PREPARATION AND CHARACTERIZATION OF NATURAL RUBBER LATEX GRAFTED WITH ETHYLACRYLATE (EA) ? METHYLMETHACRYLATE (MMA) MONOMERS MIXTURE

Weather stability is a critical factor in the service life of natural rubber latex as a water-based contact adhesive. To enhance its weather stability, natural rubber latex was modified by graft copolymerization with ethyl acrylate (EA) and methyl methacrylate (MMA) monomers mixture. The grafting reaction was carried out by emulsion polymerization at 600C using ceric ammonium nitrate as initiator. Four different weight percentage ratios of EA to MMA used in this study were 90:10, 85:15, 80:20, and 75:25. The grafting efficiency of graft-modified natural rubber latex was found to decrease with increase in MMA. 1H-nuclear magnetic resonance (1H-NMR) spectroscopy confirmed that the latexes prepared contained graft copolymers. The adhesive performance was evaluated by 900 peel strength tests. Only graftmodified natural rubber latex with monomer ratio of 75:25 gave significant results. The peel strength value of graft-modified natural rubber latex was lower than that of natural rubber latex. However, graft-modified natural rubber latex showed higher weather stability than natural rubber latex.