Uniaxial Elongational Viscosity of PC/ A Small Amount of PTFE Blend

The uniaxial elongational viscosity of blends, consisting of polycarbonate (PC) and a small amount of polytetrafluoroethylene (PTFE), have been studied. Uniaxial elongational viscosity of blends showed stronger strain-hardening property than that of PC. The structural observations at the fractured cross-section with SEM showed that PTFE fibrils less than 100 nm in diameter were produced by kneading in molten PC, which were dispersed uniformly in PC matrix. To get deeper insight into the mechanism of the strong strain-hardening, the recoverable strain of the blend samples was investigated, and it was found a large strain recovery occurred after uniaxial elongational deformation. The comparison of the phase morphology before and after strain recovery was performed by observing with SEM. It was confirmed that the diameter of PTFE fibrils increased after strain recovery. WAXD pattern showed that the crystallites of PTFE in PTFE fibrils orientated along the elongational direction by the uniaxial elongational deformation. DSC measurement revealed that 60% amorphous phase existed in fibrillated PTFE. It was supposed that PTFE fibrils deformed, resulting in the generation of a restoring force, during elongational deformation. These results suggested that the strain-hardening property should be attributed to the generation of the restoring force by stretching of PTFE fibrils.