## 3 Results  
### Structural Characterization of the Graft Copolymer  
Natural rubber latex (NRL) has unsaturated bonds where the unsaturated bonds determine the polarity, which is very important in determining the adhesion properties of a natural rubber material and its derivatives [17, 32, 33]. To be used as a binder with good adhesiveness, the polarity of NRL needs to be increased by grafting styrene (St) and methyl methacrylate (MMA) monomers in NRL. In addition, grafting certain monomers can also increase water resistance [8, 32, 34]. The grafting of monomers in a polymer chain can be viewed from the characterization of the polymer structure by looking at the FT\(-\)IR spectrum.  
The FTIR spectrum in Figure 1 shows the FT\(-\)IR of natural rubber latex (NRL), natural rubber latex grafted with 30% MMA (NRL\(-\)g\(-\)MMA), and natural rubber latex grafted with 20% styrene (NRL\(-\)g\(-\)St). Natural rubber latex (NRL) has a distinctive peak shown in the absorption peak of 2957 cm\({}^{-1}\) for C-H stretching, the absorption peak of 1637 cm\({}^{-1}\) for the double bond in the polymer chain C=C stretching, and 1345 cm\({}^{-1}\) for C-H bending from CH\({}_{3}\) deformation [35, 36, 37]. A similar observation was made on natural rubber latex grafted with 30% MMA (NRL\(-\)g\(-\)MMA). The analysis here focuses primarily on the prevalence of MMA grafted to NRL. New peaks indicating grafting were observed at 1721 and 1161 cm\({}^{-1}\) absorption peaks of the NRL\(-\)g\(-\)MMA sample. These absorption peaks showed stretching C=O carbonyl groups and C-O-C stretching when MMA was grafted onto natural rubber side chains. The emergence of a new absorption peak accompanied by a decrease in absorption intensity at the peak of 1345 cm\({}^{-1}\) proves the existence of an MMA segment on NRL\(-\)g\(-\)MMA. This is strong evidence to confirm the occurrence of a grafting reaction on NRL\(-\)g\(-\)MMA [34, 36].  
Meanwhile, in observations of natural rubber latex samples grafted with 20% Styrene (NRL\(-\)g\(-\)St), the same thing happened to the NRL\(-\)g\(-\)MMA samples. In the NRL\(-\)g\(-\)St sample, there was a decrease in absorption intensity at the peak of 1345 cm\({}^{-1}\) for C-H bending from CH\({}_{3}\) deformation. A new absorption peak appeared at 1447 cm\({}^{-1}\), indicating C-H bending from the cyclo-hexane ring. This is evidence of styrene grafting onto NRL by replacing the CH\({}_{3}\) group in the natural rubber side chain. Therefore, based on the FT\(-\)IR spectrum in Figure 1, it can be concluded that styrene and methyl methacrylate (MMA)  
\begin{table}
\begin{tabular}{l l l l} \hline \hline
**No** & **Sample** & **Sample Code** & **Binder (\%)** \\ \hline
29 & NRL\(-\)g\(-\)20\%St/ NRL\(-\)g\(-\)30\%MMA & NgSt/NgMMA-8 & 8 \\
30 & NRL\(-\)g\(-\)20\%St/ NRL\(-\)g\(-\)30\%MMA & NgSt/NgMMA-10 & 10 \\
31 & NRL\(-\)g\(-\)20\%St/PVAc (70/30) & NgSt20/PVAc-4 & 4 \\
32 & NRL\(-\)g\(-\)20\%St/PVAc (70/30) & NgSt20/PVAc -6 & 6 \\
33 & NRL\(-\)g\(-\)20\%St/PVAc (70/30) & NgSt20/PVAc-8 & 8 \\
34 & NRL\(-\)g\(-\)20\%St/PVAc (70/30) & NgSt20/PVAc -10 & 10 \\
35 & NRL\(-\)g\(-\)30\%MMA/PVAc (70/30) & NgMMA30/PVAc -4 & 4 \\
36 & NRL\(-\)g\(-\)30\%MMA/PVAc (70/30) & NgMMA30/PVAc -6 & 6 \\
37 & NRL\(-\)g\(-\)30\%MMA/PVAc (70/30) & NgMMA30/PVAc -8 & 8 \\
38 & NRL\(-\)g\(-\)30\%MMA/PVAc (70/30) & NgMMA30/PVAc -10 & 10 \\ \hline \hline \end{tabular}
\end{table}
Table 3: _Cont._monomers are proven to graft on natural rubber to form copolymers by replacing natural rubber side chains [37; 38; 39].