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Carbon Black--polyethylene Composites Studied by Positron Annihilation

100%
Dębowska M., Rudzińska-Girulska J., Pasternak A., Poźniak R.
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vol. 95
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issue 4
509-514
EN
Preliminary results of positron annihilation lifetime measurements, performed for carbon black-LDPE composites with three kinds of carbon black (PRINTEX XE2, VULCAN XC-72, and SAKAP 6) are presented. Four components with lifetimes τ_{1}≈ 120 ps, τ_{2}≈340 ps, τ_{3}≈1.2 ns, τ_{4}≈2.8 ns occurred to be the best fitted to measured positron lifetime spectra. The presence of carbon black resulted only in reduction of intensities of the components with the lifetimes τ_{1}, τ_{3}, τ_{4} (originating in our opinion from the annihilation of the positronium) and increase in the intensity of the component with the lifetime τ_{2}. The intensities depend both on the content of carbon black and its kind as well. The strongest influence of the carbon black of the highest specific surface area (PRINTEX XE2) has been observed at the intensities which correlate well with the results of studies of resistivity and tensile strength for the same samples.
2
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Polyamide 6/Layered Silicate Nanocomposites

100%
Dębowska M., Rudzińska-Girulska J., Pigłowski J., Dołęga J.
Acta Physica Polonica A
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2008
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vol. 113
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issue 5
1321-1329
EN
Polyamide 6 (PA6) and its two exfoliated nanocomposites (PA6/Nf919 and PA6/BZ-COCO), with bentonite (2.5 wt.%) organophilically treated with different cations, were studied. Improved mechanical properties, changes in crystallinity and morphology as well as higher glass transition temperature values were observed for the nanocomposites in comparison to the neat PA6. For the nanocomposite PA6/BZ-COCO, of better surface modification of platelets and better interaction between the polymeric matrix and the organobentonite, higher values of Young's modulus and yielding point together with higher contribution of larger free volume holes to free volume distributions occurred.
3
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Positron Annihilation in Chloropolystyrenes

76%
Baranowski A., Dębowska M., Jerie K., Mirkiewicz G., Rudzińska-Girulska J., Sikorski R.
Acta Physica Polonica A
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1993
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vol. 83
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issue 3
239-249
EN
Results of angular correlation of annihilation radiation and positron annihilation lifetime measurements are presented for atactic polystyrene and chloropolystyrenes. The inhibition of positronium formation follows the chlorine introduction as the decrease in intensities of the narrow component in angular correlation of annihilation radiation curves and of the longest-lived component in positron annihilation lifetime spectra prove. In general, the chlorine "activity" towards positrons seems to depend on its position in the polymer structure. The annihilation rate distribution as well as the radius and volume distributions of free-volume sites where positronium is assumed to be formed obtained with the use of CONTIN program for the raw sample in the 2nd series are given additionally.
4
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Positron Annihilation Studies of Styrene-N-X-Phenylmaleimides

76%
Baranowski A., Dębowska M., Jerie K., Rudzińska-Girulska J., Pawełka Z., Sikorski R. T.
Acta Physica Polonica A
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1995
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vol. 88
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issue 1
51-57
EN
Results of angular correlation of annihilation radiation and positron an­nihilation lifetime measurements are presented for five styrene copolymers: poly(co-styrene-phenylmaleimide) and its three derivatives with chlorine as well as for one with the OH group substituted in the benzene ring. It occurs that the chlorine substituted in three different positions in the benzene ring poly(co-styrene-o (or -m, -p)-chlorophenylmaleimide) inhibits the formation of the positronium to different extent. The greatest effect is observed in case of the chlorine atoms substituted in the benzene ring at ortho-position towards the nitrogen atom. In addition, electric dipole moments were measured for N-X-phenylmaleimide units, to check whether their magnitude influences the positron annihilation parameters. On the basis of the present results no correlation between the positron annihilation parameters and the electric dipole moments of the units was noticed.
5
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Free Volume in Epoxy-Coal Resins Studied by Positron Annihilation

76%
Baranowski A., Dębowska M., Jerie K., Kurzeja L., Hennek K., Rudzińska-Girulska J.
Acta Physica Polonica A
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1995
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vol. 88
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issue 1
43-49
EN
In this paper the macroscopic properties of the tetrafunctional epoxy resin (N, N'-tetraglycidyl ether of diaminodiphenylmethane) cured by 4, 4'-diaminodiphenylmethane, were studied. For the system the influence of various curing conditions on the glass temperature was investigated. Results obtained for two compositions: an unmodified one and a modified with coal were compared with information on the free volume given by the positron annihilation technique.
6
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Liquid Crystalline Polyurethanes Studied by Positron Annihilation Method

64%
Baranowski A., Dębowska M., Jankowski A., Jerie K., Penczek P., Rudzińska-Girulska J., Szczepaniak B., Wolińska-Grabczyk A.
Acta Physica Polonica A
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1995
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vol. 88
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issue 1
21-27
EN
A series of liquid crystalline polyurethanes of different both flexible spacer length and mesogenic group content was studied by means of positron annihilation method. The investigated polymers were targeted on the sep­aration of aromatic hydrocarbons from their mixtures with aliphatic ones. The effect of modification of the liquid crystalline polyurethane chain on the polyurethane free volume size and free volume distribution was determined on the basis of the positron annihilation lifetime spectra. In the positron annihilation lifetime spectra measured for the samples under study two long com­ponents of several nanoseconds, characteristic of o-Ps decaying by pick-off, occurred. The correlation of the values of the o-Ps lifetime with the size of the free volume region allowed to recover the free volume distributions with the use of the method employing the numerical Laplace inversion technique. The obtained results were compared with the diffusion data on the mobility of liquid hydrocarbons in the liquid crystalline polyurethanes enabling the correlations between polymer structure and its transport properties to be evaluated.
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