Preparation of cyclized deproteinized natural rubber in latex state via a combination of benzotrichloride and sulfuric acid system, and its properties

Partially cyclized deproteinized natural rubber (DPNR) in latex form was successfully prepared by using a combination of sulfuric acid (H ₂SO₄) and benzotrichloride (PhCCl₃) in the presence of Terric 320 as a non-ionic surfactant. The main parameters of the cyclization process such as various reaction times, dry rubber contents, concentrations of catalyst and temperatures were investigated. The resulting rubber was subjected to characterization by proton Nuclear Magnetic Resonance (¹H-NMR), Fourier-Transform Infrared spectrometer (FTIR), Thermal Gravimetric Analysis (TGA), and Differential Scan Calorimeter (DSC). In addition, the topology of partially cyclized rubber was also analyzed by Transmittance Electron Microscopy (TEM). The mechanism will be also discussed. It was interesting to note that the obtained partially cyclized rubber using this catalyst system contained no gel, which was easily soluble in rubber solvents. This is different from the partially cyclized rubber obtained from the other methods. Through, using structural characterization, it was found that the PhCCl₃ linked onto the rubber chain. It was also found that the thermal stability of this cyclized rubber was better than that of normal rubber. The efficiency of cyclization in this system could be increased by an increase of PhCCl₃ concentration.