Modification of tensile and impact properties of poly(butylene terephthlate) by incorporation of styrene-ethylene-butylene-styrene and maleic anhydride-grafted -SEBS (SEBS-g -MA) terpolymer

Abstract

Tensile behavior and impact strength of poly(butylene terephthlate) (PBT)/styrene-ethylene-butylene-styrene (SEBS) copolymer blends were studied at SEBS volume fraction 0-0.38. Tensile modulus and strength decreased, whereas breaking elongation increased with SEBS content. Predictive models are used to evaluate the tensile properties. Strength properties were dependent on the crystallinity of PBT and phase adhesion. The normalized notched Izod impact strength increased with the SEBS content; at F d ¼ 0.38, the impact strength enhanced to five times that of PBT. Scanning electron microscopy was used to examine phase morphology. Concentration and interparticle distance of the dispersed phase influenced impact toughening. In the presence of maleic anhydride-grafted SEBS (SEBS-g-MAH), the tensile modulus and strength decreased significantly, while normalized relative notched Izod impact strength enhanced to 7.5 times because of enhanced interphase adhesion.

Melt rheological properties of PBT/SEBS and reactively compatibilized PBT/SEBS/SEBS‐g‐MA polymer blends

“…The values of η r are 2.5 suggesting that the elastomer phase dispersion could be stable in the matrix phase as proposed by Taylor and other researchers . This was indeed observed in the morphology of the PBT/SEBS blends processed at 250°C . Similar kind of spherical domains of the minor phase dispersed in the matrix was observed in PS/PPO, PE/PA6, and other systems also where the viscosity of the minor phase is less than that of the continuous phase …”

“…The η a data increase with SEBS content compared to that of PBT. The increase in viscosity of the blends may be due to enhanced entanglement caused by the interdiffusion of the butylenes sequences of PBT and ethylene‐butylene component of SEBS copolymer as was reported in the static mechanical property of the blends . At low shear rate regions (200 s −1 to 1000 s −1 ), this chain entanglement restricted the flow causing increased melt viscosity while at higher shear rates the molecules tend to disentangle easily under the action of enhanced viscous forces.…”

“…Here also, the η a data for the blends were higher than that of PBT and lower than that of SEBS, the data were marginally higher than those of PBT/SEBS blends, however. This may be to phase interaction between PBT and SEBS‐ g ‐MA through chemical/physical bonding arising out of carboxylic acid groups of MA and OH end groups of PBT which increases the viscosity of the system. A network type of structure can form which enhances the friction for the polymer melt flow.…”

“…Individual polymers were also extruded under identical conditions to ensure the same thermal and shear history as that of the blend compositions. The blend compositions were expressed as volume fractions of the dispersed phase, Φ d , calculated from the mass and density values of the components in the blend …”

“…Styrene‐ethylene‐butylene‐styrene (SEBS) triblock copolymer was shown to enhance impact properties of PBT . Crystallinity decreased along with tensile modulus and strength, however, elongation at break enhanced significantly.…”