Radiation Effects in Polyamides

Polyamides (PAs) are largely used either as engineering materials in virgin form or as composites and a component of polymer blends. Various processes have been used to modify some properties of polymers to improve their utility. For this purpose, radiation technologies present clear, one-step procedures and offer improvement to the performance of PA materials. Irradiation by accelerated electron beams, γ-rays, and accelerated protons is applied on PAs, particularly PA-6, as well as PA composites. Variations of important characteristics, such as chemical structure, supermolecular structure, mechanical properties, thermal resistance, water absorption, and other parameters, are analyzed involving results obtained by other authors. The application of irradiation on incompatible polymer blends involving PA is presented as well. The selection of radiation treatment of PAs has to be considered to obtain optimal results

Príjem a uvoľňovanie vlhkosti vlnou ožiarenou elektrónovým lúčom

In this work, wool samples a) degreased and stored in desiccator (WD), b) degreased and stored freely (WF), c) cleaned in water and stored freely (WW) were irradiated by accelerated electron beam with doses within the range (0-400) kGy in air. Content of S-sulphonate as primary oxidation product was determined in WD using FTIR spectra inverted in the second-order derivative spectra. The uptake of humidity by all the samples at room temperature and 97% relative humidity was examined gravimetrically. As expected, the highest humidity uptake was observed for WD and the smallest one for WW. Development of the humidity uptake showed some fluctuation for all samples and, for WD the fluctuation corresponded with generated S-sulphonate, presumably due to formation of numerous H-bonds. The increasing uptake of humidity for WD and WW was observed up to 40 kGy dose while for WF, the uptake decreased below the initial level already from 16 kGy. Surface tension was measured using sink-float method combining stalagmometry. The initial surface tension of WW was higher than for WD and WF but, grew equally for all samples from 25 kGy. From 100 kGy dose the surface tension showed stabilized level. The humidity release by WD was measured using thermogravimetry. Variation of the rate humidity release around 100 °C, adequate for desorption of weakly bound water, and the mass residue of the heated wool for 120 °C corresponding to release of total water, showed an inverse dependence. It was concluded that content of S-sulphonate is responsible for variability of the sorption properties. The more S-sulphonate formed, the higher uptake of humidity and the lower rate of humidity release that can be observed. It is suggested that, within a certain range, a properly chosen dose can affect humidity uptake.V tejto práci vzorky vlny a) odmastenej a uloženej v exsikátore (WD), b) odmastenej a uloženej voľne (WF), c) čistenej vo vode a uloženej voľne (WW), boli ožiarené na vzduchu urýchleným elektrónovým lúčom s dávkami v rozsahu (0-400) kGy. Obsah S-sulfonátu ako primárneho oxidačného produktu bol stanovený vo WD pomocou druhej derivácie FTIR. Príjem vlhkosti všetkých vzoriek bol skúmaný gravimetricky pri laboratórnej teplote a relatívnej vlhkosti 97%. Ako sa dalo očakávať, najvyšší príjem vlhkosti bol pozorovaný pre WD, najnižší pre WW. Ukázalo sa, že príjem vlhkosti kolísal vo všetkých vzorkách, pre WD kolísanie korelovalo s vygenerovaným S-sulfonátom, pravdepodobne v dôsledku vzniku početných H-väzieb. Stúpajúci príjem vlhkosti pre WD a WW bol pozorovaný do dávky 40 kGy, zatiaľ čo pre WF príjem klesol pod pôvodnú úroveň už pri dávke 16 kGy. Povrchové napätie bolo merané flotačnou metódou kombinovanou so stalagmometriou. Počiatočné povrchové napätie WW bolo vyššie ako u WD a WF, avšak rástlo rovnako pre všetky vzorky od dávky 25 kGy. Od dávky 100 kGy sa povrchové napätie ustálilo. Uvoľňovanie vlhkosti vo WD bolo merané termogravimetricky. Zmeny rýchlosti uvoľňovania vlhkosti pri teplote okolo 100 °C, adekvátnej desorpcii slabo viazanej vody a hmotnosť zvyšku zahrievanej vlny pri 120 °C zodpovedajúcemu uvoľňovaniu celkovej vody, poskytli inverznú závislosť. Dospeli sme k záveru, že za variabilitu sorpčných vlastností je zodpovedný obsah S-sulfonátu. Čím viac S-sulfonátu sa vytvorilo, tým vyšší nárast vlhkosti a nižšia rýchlosť uvoľňovania vlhkosti bola pozorovaná. Predpokladá sa, že v rámci určitého rozmedzia a pri vhodne zvolenej dávke je možné ovplyvniť príjem vlhkosti

Testing of electron beam irradiated sheep wool for adsorption of Cr(III) and Co(II) of higher concentrations

