In English. Summaries in Estonian

Proceedings of the Estonian Academy of Sciences.



Volume 12 No. 2 June 2006


Special  issue  on  polymer  science

Foreword; 83–84

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Andres Öpik

Rheology and surface properties of filled dispersions; 85–95

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Eglë Fataraitë, Pranas Narmontas, Virginija Jankauskaitë,

Asta Milinavièiûtë and Algimantas Juraitis

Abstract. Rheology and wetting properties of commercial water-born dispersion of the copolymer of vinyl ester of a synthetic saturated monocarboxylic acid and acrylate, obtained by emulsion polymerization, have been investigated. For composition modification, 0.8 phr of dibutylglycol as plasticizer and from 0 to 10 phr of TiO2 and Al2O3 particles as filler were added. It has been shown that dispersion behaviour under shear between two coaxially placed cylinders depends not only on the dispersion composition, but on the shear rate as well. At low shear rates (up to 40 s–1), an increase of the viscosity was found, while at higher shear rates dispersion shows pseudoplastic behaviour. Effective amount of TiO2 decreases the intensity of determined anomalies. For pure, plasticized and TiO2 modified dispersions, a tendency to restore viscosity value by decreasing the shear rate was found. This effect for Al2O3 filled dispersion was insignificant. The results of advancing contact angle measurements showed that an addition of up to 3 phr of mineral filler to the dispersion does not change its wetting properties. Higher amounts of fillers worsen wettability properties.

Key words: water-born dispersion, mineral filler, copolymer, rheology, wetting.


Täidetud dispersioonide reoloogia ja pinnaomadused

Küllastatud monokarboksüülhappe vinüülestri ja akrülaadi kopolümeeri vesidispersiooni modifitseerimiseks on kasutatud TiO2 või Al2O3 täiteainena ja dibutüülglükooli plastifikaatorina. Dispersiooni reoloogilise käitumise uurimisel koaksiaalsete silindritega reomeetri abil on leitud erinevate modifikatsioonide reoloogiliste omaduste sõltuvus täiteainete kontsentratsioonist ja nihkedeformatsiooni kiirusest. Kontaktnurga mõõtmise teel on tuvastatud kopolümeeri vesidispersiooni märgamisomaduste sõltuvus täiteainete kontsentratsioonist.

Investigation of solid hybrid solar cells based on molecular glasses; 96–110

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Fabrice Goubard, Reda Aîch, François Tran-Van, Asta Michaleviciute, Franek Wünsch, Marinus Kunst, Josas Grazulevicius, Bernard Ratier and Claude Chevrot

Abstract. We have synthesized new carbazole and ethylenedioxythiophene based molecular glasses with hydrazone and imine goups. Thermal analysis confirms the metastable amorphous properties of these molecules with glass temperature in the range of 62 to 76 °C. Electrochemical properties have been studied and show the effect of the conjugated imine or hydrazone groups on the electronic delocalization of the structures. A decrease of the oxidation potential, compared to the parent unsubstituted molecules, is observed, which decreases the HOMO energetic level and improves the donor properties of the molecules. Amorphous materials of low molecular weight should allow the regeneration of the oxidized sensitizer in agreement with their respective energetic levels. Moreover, all the molecules absorb light in the range of the wavelength, blue-shifted in comparison with the ruthenium dye, which limits the shield effect for a good photogeneration of charge carrier in the dye. Results suggest that such molecular glasses could find applications in photovoltaic devices.

Key words: molecular glasses, photovoltaic cells, TiO2, hybrid materials, TRMC experiments.


Molekulaarklaasidel põhinevate tahkete hübriidpäikesepatareide uurimine

On sünteesitud molekulaarklaasidel põhinevad hüdrasoon- ja imiinrühmadega karbasooli ja etüleendioksütiofeeni derivaadid. Termiline analüüs kinnitab saa­dud molekulide metastabiilseid amorfseid omadusi. On uuritud nende ühendite elektrokeemilisi omadusi ja näidatud hüdrasoon- ja imiinrühmade konjugatsiooniefekti struktuuride elektroonsele delokalisatsioonile. Uurimuse tulemused näitavad, et sellised molekulaarklaasid võiksid leida kasutamist fotogalvaanilistes seadistes.

Stress distribution in polymeric film laminated leather under biaxial loading; 111–124

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Virginija Jankauskaitë, Eugenija Strazdienë and Agnë Laukaitienë

Abstract. The needle and stitch parameters on pigment-coated and polymeric film laminated leather behaviour under biaxial loading have been investigated. Simulation by finite element analyses (FEA) was used to determine the influence of the stitch number upon the distribution of principal stresses under the membrane deformation, while by experiments punching of the investigated materials was performed using a special punching unit. Investigations by FEA show that the stress in the middle of a stitch is four to five times higher than stresses at the beginning or at the end of the stitch. Besides, the increase of the stitch density increases stress values. Leather and polyurethane film break up straight below the specimen and punch contact zone. On the other hand, crack formation and propagation depend on the stitch density and shape of the needle.

Key words: laminated leather, biaxial deformation, stress distribution, punching strength.


Pingete jaotus polümeerkilega kaetud nahas kahesuunalise koormuse korral

On uuritud nõela ja piste parameetrite mõju pigmendiga töödeldud ja polümeerkilega kaetud parknaha käitumisele kahesuunalisel koormamisel. Nahka on mulgustatud spetsiaalse stantsi abil, pistete arvu mõju pingetele on analüüsitud ka lõplike elementide meetodil. On leitud, et pinged pistete keskosas on 4–5 korda suuremad kui otstes ja kasvavad pistete tihenedes. Nahk ja polüuretaankile katkevad otse proovi ja stantsi kokkupuutetsooni all. Pragude teke ja levik sõltuvad pistete tihedusest ja nõela kujust.

