ABSTRACT:The hydrogenation of natural rubber (NR) and various epoxidized natural rubbers (ENR) was investigated by using diimide generated in situ from the thermal decomposition of p-toluenesulfonylhydrazide (TSH) in oxylene solution at 135°C.1 H-NMR analysis indicated that approximately 85-95% of hydrogenation was performed with a twofold excess of TSH. FT-IR and Raman spectroscopy were employed to confirm the microstructure characteristics of the hydrogenated rubbers. The cis-trans isomerization was also observed by 1 H-and 13 C-NMR. The signal in 1 H-NMR of the epoxide group of the ENR disappears after hydrogenation while the signal of the opened epoxide ring product was detected. This may be due to the epoxide ring opening reaction caused by the p-toluenesulfinic acid by-product. The high temperature of the reaction condition leads to chain degradation in both NR and ENR. Thermal behaviors of the hydrogenated rubbers characterized by differential scanning calorimetry showed that the glass transition temperatures of the hydrogenated rubbers were increased about 10 -20°C compared with the starting rubbers.

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An in-situ composite f i l m of a thermotropic liquid crystalline polymer (LC3000)/ polypropylene (TLCP/PP) was produced using the extrusion cast f i l m technique.The compatibiljzing effect of thermoplastic elastomers, styrene-ethylene butylenestyrene (SEBS), maleic anhydride grafted SEBS (MA-SEBS). and maleic anhydride grafted polypropylene (MA-PP) on the mechanical properties and morphology of the TLCP/PP composite films was investigated. It was found that SEBS provided a higher value of tensile modulus than MA-SEBS, which in turn was higher than MA-PP, despite the expected stronger interaction between the MA chain and TLCP. The observation of the morphology under optical and scanning electron microscopes suggested that all three compatibilizers helped improve the dispersion of the TLCP fibers and increased the fiber aspect ratio to a different extent. The fractured surface of the specimens showed more fiber breakage than pull-out when a compatibih e r was added, which suggested the improvement of interfacial adhesion. The surface roughness of fibers with an added elastomeric compatibilizer may also provide mechanical interloclang at the interface. It is suggested that the increase in the viscosity ratio of TLCP/PP due to the added elastomeric compatibilizer, SEBS and MA-SEBS, compared with the thermoplastic compatibilizer, MA-PP, is more effective in improving the composite mechanical properties.

The non-catalytic hydrogenation of natural rubber (NR) and two epoxidized NRs (ENRs) i.e. ENR-22 and ENR-40 containing 22 and 40 mol% of epoxide, respectively, was carried out using ptoluenesulfonylhydrazide (TSH) as a hydrogenating agent. A two-fold molar excess of TSH compared with unsaturated units of the rubber was used. The evidence of hydrogenation is a decrease in the intensity of the characteristic signal of the carbon-carbon double bond stretching vibration of the rubber in both the Raman and FT-IR spectra. The percentage hydrogenation was successfully determined by Raman spectroscopy since the vibrational mode of the carbon-carbon unsaturation is strongly Raman active. The progress of the hydrogenation could be monitored by means of the techniques mentioned above as a function of reaction time. The maximum degree of hydrogenation of NR is ∼89% whereas in the case of ENR-22 and ENR-40 it reaches 94 and 96%, respectively. Solid-state 13 C NMR spectroscopy was also used to confirm the microstructure characteristics of the hydrogenated rubbers. 13 C NMR analysis showed that cis-trans isomerization of carbon-carbon unsaturations occur during hydrogenation.

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.