Architectural characteristics of stochastic honeycombs fabricated from varying melt strength polypropylenes



Stochastic honeycombs are a cellular polymer fabricated through a simple melt-stretching process. In this study, five polypropylenes (PP) with varying rheological properties were used to fabricate stochastic honeycombs over a range of densities. Rheology tests were performed to determine the melt behavior, while micro-CT scans were used as a nondestructive characterization technique to determine the internal architecture. The sandwich structure consists of parallel skins separated by a network of interconnected webs. The cross-sectional area decreased from unit area at the skins to a plateau over the middle third of the honeycomb height where the cross-sectional area and total edge length of the webs were relatively constant. The rheological properties of the polymer were found to determine the web length per unit area, while the starting areal density of the polymer controlled the mid-height cross-sectional area. Other features, such as archways and buttresses, act as secondary structures that support the webs. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40074.