Structure and performance of impact modified and oriented sPS/SEBS blends

Blends of syndiotactic styrene/p-methyl styrene copolymer (SPMS) and poly(s tyrene)-block-poly(ethene-co-butyl (SEBS) as well as their uniaxial drawing behavior and performance were investigated. Mixing was performed using a b atch mixer at 280 degreesC. Morphology was evaluated using scanning electro n microscopy (SEM). Thermal properties, orientation acid tensile properties were determined using differential scanning calorimetry (DSC), the spectro graphic birefringence technique, and a tensile testing machine, respectivel y. The blends of SPMS/SEBS, 90/10 and 80/20 showed a two-phase structure wi th an SEES disperse phase In SPMS matrix. The average sizes of the SEES par ticles and tensile properties of the blends were affected by blending time and compositions. No significant effects on the tensile modulus and strengt h were observed for the blends containing 10% SEES or below. The quenched S PMS and SPMS/SEBS (90/10) blends were drawn at 110 degreesC, and their crys tallinity and orientation development compared. These were similar for both samples at low draw ratios (<3.2), but were much faster for SPMS at higher draw ratios. The orientation process is shown to substantially Increase th e strength and modulus in the drawing direction for SPMS and the blends. Th e toughness (energy under the stress-strain curve) increased upon addition of SEES and orientation, with a marked effect of the latter. SEM observatio n reveals that the dispersed SEES has been extended to about the same draw ratio as the bulk blend in the drawn blends, indicating efficient stress tr ansfer at the interface.