melt during flow was employed for experiments. Pressure sensitivity was evaluated through pressure coefficient calculated via fitting of obtained viscosity data by the help of Carreau‐Yasuda model. It was found that pressure coefficient of PLAs is strongly affected by the internal structure of tested polymer.

Synthesis and Effect of Hierarchically Structured Ag-ZnO Hybrid on the Surface Antibacterial Activity of a Propylene-Based Elastomer Blends

In this study, a hybrid Ag-ZnO nanostructured micro-filler was synthesized by the drop technique for used in plastic and medical industry. Furthermore, new antibacterial polymer nanocomposites comprising particles of Ag-ZnO up to 5 wt % and a blend of a thermoplastic polyolefin elastomer (TPO) with polypropylene were prepared using twin screw micro-compounder. The morphology and crystalline-phase structure of the hybrid Ag-ZnO nanostructured microparticles obtained was characterized by scanning electron microscopy and powder X-ray diffractometry. The specific surface area of this filler was investigated by means of nitrogen sorption via the Brunauer-Emmet-Teller method. A scanning electron microscope was used to conduct a morphological study of the polymer nanocomposites. Mechanical and electrical testing showed no adverse effects on the function of the polymer nanocomposites either due to the filler utilized or the given processing conditions, in comparison with the neat polymer matrix. The surface antibacterial activity of the compounded polymer nanocomposites was assessed against Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538P, according to ISO 22196:2007 (E). All the materials at virtually every filler-loading level were seen to be efficient against both species of bacteria.

In vivo efficacy and properties of semisolid formulations containing panthenol

Panthenol is an active substance used in dermatology to protect the health of the skin, to treat defects in the morphology of the stratum corneum. In cosmetology, hydrating, softening, and barrier function of panthenol are utilized. Detailed studies evaluating the efficacy of panthenol in cosmetic and pharmaceutical semisolid formulations and establishing its optimum concentration are needed.

Processing Techniques for Polyolefins

Without any doubts it could be stated that among the other types of polymeric materials only polyolefins are processed into such amount of products: blown packaging and agriculture films; extruded hygienic foils, building and car industry sheets and foams, pressure pipes, wires and cables insulation; blown moulded containers, tanks, detergent bottles or car defrost air systems; injection moulded consumer (end use) products; melt blown non-woven fabrics; coated and laminated paper or its substitution. Easiness of polyolefins processing connected with relative high melt stability and low processing temperature, possibility to modify properties of final products via molecular tailoring—copolymerization, alloying, grafting, crosslinking and high recycling potential guarantee further successful future for polyolefins for a wide range of applications. Deeper discussion of selected individual continuous processes and processing aspects is presented in this chapter.