(A) study on polyurethane network and polyurethane/clay nanocomposites

Abstract

Polyurethane networks were prepared from polyethyleneglycol-copolytetrahydrofuran diol (TPEG, trade name), polyfunctional aliphatic isocyanate (N-100, trade name, crosslinker) and isophoron diisocyanate (IPDI). They were synthesized by two different systems with controlling the equivalent (isocyanate group/hydroxyl group) ratio or N-100/IPDI ratio. The thermal and mechanical properties of these polyurethane networks were studied by differential scanning calorimeter and tensile tester, respectively. In TPEG/N-100 system, the melting temperature(Tm) and the heat of fusion (AHf) decreased with increasing equivalent ratio (isocyanate group/hydroxyl group). In case of TPEG/N-100/IPDI system, Tm and AHf decreased with increasing N-100/IPDI ratio. These results could be related with chain length between crosslink points, which increased to make the size and quantity of crystalline domain larger. Swelling behaviors in 19 solvents were also investigated to evaluated solubility parameter and the crosslink density of networks. The swelling data were obtained by immersing polyurethane networks in 19 solvents until the equilibrium state was reached, and then solubility parameter from Gee``s plot and interaction parameter from Flory-Huggins equation were calculated. The Mc values (the average molecular weight between two adjacent crosslink points) of networks could be calculated by Flory-Rehner model. It was observed that the solubility parameter of network increased with increasing the content of isocyanante and Mc values decreased with increasing N-100 content. Organoclay was prepared to make polyurethane/clay nanocomposite. The organifier was synthesized to treat clay and characterized by NMR, IR and Mass spectrum. The characteristic of organoclay with different polyol-ends were investigated. PEGs were intercalated between clay layers before proper ion exchange reaction due to their hydrophilicity. Organoclays with PTMG were made and used for polyurethane/clay nanocomposi...