DSC valuation of PRI of raw natural rubber

Thermal oxidation of raw natural rubber from Hevea brasiliensis was analyze d by differential scanning calorimetry (DSC) in dynamic mode. The results o btained revealed a linear relation between the PRI and onset temperature ob tained by DSC (r(2) = 0.91), for PRI values <70. On the other hand, when th e natural rubber PRI was over 70, DSC was unable to assess that criterion a ccurately. This was probably because the two techniques were not equivalent regarding the phenomenon measured. Oxidation primarily results in chain sc issions during PRI measurement. In DSC, the transition seen during thermal oxidation was associated with crosslinking. In fact, thermo-oxidation is in the initial phase when PRI is measured, but in the terminal phase at the o nset of transition in DSC. (C) 2001 John Wiley & Sons, Inc.