Editor-in-Chief: Agarwal, Seema / Greiner, Andreas
6 Issues per year
IMPACT FACTOR 2017: 1.111
CiteScore 2017: 1.02
SCImago Journal Rank (SJR) 2017: 0.335
Source Normalized Impact per Paper (SNIP) 2017: 0.430
Effect of styrene/ethylene/butylene/styrene block copolymer on the dynamic mechanical behaviour and processability of high-impact polystyrene
Blends of high-impact polystyrene (PS-HI) and styrene/ethylene/butylene/ styrene block copolymer (SEBS) were investigated to determine the effects of rubber on the polymer properties. The processing behaviour of the PS-HI + SEBS blends was analyzed and the dynamic mechanical behaviour of the processed blends was examined. The rheological behaviour of the prepared blends during processing was followed by measuring the torque, output and melt pressure in a twin extruder. Dynamical mechanical analysis was performed in the temperature range of -150 to 160°C. The blends were also investigated in the creep fatigue regime and relaxations were determined at 25 - 65°C. Master curves for the reference temperature 25°C were created using the time-temperature superposition principle. With increasing SEBS content there was not significant increase of the torque value for blends below a rubber content of 70 wt.-% with respect to neat PSHI. An influence of SEBS content on the increase of the apparent viscosity was observed above 40 wt.-% of SEBS. The curves of storage modulus E’, loss modulus E’’ and loss tangent tan δ vs. temperature are affected by lowering the hard phase (PS) content: tan δ of the soft phase ethylene/butylene (EB) increases, while tan δ for the hard phase and storage modulus decrease. All samples exhibit a single glass transition of the hard phase. At constant load the creep of PS-HI, SEBS and PS-HI + SEBS blends increases and the creep modulus decreases over a period of time for all samples examined. These effects are more pronounced in samples with lower hard phase content. The energy-time-temperature correspondence principle was applied to create master curves for the reference temperature 25°C for the creep modulus of PS-HI, SEBS and PS-HI + SEBS blends. Microscopic morphology results confirm the main conclusions obtained from the processing and dynamic mechanical behaviour of the blends. The phase-separated microstructure is more pronounced in PS-HI + SEBS blends. The rise in fracture energy with SEBS introduction appears in the whiteness of the SEM microphotographs, first as white crests, and in PS-HI + SEBS blends with higher SEBS content as globular structures.