Enhancement of the rheological, dynamic mechanical, and morphological properties of thermoplastic natural rubber based on NR/PP blends using ENR/PP-g-MA as a compatibilizer

Abstract

This study investigates the effects of incorporating a 50/50 blend of Epoxidized Natural Rubber/Polypropylene-grafted maleic anhydride (ENR/PP-g-MA) as a compatibilizing agent (CA) for a 70/30 Natural Rubber/Polypropylene (NR/PP) thermoplastic elastomer (TPE) on the technical properties such as structural analysis, rheological, dynamic mechanical and morphological properties. Formulations with varying CA concentrations (5 to 15 phr) were prepared using a Brabender plasticorder at 180°C for 10 min. The structural analysis was examined by Fourier transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance (1H-NMR). The rheological behavior was examined using a Rubber Process Analyser (RPA). The dynamic mechanical properties were investigated by DMA. Atomic Force Microscopy (AFM) was used for the morphological examination. FTIR analysis confirmed reactions between the MA group in PP-g-MA and the epoxy groups in ENR, resulting in ENR-grafted PP with an ester and acid-based linkage. This reaction was evident during compatibilizer preparation. RPA results showed increased viscosity for both types of CAs compared to their individual values, confirming crosslinking reactions. Higher CA concentrations led to elevated viscosity and storage modulus. DMA results indicated that the compatibilization led to a significant enhancement in the storage modulus of the blends. Moreover, an increase in the glass transition temperatures (Tg) of the blends was produced. AFM examination revealed a more homogenous distribution of the dispersed PP phase for the CA-containing blends compared to the control NR/PP system.