Synthesis and characterization of hydroxyl terminated natural rubber-grafted graphene oxide

Abstract

Hydroxyl terminated natural rubber (HTNR) was prepared from deproteinized natural rubber (DPNR) via oxidative degradation method in toluene at 80 ?, in the presence of cobalt (II) acetyl acetonate (CAA) as oxidizing agent and sodium borohydride (NaBH4) as reducing agent. Gel Permeation Chromatography (GPC) analysis revealed the molecular weight (MW) of the obtained HTNR were 69 000 g/mol (Mn) and 244 000 g/mol (Mw), respectively; while Fourier Transform Infrared (FTIR) analysis confirmed the presence of hydroxyl groups in the prepared HTNR. Subsequently, graphene oxide (GO) was grafted onto HTNR structure for the improvement of thermal property using tetrahydrofuran (THF) as solvent with GO loading of 5 and 10 wt%. The degree of crosslinking was determined based on the residue analysis from thermal gravimetry analysis (TGA) and revealed almost no grafting occurs for HTNR-g-GO of 5 wt% GO while HTNR-g-GO for 10 wt% GO resulted in 8.5 % grafting. FTIR analysis of both samples show consistent finding with the degree of crosslinking where the intensity of hydroxyl and epoxide peaks for HTNR-g-GO (10 wt%) was higher compared to HTNR-g-GO (5 wt%). Meanwhile, differential scanning calorimetry (DSC) analysis showed an improved thermal stability of the prepared HTNR-g-GO in comparison to the HTNR and DPNR sample. In conclusion, the addition of GO into HTNR via grafting process can be an effective method for the preparation of nanocomposite with enhance properties.