Rheological, thermal and morphological properties of maleated natural rubber and its reactive blending with poly(methyl methacrylate)

Maleated natural rubbers (MNRs) were prepared by blending natural rubber with maleic anhydride (MA) at 135 degrees C for 10 min. We found the IR absorption peaks at 1784 and 1854 cm(-1) due to the C=O symmetric and assymetric stretching vibration of the grafted MA on the NR molecules, respectively. Increasing trends of the grafted MA were observed with increasing concentrations of MA in the graft reaction. Increasing Mooney viscosity and shear viscosity with increasing levels of MA monomer were also observed. The levels of chemical interaction and chemical crosslinks between the polar groups in the MNR molecules might be the reasons for these increasing trends. Themogravimetry and dynamic mechanical analysis were used to characterize the MNRs. It was found that the decomposition temperature (T-d) and glass transition temperature (T-g) of the MNRs increased with increasing levels of monomeric MA. Reactive blending of MNRs and poly(methyl methacrylate) (PMMA) was later prepared. In reactive blends of MNR/PMMA, the shear stress and shear viscosity increased until reaching the maximum at a MNR content of 60 wt%. Increasing MNRs higher than this value caused a decrease of the shear stress and viscosity. It was therefore concluded that the MNR/PMMA blends are compatible blends according to the log-additive rule. SEM micrographs were also analyzed. We observed decreasing sizes of dispersed PMMA domains as the MA concentration increased. That is, increasing levels of MA caused increasing levels of chemical interaction between the MNR and PMMA phases. As a consequence, decreasing sizes of the PMMA domains dispersed in the MNR matrix were observed. (C) 2006 Elsevier Ltd. All rights reserved.