Gallery Distance Research Articles

Gallery structure and exfoliation of organophilized montmorillonite: effect on composite properties

Wyoming montmorillonite was organophilized to different extents with N-cetylpyridinium chloride and its gallery structure was studied by WAXS. PP nanocomposites were prepared using this silicate and their structure, as well as tensile properties were determined as a function of composition. Two peaks were observed in the WAXS patterns of some of the treated silicates, one of which disappeared during processing. The orientation of the organic compound in the galleries depends on its size and amount, as well as on the ion density of the filler. Multiple peaks appearing in the WAXS pattern of organophilized silicate may arise from interference, but they may also indicate the presence of several populations of layer distances. Water is absorbed between the galleries of partially organophilized silicates leading to the separation of the layers resulting in the appearance of new scattering peaks. Exfoliation occurs only above a critical gallery distance, which corresponds to the thickness of two aliphatic chains. Although exfoliation of the silicate is determined by its organophilization and gallery structure, composite properties are dominated by interfacial interaction.

Rheology of Organoclay Nanocomposites: Effects of Polymer Matrix/Organoclay Compatibility and the Gallery Distance of Organoclay

The linear dynamic viscoelasticity, and transient and intermittent shear flows of organoclay nanocomposites, which were prepared with poly(ethylene-ran-vinyl acetate) (EVA), poly(ethylene-ran-vinyl alcohol) having 53 mol % vinyl alcohol (EVOH-53), or poly(ethylene-ran-vinyl acetate-ran-vinyl alcohol) having 5 mol % vinyl alcohol (EVAOH-5) were investigated. For the study, two organoclays (Southern Clay Products) were employed: (i) Cloisite 30B (having the gallery distance of 1.85 nm) treated with a surfactant (MT2EtOH) containing tallow, quaternary ammonium chloride, and hydroxyl groups and (ii) Cloisite 15A (having the gallery distance of 3.15 nm) treated with a surfactant (2M2HT) containing hydrogenated tallow, quaternary ammonium chloride but no hydroxyl group. Thus, a total of six nanocomposites were prepared by melt blending using a Brabender mixer. Before taking rheological measurements, the nanocomposites were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM). ...

NUCLEATING EFFECT OF MONTMORILLONITE NANOPARTICLES IN POLYPROPYLENE

The nucleation effect of two layered montmorillonite silicates of different origin was studied in polypropylene (PP). Composites were prepared as a function of composition in an internal mixer or by homogenization in a twin-screw compounder. Melting and crystallization characteristics were determined by differential scanning calorimetry. The gallery distance of the silicates and the structure of the composites were studied by WAXS. The results prove that montmorillonite may considerably influence the crystallization of PP. The effect depends very much on the origin and treatment of the filler. Both treatment and composite preparation lead to considerable changes in the separation distance of the silicate layers. Even though the composites contain fillers with more than one population of layer distances, the nucleating effect is related to the completely collapsed galleries of 1 nm distance. Besides gallery distance, organophillization also modifies the surface tension of the filler, but this apparently does not influence its nucleating efficiency. The efficient gallery distance is twice as large as the characteristic matching lattice dimension determined by Lotz et al. Although a few observations could not be explained and the tentative explanation given earlier may need further verification, the results prove that nucleation does not occur at the flat surface of the filler but between its galleries, where polymer molecules may adsorb preferentially.

Synthesis and characterization of elastomeric polyurethane/clay nanocomposites

AbstractAn elastomeric polyurethane/clay (PU/clay) nanocomposite based on poly(propylene glycol) (PPG), glycerol propoxylate, and toluene‐diisocyanate (TDI) was synthesized by intercalative polymerization technology. The results of wide angle X‐ray diffraction (WAXD) studies showed that the gallery distance of the clay in the hybrid was enlarged from 1.9 to 4.5nm or more. Introducing clay in the PU matrix resulted in an increase in both the tensile strength and elongation at beak. When the clay content reached about 8%, the tensile strength and elongation at break were two times and five times respectively to that of the pure PU. In addition, the clay intercalative route to the nanocomposite synthesis also effected the thermal properties of the nanocomposites. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1444–1448, 2001

The geometry of the chamber system of a semimodular lattice

In this paper geometric properties of the following metric space C are studied. Its elements are called chambers and are the maximal chains of a semimodular lattice X of finite height and its metric d is the gallery distance. We show that X has many properties in common with buildings. More specifically, Tits [17] has recently described buildings in terms of “Weyl-group valued distance functions”. We consider the Jordan-Holder permutation π(C, D) corresponding to a pair C, D of chambers and show that it has most properties of such a distance with values in the symmetric group.

The gallery distance of flags

An explicit formula for the gallery distance of two maximal flags in a vector space is given. The main tool of the proof is the Jordan-Holder permutation. The result and its proof hold more generally for any semimodular lattice of finite height and with minor changes also for the distance of two chambers in the Bruhat-Tits building of the general linear group.

How Bark Beetles Avoid Interference with Squatters: An ESS for Colonization by Ips typographus

Bark beetles aggregate on suitable host trees and their larvae incur severe competition for food from larvae in neighbouring galleries. To maximize their fitness parental bark beetles should therefore balance the bark area claimed for their offspring and the probability of being competitively interfered by squatters. It was shown that the unbeatable colonization strategy is to position the gallery relative to a neighbour so as to prevent newcomers from excavating a gallery in between, provided that the probability of interference by squatters exceeds 0.8. A test of the theory was carried out for the case of Ips typographus attacking spruce trees. It was found that the mean (and the modal) gallery distance was close to the critical threshold distance above which a squatter would be able to raise at least one offspring with sufficient energy reserves to find a suitable host.