Spectroscopic Study of Di‐Imide Hydrogenation of Natural Rubber

Abstract

The diimide hydrogenation of natural rubber (NR) was studied by using p‐toluenesulfonylhydrazide (TSH) as a diimide‐releasing agent. The microstructure and the percentage of hydrogenation were studied by Raman, 1H‐NMR and 13C‐NMR spectroscopic techniques. Quantitative measurements on fraction of hydrogenated part gave the results in good agreement by using these techniques. The results indicated that percent hydrogenation increased with increasing of reaction time and about 80‐85 % hydrogenation was achieved when a two‐fold excess of TSH was used. The vibrational characteristic of C=C bond of NR is strongly Raman active and noted at 1663 cm−1. The decrease of this signal was clearly observed during the progress of hydrogenation but the vibrational frequency of the cis and trans structures of the trisubstituted olefin unit of NR can not be differentiated by this technique. While 1H‐ and 13C‐NMR analysis showed that cis‐trans isomerization of carbon‐carbon unsaturation of NR occurred during hydrogenation.

Study of Solvent and Catalyst in Diimide Biphasic Hydrogenation System of Natural Rubber

“…These peaks are observed at 19.7 ppm, 25.6 ppm, 29.9 ppm, and 37.4 ppm, attributed to -CH3, -CH2, -CH-, and -C(CH3)-CH2 indicating that some reduction in the C=C double bond has occurred and PHNR was produced. This is in line with the results from other literature (Mahittikul, Prasassarakich, Rempel, 2006;Samran, 2005). This evidence provided by 13 C-NMR spectra also aligns with FTIR spectra observed in Figure 3 and confirms that partial hydrogenation has occurred.…”

“…NR was found to be soluble in all selected organic solvents. Researchers used xylene, toluene, and hexane to hydrogenate rubbers with a concentration between 1.00% and 2.00% (Samran et al, 2004;Phinyocheep, Pasiri, and Tavichai, 2003). However, based on the calculation of total solubility parameters, toluene and xylene were predicted to be the most suitable solvents for dissolving NR.…”

Improvement of thermal properties of Vietnam deproteinized natural rubber via graft copolymerization with styrene/acrylonitrile and diimide transfer hydrogenation

“…Over the past decades, the hydrogenation of NR has been achieved in either catalytic or non‐catalytic systems. In the first approach, the hydrogenation of NR was carried out in an organic solvent showing very high hydrogenation degrees 20 . However, due to the difficulties in the separation process and the negative environmental effect caused by organic solvent waste, the hydrogenation of NR in latex form has been of great interest, 21,22 thereby avoiding the use of organic solvents.…”

Mechanical Characterization and Structural Analysis of Latex-Containing and Latex-Free Intermaxillary Orthodontic Elastics

“…The most salient features were the peak at 1667 cm −1 and the peak at 2914 cm −1 . The peak at 1667 cm −1 was assigned earlier [ 28 , 29 , 30 ] as a C=C stretch. The strong signal at ~2914 cm −1 is rather a combination of three poorly resolved peaks, as seen earlier [ 30 ].…”