Melt rheology and morphology of physically compatibilized natural rubber-polystyrene blends by the addition of natural rubber-g-polystyrene

Abstract

Blends of natural rubber (NR) and polystyrene (PS) were prepared by melt mixing in a Brabender plasticorder and by solution casting using chloroform as the casting solvent. Earlier studies have indicated that these blends are incompatible and immiscible, and their compatibility can be improved by the addition of a graft copolymer of NR and PS (NR-g-PS). The rheological behavior of these blends has been carried out in the presence and absence of the compatibilizer using a capillary rheometer and a melt flow indexer. The effects of blend ratio, processing techniques (melt mixing versus solution casting), shear stress, and temperature on the rheological behavior have been studied in detail. Both in the presence and absence of the copolymer, the blends showed a decrease in viscosity with an increase of shear stress, indicating pseudoplastic nature. Solution-cast blends showed a higher viscosity as compared to melt-mixed blends. The viscosity versus composition curve of both melt-mixed and solution-cast blends showed negative deviation from the additivity at a higher shear rate region. This is associated with the interlayer slip between the highly incompatible NR and PS phases. The effects of graft copolymer loading and temperature on solution-cast blends were studied, and it was found that as the copolymer loading increases, the shear viscosity increases. This is due to the high interfacial interaction between the two components in the presence of the copolymer. The copolymer, in fact, locates at the interface and makes the interface more broad. However, at higher loading of the copolymer, the viscosity of the blends decreases. This may be associated with the formation of micelles, which have a plasticizing action on the viscosity of the blends. Melt elasticity parameters like principal normal stress difference, recoverable elastic shear strain, and die swell were evaluated. Master curves have been generated using modified viscosity and shear rate functions that contain the melt flow index as a parameter. The extrudate morphology of the blends was studied using a scanning electron microscope. Addition of the copolymer reduces the domain size of the dispersed phase, followed by a leveling off at a higher concentration. The leveling off is an indication of interfacial saturation. The interparticle distance also decreased followed by a leveling off at a higher loading of the copolymer.

Electrically Conductive Polystyrene/Polypyrrole Nanocomposites Prepared via Emulsion Polymerization

“…1a) the peaks at 3028 cm À1 and 2924 cm À1 indicated the stretching of aromatic C-H and aliphatic CH 2 , respectively and that the aromatic C¼C stretching peak range around 1602-1453 cm À1 [30,34] . The bands at 757 and 699 cm À1 are assigned to the deformation of five adjacent hydrogen atoms in the benzene ring [30,34,36,37] . The spectrum of the PPy (Fig.…”

Influence of Compatibilizer on Morphology and Dynamic Rheological Behavior of Polyethylene-Octene Elastomer/Starch Blends

“…Further addition of compatibilizer unexpectedly leads to a sharp decrease in blend complex viscosity as well as the viscoelastic modulus. This may be associated with the generation of micelles inside the continuous phase which have a plasticizing effect on the viscosity and modulus of the blends [24]. The compatibilizer itself is high molecular weight and has copolymer chains with high molecular weight.…”

Utilization of waste expanded polystyrene: Blends with silica-filled natural rubber

“…Although there is hardly any information in the literature about NR-EPS blends, there are some detailed references about studies on thermoplastic elastomers based on NR-PS blends [5,6].…”