Rheological and curing behavior of reactive blending. I. Maleated natural rubber–cassava starch

Abstract

AbstractMaleated natural rubber (MNR) was prepared and used as a blending composition and a compatibilizer for blending of natural rubber (STR 5L) and cassava starch. The melt rheological behavior in terms of Mooney viscosity, apparent shear stress, and shear viscosity at 100°C were quantified. We found that the pure MNR gave the lower apparent shear stress, shear viscosity than did those of the blends with cassava starch. The rheological data of the MNR blends increased with increasing quantity of cassava starch. The highest value was observed for the blend of MNR. The rheological value was as follows: MNR > STR 5L with MNR (as the compatibilizer) > STR 5L compounds. Furthermore, rheological properties increased with increasing the levels of compatibilizer (MNR). The rheological results were described in terms of intermolecular interaction between the polar groups in the natural rubber and cassava starch molecules. Each rubber blend was compounded, and their curing characteristics were studied. The pure MNR compounds exhibited a long delayed onset of vulcanization for approximately 10 min. The retardation was found, because the accelerator (MBT) reacted with the anhydrides in the compound instead of acting as an accelerator. The retardation was not observed for the compound with the cassava starch. The curing curves for all MNRs were not in equilibrium at a maximum torque, while the pure STR 5L compound gave a curing curve with a maximum torque and a slight reversion. The curing curve for the compound with MNR as the compatibilizer was a combination of the curing curves of MNR and STR 5L. That is, the curve was in equilibrium at the maximum torque and the short delayed action. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2803–2813, 2001