Novel method for toughening of polystyrene based on natural rubber latex

Abstract

␥-Radiation vulcanized natural rubber latex/phase transfer/bulk polymerization is a novel process for the preparation of toughened polystyrene based on natural rubber latex. The negatively charged ␥-radiation vulcanized natural rubber latex was first titrated with benzyldimethylhexadecylammonium chloride in the presence of a styrene monomer. At a critical transfer concentration, the crosslinked rubber particles transferred from the aqueous phase into the styrene phase in which they swelled, depending on the irradiation dose used. By bulk polymerization of the styrene phase containing transferred particles, the polymer blends exhibited two-phase morphology similar to that of commercial high-impact polystyrene that was microscopically obtained. The final product showed an increase in the unnotched Izod impact energy over the unmodified polystyrene. The effect of irradiation dose, rubber content, and initiator concentration on the impact property and morphology of toughened polystyrene prepared was investigated.

Composite natural rubber based latex particles: a novel approach

“…The resistance to hydrophobic liquid of the films was determined by immersing a known weight of rubber sheet (about 0.05 g) in toluene (50 mL) at room temperature for 22 h. The swollen rubber was weighed after blotting with filter paper and percentage swelling ratio was consequently calculated [22].…”

Particle Morphology of Epoxidised Natural Rubber Latex Prevulcanized by Peroxide System

“…After staining with osmium tetroxide (OsO 4 ) which reacts with unsaturated double bond of rubber molecule, it was observed under TEM that the sulphur and γ-radiation systems caused homogenous crosslink inside each rubber particle. However, a non-uniform network, a dense network near the particle surface, was noticed in the sample employing peroxide [2,3].…”

“…Similar to PP-NR, the dark threads of crosslinked rubber separated by unstained PS was caused by polymerization of the swollen styrene. When polymerization started, the produced long-chain PS provoked the phase separation between the two incompatible polymers leading to the expansion of the rubber networks [2,3]. The size of PS domain occluded in rubber particles was controlled by crosslink density of the rubber as normally occurred in interpenetrating polymer networks (IPNs) [13].…”

“…A coherent film would not be achieved if the particles are highly crosslinked near their surface whereas homogeneously crosslinked particles fuse well and form a film with optimum physical properties [1,2]. In order to elucidate the internal morphology of prevulcanized NR latex particles, the phase transfer/bulk polymerization/transmission electron microscopy (TEM) technique has been successfully applied [2][3][4][5]. The negatively charged latex particle was titrated with an aqueous solution of a cationic surfactant, e.g., benzyldimethylhexadecylammonium chloride (BHAC), in the presence of styrene.…”

Applications of phase transfer technique to the study and development of natural rubber

“…9 The negatively charged RVNR latex was titrated with BHAC in the presence of a styrene monomer. The crosslinked rubber particles transferred from the aqueous phase into the styrene phase in which they swelled depending on the irradiation dose used.…”