In this work, three linear isotactic polypropylenes with different weight-average molecular weights, Mw, and comparable polydispersities were used to produce nonwovens by melt blowing technology at two different temperatures, T. The air/polymer flow rate was changed to maintain the same average fiber diameter, resulting in a different broadness of fiber diameter distribution, which was quantified by the coefficient of variation, CV. The elasticity of the material was evaluated by the reptation-mode relaxation time, λ1, and the Rouse-mode reorientation time, λ2, determined from the deformation rate dependent shear viscosity data. Extensional rheology was evaluated using uniaxial extensional viscosity measured over a very wide range of strain rates (2 × 104 s−1–2 × 106 s−1) using entrance pressure drop and Gibson methods. An obtained plateau value of uniaxial extensional viscosity at the highest extensional strain rates, ηE,∞ (normalized by the three times zero-shear rate viscosity, η0), and the minimum uniaxial extensional viscosity, ηE,min, were related to Mw and T using simple equations. It has been found that the stability of fiber production captured by CV depends exclusively on the extensional properties of the polypropylene melts, namely, ηE,U,∞3η0 and ηE,U,min. These findings are important especially with regard to the stable production of polymeric nanofibers by melt blowing technology.

中文翻译：

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分子量、温度和拉伸流变学对线性全同立构聚丙烯熔喷工艺稳定性的影响

在这项工作中，通过熔喷技术在两种不同的温度 T 下，使用三种具有不同重均分子量 Mw 和可比多分散性的线性全同立构聚丙烯生产非织造布。改变空气/聚合物流速以保持相同的平均值纤维直径，导致纤维直径分布的不同宽度，这由变异系数 CV 量化。材料的弹性通过蠕动模式松弛时间 λ1 和劳斯模式重定向时间 λ2 进行评估，这些时间由变形速率相关的剪切粘度数据确定。使用入口压降和 Gibson 方法在很宽的应变速率范围 (2 × 104 s-1–2 × 106 s-1) 上测量单轴拉伸粘度，评估拉伸流变学。在最高拉伸应变速率下获得的单轴拉伸粘度的平台值 ηE,∞（通过三倍零剪切速率粘度标准化，η0）和最小单轴拉伸粘度 ηE,min，与 Mw 和 T 相关使用简单的方程。已经发现，由 CV 捕获的纤维生产的稳定性完全取决于聚丙烯熔体的拉伸性能，即 ηE,U,∞3η0 和 ηE,U,min。这些发现对于通过熔喷技术稳定生产聚合物纳米纤维尤其重要。已经发现，由 CV 捕获的纤维生产的稳定性完全取决于聚丙烯熔体的拉伸性能，即 ηE,U,∞3η0 和 ηE,U,min。这些发现对于通过熔喷技术稳定生产聚合物纳米纤维尤其重要。已经发现，由 CV 捕获的纤维生产的稳定性完全取决于聚丙烯熔体的拉伸性能，即 ηE,U,∞3η0 和 ηE,U,min。这些发现对于通过熔喷技术稳定生产聚合物纳米纤维尤其重要。