New developments in the melt rheology of nylons. I: Effect of moisture and molecular weight
New developments in the melt rheology of nylons. I: Effect of moisture and molecular weight
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DOI：
10.1002/pen.10570
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发表时间：
1996-07
影响因子：
3.2
通讯作者：
Y. P. Khanna;P. K. Han;E. Day
中科院分区：
文献类型：
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作者：
Y. P. Khanna;P. K. Han;E. Day
报告了对超干尼龙树脂（特别是尼龙 6）熔体流变学的特殊观察。这项研究的一个方面涉及当尼龙 6 树脂水分从 0.10 降至 0.00% 时，零剪切熔体粘度急剧增加（例如 2 至 5 倍）；效果是可逆的。考虑到当经受所施加的干燥条件时，起始树脂中没有可检测到的化学/组成/分子量类型的变化，这种幅度的变化是出乎意料的。这项研究的另一个方面涉及尼龙（6、6,6 和 12）与 Bueche (1952) 关系的偏差，迄今为止，该关系已被聚合物广泛接受。在中等干燥条件下（例如 50°C/17 小时/110 毫托），发现分子量指数为 3.8，在尼龙 6 报道的 3.4 至 3.8 范围内。然而，在更严格的干燥条件下（例如 110°C/17 小时/110 毫托），尼龙 6、尼龙 66 和尼龙 12 的分子量指数为4.8、5.4 和 分别为4.6。我们认为，超干尼龙 6 熔体粘度的急剧增加部分是由于熔体（挤出物）分子量的增加，鉴于 4.8 指数，这对熔体粘度具有更显着的影响。与聚乙烯（自由基聚合物）和聚对苯二甲酸乙二醇酯（缩聚物）相比，这种独特的结果暂时归因于尼龙熔体中的氢键。这项研究的另一个方面涉及过冷熔融聚合物的流变学，它可以为分析表征提供优势。
Peculiar observations on the melt rheology of ultra-dry nylon resins, nylon 6 in particular, are reported. One aspect of this study deals with a sharp increase in zero shear melt viscosity (e.g. 2 to 5 times) as the nylon 6 resin moisture is taken from 0.10 down to 0.00%; the effect being reversible. Changes of such magnitude are unexpected considering that there are no detectable variations of the chemical/compositional/molecular weight type in the starting resin, when subjected to the imposed drying conditions. Another aspect of this study deals with a deviation of nylons (6, 6,6, and 12) from the Bueche (1952) relationship, well accepted for polymers to date. Under moderate drying conditions (e.g. 50°C/17 h/110 millitorr), the molecular weight exponent is found to be 3.8, which is within the range of 3.4 to 3.8 reported for nylon 6. However, under more severe drying conditions (e.g. 110°C/17 h/110 millitorr), the molecular weight exponents for nylon 6, nylon 66, and nylon 12 are 4.8, 5.4, and 4.6, respectively. We are proposing that a sharp increase in melt viscosity of ultra-dry nylon 6 is partly due to an increase in the molecular weight of the melt (extrudate) which then, has a more pronounced impact on melt viscosity in view of the 4.8 exponent. Such unique results, in contrast to polyethylene (free radical polymer) and poly(ethylene terephthalate) (condensation polymer) are tentatively attributed to H-bonding in nylon melts. Yet another aspect of this study deals with the rheology of supercooled molten polymers that can offer advantages for analytical characterization.