Mechanical properties of pinewood (Pinus Sylvestris) swollen in organic liquids; 125–133

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Pille Meier, Eve Stöör, Tiit Kaps and Urve Kallavus

Abstract. The aim of this research was to determine the mechanical properties of pinewood, swollen in water and aqueous solutions of ethanol and acetone. For this purpose, pine sapwood specimens were swollen in water, ethanol, acetone and aqueous solutions of ethanol and acetone. Static bending and compression strength along the grain and deflection in bending were determined. The results of this study show that a strong correlation exists between the strength properties and the swelling degree of pine sapwood. Pure substances and aqueous solutions influenced the mechanical properties of wood in different ways. Pine sapwood, swollen in aqueous solutions of ethanol, has better elastic properties compared to wood, swollen in other organic liquids used in this study.

Key words: pinewood, swelling, organic liquid, strength, deflection.


Orgaanilistes ainetes pundunud puidu mehaanilised omadused

On uuritud vees, etanoolis, atsetoonis ja nende vesilahustes punnutatud männi maltspuidu mehaanilisi omadusi (tugevus staatilisel paindel ja survel piki puidukiude). Kõik katsed on teostatud olekus, kus puit on maksimaalselt pundunud. Kasutatud vedelikud on mõjutanud erinevalt nii puidu struktuuri kui ka mehaanilisi omadusi. On täheldatud puidu tugevusomaduste sõltuvust pundumisest. Vees, puhastes ainetes ja vesilahustes käitub puit erinevalt. Kõige suuremad muudatused on aset leidnud puidu pundumisel etanooli vesilahuses moolimurru 0,5 juures, kus pundumise käigus on rakud deformeerunud ja üksteisest täielikult eraldunud. Tugevusnäitajad on etanooli vesilahustes punnutatud puidul samaväärsed vee ja atsetooni vesilahuses punnutatud puiduga, kuid erinevus esineb puidu elastsusomadustes: punnutatud puidu läbipaine staatilisel paindekatsel on etanooli vesilahuse puhul suurem.

Rotational viscometry for the study of urea-formaldehyde resins; 134–146

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Aime Suurpere, Peep Christjanson and Kadri Siimer

Abstract. Rotational viscometry as a generally recognized method for rheological measurements of non-Newtonian liquids was used for the study of commercial urea-formaldehyde resins. The measurement results were analysed using the power law function with evaluation of the consistency and flow indices. The resins were observed during their storage until alkali-promoted polycondensation led to gelation. It is suitable to differentiate two periods in the course of the polycondensation process – the initial period of slow viscosity growth and the following period of fast structuration. Regularity in the change of values of the flow index, calculated from data obtained with two rotational viscometer models, permits to characterize the flow behaviour of urea-formaldehyde resins in the initial period of polycondensation. The results of the rheokinetic study were compared with the data obtained with standard methods. In the relationships trends were found, which are consistent with conceptions about the formation of the resin structure and processes, occurring during the initial period of polycondensation.

Key words: rotational viscometry, rheokinetics, urea-formaldehyde resins, polycondensation.


Rotatsiooniviskosimeetria karbamiidformaldehüüdvaikude uurimiseks

On kirjeldatud rotatsiooniviskosimeetria kasutamist tööstuslike karbamiid-formaldehüüdvaikude vanandamise uurimisel. Mõõtmistulemusi on töödeldud astme-funktsiooni abil, arvutades konsistentsi ja voolamise indeksid K ja n. On näidatud, et polükondensatsiooniprotsessis on otstarbekas eristada esialgset aeglast viskoossuse tõusu järgnevast kiirest struktureerumisest. Reokineetilise uuringu tulemusi on seostatud karbamiidformaldehüüdvaikude standardanalüüsi näitajatega.

The influence of microstructural stiffness changes on the stress concentration factor of porous polymer materials; 147–155

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Daiva Zeleniakiene

Abstract. The numerical finite element analysis was used to determine the stress concentration factor in the microstructure of porous polymer materials as a function of porosity, distribution mode of pores and loading direction under tensile loading. The results show that the lowest stress concentration factor is characteristic for such polymer materials that exhibit the lowest stiffness changes of matrix adjacent zones in their microstructure. Low stiffness changes of matrix adjacent zones are obtained when the porosity value is high, pores are heterogeneous and the longitudinal axis of thin microstrips between the pores form an angle of 45° with the direction of tensile.

Key words: polymer, porosity, distribution mode of pores, microstructure, stress concentration factor, finite element analysis.


Mikrostruktuurse jäikuse muutuste mõju poorsete polümeersete materjalide pingekontsentratsiooni tegurile

Poorsete polümeersete materjalide mikrostruktuuri pingekontsentratsiooni teguri kindlaks-tegemiseks sõltuvalt poorsusest, pooride suuruse jaotusest ja tõmbepingega koormamise suunast on kasutatud lõplike elementide meetodit. On näidatud, et väikseim pingekontsentratsiooni tegur on iseloomulik sellistele polümeersetele materjalidele, mille mikrostruktuuri jäikus muutub vähe maatriksi naaberalades. Sellist mikrostruktuuri iseloomustab kõrge poorsus, pooride suuruse heterogeenne jaotus ja pooridevaheliste õhukeste mikroribade pikitelgede nurk 45º tõmbepingete suuna suhtes.

Instructions to authors; 156–158

Copyright Transfer Agreement; 159