Porous Polyimide-Silica Composite: A New Thermal Resistant Flexible Material. Issue 1645 (2014)

• Record Type: Journal Article
• Authors: Fukubayashi, Yumeto; Yoda, Satoshi
• Is Part Of: MRS proceedings. Issue 1645:(2014)
• Publication Date: 2014
• Subjects: polymer, -- sol-gel, -- porosity; Electrical engineering -- Congresses; Physics -- Congresses; Materials -- Research -- Congresses; Materials science -- Congresses; 620.11
• DOI: 10.1557/opl.2014.278
• Languages: English
• ISSNs: 0272-9172

Abstract

ABSTRACT: We developed a new highly porous polyimide (PI) -silica composite with high flexibility, mechanical strength, and heat resistance. The composite was prepared by a new process consisting of (1) phase separation of a mixture of PI precursor (polyamic acid), solvent, and silicon alkoxide, induced by high-pressure CO2 (40 °C, 20 MPa), (2) silicate formation by sol-gel reaction, and (3) supercritical CO2 extraction of the solvent. The composite had a bimodal porous structure with micropores of 10-30 μm and nanopores of ∼50 nm. In the PI matrix, silica nanoparticles (< 100 nm in diameter) were highly dispersed. Porosity of the composite was 78%, which is higher than that of conventional porous PI prepared by physical foaming technique. Relative dielectric constant of the material was lower than 1.4 at 1 MHz. The porous PI-silica composite sheet was flexible enough to be folded without cracking. Notably, the Young's modulus (0.80 GPa) and the onset decomposition temperature (600 °C) of the PI-silica composite were higher than those of conventional porous PI with similar porosity, respectively. The porous PI-silica composite is promising as a flexible thermal insulator for high-temperature use and as a thermal resistant low- k material.