Bimodal <sup>1</sup>H Double Quantum Build-Up Curves by Fourier and Laplace-like Transforms on Aged Cross-Linked Natural Rubber
The <sup>1</sup>H DQ Fourier and Laplace-like spectra for a series of cross-linked natural rubber (NR) samples naturally aged during six years are presented and characterized. The DQ build-up curves of these samples present two peaks which cannot be described by classical functions. The...
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| Format: | Article |
| Language: | English |
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MDPI AG
2021-10-01
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| Series: | Polymers |
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| Online Access: | https://www.mdpi.com/2073-4360/13/20/3523 |
| _version_ | 1797513262592425984 |
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| author | Dumitrița Moldovan Radu Fechete |
| author_facet | Dumitrița Moldovan Radu Fechete |
| author_sort | Dumitrița Moldovan |
| collection | DOAJ |
| description | The <sup>1</sup>H DQ Fourier and Laplace-like spectra for a series of cross-linked natural rubber (NR) samples naturally aged during six years are presented and characterized. The DQ build-up curves of these samples present two peaks which cannot be described by classical functions. The DQ Fourier spectra can be obtained after a numeric procedure which introduces a correction time which depends less on the chosen approximation, spin-½ and isolated CH<sub>2</sub> and CH<sub>3</sub> functional groups. The DQ Fourier spectra are well described by the distributions of the residual dipolar coupling correlated with the distribution of the end-to-end vector of the polymer network, and with the second and fourth van Vleck moments. The deconvolution of DQ Fourier spectra with a sum of four Gaussian variates show that the center and the width of Gaussian functions increase linearly with the increase in the cross-link density. The Laplace-like spectra for the natural aged NR DQ build-up curves are presented. The centers of four Gaussian distributions obtained via both methods are consistent. The differences between the Fourier and Laplace-like spectra consist mainly of the spectral resolution in the favor of Laplace-like spectra. The last one was used to discuss the effect of natural aging for cross-linked NR. |
| first_indexed | 2024-03-10T06:14:12Z |
| format | Article |
| id | doaj.art-5372e228519a41fb84b03b407867f443 |
| institution | Directory Open Access Journal |
| issn | 2073-4360 |
| language | English |
| last_indexed | 2024-03-10T06:14:12Z |
| publishDate | 2021-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Polymers |
| spelling | doaj.art-5372e228519a41fb84b03b407867f4432023-11-22T19:47:04ZengMDPI AGPolymers2073-43602021-10-011320352310.3390/polym13203523Bimodal <sup>1</sup>H Double Quantum Build-Up Curves by Fourier and Laplace-like Transforms on Aged Cross-Linked Natural RubberDumitrița Moldovan0Radu Fechete1Physics and Chemistry Department, Technical University of Cluj-Napoca, Memorandumului 28, R-400114 Cluj-Napoca, RomaniaPhysics and Chemistry Department, Technical University of Cluj-Napoca, Memorandumului 28, R-400114 Cluj-Napoca, RomaniaThe <sup>1</sup>H DQ Fourier and Laplace-like spectra for a series of cross-linked natural rubber (NR) samples naturally aged during six years are presented and characterized. The DQ build-up curves of these samples present two peaks which cannot be described by classical functions. The DQ Fourier spectra can be obtained after a numeric procedure which introduces a correction time which depends less on the chosen approximation, spin-½ and isolated CH<sub>2</sub> and CH<sub>3</sub> functional groups. The DQ Fourier spectra are well described by the distributions of the residual dipolar coupling correlated with the distribution of the end-to-end vector of the polymer network, and with the second and fourth van Vleck moments. The deconvolution of DQ Fourier spectra with a sum of four Gaussian variates show that the center and the width of Gaussian functions increase linearly with the increase in the cross-link density. The Laplace-like spectra for the natural aged NR DQ build-up curves are presented. The centers of four Gaussian distributions obtained via both methods are consistent. The differences between the Fourier and Laplace-like spectra consist mainly of the spectral resolution in the favor of Laplace-like spectra. The last one was used to discuss the effect of natural aging for cross-linked NR.https://www.mdpi.com/2073-4360/13/20/3523natural rubber (NR)natural aged NRDQ Fourier spectraDQ Laplace-like spectradistribution of <sup>1</sup>H residual dipolar coupling in elastomers |
| spellingShingle | Dumitrița Moldovan Radu Fechete Bimodal <sup>1</sup>H Double Quantum Build-Up Curves by Fourier and Laplace-like Transforms on Aged Cross-Linked Natural Rubber Polymers natural rubber (NR) natural aged NR DQ Fourier spectra DQ Laplace-like spectra distribution of <sup>1</sup>H residual dipolar coupling in elastomers |
| title | Bimodal <sup>1</sup>H Double Quantum Build-Up Curves by Fourier and Laplace-like Transforms on Aged Cross-Linked Natural Rubber |
| title_full | Bimodal <sup>1</sup>H Double Quantum Build-Up Curves by Fourier and Laplace-like Transforms on Aged Cross-Linked Natural Rubber |
| title_fullStr | Bimodal <sup>1</sup>H Double Quantum Build-Up Curves by Fourier and Laplace-like Transforms on Aged Cross-Linked Natural Rubber |
| title_full_unstemmed | Bimodal <sup>1</sup>H Double Quantum Build-Up Curves by Fourier and Laplace-like Transforms on Aged Cross-Linked Natural Rubber |
| title_short | Bimodal <sup>1</sup>H Double Quantum Build-Up Curves by Fourier and Laplace-like Transforms on Aged Cross-Linked Natural Rubber |
| title_sort | bimodal sup 1 sup h double quantum build up curves by fourier and laplace like transforms on aged cross linked natural rubber |
| topic | natural rubber (NR) natural aged NR DQ Fourier spectra DQ Laplace-like spectra distribution of <sup>1</sup>H residual dipolar coupling in elastomers |
| url | https://www.mdpi.com/2073-4360/13/20/3523 |
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