ABSTRACT:Oxidative degradation of epoxidized natural rubber (ENR) was effectively performed in latex phase by using periodic acid at 30°C. The ENR was prepared from the epoxidation of natural rubber in latex phase using performic acid generated in situ by the reaction of hydrogen peroxide and formic acid. The prepared ENR latex was subsequently treated with periodic acid. It was found that the higher the amount of the periodic acid employed the faster the molecular weight of the ENR decreased. Different epoxidation levels of the ENR had no significant effect on the degradation reaction. Based on 1 H NMR analysis, the epoxide content in the epoxidized liquid natural rubber (ELNR) obtained was about the same as that observed in the ENR before degradation. FT-IR analysis showed an increase in carbonyl signal after prolonged reaction time or when higher amounts of periodic acid were employed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 6 -15, 2005

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Novel flexible polyurethane foams were successfully prepared from a renewable source, hydroxytelechelic natural rubber (HTNR) having different molecular weights (1000-3400 g mol À1 ) and variation of epoxide contents (EHTNR, 0-35% epoxidation) by a one-shot technique. The chemical and cell structures as well as physico-mechanical, thermal, and acoustic properties were characterized and compared with commercial polyol analogs. The obtained HTNR based foams are open cell structures with cell dimensions between 0.38 and 0.47 mm. The HTNR1000 based foam exhibits better mechanical properties but lower elongation at break than those of commercial polyol analog.However, the HTNR3400 based foam shows the best elastic properties. In a series of EHTNR based foams, the tensile and compressive strengths show a tendency to increase with increasing epoxide content and amount of 1,4-butanediol (BD). The HTNR based foams demonstrate better low temperature flexibility than that of the foam based on commercial polyol. Moreover, the HTNR based polyurethane foams was found to be an excellent absorber of acoustics.

Isoprene-styrene diblock copolymers of various molecular weights were prepared by anionic polymerization with n-BuLi in cyclohexane. Hydrogenation of the unsaturated backbone of the block copolymers was performed with diimide generated in situ by the thermolysis of p-toluenesulfonylhydrazide (TSH). The reaction was carried out in xylene at 135°C. A molar ratio of TSH to double bonds equal to 4:1 was found to be the optimum ratio, which provided the highest percentage of hydrogenation. The percentage of hydrogenation analyzed by 1 H-NMR, IR spectroscopy, and iodine value (the Wijs method) were compared. Evidence from 1 H-NMR also revealed a change in the ratio of the cis-trans configuration after hydrogenation. The thermal stability of the hydrogenated products was improved as shown by the results from thermogravimetric analysis. From differential scanning calorimetry measurements, the glass-transition temperatures of the hydrogenated products were found to increase about 10 -20°C above those of the original block copolymers.

High performance eco-friendly natural rubber biocomposites with various contents up to 40 parts per one hundred rubber by weight of lignin were successfully prepared from sodium lignosulfonate and natural rubber latex using the soft process.