Synthesis and thermal properties of natural rubber grafted with poly(2-hydroxyethyl acrylate)

A novel modified natural rubber with grafted poly(2-hydroxyethyl acrylate) (NR-g-PHEA) was synthesized by emulsion polymerization in latex stage. Cumene hydroperoxide and tetraethylene pentamine were used as redox initiators (1:1 M ratio). The influences of reaction temperature, reaction time, initiator concentration and monomer concentration on percent grafting and grafting efficiency were investigated. Transmission electron microscopy was used to observe the NR-g-PHEA particles, which exhibited core-shell morphology. Chemical structure of purified NR-g-PHEA was confirmed by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance spectroscopy. The thermal properties were examined by thermogravimetric analysis and by differential scanning calorimetry. The modified NR had improved thermal stability, and the NR-g-PHEA also presented slightly higher glass transition temperature than virgin NR.