Electron beam irradiated sheep wool dosed (0–410) kGy showing good adsorption properties was tested for Cr(III) and Co(II) of higher concentrations. Fitting to ten isotherm models was examined as follows: Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, Flory-Huggins, Halsey, Harkins-Jura, Jovanovic, Elovich and Redlich-Peterson. Both cations being Lewis acids generate complex salts, such as carboxylates or cysteinates, with ligands from keratin. Various composition and architecture of the complexes are responsible for different isotherm model fitting. The chromic cation showed adherence to Freundlich, Temkin, Halsey, Harkins-Jura and Jovanovic models for all or almost all dosed samples unlike cobaltous cation matching Langmuir, Flory-Huggins and Redlich-Peterson isotherm models. No model fitted the both examined cations simultaneously. On the contrary, simultaneously non-fitting to all dosed samples was observed for Elovich and partially Dubinin-Radushkevich models. © 2021 The Author(s)Univerzita Palackého v Olomouc

Radiation-modified wool for adsorption of redox metals and potentially for nanoparticles

Electron beam irradiated sheep wool with absorbed radiation doses ranging from 0 to 165 kGy showed good adsorption properties toward copper cations. The Cu(ii) being Lewis acid generated several types of complex salts based on carboxylates or cysteinates with ligands available in keratin. Under these conditions, cross-links were formed between the keratin chains. Experimental data obtained from Cu(ii) adsorption using the concentration of 800-5,000 mg/L were tested for fitting to 10 isotherm models. Various compositions and architectures of the Cu(ii)-complexes were specified to be responsible for different isotherm model fittings. The copper cation showed adherence to Langmuir, Flory-Huggins, and partially Redlich-Peterson models. The latter clearly distinguished the native wool from the modified ones. Another aim is to investigate the conditions for the adsorption of anti-microbial nanoparticles in addition to the redox-active metals on radiation-modified wool taking into account that the diffusion of nanoparticles into the modified wool is governed by electrostatic interactions. © 2020 Mária Porubská et al., published by De Gruyter 2020.Research and Developments Support Agency [APVV-15-0079

INCREASING OF PROFESSIONAL COMPETENCES OF FUTURE TEACHERS – EDUCATION TO OHS

Nebezpečenstvo je stav alebo charakteru pracovného procesu, ktorý môže poškodiť zdravie študenta alebo zamestnanca. To je dôvod, prečo prevencia - vo forme pravidelných stretnutí organizovaných ako súčasť vzdelávacieho procesu - je nevyhnutná. Cieľom pravidelne organizovaných stretnutí (napr. odborné semináre, prednášky a praktické cvičenia) pre študentov je zoznámiť sa s dôležitosťou vzdelávania v oblasti BOZP (vrátane chemickej bezpečnosti, správnej manipulácie s chemickými látkami, poskytnutím prvej pomoci pri ohrození života a zdravia a neodkladným zásahom pri záchrane majetku). Príspevok poukazuje na dôležitosť vzdelávania v oblasti dodržiavania zásad bezpečnej práce a ochrany zdravia študentov - budúcich učiteľov chémie.The danger is the state or the characteristics of working process that can damage the health of a student or an employee. That is why the prevention – in the form of regular organized sessions as a part of educational process – is inevitable. The aim of the sessions (such as seminars, lectures and as well as practical trainings) for students is to become familiar with the importance of OHS education (including chemical safety, proper manipulation with chemical substances, providing first aid when life-threatening situations take place, as well as immediate intervention when material assets are in danger). The article proves the importance of education in field of respecting the safe work and the prevention of students health – future teachers of chemistry

Competitive Cation Adsorption on Electron-Irradiated Sheep Wool Changes the Fitting of Adsorption Isotherms for Single-Component Solutions

This work analyses 10 adsorption isotherm models applied to adsorption of Cr(III) and Cu(II) from binary solutions on electron-irradiated sheep wool (0-24-100) kGy. The results are compared with fitting the same adsorbates from corresponding single solutions. The competing cation significantly changes the fitting of the selected isotherms to the extent that even simultaneous fitting of the same cation in the single and binary solution is rare. In the case of Cr(III), 4 favourable matches were found out of 30 compared cases, while in the case of Cu(II), only 2 conformities were found. Having the Cr(III) coordination number exclusively of 6, but Cu(II) up to 4, 5, 6, the last coordinates more easily with the ligands provided by keratin, resulting in preferential chemisorption. If there is still a lack of cysteic acid in the wool to interact with Cr(III) also, this is adsorbed on the wool physically, too. The amount of cysteic acid increasing in the wool with the absorbed dose of energy improves the chemisorption of Cr(III), as well. It can be summarized that during competitive adsorption, Cu(II) binds by chemisorption and Cr(III) by both physisorption and chemisorption, depending on the dose of energy absorbed by the wool

