Thermomechanical behavior and thermal stability of polyurethane rigid nanocomposite foams containing binary nanoparticle mixtures

Abstract

Polyurethane (PU) rigid nanocomposite foams containing binary nanoparticle mixtures were prepared via reactive foaming process by using the synergy of mixing based on H-bonding interactions between nanofillers and polymer matrix. Using a very high surface area hydrophilic fumed nanosilica with a primary particle size of 7 nm and a concentration of less than 0.2 wt% in addition to carboxylic acid functionalized multiwalled carbon nanotubes (MWCNTs-COOH) in PU rigid foams leads to improved thermal stability, thermomechanical and mechanical properties. Particularly, the system containing both 0.4 wt % CNT and 0.1 wt% nanosilica has a much higher value in terms of T-g, storage modulus value at T-g, reduced compressive strength, thermal stability and cell density compared to the sample containing only 0.5 wt% CNT. Based on FT-IR results, favorable and enhanced H-bonding interactions of N-H and carbonyl functional groups of the urethane linkage in PU chains with surface silanols of hydrophilic nanosilica particles and carboxylic acid functional groups of MWCNT-COOH were shown to be the main reasons for the reinforcement effect in PU rigid foams.