Mendoza-Cedeno Steven, Kweon Mu Sung, Newby Sarah, Shivokhin Maksim, Pehlert George, Lee Patrick C
Department of Mechanical and Industrial Engineering, University of Toronto, 5 King's College Road, Toronto, ON M5S 3G8, Canada.
ExxonMobil Chemical Company, 5200 Bayway Drive, Baytown, TX 77520, USA.
Polymers (Basel). 2021 Jul 22;13(15):2404. doi: 10.3390/polym13152404.
Long-chain branched polypropylene (LCB PP) has been used extensively to improve cell morphologies in foaming applications. However, most research focuses on low melt flow rate (MFR) resins, whereas foam production methods such as mold-opening foam injection molding (MO-FIM) require high-MFR resins to improve processability. A systematic study was conducted comparing a conventional linear PP, a broad molecular weight distribution (BMWD) linear PP, and a newly developed BMWD LCB PP for use in MO-FIM. The effects of foaming temperature and molecular architecture on cell morphology, surface roughness, and mechanical properties were studied by utilizing two chemical blowing agents (CBAs) with different activation temperatures and varying packing times. At the highest foaming temperatures, BMWD LCB PP foams exhibited 887% higher cell density, 46% smaller cell sizes, and more uniform cell structures than BWMD linear PP. Linear PP was found to have a surface roughness 23% higher on average than other resins. The BMWD LCB PP was found to have increased flexural modulus (44%) at the cost of decreased toughness (-88%) compared to linear PP. The branched architecture and high molecular weight of the BMWD LCB PP contributed to improved foam morphologies and surface quality in high-temperature MO-FIM conditions.
长链支化聚丙烯（LCB PP）已被广泛用于改善发泡应用中的泡孔形态。然而，大多数研究集中在低熔体流动速率（MFR）树脂上，而诸如开模发泡注塑成型（MO-FIM）等泡沫生产方法需要高MFR树脂来提高加工性能。进行了一项系统研究，比较了用于MO-FIM的常规线性PP、宽分子量分布（BMWD）线性PP和新开发的BMWD LCB PP。通过使用两种具有不同活化温度和不同保压时间的化学发泡剂（CBA），研究了发泡温度和分子结构对泡孔形态、表面粗糙度和力学性能的影响。在最高发泡温度下，BMWD LCB PP泡沫的泡孔密度比BMWD线性PP高887%，泡孔尺寸小46%，泡孔结构更均匀。发现线性PP的表面粗糙度平均比其他树脂高23%。与线性PP相比，BMWD LCB PP的弯曲模量提高了44%，但韧性降低了8%。BMWD LCB PP的支化结构和高分子量有助于在高温MO-FIM条件下改善泡沫形态和表面质量。
