Abstract
AbstractThe present paper deals with experiments in which the angle resolved X‐ray photoelectron spectroscopy (ARXPS) technique was applied to investigate the phenomenon of migration in polyamide 6 with organically modified montmorillonite (PA6‐OMMT) nanocomposites. This is the first time ARXPS was used, to gain a more detailed insight into the migration process. Curve‐fitting analyses are reported which enable the differentiation between a manual mixture of PA6 with OMMT at room temperature from a nanocomposite structure. The ARXPS technique was applied to annealed samples at 250, 275, and 285°C, for 2 hr, and with three take of angles, α, of 90, 60, and 30°. The depth of the layer investigated is 9 nm in case the sample surface is well defined. By tilting the take‐off angle of the beam‐out electrons one can determine the intensity of the signals at various distances from the surface within the investigated layer. The concentration gradient of the Si signals is observed. The rate of migration is found to be more rapid in the layer closest to the surface. The intensity of the Si signals in the investigated layer is found to be 1.8 to 9.1 times that of the same composite sample at room temperature. This ratio determines the extent of migration. At temperatures higher than 250°C and times of annealing greater than 30 min a decrease in the extent of migration is observed. This decrease is explained by the gradual decomposition of the surfactant and the consequent removal of the polymeric matrix molecules from the migrating exfoliated units, culminating in denuded alumino‐silicate layers. These layers aggregate to noncolloidal microcomposite particles which do not migrate. The concentration of the exfoliated units decreases with consequent decrease in migration. A gradient of decreasing concentration of Si2p signals was observed after various times of annealing, where the gradient becomes more uniform with increase in time. Copyright © 2008 John Wiley & Sons, Ltd.
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