Measurement of the first and second normal stress differences in a polystyrene melt with a cone and partitioned plate tool
Measurement of the first and second normal stress differences in a polystyrene melt with a cone and partitioned plate tool
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使用锥体和分区板工具测量聚苯乙烯熔体中的第一和第二法向应力差
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
T. Schweizer
中科院分区：
文献类型：
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作者：
T. Schweizer
抽象的。在以下范围内的阶跃剪切速率实验
$$0.1；点伽马<；30s^{-1}$$
(0.14；Wi<；42)在190℃PS 158K熔体中进行，使用锥体(间隙角=0.148 Grad)和隔板工具测量随时间变化的第一(N1)和第二(N2)法向应力差。从具有不同R/RStem比率的一系列测量中提取N1和N2，R是样本半径，RStem是连接到换能器的板的中心部分的半径。测量的扭矩具有很好的重复性。观察到≥18应变的边缘断裂，与剪切速率无关。对于较大的样本，换能器看到的边缘骨折的开始延迟到较大的应变。这是由于样品边缘和阀杆之间的熔体抑制了干扰。-n2/n1的稳态值从0.1%S-1剪切速率下的0.24%下降到30%S-1时的0.05%。对于$$点伽马；10s^{-1}$$
当使用较小的锥角时，-n2/n1的稳态值变大。α=0.148的数据与粘度η和第一法向应力系数$$psi_1=N_1/点伽马^2$$的线性粘弹性预测更符合
与更小的圆锥体相比。
Abstract. Step shear rate experiments in the range of
$$0.1 < dot gamma < 30s^{ - 1} $$
(0.14<Wi<42) were performed with a PS 158K melt at 190 °C. A cone (gap angle=0.148 rad) and partitioned plate tool was used to measure the time dependent first (N1) and second (N2) normal stress difference. N1 and N2 were extracted from a series of measurements with different ratios of R/RStem, R being the sample radius, RStem the radius of the central part of the plate connected to the transducer. A very good reproducibility was found for the measured torque. Edge fracture was observed for strains ≥18, independent of shear rate. For larger samples, the onset of edge fracture as seen by the transducer was delayed to larger strains. This is due to damping of the disturbances by the melt between the rim of the sample and the stem. The steady state value of the ratio –N2/N1 decreases from 0.24 at 0.1 s–1 shear rate to 0.05 at 30 s–1. For $$dot gamma > 10s^{ - 1} $$
the steady state value of –N2/N1 becomes larger if smaller cone angles are used. Data for α=0.148 rad showed a better coincidence with the linear viscoelastic predictions of viscosity η and first normal stress coefficient $$psi _1 = N_1 /dot gamma ^2 $$
compared to smaller cones.