Agnese Grigaloviča

The effect of nanosize ZnO on the properties of the selected polymer blend composites

In the current research the effect of ZnO nanoparticles on the structure and properties of common thermoplastic polymers (polyoxymethylene (POM), polypropylene (PP), ethylene--octene copolymers (EOC)) and their binary blends is investigated. EOC content in the composites varies from 0 to 50 wt. %. The amount of nanostructured ZnO filler in the composites is changed in the interval from 0 to 5 wt. %. Tensile and frictional properties of ZnO modified nanocomposites are investigated. Results of the investigation show that ZnO additions cause increment in stiffness and strength as well as coefficient of friction of the investigated nanocomposites. The effect of ZnO modifier is the highest at low EOC content. The effect of ZnO is strongly dependent on the compatibility and crystallinity of the investigated nanocomposites.

Structural characterization of cevimeline and its trans-impurity by single crystal XRD.

Cevimeline is muscarinic receptor agonist which increases secretion of exocrine glands. Cevimeline base is a liquid (m.p. 20-25 °C) at ambient conditions, therefore its pharmaceutical formulation as a solid hydrochloride hemihydrate has been developed. The synthesis of cevimeline yields its cis- and trans-isomers and only the cis-isomer is recognized as the API and used in the finished formulation. In this study structural and physicochemical investigations of hydrochloride hemihydrates of cis- and trans-cevimelines have been performed. Single crystal X-ray analyses of both cis- and trans-isomers of cevimeline are reported here for the first time. It was found that the cis-isomer, the API, has less dense crystal packing, lower melting point and higher solubility in comparison to the trans-isomer.

Impact of non-functionalized and ionic liquid modified carbon nanotubes on mechanical and thermal properties of ethylene- octene copolymer nanocomposites

In this article the development and characterization of composites made from metallocene based ethylene-octene copolymer (EOC) with 38% octene content, non-modified or modified multi walled carbon nanotubes (MWCNTs), covalently functionalised with long chain hexadecyl moiety imidazolium ionic liquid (IL-f-MWCNTs), is presented. The procedure of MWCNTs functionalization is discussed. In order to obtain a good dispersion of the filler, composites with MWCNTs and IL-f-MWCNTs in the concentration range of 0.5-12 wt.% were made by ultrasonication / thermoplastic mixing method. The results indicated improvement in mechanical properties with increase of the filler content. The methodology of the development of EOC matrix nanocomposites with IL-f-MWCNTs showed advantages of the conductive material creation with high mechanical stiffness compared to direct melt mixing of EOC with non-modified MWCNTs. A notable enhancement of thermal stability was observed in case of both pristine MWCNTs and IL-f-MWCNTs containing EOC nanocomposites, which was attributed to scavenging action of the nanofiller. Modification of EOC with IL-f-MWCNTs showed somewhat increased efficiency in enhancing overall thermal stability of the composites because of better dispersion of the nanofiller due to compatibilizing effect of IL modifier.

Thermal stability of polyacetal/ethylene-octene copolymer/zinc oxide nanocomposites

In this work we investigate binary blends of polyoxymethylene and ethylene octene copolymer (EOC) and their composites with nanostructured zinc oxide (ZnO). EOC content in the composites varies from 0 to 50 wt. %. The amount of ZnO filler in the composites is changed in the interval from 0 to 5 wt. %. Thermal properties of composites are investigated with thermogravimetric analysis and differential scanning calorimetry. It is observed that ZnO addition increases thermal stability of the investigated composites.

Aging of Nanosized ZnO Modified Polyoxymethylene Blends with Ethylene–octene Copolymer

The influence of ethylene–octene copolymer and zinc oxide (ZnO) on structure and tensile stress–strain behavior of polyoxymethylene were investigated before and after ultraviolet weathering. Addition of ZnO considerably improved stress–strain characteristics of the ultraviolet-irradiation impaired composites. Crystallinities of ultraviolet-irradiated composites were affected by numerous competitive processes, including suppression of crystallization in the presence of multiple components in the system, nucleation induced by nanofiller, secondary crystallization and amorphization because of the chain scissions of the macromolecules. Addition of ZnO considerably improved stability of the composites, as testified by corresponding changes in the intensities of hydroxyl and carbonyl absorption peaks. GRAPHICAL ABSTRACT

Elastic Properties and Phase Transition of Polyoxymethylene and Ethylene-Octene Copolymer Composites

Multifunctional heterogeneous blends offer great possibilities of tailoring properties of materials. In this work polyoxymethylene (POM) co-polymer is blended with ethylene- octene co-polymers with various alpha-octene contents (EOC38 and EOC17) in a complete volumetric content range to fabricate specific multifunctional materials with tailored stress-strain properties. Elastic properties of POM/EOC38 and POM/EOC17 binary blends are evaluated by considering Voigt, Reuss and Kerner models. It is shown that Kerner approach is more suitable for prediction of the modulus of the investigated blends in comparison to Voigt and Reuss models. It is shown that in both blends POM has a tendency to form continuous phase up to EOC contents of 0.61 and 0.78 vol. p. for POM/EOC38 and POM/EOC17 respectively. The tendency of EOC to form a matrix is not so expressed.

Thermal and Mechanical Properties of Unvulcanized Polypropylene Blends with Different Elastomers: Ethylene-Propylene-Diene Terpolymer, Nitrile-Butadiene Copolymer and Chlorinated Polyethylene

In this work, composites of isotactic polypropylene (PP) with three unvulcanized elastomers – terpolymer of ethylene-propylene-dicyclopentadiene (EPDM), chlorinated polyethylene (CPE) and copolymer of acrylonitrile-butadiene (NBR) – have been investigated. The purpose of the investigation was to create PP/elastomer blend composites of significantly different compositions (with an excess of PP, intermediate ones, and with an excess of elastomer) and to study the dependence of tensile behaviour and elastic properties on the blends with different component ratio. Tensile properties have been recognized from the stress-strain curves. The changes of elastic modulus have been characterized with respect to the Hashin-Shtrikman upper and lower bounds and the Davies equation. Calorimetric properties of PP blends with elastomers (crystallinity and melting behaviour of polypropylene phase) have also been investigated with the method of differential scanning calorimetry (DSC).

Mechanical and thermomechanical properties of radiation modified poly(ethylene-octene)/Ni-Zn ferrite nanocomposites

Poly(ethylene-1-octene) copolymer (POE) composites filled with nickel-zinc ferrite nanoparticles have been modified by exposure to an electron beam at doses up to 500 kGy. The influence of radiation dose and ferrite content on mechanical properties has been investigated. Thermomechanical properties – thermorelaxation stresses formed in thermal heating and thermo residual stresses resulting in the process of full setting and cooling of materials have been investigated for radiation cross-linked oriented (extended up to 100%) composite samples. Increase of concentration of ferrite particles and increase of radiation dose affects a notable increase of elastic modulus and reduces the deformability in comparison to entire elastomer. Improvement of thermomechanical properties especially at low irradiation doses (100–150 kGy) have been detected for composites with increase of ferrite filler content up to 5 wt. %. It was found that gel content of POE increased up to 85% for pristine POE material with increase of irradiation dose up to 500 kGy due to the formation of cross-linked structure, increase of filler concentration up to 5 wt. % affect reduction in gel fraction due to uniform dispersion in amorphous (ethylene and substituted with hexyl branches) POE phases.