P. Potschke et al., MORPHOLOGY AND PROPERTIES OF BLENDS WITH DIFFERENT THERMOPLASTIC POLYURETHANES AND POLYOLEFINS, Journal of applied polymer science, 64(4), 1997, pp. 749-762
Unmodified blends of two thermoplastic polyurethanes (TPU) and six pol
yolefines were used to study the influence of the component viscositie
s on the blend morphology and mechanical properties. Blends were produ
ced by melt mixing using a twin screw extruder. Interactions between t
he blend components could not be detected by DSC, DMA, selective extra
ction, and SEM micrographs of cryofractures. The variation in tensile
strength with blend composition produce a U-shaped curve with the mini
mum between 40 and 60 wt % of polyolefine. At similar viscosity ratios
(eta(d)/eta(m)), blends with polyether based TPU(TPU-eth) have a fine
r morphology than blends with polyester based TPU (TPU-est). This is d
ue to the lower surface free energy of the polyether soft segments com
pared to the polyester soft segments. Different morphologies also lead
to changes in mechanical behavior. Blends with TPU-eth show a lower d
ecrease in tensile strength with blend composition than blends with TP
U-est. The viscosity ratio between TPU and polyolefines can be directl
y correlated to the blend morphology obtained under similar blending c
onditions. TPU/PE blends show a lower dispersity than TPU/PP blends, d
ue to the higher viscosity ratios of TPU/PE blends. This results in a
greater reduction in tensile strength with the disperse phase content.
(C) 1997 John Wiley & Sons, Inc.