Preparation and characterization of 4,4′-bis(4-aminophenoxy)diphenyl sulfone based fluoropoly(ether-imide)/organo-modified clay nanocomposites

Abstract

A series of fluoropoly(ether-imide) (6F-PEI), and [6F-PEI/montmorillonite (MMT) clay) nanocomposites films were made by thermal curing of respective formulations containing fluoropoly(ether-amic acid) (6F-PEAA), synthesized from 2,2′-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) and 4,4′-bis(4-aminophenoxy)diphenyl sulfone (p-SED), and increasing concentration of p-SED treated montmorillonite clay (modified MMT clay) at temperature from RT to 350 °C. These films showed excellent solvent resistance as well as very good thermal stability, and increased glass transition (Tg) values with increasing % clay. In addition, these trifluoromethyl groups-containing nano-composites films showed sharp lowering of coefficient of thermal expansion (CTE) by 22%. Furthermore, they exhibited increased long-term thermo-oxidative stability (TOS), with % weight retention in the range of 86 to 92% in isothermal heating at 300 °C for 300 h in air, reduced water absorption at 100 RH at 50 °C in the range of 0.5 to 1.15%. These data are still much lower than those of neat ULTEM® 1000 and Kapton® H film. The modulus of elasticity is on an average 38% higher for the nanocomposite films relative to neat fluoropoly(ether-imide) (6FDA + p-SED), and above non-fluorinated polyimide films. The surface energy measurement by One-Liquid and Two-Liquid method showed a comparable trend of decreasing contact angle. For the nano-composite films having 15% hydrophobic clay, the contact angle decreased by 21 and 20% for DI-water and formamide, respectively. The surface energy increase was in the range of 8.21-8.54 mJ/m2.