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Foaming Performance of Linear Polypropylene Ionomers
Macromolecules ( IF 5.1 ) Pub Date : 2022-06-16 , DOI: 10.1021/acs.macromol.2c00759
Mahmoud Embabi 1 , Mu Sung Kweon 1 , Ya Xian Wang 2 , Tzu-Pin Lin 3 , Carlos R. López-Barrón 3 , Patrick C. Lee 1
Affiliation  

Linear polypropylene (PP) exhibits poor foamability because of its inherently low melt strength. Incorporation of long-chain branches is a common approach to increase melt strength; however, it is a costly process. To bridge this gap, we set out to study the effect of ionic content on the foaming behavior of linear PP ionomers using a PP homopolymer as a control and a commercial high melt strength long-chain branched PP as a benchmark. Small-angle X-ray scattering confirms the presence of ion clusters in the ionomers, which act as physical cross-linking points as was recently shown, providing enhancement to the dynamic moduli, complex viscosity, and strain hardening behavior, even at ion contents below 0.1 mol %. We found that, upon foaming, the PP ionomer with a higher ionic content exhibited higher foam uniformity, higher cell density (∼108 cells/cm3), and smaller cell size (as small as 37 μm) compared to those of its linear counterpart. Furthermore, the linear ionomer resin and the commercial branched PP showed similar foam morphologies and mechanical responses under cyclic indentations over the temperature range 155–175 °C. These findings reveal a new, and potentially cost-effective, route to produce high performance foams using linear PPs that are compliant to industrial standards.

中文翻译:

线性聚丙烯离聚物的发泡性能

线性聚丙烯 (PP) 由于其固有的低熔体强度而表现出较差的发泡性。加入长链支链是提高熔体强度的常用方法;然而,这是一个代价高昂的过程。为了弥合这一差距,我们开始研究离子含量对线性 PP 离聚物发泡行为的影响,使用 PP 均聚物作为对照,并以商业高熔体强度长链支化 PP 为基准。小角 X 射线散射证实了离聚物中离子簇的存在,它们作为最近显示的物理交联点,增强了动态模量、复数粘度和应变硬化行为,即使在离子含量低于0.1 摩尔%。我们发现,在发泡时,具有较高离子含量的 PP 离聚物表现出更高的泡沫均匀性、更高的泡孔密度(~108个细胞/cm 3),与线性对应物相比,细胞尺寸更小(小至 37 μm)。此外,线性离聚物树脂和商业支化 PP 在 155-175 °C 温度范围内的循环压痕下表现出相似的泡沫形态和机械响应。这些发现揭示了一种使用符合工业标准的线性 PP 生产高性能泡沫的新途径,并且具有潜在的成本效益。
更新日期:2022-06-16
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