Effect of the average soft‐segment length on the morphology and properties of segmented polyurethane nanocomposites

Abstract

Two organically modified layered silicates (with small and large diameters) were incorporated into three segmented polyurethanes with various degrees of microphase separation. Microphase separation increased with the molecular weight of the poly(hexamethylene oxide) soft segment. The molecular weight of the soft segment did not influence the amount of polyurethane intercalating the interlayer spacing. Small-angle neutron scattering and differential scanning calorimetry data indicated that the layered silicates did not affect the microphase morphology of any host polymer, regardless of the particle diameter. The stiffness enhancement on filler addition increased as the microphase separation of the polyurethane decreased, presumably because a greater number of urethane linkages were available to interact with the filler. For comparison, the small nanofiller was introduced into a polyurethane with a poly-(tetramethylene oxide) soft segment, and a significant increase in the tensile strength and a sharper upturn in the stress-strain curve resulted. No such improvement occurred in the host polymers with poly(hexamethylene oxide) soft segments. It is proposed that the nanocomposite containing the more hydrophilic and mobile poly(tetramethylene oxide) soft segment is capable of greater secondary bonding between the polyurethane chains and the organosilicate surface, resulting in improved stress transfer to the filler and reduced molecular slippage.

Transport properties in polyurethane/clay nanocomposites as barrier materials: Effect of processing conditions

“…The higher surface area for the sonicated C10A series introduces a greater number of hydrogen bonding sites between the -OH groups, present on the silicate surface and the ether groups in the soft segment, as well as the isocyante groups in the hard phase of the polyurethane [30,31]. Thus anchored, the clay platelets increase the glass transition temperature of the soft-phase by restricting segmental chain motion [32,33], and generating an interphase region [34]. These restriction effects may also be responsible for broadening the tan ı peak, and the decrease in intensity of this peak [35], as well as the reduction of the damping capacity [27,28,36].…”

Reduction of aspect ratio of fluoromica using high-energy milling

“…The interlayer spacing (d 001 ) is 0.95 nm (Peeterbroeck et al, 2005;Utracki and Rapra Technology Limited., 2004). The chemical formulation is Na 0.66 Mg 2.68 (Si 3.98 Al 0.02 )O 10.02 F 1.96 (Finnigan et al, 2006). As received ME100 powder was prepared as a slurry in deionized water and subjected to high-energy milling in both a smaller lab scale mill and a larger semi-commercial scale mill (both from Netzsch, Germany), and the finest fractions were then separated using centrifugation.…”

Polyurethane Nanocomposites

“…The effects of organoclays on the properties of PU were studied [1,3,[18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. PU were prepared by the following procedures: (i) distribution of clay in polyol with a subsequent reaction with diisocyanate; (ii) interaction of PU with clay in organic solvent with a subsequent evaporation of solvent; (iii) reaction of diisocyanate with hydroxyalkyl groups of organic modifier in the clay with a subsequent reaction with polyol.…”

“…Exfoliated in a solvent unmodified clay laponite as a hydrophilic compound interacts with polar soft segments (polyol) in PU like poly(ethylene oxide) or poly(propylene oxide) where as in PU with hydrophobic soft segments like poly(tetramethylene oxide) clay interacts with the hard domain (urethane links) [24]. Thus, in the first case a decrease toughness and elongation-to-break is observed, whereas in the second case an increase of the same properties is observed [24]. Such a study gives a better understanding of the nanoclay effect of PU nanocomposites properties.…”