Kinetics and Parameters Affecting Degradation of Purified Natural Rubber

Abstract

Purified natural rubber (PNR) was obtained by treatment of high ammonia NR latex with proteinase enzyme for 24 h, followed by double centrifugation. The PNR was later redispersed into latex form with 0.5% (w/v) sodium dodecyl sulfate. The degradation of PNR was performed in latex form by using a combination of the radical initiator potassium persulfate (K2S 2O8) and propanal. The intrinsic viscosity [ν] of the degraded rubber or liquid rubber that was obtained depended on various parameters such as the initiator concentration, amount of propanal, dry rubber content, reaction time, and temperature. It was found that the [ν] of the rubber can be reduced from 4.31 to 0.19 for the PNR after a 25-h reaction time using 5% dry rubber content PNR latex, 1 part per hundred rubber (phr) of K 2S2O8, and 32 phr of propanal at 80°C. The kinetics of the degradation reaction were investigated. The highest rate constant found was 11.33 × 10-2 s-1. The activation energy of the degradation reaction was 76.56 kj mol-1. © 2003 Wiley Periodicals, Inc.