NMR による市販天然ゴムの劣化の解析

抄録

Degradation of natural rubber (NR) during processing was investigated through NMR spectroscopy. Various commercial rubbers were used in the present study such as Pale Crepe (PC), Rubber Smoked Sheet (RSS 3), Technically Specific Sheet (TSS 8^®), Standard Thai Rubber (STR 5L), Standard Vietnamese Rubber (SVR 10) and Standard Malaysian Rubber (SMR 20). As-cast films of the rubbers were prepared by solution casting method and followed by purification by acetone extraction. Chemical structures of the rubbers were elucidated through ¹H, ¹³C-NMR, and DEPT spectroscopy. The ¹³C-NMR signals at 39.8 and 40.0 ppm were assigned to the trans-1,4-isoprene unit in the trans-trans and cis-trans sequences, respectively, while the signals at 60.8 and 64.5 ppm were assigned to C 2 and C 3 of a cis epoxy group. The cis epoxy groups were identified for PC, STR 5L, RSS 3, TSS 8^®, SVR 10 and SMR 20, whereas the trans-1,4-isoprene units from cis-trans isomerization were detected for TSS 8^®, SVR 10 and SMR 20.