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Proceedings Paper

Porous materials with stress and temperature activated porosity
Author(s): Navid Namdari; Bilal Nizar Abdul Halim; Sheikh Rasel; Md Emran Hossain Bhuiyan; Raghavendra Alwala; Reza Rizvi
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Paper Abstract

The fabrication of micro-structured films with dynamic porosity is useful in various applications. This article presents fabrication of microcellular films exhibiting dynamic porosity upon applying an external pressure stimulus. Interestingly, we show that the dynamic porosity is in conjunction with an opaque to transparent transition (OTT) that imparts the material with a unique optomechanical behavior. The OTT experienced foams will have a transparency almost equal of the as-cast films. The foaming process used for this study is solid-state foming technique with CO2 gas as physical blowing agent. A styrene-ethylene-butylene-styrene (SEBS) triblock copolymer was used as the foaming material. Polystyrene (PS) blocks in SEBS play a key role in this process since CO2 reduces the Tg of PS and enable ethylenebutylene (EB) parts to swell during saturating stage while upon depressurization their Tg increases again that prevents the forming pores from collapse. A custom-made in-situ optomechanical setup was used to characterize the optical and mechanical behavior of the produced foams. Optomechanical tests at different strain rates and loads revealed that the films undergo a gradual OTT behavior indicating their ability to be used as optical pressure-sensitive films. Quenching temperature is of great importance in this process since the foams show various OTT behavior once the quenching temperature changes. Moreover, here we show after pressing the foams, the transparent films can be re-foamed by the same process for many cycles.

Paper Details

Date Published: 29 March 2019
PDF: 7 pages
Proc. SPIE 10968, Behavior and Mechanics of Multifunctional Materials XIII, 109680X (29 March 2019); doi: 10.1117/12.2515380
Show Author Affiliations
Navid Namdari, The Univ. of Toledo (United States)
Bilal Nizar Abdul Halim, The Univ. of Toledo (United States)
Sheikh Rasel, The Univ. of Toledo (United States)
Md Emran Hossain Bhuiyan, The Univ. of Toledo (United States)
Raghavendra Alwala, The Univ. of Toledo (United States)
Reza Rizvi, The Univ. of Toledo (United States)

Published in SPIE Proceedings Vol. 10968:
Behavior and Mechanics of Multifunctional Materials XIII
Hani E. Naguib, Editor(s)

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