Emulsion Polymerization of PMMA onto Natural Rubber

Abstract

PMMA-grafted natural rubber copolymers (NR-PMMA) are successfully synthesized by using emulsion polymerization. The effects of the two types of the radical initiator with or without a reversible addition-fragmentation chain transfer (RAFT) agent to polymerize methyl methacrylate (MMA)-grafted natural rubber are elucidated. In this work, a dibenzoyl peroxide (DBP) initiator shows a higher grafting rate (24.63%) as compared to a 2,2′-azobis(isobutyronitrile) (AIBN) initiator without a RAFT agent. The structural characterization of the obtained copolymers is conducted by proton nuclear magnetic resonance ( 1 H NMR) and attenuated total reflectance/Fourier transform infrared (ATR-FTIR). According to the GPC analysis, RAFT in the emulsion polymerization process is difficult to happen in this current system as a high PDI (4.72) and a low molecular weight (3.43 × 10 5 ) are acquired. Further investigation is needed to allow RAFT in the emulsion process to proceed more rapidly. The changes in the glass transition temperature (T g ) and degradation temperature (T d ) confirmed the improvement of the thermal properties of the graft copolymers. In addition, the mechanical properties of NR-PMMA copolymers increased with an increase of the grafting efficiency of PMMA. Thus, this approach is an effective way to produce natural rubber-based products.