Sorpcja pranej wełny owczej

Sheep wool intended for sorption examination was scoured using three procedures consisting of (1) an ultrasonic tempered bath with tap water, (2) the same as (1) but with detergent, and (3) dichloromethane extraction. The loss of wool mass and removal of Cu, Zn and Pb-cations by the scoured wool as a sorbent were tested. While the loss of mass indicated consistency among all procedures, the cation removal was slightly variable. However, the differences are acceptable, concluding that an ultrasonic water bath without any agent is most favoured. The omission of a detergent or carcinogenic solvent can make the scouring process cleaner and environmentally-friendlier.Wełnę owczą przeznaczoną do badania sorpcji oczyszczono stosując trzy sposoby: (1) kąpiel ultradźwiękowa z użyciem wody wodociągowej; (2) to samo, jak (1), ale z detergentem i (3) ekstrakcja dichlorometanem. Badano utratę masy wełny i usuwanie kationów Cu, Zn i Pb. Podczas, gdy utrata masy występowała we wszystkich trzech przypadkach, usuwanie kationów było nieznacznie zmienne. Stwierdzono, że kąpiel ultradźwiękowa bez jakiegokolwiek środka jest najbardziej optymalna. Pominięcie detergentu lub rakotwórczego rozpuszczalnika może sprawić, że proces prania stanie się bardziej przyjazny dla środowiska

Why Natural or Electron Irradiated Sheep Wool Show Anomalous Sorption of Higher Concentrations of Copper(II)

Sorption of higher concentrations of Cu(II) solution onto natural sheep wool or wool irradiated by an electron beam was studied. Sorption isotherms were of unexpected character, showing extremes. The samples with lower absorbed doses adsorbed less than non-irradiated wool, while higher doses led to increased sorption varying with both concentration and dose. FTIR spectra taken from the fibre surface and bulk were different. It was concluded that there was formation of Cu(II)-complexes of carboxylic and cysteic acids with ligands coming from various keratin macromolecules. Clusters of chains crosslinked through the ligands on the surface limit diffusion of Cu(II) into the bulk of fibre, thus decreasing the sorption. After exhausting the available ligands on the surface the remaining Cu(II) cations diffuse into the keratin bulk. Here, depending on accessibility of suitable ligands, Cu(II) creates simple or complex salts giving rise to the sorption extremes. Suggestion of a mechanism for this phenomenon is presented

Time-Dependent Variations in Structure of Sheep Wool Irradiated by Electron Beam

Wool scoured in tap water with no special degreasing and containing a balanced humidity responding to usual laboratory conditions was irradiated by accelerated electron beam in the range of 0–350 kGy dose. Time variations of the wool structure were measured using FTIR, Raman, and EPR spectroscopy. The aim was to determine whether preexposure treatment of the wool, as well as postexposure time, affects the properties of the irradiated wool. Reactive products such as S-sulfonate, cystine monoxide, cystine dioxide, cysteic acid, disulphides, and carboxylates displayed a considerable fluctuation in quantity depending on both the absorbed dose and time. Mutual transformations of S-oxidized products into cysteic acid appeared to be faster than those in dry and degreased wool assuming that the present humidity inside the fibres is decisive as an oxygen source. EPR results indicated a longer lifetime for free radicals induced by lower doses compared with the radicals generated by higher ones. The pattern of the conformational composition of the secondary structure (α-helix, β-sheet, random, and residual conformations) also showed a large variability depending on absorbed dose as well as postexposure time. The most stable secondary structure was observed in nonirradiated wool but even this showed a small but observable change after a longer time, too

Some Properties of Electron Beam-Irradiated Sheep Wool Linked to Cr(III) Sorption

We examined the characteristics of an electron beam irradiated wool with an absorbed dose of (21–410) kGy in comparison with natural wool with respect to the determination of the isoelectric point (IEP), zero charge point (ZCP), mechanism of Cr(III) sorption from higher concentrated solutions, and the modelling of the wool-Cr(III) interaction. The data of ZPC and IEP differed between natural and irradiated samples. Increasing the dose shifted the pH of ZPC from 6.85 for natural wool to 6.20 for the highest dosed wool, while the natural wool IEP moved very little, from pH = 3.35 to 3.40 for all of the irradiated samples. The sorption experiments were performed in a pH bath set at 3.40, and the determination of the residual Cr(III) in the bath was performed by VIS spectrometry under optimized conditions. The resulting sorptivity showed a monotonically rising trend with increasing Cr(III) concentration in the bath. Lower doses, unlike higher doses, showed better sorptivity than the natural wool. FTIR data indicated the formation of complex chromite salts of carboxylates and cysteinates. Crosslinks via ligands coming from different keratin chains were predicted, preferably on the surface of the fibers, but to a degree that did not yet inhibit the diffusion of Cr(III)-cations into the fiber volume. We also present a concept of a complex octahedral structure