The influences of molecular weight

residual monomer

end-group type and content

Fries rearrangement structure on capillary rheology of bisphenol A polycarbonates (PC) were systematically investigated in this study. No obvious thermo-oxidative degradation was observed and changes in the end-hydroxyl content

capping type and residual monomer did not deteriorate the degradation of PC chains

suggesting that rheological tests carried out near to 270 ℃ are stable and repeatable. A typical shear-thinning effect was found in the viscosityshear rate curves without accompanying a Newtonian characteristic in the zero-shear-rate region. At the low shear-rate region

the viscosity increases with decreasing the shearing rate to different extents for different PCs. Further studies revealed that the non-Newtonian flow index

n

in the low shear-rate region remains constant for PC melts with different molecular weights and different testing temperatures. It decreases linearly with the increase of the content of Fries rearrangement structure involved in the PC chains. As PCs fabricated by the melt transesterification have to experience high temperature and high vacuum environment during the long polymerization process

they involve many Fries rearrangement-derived heterogeneous structure. This should be the reason why the

n

value is significantly lower than that of the phosgene PC

thus leading to higher melt strength and flow activation energy.