Graft copolymers, deproteinized natural rubber-graft-polystyrene (DPNR-g-PS) and deproteinized natural rubber-graft-polyacrylonitrile (DPNR-g-PAN), were prepared by the grafting of styrene (St) or acrylonitrile (AN) monomers onto DPNR latex via emulsion copolymerization. Then, ultrafine fully vulcanized powdered natural rubbers (UFPNRs) were produced by electron beam irradiation of the graft copolymers in the presence of di-trimethylolpropane tetra-acrylate (DTMPTA) as a crosslinking agent and, subsequently, a fast spray drying process. The effects of St or AN monomer contents and the radiation doses on the chemical structure, thermal stability, and physical properties of the graft copolymers and UFPNRs were investigated. The results showed that solvent resistance and grafting efficiency of DPNR-g-PS and DPNR-g-PAN were enhanced with increasing monomer content. SEM morphology of the UFPNRs showed separated and much less agglomerated particles with an average size about 6 μm. Therefore, it is possible that the developed UFPNRs grafted copolymers with good solvent resistance and rather high thermal stability can be used easily as toughening modifiers for polymers and their composites.
In this study, we investigated the improvement of thermal properties of Vietnam deproteinized natural rubber (DPNR) via graft copolymerization of styrene/acrylonitrile and transfer hydrogenation. The graft copolymerization was achieved successfully in the latex stage using tert‐butyl hydroperoxide and tetraethylenepentamine as radical initiators at 30°C. The obtained graft copolymer was hydrogenated by a diimide reduction system in the presence of different copper (II) homogeneous catalysts. The effects of styrene to acrylonitrile on the total conversion and the grafting efficiency have been studied. The structural characterization of the obtained copolymers was made by 1H NMR and ATR‐FTIR. The graft DPNR was then characterized by gel permeation chromatography (GPC). The effects of different copper (II) catalysts on the system have been evaluated by the hydrogenation degree of each hydrogenated sample. The improvement of the thermal properties of the graft copolymers was confirmed by thermal gravimetric analysis/differential thermal analysis. The core‐shell arrangement was obtained in both DPNR‐graft‐PS/PAN and hydrogenated‐DPNR‐graft‐PS/PAN by transmission electron microscopy.
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