(A) study on the exfoliation and physical properties of polyurethane/organoclay nanocomposites at high clay concentration

Abstract

Organoclays were formed by modifying the pristine clays with organifiers Disperse organoclay with high shearing, and the series of HTPB (hydroxyl terminated polybutadiene)/organo-clay nanocomposite was formed. Then, this composite were crosslinked with IPDI (isophorone diisocyanate) and PU nanocomposite was formed. In Caphter 2, as the length of organifier increased, the gap size between layers of organoclay became broader. The clays modified with octadecylamine(C18) and dodecyl amine(C12) showed wider gap sizes than that modified with octyl amine(C8). This gap size affected the dispersion state of clays, exfoliation/intercalation in HTPB polymer medium. The mixtures of HTPB with C18 and C12 were transparent without sedimentation and showed almost exfoliated structure. HTPB/C18 mixture showed the higher viscosity and yield strength than HTPB/C12 due to more exfoliation. HTPB/C12 showed more elastic behavior than HTPB/C18 mixture because the organoclay C12 had less content of organifier. The dodecylamine is more polar than octadecylamine, and the diffusion rate of IPDI was faster in HTPB/C12 than HTPB/C18 meidum during crosslinking reaction. The faster crosslinking aided to achieve complete exfoliation in PU(HTPB)/C12 even at 15wt% of clay. Furthermore, the crosslinking density of PU(HTPB)/C12 was higher than PU(HTPB)/C18. This phenomena was confirmed in swelling test, DSC results. Even at 10wt% of clay PU nanocomposites, tensile properties were enhanced than PU binder. In Chpater 3, Organoclay (cloisite10A and cloisite20A) was dispersed in HTPB (Hydroxyl terminated polybutadiene) at 5, 10, and 15 wt% of clay. Then, HTPB was crosslinked with IPDI (Isophorone diisocyanate), and a PU nanocomposite was formed. Even at 15 wt% of clay, the complete exfoliation of clay was achieved in PU. The diffusion rate of IPDI was affected by the polarity of the HTPB/organoclay composite because IPDI is relatively polar molecule, and it determined the exfoliation sta...