高分子溶液の非定常流における複屈折 I.

瞬間的なねじり変形後の測定

抄録

Flow birefringence was measured for a 20% polystyrene solution in chlorinated biphenyl on sudden application of shear strain. The sample was torsionally sheared between two parallel glass plates and the time-dependent birefringence was measured with a light beam directed perpendicularly to the shearing plane. Measurements were performed over the range of shear 0.8?γ?5.4 and the range of time 5s?t?300s. The normal stress difference δ₁₁-δ₃₃ evaluated from the birefringence with the use of stress-optical law was slightly smaller than the product γδ₁₂ over the whole range of measurements. Here the subscript 1 denotes the direction of flow, 2 the direction perpendicular to the shearing plane, and 3 the neutral direction. According to the Lodge theory that γδ₁₂ should be equal to the first normal stress difference δ₁₁-δ₂₂, we deduced from the experimental results that the second normal stress difference δ₂₂-δ₃₃ was negative and its magnitude was less than 10% of δ₁₁-δ₂₂.