ABSTRACT:Narrow-distribution fractions of bisphenol A polycarbonate in tetrahydrofuran (THF) and chloroform were studied by light-scattering, sedimentation velocity, and viscosity measurements over the range of molecular weights from 4x 103 to 5x 10 5 • The asymptotic values of a dimensionless quantity A2Mwl[r;] and the interpenetration function lJf where significantly lower than those usually expected for flexible polymers, suggesting a certain stiffness of the polycarbonate chain. Here A2 is the second virial coefficient, Mw is the weight-average molecular weight, and [r;] is the intrinsic viscosity. Data for statistical radii

The high strength Al alloys, 7N01, 6061 and 5083, were examined using slow strain rate testing in chloride-containing acid to neutral solutions under potentiostatic control. Large amounts of hydrogen absorption occurred at potentials above the breakdown potential. In this potential range, the mechanical strength of the alloys is degraded manly by severe general corrosion but hydrogen embrittlement may also occur. On the other hand, polarisation at more negative potentials where there is intense hydrogen evolution does not necessarily lead to a large amount of hydrogen entry except for the case of the alloy 5083, which suffered from hydrogen embrittlement induced by hydride formation around precipitates.

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