Lamellar bundle

There are regional differences in the orientation of scleral collagen fibrils. In the equatorial region, collagen fibrils are heterogeneous in diameter (25-300 nm) and are arranged in lamellar bundles with random orientations. 

Figure 3.37 Optical micrographs of single compact polyethylene axiahte grown from a 1% solution in xylene at ca. 86°C. View (a) is nearly normal to the truncated lonzenge lamellar surfaces, (b) is 90° away, showing the edges of lamellae/lamellar bundles, and (c) is along the axis of the symmetry axis or spine. The width of each optical micrograph is 60 pm. From Bassett et al. [54] with permission of John Wiley Sons, Inc.

Figure 3.55 Polarized optical micrograph of istotactic polypropylene crystallized at an unspecified but small undercooling width of the micrograph is 1500 pm. The coarse open structure is a consequence of the large diffusion length 5 = DIG. Radially directed features are lamellar bundles of dominant lamellae as wide as 50 pm in tangential directions. Branching maintains an approximately constant proportion of crystals at increasing distances from the center. Note that the orientation of crystals is not strictly radial. From Keith and Padden [91] with permission from the American Institnte of Physics.

Figure 30(a) Radiating lamellar bundles separated by non-crystalline regions. A 1 1 blend of isotactic and atactic... 

If the concentration of nucleation events is extremely dense, there will be insufficient room for the spherulites to mature. Under such circumstances a multitude of lamellar bundles, termed sheaves, are produced. Toward either end of the bundle the lamellae splay out from each other to form a waisted structure. Sheaves are so named because of their outward similarity to wheat sheaves (albeit on a very different scale). Each sheaf is equivalent to the core of a spherulite. The middle of each sheaf consists of a small bundle of parallel lamellae. 

At this point a third intermediate approach deserves mentioning. It is due to Allegra [43] who proposed that polymer crystallization is controlled by a metastable equilibrium distribution of intramolecular clusters, the so-called bundles , forming in the liquid phase. These subsequently aggregate to the side surfaces of the crystals, driven by van der Waals interactions. The lamellar thickness is determined by the average contour length of the loops within the bundles. Although the model can... 

Fig. 4 Left Two bundles with the same lamellar thickness L, separated by a bridge. Right After aggregation, in principle the bundles may either retain the previous thickness L while the bridge produces new crystalline stems (old model), or the bridge is reeled in with an increase of L to U (new model)...

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