Improvement in Thermal and Mechanical Properties of Vietnam Deproteinized Natural Rubber Via Graft Copolymerization with Styrene/acrylonitrile and Diimide Transfer Hydrogenation

Natural rubber is biopolymer with high mechanical strength and excellent elasticity, but its main drawback is poor thermal stability. Many techniques have been employed to improve its thermo-mechanical properties. In this study, graft copolymerization of styrene, acrylonitrile onto deproteinized natural rubber using tert-butyl hydroperoxide and tetraethylene pentamine as redox initiator and diimide transfer hydrogenation have been investigated. The structural characterization of the obtained products was carried out by Attenuated Total Reflectance Fourier-Transform Infrared Spectroscopy and proton Nuclear Magnetic Resonance. The thermal properties of materials were studied by Thermal Gravimetric Analysis/Differential Thermal Gravimetric Analysis and Differential Scanning Calorimetry. The mechanical properties of the obtained copolymers were confirmed via tensile testing, where the tensile strength of the graft copolymer (DPNR-g-PS.PAN) (3.4 MPa) and hydrogenated-DPNR-g-PS.PAN (H-DPNR-g-PS.PAN) (2.6 MPa), nearly doubled when compared to untreated deproteinized natural rubber (1.5 MPa). The molecular weight distributions of products were determined by Gel Permeation Chromatography, in which the symmetry of molecular weight distribution was improved after each step of the modification.