Zakład Fizyki Makromolekularnej
Strona główna


od 2020-09-20

Dr Maciej Garbarczyk  | 1995-10 <> 2002-12



Publikacje                          Seminaria


Garbarczyk M., Kuhn W., Klinowski J., Jurga S.

Characterization of aged nitrile rubber elastomers by NMR spectroscopy and microimaging H-1 spin-lattice and spin-spin NMR relaxation times change markedly during the aging of nitrile rubber elastomers. NMR microimaging reveals heterogeneous changes in the aged samples. Aging proceeds mainly via additional chain cross-linking, and scission of the polymer chains does not appear to contribute. T-1 imaging shows that there is no spatial distribution of spin-lattice relaxation times.
© 2002 Elsevier Science Ltd. All rights reserved.

Polymer, 43(11), 3169-3172 (2002)

DOI: 10.1016/S0032-3861(02)00142-8


Garbarczyk M., Grinberg F., Nestle N., Kuhn W.

A novel approach to the determination of the crosslink density in rubber materials with the dipolar correlation effect in low magnetic fields We present a novel NMR approach to the determination of crosslink densities in rubber materials. The method is based on the dipolar correlation effect (DCE) on the stimulated echo examined in a series of rubber samples and linear polyisoprene. The parameter evaluated from the echo attenuation curves is the mean-squared dipolar fluctuation associated with anisotropic reorientations of macromolecular backbones. The contributions to the DCE of the constraints due to excluded volume effects and chemical crosslinks are estimated. A strong dependence of the mean-squared dipolar fluctuation on the crosslink density of rubber combined with the simplicity of performing the measurements with inexpensive low-field instruments suggests that the ME is a useful tool for routine applications. The potential and problems of performing DCE measurements in low-magnetic-field conditions are discussed in detail.
© 2001 John Wiley & Sons, Inc.

Journal of Polymer Science, Part B: Polymer Physics, 39(18), 2207-2216 (2001)

DOI: 10.1002/polb.1194


Garbarczyk M., Kuhn W., Jurga S.

Characterization of aged elastomers by NMR spectroscopy and microimaging In the following study we present the results of the investigation of aged elastomers by the NMR spectroscopic and microimaging methods. The series of nitrile rubber samples was investigated both filled and unfilled before and after aging. The samples were aged in a well-defined manner in the air stream at elevated temperature for several days. The T-1 and T-2 measurements and microimaging were done using the spin-echo with relaxation filters. Parameter selective images were obtained. The results show that there is a strong dependence of the relaxation times on the aging process. It is also shown that there are heterogeneous changes across the aged sample.

Molecular Physics Reports, 33, 106-110 (2001)

ISSN: 1505-1250   (Pobrane:  2021-01-07)


Grinberg F., Garbarczyk M., Kuhn W.

Influence of the cross-link density and the filler content on segment dynamics in dry and swollen natural rubber studied by the NMR dipolar-correlation effect Chain dynamics in a series of natural rubbers with different cross-link densities was studied using the dipolar correlation effect (DCE) on the stimulated echo. In dry samples, amplitudes of the stimulated echo were shown to be affected by attenuation mechanisms due to the DCE and spin exchange which occurs between the protons of CH and CH3 (and/or CH2) groups of polyisoprene chains. The estimated spin exchange time was 0.04 s. The DCE free of undulations due to spin exchange was examined using a special modification of the radio frequency pulse sequence with additional pi-pulses inserted in the free-evolution intervals. Modulations of stimulated echo amplitudes could completely be suppressed. A strong dependence of the DCE on the cross-link density was observed. Attenuation curves of the dipolar-correlation quotient, that is, the quotient of the stimulated and the primary echo amplitudes, were fitted using analytical expressions. The mean-squared fluctuation of the dipolar coupling constant, , and correlation times were determined. In dry samples, values of were shown to scale with the number of segments between cross-links (N) as proportional to N-1.3 ± 0.2. The attenuation of echo amplitudes due to the DCE was insensitive to the increase of a carbon black content by approximately a factor of two. In swollen samples, attenuations of the stimulated echo were free of modulations by spin exchange thus permitting measurements of the DCE with a standard three-90 degrees pulse sequence. Contrary to dry samples, the attenuation curves contained slowly decaying components with relative intensities less than or equal to 10%. These components were subtracted from the total signal before the dipolar-correlation quotient was evaluated. scales with N with nearly the same exponent as in dry rubber. The DCE of dry and swollen rubber is suggested as a method for the determination of cross-link densities.
(C) 1999 American Institute of Physics.

Journal of Chemical Physics, 111(24), 11222-11231 (1999)

DOI: 10.1063/1.480478   (Pobrane:  2020-10-25)

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