ポリエチレン溶融物の流動複屈折

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It is well known that normal stresses appear as well as shear stress when polymer melts are subjected to shear. Various manifestations of this effect have been described in literature, but comparatively few experiments have been made to measure this effect quantitatively. The measurement of the flow birefringence in the slit-like duct is considered to give facilities to get normal stress effect of polymer melts in shear flow. The slit-like ducts which have side walls made of glass were made for this purpose. The photographs of isochromatic patterns were taken and the pressure gradient along with the flow were measured on the flow of polyethylene melts. From these experiments the normal stress difference S_<11>-S_<22> were obtained through the following equation. [numerical formula] where c is stress optical coefficient, ΔΔn_<12> is flow birefringence in the "1-2" plane and S_<12> is shear stress. Using the values of S_<11>-S_<22> the elastic energy in capillary flow that is imparted to the melt at the entrance of the capillary were calculated, and these results were compared with the values of total entrance pressure loss subtracted Couette loss which were obtained from the capillary experiment. As the results of these experiments it has been ascertained that the former is far less than the latter. This result is considered to show that the greater part of the total entrance pressure loss in capillary flow has been consumed as the viscous energy loss at the entrance region, and that the elastic energy imparted to the melt and therefore normal stress difference S_<11>-S_<22> or recoverable strain S_R in shear flow cannot be obtained by Philippoff-Bagler's method in a capillary experiment.
社団法人日本材料学会の論文
1967-07-15

ポリエチレン溶融物の流動複屈折

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