Simulation results in polycarbonate

Plastic-flow simulations of Hutnik et al. (1993) on PC give generally quite similar results to the PP simulations presented above but additionally furnish much further insight resulting from the more structured form of the PC molecule with its several well-established prominent p-relaxations, rather than the relatively smooth structure of the PP molecule. 

10 An ensemble-average shear-stress-shear-strain curve of 12 pure shear simulations of PC (top part), for a simulation method similar to the simulations for polypropylene of Fig. 8.8. The lower part shows the ensemble-average system pressure associated with the shear behavior (from Hutnik et al. (1993) courtesy of the ACS). 

To obtain information on the actual sizes Of of the relaxation clusters in glassy polymers it is necessary to associate the simulation results with experimental results on shear activation volumes Av that relate directly to the product Qfy. This, together with the simulation results for the transformation shear strain (= 7 ) j offsr a means of estimating the actual values of Of of relaxing clusters and the number of molecular segments n in the clusters that take part in the shear relaxations. Before considering such an evaluation, we first present experimental results on the temperature dependences of the yield stresses of several flexible-chain and stiff-chain glassy polymers. 

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