PHOTON-CORRELATION VELOCIMETRY OF POLYSTYRENE SOLUTIONS IN EXTENSIONAL FLOW-FIELDS
PHOTON-CORRELATION VELOCIMETRY OF POLYSTYRENE SOLUTIONS IN EXTENSIONAL FLOW-FIELDS
复制标题
DOI：
10.1016/0032-3861(82)90240-3
复制
发表时间：
1982-01-01
期刊：
影响因子：
4.6
通讯作者：
TANAKA, K
中科院分区：
文献类型：
--
作者：
GARDNER, K;PIKE, ER;TANAKA, K
十字槽装置已用于在高分子量（M ̄ w 介于 2.8× 10 6 和 2× 10 7 之间）无规聚苯乙烯窄组分的稀溶液中产生拉伸流场。可获得的菌株足以延伸单个分子。光子相关微测速法已用于测量十字槽通道中的速度分布，作为距十字中心的距离、聚合物浓度和流速的函数。已经发现，在浓度约为或大于 c* 的溶液中，并且在足以延伸聚合物分子的流速下，在通道中心观察到速度最小值。该最小值设定在通过双折射观察首次观察到聚合物分子延伸的流速附近，但最小值的深度随着聚合物浓度降低到 c* 以下而迅速减小。远离拉伸流区域，速度分布演变为通常的抛物线分布。在较高的应变率下，还观察到通道壁附近的溶液中的双折射，并且初步测量表明速度分布中的两个对称最小值或肩部可能与该观察结果相关。
A cross slot device has been used to produce elongational flow fields in dilute solutions of narrow fractions of high molecular weight (M ̄ w between 2.8× 10 6 and 2× 10 7) atactic polystyrene. Strainrates obtainable were sufficient to extend individual molecules. Photon-correlation microvelocimetry has been used to measure velocity profiles in a channel of the cross slot as a function of distance from the centre of the cross, polymer concentration and flow rate. It has been found that in solutions of concentration about or greater than c∗ and at flow rates sufficient to extend the polymer molecules a minimum in velocity is observed at the centre of the channel. This minimum sets in at flow rates around that at which extension of the polymer molecules is first observed through birefringence observations, but the depth of the minimum decreases rapidly with decreasing polymer concentration below c∗. The velocity profile evolves into the usual parabolic profile away from the region of elongational flow. At higher strain rates a birefringence in the solution near the channel walls was also observed and preliminary measurements indicate that two symmetrical minima or shoulders in the velocity profile may be associated with this observation.