Evaluation of structural change during fast transformation process of cross-linked NR into liquid NR by light pyrolysis

The presence of cross-linked networks in rubber creates a tremendous problem for recycling and reusing of waste rubber. Fast transformation of cross-linked natural rubber (NR) into liquid natural rubber was carried out by light pyrolysis in temperature range from 240 to 300 degrees C in variable time (in range: 1 30 min). The transformation efficiency was evaluated by measuring the sol fraction and the cross-link density of the gel fraction. Over 80 wt%, sol fraction was obtained at 280 degrees C in 15 min and 100 wt% sol fraction was obtained at 300 degrees C in 3 min. The chemical structure of sol fraction was characterized by gel permeation chromatography, nuclear magnetic resonance and infrared spectroscopy. The molecular weight of sol fraction in cross-linked NR processed at 280 degrees C and 300 degrees C decreased when gel fraction is over 50%. The nuclear magnetic resonance results showed that mono-sulfidic linkages occurred mainly in the sol fraction of liquid NR obtained at 300 degrees C. lsomerization from cis to trans form of isoprene unit in NR increased with extending pyrolysis time. (C) 2016 Elsevier Ltd. All rights reserved.