Effects of a silane coupling agent on the exfoliation of organoclay layers in polyurethane/organoclay nanocomposite foams

• Published in: Journal of applied polymer science Vol. 110; no. 1; pp. 376 - 386
• Main Authors: Han, Mi Sun, Kim, Youn Hee, Han, Sung Jae, Choi, Seok Jin, Kim, Sang Bum, Kim, Woo Nyon
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 05.10.2008; Wiley
• Subjects: Applied sciences; Cellular; Composites; Exact sciences and technology; Forms of application and semi-finished materials; nanocomposites; organoclay; Polymer industry, paints, wood; polyurethanes; Technology of polymers; Organic clay; Dispersion degree; Mechanical properties; Organic silane; Dispersion reinforced material; Compressive strength; Experimental study; Cellular plastic; nanocomposites; polyurethanes; Composite material; Thermal stability; Surface treatment; Coupling agent; Thermal properties; Bending strength; Morphology; Polyurethane; Thermal conductivity; organoclay; Nanocomposite; Plastics
• ISSN: 0021-8995; 1097-4628
• DOI: 10.1002/app.28521

An attempt was made to synthesize polyurethane (PU)/organoclay nanocomposite foams with high thermal insulation properties. The organoclay was modified by polymeric 4,4'-diphenylmethane diisocyanate (PMDI) with a silane coupling agent. The structure of the organoclay-modified PMDI with the silane coupling agent was determined by Fourier transform infrared spectroscopy and nuclear magnetic resonance. Transmission electron micrographs and wide-angle X-ray diffraction patterns showed that the interlayer distance increased for the PU/organoclay nanocomposites with the addition of the silane coupling agent. It was expected that the distance between the organoclay layers would increase and that the organoclay would be dispersed on a nanoscale in the PU matrix because of the organic/inorganic hybrid bond formation between the organoclay and silane coupling agent. Compressive and flexural strengths of the PU/silane coupling agent/organoclay nanocomposite foams were similar to those of the PU/organoclay nanocomposite foams. However, the thermal conductivity appreciably decreased from 0.0250 to 0.0230 W/m h °C in the PU/silane coupling agent/organoclay nanocomposite foams. Scanning electron micrographs showed that the cell size of the PU/silane coupling agent/clay nanocomposite foams also decreased. On the basis of these results, it is suggested that the smaller cell size and lower thermal conductivity of the PU/silane coupling agent/organoclay nanocomposite foams were mainly due to enhanced exfoliation of the organoclay layers by the silane coupling reaction.