Properties of polyurethane/hectorite nanocomposite elastomer using reactive organifier

Abstract

In this study, elastomers were prepared by using organoclays having reactive organifiers. The objective of this dissertation was to form ionic bonding between the polyurethane main chain and the silicate layer surface and to provide the polyurethane elastomer physical crosslinking. The effect of the chemical structure of the organifier on properties of the organoclay such as d-spacing, ion-exchanged fraction was investigated. The effect of the dispersibility of the organoclays on the properties of the polyurethane nanocomposites such as the morphology, thermal stability, and tensile properties were also investigated. The organoclays were synthesized with three types of chain-extended organifiers prepared using poly(tetramethylene ether)glycol (PTMG) ($M_n$ =2000, 3000), hexamethylene diisocyanate (HDI) and N-methyl diethanol amine (MDEA). Polyurethane elastomers were synthesized from poly(tetramethylene ether)glycol (PTMG) ($M_n$ =1000), 4,4’-diphenylmethane diisocyanate (MDI) and 1,4-butanediol as a chain-extender by the prepolymer method. The equivalent weight ratio of the components were 1.5:4.2:2.5, 2:4.2:2, and 2.5:4.2:1.5 for PTMG:MDI:1,4-BD. Relative hardness of each polyurethane was classified as hard, regular and soft according to the ratio of soft segment (PTMG) to hard segment(MDI). For the clay, Laponite RD was used that had the synthetic hectorite structure. The organifier having urethane group had high value of IEF (Ion-Exchanged Fraction) due to the formation of hydrogen bonding between the urethane groups in the organifiers and the layered silicates. The d-spacing and IEF of organoclays increased with increasing the molecular weight of organifier due to the increase of its chain length. The PTMG chain of the organifier tries to retain coil-like conformation due to hydrophobic nature, the d-spacing increased and the regularity of silicate layers decreased with increasing the molecular weight of PTMG chain end of the organifier. The properti...