Gg. Ferrer et al., Blends of styrene-butadiene-styrene triblock copolymer and isotactic polypropylene: morphology and thermomechanical properties, POLYM INT, 49(8), 2000, pp. 853-859
A set of blends of styrene-butadiene-styrene triblock copolymer (SBS) and i
sotactic polypropylene (i-PP) in a composition range 0-100% polypropylene b
y weight was prepared in a twin screw extruder. The morphology of the blend
s has been studied by transmission electron microscopy. The blends present
phase separation, Dynamic mechanical measurements show an improvement of th
e mechanical properties of SBS when i-PP is the dispersed phase. This reinf
orcing effect can be observed even at high temperatures when i-PP is in the
rubbery state. The mechanical properties of the blends have been interpret
ed using Takayanagi's block model. The melting and crystallization behaviou
r of the i-PP in the blends has been studied by differential scanning calor
imetry. The fractionated crystallization phenomenon has been observed in th
e blends where i-PP forms the dispersed phase. The results are consistent w
ith the morphology shown by the blends, in particular, with its phase inver
sion, which occurs at a composition near to 50% i-PP. (C) 2000 Society of C
hemical Industry.